Oxygen hyperstoichiometric hexagonal ferrite CaBaFe4O7+δ (δ≈0.14): Coexistence of ferrimagnetism and spin glass behavior

NASA Astrophysics Data System (ADS)

Sarkar, Tapati; Duffort, V.; Pralong, V.; Caignaert, V.; Raveau, B.

2011-03-01

An oxygen hyperstoichiometric ferrite CaBaFe4O7+δ (δ ≈ 0.14) has been synthesized using “soft” reduction of CaBaFe4O8. Like the oxygen stoichiometric ferrimagnet CaBaFe4O7, this oxide also keeps the hexagonal symmetry (space group P63mc), and exhibits the same high Curie temperature of 270 K. However, the introduction of extra oxygen into the system weakens the ferrimagnetic interaction significantly at the cost of increased magnetic frustration at low temperature. Moreover, this canonical spin glass (Tg~166 K) exhibits an intriguing crossover from de Almeida-Thouless type to Gabay-Toulouse type critical line in the field temperature plane above a certain field strength, which can be identified as the anisotropy field. Domain-wall pinning is also observed below 110 K. These results are interpreted on the basis of cationic disordering on the iron sites.

Characterization of SrCo1.5Ti1.5Fe9O19 hexagonal ferrite synthesized by sol-gel combustion and solid state route

NASA Astrophysics Data System (ADS)

Vinaykumar, R.; Mazumder, R.; Bera, J.

2017-05-01

Co-Ti co-substituted SrM hexagonal ferrite (SrCo1.5Ti1.5Fe9O19) was synthesized by sol-gel combustion and solid state route. The effects of sources of TiO2 raw materials; titanium tetra-isopropoxide (TTIP) and titanyl nitrate (TN) on the phase formation behavior and properties of the ferrite were studied. The thermal decomposition behavior of the gel was studied using TG-DSC. The phase formation behavior of the ferrite was studied by using X-ray powder diffraction and FTIR analysis. Phase formation was comparatively easier in the TN-based sol-gel process. The morphology of powder and sintered ferrite was investigated using scanning electron microscope. Magnetic properties like magnetization, coercivity, permeability, tan δμ and dielectric properties were investigated. The ferrite synthesized by sol-gel based chemical route showed higher saturation magnetization, permeability and permittivity compared to the ferrite synthesized by solid state route.

Investigation of Hexagonal Ferrite Film Growth Techniques for Millimeter-Wave Systems Applications.

DTIC Science & Technology

1987-03-15

hexaferrite LPE layer on CoGa 204 substrate. Some areas of the film exhibit a terraced structure .................................... 32 Figure 17 (a) Layer...49 G), which is the standard substrate for yttrium iron garnet epitaxial film growth. The dielectric constant is slightly larger than values for...Details are given ’.- in Appendices III a:d IV. 4.1 INTIODUCTION In LPE , a small lattice mismatch between film and substrate is .r..r ial tc gro.w good

Crystal structure, magnetic properties and advances in hexaferrites: A brief review

NASA Astrophysics Data System (ADS)

Jotania, Rajshree

2014-10-01

Hexaferrites are hard magnetic materials and specifically ferri-magnetic oxides with hexagonal magnetoplumbite type crystallographic structure. Hexagonal ferrites are used as permanent magnets, high-density perpendicular and magneto-optical recording media, and microwave devices like resonance isolators, filters, circulators, phase shifters because of their high magnetic permeability, high electrical resistivity and moderable permittivity. In addition to these; hexagonal ferrites have excellent chemical stability, mechanical hardness and low eddy current loss at high frequencies. The preparation of hexaferrites is a complicated process. Various experimental techniques like standard ceramic techniques, solvent free synthesis route, co precipitation, salt-melt, ion exchange, sol-gel, citrate synthesis, hydrothermal synthesis, spray drying, water-in-oil microemulsion, reverse micelle etc are used to prepare hexaferrite materials. Structural, dielectric and magnetic properties, crystallite size of hexaferrites depend upon nature of substituted ions, method of preparation, sintering temperature and time. The recent interest is nanotechnology, the development of hexaferrite fibres and composites with carbon nano tubes (CNT). Magnetic properties of some doped and un-doped hexaferrites are discussed here. Recent advances in hexaferrites also highlighted in present paper.

The effect of precursor types on the magnetic properties of Y-type hexa-ferrite composite

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

Kim, Chin Mo; Na, Eunhye; Kim, Ingyu

2015-05-07

With magnetic composite including uniform magnetic particles, we expect to realize good high-frequency soft magnetic properties. We produced needle-like (α-FeOOH) nanoparticles with nearly uniform diameter and length of 20 and 500 nm. Zn-doped Y-type hexa-ferrite samples were prepared by solid state reaction method using the uniform goethite and non-uniform hematite (Fe{sub 2}O{sub 3}) with size of <1 μm, respectively. The micrographs observed by scanning electron microscopy show that more uniform hexagonal plates are observed in ZYG-sample (Zn-doped Y-type hexa-ferrite prepared with non-uniform hematite) than in ZYH-sample (Zn-doped Y-type hexa-ferrite prepared with uniform goethite). The permeability (μ′) and loss tangent (δ) atmore » 2 GHz are 2.31 and 0.07 in ZYG-sample and 2.0 and 0.07 in ZYH sample, respectively. We can observe that permeability and loss tangent are strongly related to the particle size and uniformity based on the nucleation, growth, and two magnetizing mechanisms: spin rotation and domain wall motion. The complex permeability spectra also can be numerically separated into spin rotational and domain wall resonance components.« less

Investigation of Microwave Monolithic Integrated Circuit (MMIC) Non-Reciprocal Millimeterwave Components

DTIC Science & Technology

1991-09-01

nickel zinc ferrite films and (2) sputtering of barium hexaferrites with C-axis oriented normally to the film plane. The SSP tech- nique potential for...M-Wave, Components, Ferrites, Films , Yig, Nickel, Zinc , Hexagonal, R96E Measurements, Frequency, Magnetic, Barium Ferrite 17. SECURITY CLASSIFICATION...techniques to integrate millimeter-wave ferrite devices with GaAs VI&Cs. APPROACH Our approach was to deposit ferrite thin films on GaAs sub- strates in a

Ferrite-Ferroelectric Heteroepitaxial Structures and Frequency Agile Multiferroic RF Components

DTIC Science & Technology

2012-11-27

crystal LPE YIG films -PZT. (2) Eutectic bonding techniques for ferrite-piezoelectric bilayer synthesis: Samples of YIG/PMN-PT and hexagonal ferrite...Materials: (1) Growth of ferrite films on piezoelectric substrates by electrophoretic deposition techniques: Studies focused on 1-10 u.m thick...polycrystalline YIG films on PZT. The strength of magneto-electric (ME) interactions measured over 1 -40 GHz was comparable to results for bilayers of single

Effect of Powder Grain Size on Microstructure and Magnetic Properties of Hexagonal Barium Ferrite Ceramic

NASA Astrophysics Data System (ADS)

Shao, Li-Huan; Shen, Si-Yun; Zheng, Hui; Zheng, Peng; Wu, Qiong; Zheng, Liang

2018-05-01

Compact hexagonal barium ferrite (BaFe12O19, BaM) ceramics with excellent magnetic properties have been prepared from powder with the optimal grain size. The dependence of the microstructure and magnetic properties of the ceramics on powder grain size was studied in detail. Single-phase hexagonal barium ferrite powder with grain size of 177 nm, 256 nm, 327 nm, and 454 nm was obtained by calcination under different conditions. Scanning electron microscopy revealed that 327-nm powder was beneficial for obtaining homogeneous grain size and compact ceramic. In addition, magnetic hysteresis loops and complex permeability spectra demonstrated that the highest saturation magnetization (67.2 emu/g) and real part of the permeability (1.11) at 1 GHz were also obtained using powder with grain size of 327 nm. This relationship between the powder grain size and the properties of the resulting BaM ceramic could be significant for development of microwave devices.

Crystallographic and magnetic properties of Cu2U-type hexaferrite

NASA Astrophysics Data System (ADS)

Kamishima, K.; Tajima, R.; Watanabe, K.; Kakizaki, K.; Fujimori, A.; Sakai, M.; Watanabe, K.; Abe, H.

2015-02-01

We have investigated the synthesis conditions, and the magnetic properties of the Cu2U-type hexagonal ferrite, Ba4Cu2Fe36O60. The Cu2U-type hexaferrite was synthesized at the sintering temperature of 1050 °C with the initial composition of Ba4.4Cu2Fe37.6O62.8 (Cu2U+0.2T-block). The saturation magnetizations at 300 K and 5 K are 46.8 A m2/kg and 65.0 A m2/kg, respectively. The Curie temperature is 420 °C which is lower than that of the M-type ferrite (450 °C) but higher than that of the Cu2Y-type ferrite (320 °C). The amount of the nonmagnetic impurity in this sample is estimated to be about 10 wt% by the electron probe micro analysis. We estimated the expected saturation magnetization to be 65.2 A m2/kg, by assuming the model of a Néel-type ferrimagnetic structure and the reduction of magnetization by the 10 wt% nonmagnetic impurity. This is consistent with the observed magnetization of 65.0 A m2/kg at 5 K.

Influence of samarium substitution on the structural and magnetic properties of M-type hexagonal ferrites

NASA Astrophysics Data System (ADS)

Yasmin, Nazia; Mirza, Misbah; Muhammad, Safdar; Zahid, Maria; Ahmad, Mukhtar; Awan, M. S.; Muhammad, Altaf

2018-01-01

The M-type hexagonal ferrites with chemical formula SrFe12-xSmxO19 (x = 0, 0.01, 0.02, 0.03) were synthesized via sol-gel method. We studied the effects of substitution of rare earth on the structural and magnetic temperament of M-type hexaferrites. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) strategies are employed for the systematical examination of micrographs and structures of the samples. The magnetic particularities are studied by the use of vibrating sample magnetometery. The M-H loops are used to investigate the hard magnetic behavior of all the samples. The substantial value of coercivity (>1 kOe) for all the samples shows that the particular sample is permanent magnet and reveals the hard magnetic action. It is observed that values of saturation magnetization (Mr) and remanence (Ms) decline with increasing the rare earth ions substitution. This decrease may follow spin canting and the magnetic dilution, which results in dislocation of superexchange interactions. The improvement in Hc may be because of large anisotropy of magnetocrystalline, where ion anisotropy of Fe2+ ion on the 2a site probably overriding in all hexaferrites series. The synthesized composites were useful for applications in magnetic microwave absorbing materials.

Coexistence of ferromagnetism and spin glass freezing in the site-disordered kagome ferrite SrSn2Fe4O11

NASA Astrophysics Data System (ADS)

Shlyk, Larysa; Strobel, S.; Farmer, B.; De Long, L. E.; Niewa, R.

2018-05-01

Single-crystal x-ray diffraction refinements indicate SrSn2Fe4O11 crystallizes in the hexagonal R-type ferrite structure with non-centrosymmetric space group P63mc and lattice parameters a = 5.9541(2) Å, c = 13.5761(5) Å, Z = 2 (R(F) = 0.034). Octahedrally coordinated sites are randomly occupied by Sn and Fe; whereas tetrahedrally coordinated sites are exclusively occupied by Fe, whose displacement from ideal trigonal-bipyramidal coordination causes the loss of inversion symmetry. DC magnetization data indicate SrSn2Fe4O11 single crystals undergo ferro- or ferri-magnetic order below a transition temperature TC = 630 K with very low coercive fields Hc ⊥ = 0.27 Oe and Hc// = 1.5 Oe at 300 K, for applied fields perpendicular and parallel to the c-axis, respectively. The value for TC is exceptionally high, and the coercive fields exceptionally low, among the known R-type ferrites. Enhanced coercivity and thermomagnetic hysteresis suggest the onset of short-range, spin glass order occurs below Tf = 35 K. Optical measurements indicate a band gap of 0.8 eV, consistent with wide-gap semiconducting behavior and a previously established empirical correlation between the semiconducting gap and TC for R-type ferrites based upon Ru.

Preparation of Scandium-Doped, Textured, M-Type Barium Ferrite via a Wet Magnetizing Orientation Process

NASA Astrophysics Data System (ADS)

Wang, Yu; Liu, Yingli; Zhang, Huaiwu; Li, Jie; Gao, Liwen; Chen, Daming; Chen, Yong

2018-02-01

In this paper, a wet magnetizing orientation process was applied to synthesize c-axis-textured, M-type barium ferrite (BaFe12O19 or BaM), which is widely used to produce hard magnetic materials. To modify the magnetic properties of the BaM ferrite and make it suitable for certain operating frequencies, Sc3+ was substituted into Fe3+ sites of the BaM crystal structure. A BaSc x Fe12- x O19 ferrite with a typical relative density of ˜ 75% was successfully obtained. We used x-ray diffraction, scanning electronic microscopy, and a vibrating sample magnetometer to obtain phase information, detail of the microstructure, and magnetic properties of the BaSc x Fe12- x O19, respectively. The composition BaSc x Fe12- x O19 ( x = 0.1) featured a superior squareness ratio of ˜ 67% and a saturation magnetization ( M S) of ˜ 5300 Gauss in magnetic hysteresis loop measurements. These features match well with requirements for self-biased passive devices. Moreover, the site preference of Sc3+ in the hexagonal crystal structure was investigated.

Structural phases, magnetic properties and Maxwell-Wagner type relaxation of CoFe2O4/Sr2Co2Fe12O22 ferrite composites

NASA Astrophysics Data System (ADS)

Patel, Chirag K.; Solanki, Neha P.; Singh, Charanjeet; Jotania, Rajshree B.; Chauhan, Chetna C.; Kulkarni, Shailja D.; Shirsath, Sagar E.

2017-07-01

CoFe2O4 (S:Y-1:0) and Sr2Co2Fe12O22 (S:Y-0:1) ferrites were synthesized separately by using chemical coprecipitation technique and calcined at 1000 °C for 5 h. The mixed ferrite composites (S:Y-3:7, 4:6, 5:5, 6:4 and 7:3) were prepared by physical mixing of individual ferrite powders in required weight proportions. The prepared composites were heated at 1150 °C for 5 h in a muffle furnace and then slowly cooled to room temperature. The prepared ferrites were characterized using various instrumental techniques like FTIR, XRD, SEM, VSM and dielectric measurements. The x-ray diffraction studies of pure Sr2Co2Fe12O22 ferrite sample show the presence of M and Y-type hexagonal phases, while the composites consist of spinel and Y-type phases. FTIR spectra of all samples show two bands of Fe-O stretching vibrations. VSM results of composites reveal that the values of the saturation magnetization (M s) vary from 50.44 emu g-1 to 31.21 emu g-1, while remanent magnetization values found from 11.18 emu g-1 to 3.70 emu g-1. A higher value of coercivity (H c  =  562 emu g-1) is observed in the composite S:Y-3:7 but M r/M s ratio of pure and composites is found to be less than 0.5. The dielectric behavior is explained using Maxwell-Wegner type interfacial polarization and N. Rezlescu’s model.

The effects of laser welding parameters on the microstructure of ferritic and duplex stainless steels welds

NASA Astrophysics Data System (ADS)

Pekkarinen, J.; Kujanpää, V.

This study is focused to determine empirically, which microstructural changes occur in ferritic and duplex stainless steels when heat input is controlled by welding parameters. Test welds were done autogenously bead-on-plate without shielding gas using 5 kW fiber laser. For comparison, some gas tungsten arc welds were made. Used test material were 1.4016 (AISI 430) and 1.4003 (low-carbon ferritic) type steels in ferritic steels group and 1.4162 (low-alloyed duplex, LDX2101) and 1.4462 (AISI 2205) type steels in duplex steels group. Microstructural changes in welds were identified and examined using optical metallographic methods.

Significant reduction of saturation magnetization and microwave-reflection loss in barium-natural ferrite via Nd3+ substitution

NASA Astrophysics Data System (ADS)

Widanarto, W.; Ardenti, E.; Ghoshal, S. K.; Kurniawan, C.; Effendi, M.; Cahyanto, W. T.

2018-06-01

To minimize the signal degradation, many electronic devices require efficient microwave absorbers with very low reflection-losses within the X-band. We prepared a series of trivalent neodymium-ion (Nd3+) substituted barium-natural ferrite using a modified solid-state reaction method. The effect of the Nd3+-ion content on the structure, surface morphology, magnetic properties, and microwave reflection loss was studied. The composites were characterized using X-ray diffraction, a vibrating sample magnetometer, scanning electron microscopy, and a vector network analyzer. The XRD patterns of the sample without Nd3+ reveal the presence of BaFe12O19 (hexagonal) and BaFe2O4 (rhombohedral) phases. Furthermore, a new hexagonal crystal phase of Ba6Nd2Fe4O15 appeared after substituting Nd3+. The average size of the prepared barium-natural ferrite particles was estimated to be between 0.4 and 0.8 μm. Both saturation magnetization and microwave reflection losses of these barium-ferrites were significantly reduced by increasing the Nd3+ content.

Oriented Y-type hexagonal ferrite thin films prepared by chemical solution deposition

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

Buršík, J., E-mail: bursik@iic.cas.cz; Kužel, R.; Knížek, K.

2013-07-15

Thin films of Ba{sub 2}Zn{sub 2}Fe{sub 12}O{sub 22} (Y) hexaferrite were prepared through the chemical solution deposition method on SrTiO{sub 3}(1 1 1) (ST) single crystal substrates using epitaxial SrFe{sub 12}O{sub 19} (M) hexaferrite thin layer as a seed template layer. The process of crystallization was mainly investigated by means of X-ray diffraction and atomic force microscopy. A detailed inspection revealed that growth of seed layer starts through the break-up of initially continuous film into isolated grains with expressive shape anisotropy and hexagonal habit. The vital parameters of the seed layer, i.e. thickness, substrate coverage, crystallization conditions and temperature rampmore » were optimized with the aim to obtain epitaxially crystallized Y phase. X-ray diffraction Pole figure measurements and Φ scans reveal perfect parallel in-plane alignment of SrTiO{sub 3} substrate and both hexaferrite phases. - Graphical abstract: XRD pole figure and AFM patterns of Ba{sub 2}Zn{sub 2}Fe{sub 12}O{sub 22} thin film epitaxially grown on SrTiO{sub 3}(1 1 1) single crystal using seeding layer templating. - Highlights: • Single phase Y-type hexagonal ferrite thin films were prepared by CSD method. • Seed M layer breaks into isolated single crystal islands and serves as a template. • Large seed grains grow by consuming the grains within the bulk of recoated film. • We explained the observed orientation relation of epitaxial domains. • Epitaxial growth on SrTiO{sub 3}(1 1 1) with relation (0 0 1){sub M,Y}//(1 1 1){sub ST}+[1 0 0]{sub M,Y}//[2 −1 −1]{sub ST}.« less

Chlorine gas sensing performance of palladium doped nickel ferrite thin films

NASA Astrophysics Data System (ADS)

Rao, Pratibha; Godbole, R. V.; Bhagwat, Sunita

2016-05-01

NiFe2O4 and Pd:NiFe2O4 (Pd=1 w/o, 3 w/o and 5 w/o) thin films, p-type semiconducting oxides with an inverse spinel structure have been used as a gas sensor to detect chlorine. These films were prepared by spray pyrolysis technique and XRD was used to confirm the structure. The surface morphology was studied using SEM. Magnetization measurements were carried out at room temperature using SQUID VSM, which shows ferrimagnetic behavior of the samples. The reduction in optimum operating temperature and enhancement in response was observed on Pd-incorporation in nickel ferrite thin films. Faster response and recovery characteristic is observed Pd-incorporated nickel ferrite thin films. The long-term stability is evaluated over a period of six months. This feature may be regarded as a significant facet towards their practical application as gas sensors.

Friction and wear of single-crystal manganese-zinc ferrite

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1979-01-01

Sliding friction experiments were conducted with single crystal manganese-zinc ferrite in contact with itself and with transition metals. Results indicate mating highest atomic density directions (110) on matched crystallographic planes exhibit the lowest coefficient of friction, indicating that direction is important in the friction behavior of ferrite. Matched parallel high atomic density planes and crystallographic directions at the interface exhibit low coefficients of friction. The coefficients of friction for ferrite in contact with various metals are related to the relative chemical activity of these metals. The more active the metal, the higher the coefficient of friction. Cracking and the formation of hexagon- and rectangular-shaped platelet wear debris due to cleavages of (110) planes are observed on the ferrite surfaces as a result of sliding.

Characterization and Applications of Micro- and Nano- Ferrites at Microwave and Millimeter Waves

NASA Astrophysics Data System (ADS)

Chao, Liu

Ferrite materials are one of the most widely used magnetic materials in microwave and millimeter wave applications such as radar, wireless communication. They provide unique properties for microwave and millimeter wave devices especially non-reciprocal devices. Some ferrite materials with strong magnetocrystalline anisotropy fields can extend these applications to tens of GHz range while reducing the size, weight and cost. This thesis focuses on characterization of such ferrite materials as micro- and nano-powder and the fabrication of the devices. The ferrite materials with strong magnetocrystalline anisotropy field are metal/non-metal substituted iron oxides oriented in low crystal symmetry. The ferrite materials characterized in this thesis include M-type hexagonal ferrites such as barium ferrite (BaFe12O19), strontium ferrite (SrFe12O19), epsilon phase iron oxide (epsilon-Fe 2O3), substituted epsilon phase iron oxide (epsilon-Ga xFe2-xO3, epsilon-AlxFe2-xO 3). These ferrites exhibit great anisotropic magnetic fields. A transmission-reflection based in-waveguide technique that employs a vector network analyzer was used to determine the scattering parameters for each sample in the microwave bands (8.2--40 GHz). From the S-parameters, complex dielectric permittivity and complex magnetic permeability are evaluated by an improved algorithm. The millimeter wave measurement is based on a free space quasi-optical spectrometer. Initially precise transmittance spectra over a broad millimeter wave frequency range from 40 GHz to 120 GHz are acquired. Later the transmittance spectra are converted into complex permittivity and permeability spectra. These ferrite powder materials are further characterized by x-ray diffraction (XRD) to understand the crystalline structure relating to the strength and the shift of the ferromagnetic resonance affected by the particle size. A Y-junction circulator working in the 60 GHz frequency band is designed based on characterized M-type barium micro- and nano-ferrite. A new fabrication process using ferrite composite is proposed to integrate the Y-junction circulator into the semiconductor substrate. Theoretical design of a high gain Traveling Wave Tube (TWT) amplifier using a metamaterial (MTM) structure and cold-test of the MTM structure are also included in this dissertation. An SWS working around 6 GHz below the X-band waveguide TE10 cutoff frequency is fabricated.

Solidification and solidification cracking in nitrogen-strengthened austenitic stainless steels

NASA Astrophysics Data System (ADS)

Ritter, Ann M.; Savage, Warren F.

1986-04-01

The solidification behavior of three heats of nitrogen-strengthened austenitic stainless steel was examined and was correlated with solidification mode predictions and with hot cracking resistance. The heat of NITRONIC* 50 solidified by the austenitic-ferrite mode, and the NITRONIC 50W and NITRONIC 50W - Nb heats solidified by the ferritic-austenitic mode. This behavior was in good agreement with predictions based on Espy’s formulas for Cr and Ni equivalents. Both the NITRONIC 50W and NITRONIC 50W + Nb welds contained primary delta-ferrite, with the latter weld and the NITRONIC 50 weld also containing some eutectic ferrite. Solute profiles in austenite near the eutectic ferrite showed decreasing Fe and increasing Cr, Ni, Mn, and Mo relative to austenite in the dendrite cores. Numerous Nb-rich precipitates were found on the eutectic ferrite/austenite interfaces and within the eutectic ferrite. The precipitates were mainly Nb(C, N), with some Z-phase, a Nb-rich nitride, also detected. One instance of the transformation of eutectic ferrite to sigma-phase was observed to have occurred during cooling of the NITRONIC 50 weld. Hot cracking was seen in the NITRONIC 50 and NITRONIC 50W + Nb welds and resulted from the formation of a niobium carbonitride eutectic in the interdendritic regions. In the absence of Nb, the NITRONIC 50W heat formed no observable eutectic constituents and did not hot crack. The presence of hot cracks in the NITRONIC 50W + Nb weld indicates that solidification by the ferritic-austenitic mode did not counteract the effects of small Nb additions.

Microwave and millimeter wave dielectric permittivity and magnetic permeability of epsilon-gallium-iron-oxide nano-powders

NASA Astrophysics Data System (ADS)

Chao, Liu; Afsar, Mohammed N.; Ohkoshi, Shin-ichi

2015-05-01

In millimeter wave frequency range, hexagonal ferrites with high uniaxial anisotropic magnetic fields are used as absorbers. These ferrites include M-type barium ferrite (BaFe12O19) and strontium ferrite (SrFe12O19), which have natural ferromagnetic resonant frequency range from 40 GHz to 60 GHz. However, the higher frequency range lacks suitable materials that support the higher frequency ferromagnetic resonance. A series of gallium-substituted ɛ-iron oxides (ɛ-GaxFe2-xO3) are synthesized, which have ferromagnetic resonant frequencies appearing over the frequency range of 30 GHz to 150 GHz. The ɛ-GaxFe2-xO3 is synthesized by the sol-gel method. The particle sizes are observed to be smaller than 100 nm. In this paper, in-waveguide transmission and reflection method and the free space magneto-optical approach have been employed to study these newly developed ɛ-GaxFe2-xO3 particles in millimeter waves. These techniques enable to obtain precise transmission spectra to determine the dielectric and magnetic properties of both isotropic and anisotropic ferrites in the microwave and millimeter wave frequency range from single set of direct measurements. The complex dielectric permittivity and magnetic permeability spectra of ɛ-GaxFe2-xO3 are shown in this paper. Strong ferromagnetic resonances at different frequencies determined by the x parameter are found.

Epitaxial Hexagonal Ferrites for Millimeter Wave Tunable Filters.

DTIC Science & Technology

1982-12-13

form of thin films or slabs, the LPE format should be particularly suitable. Another potential advantage of the LPE format is that the insulating...flux (solvent). In effect, this emulates the successful LPE garnet (YIG) technology which employs this flux. In contrast to garnets , Pb atoms can be...member for a workshop entitled "Application of Garnet and Ferrite Thin Films to Microwave Devices." The principal investigator also attended the 6th

Effect of cobalt substitution on magnetic properties of Ba4Ni2-xCoxFe36O60 hexaferrite

NASA Astrophysics Data System (ADS)

Jiang, Xiaona; Li, Songze; Yu, Zhong; Harris, Vincent G.; Su, Zhijuan; Sun, Ke; Wu, Chuanjian; Guo, Rongdi; Lan, Zhongwen

2018-05-01

Co-substituted U-type hexagonal ferrite bulks, with composition of Ba4Ni2-xCoxFe36O60 (x=0.2, 0.4, 0.6, 0.8), were prepared by a conventional ceramic method. Saturation magnetization (4πMs), coercivity (Hc), and Curie temperature (Tc) were investigated. Anisotropy constant (K1) was calculated by fitting the magnetization curve (M-H) according to the law of approach to saturation, and anisotropy field (Ha) was calculated accordingly. The results reveal that all the samples possess the U-type hexagonal crystallographic structure. With increasing cobalt substitution content (x), the lattice parameters (a and c) almost remain the same owing to the similar radii of Ni2+ (0.72 Å) Co2+ (0.74 Å) ions. 4πMs goes up, while Hc Hc shows an opposite trend. K1 and Ha monotonously decrease resulting from that cobalt substitution weakens the c-axis orientation. Additionally, Tc increases from 467 °C to 484 °C.

Sigma phases in an 11%Cr ferritic/martensitic steel with the normalized and tempered condition

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

Shen, Yinzhong, E-mail: shenyz@sjtu.edu.cn

At the present time 9–12% Cr ferritic/martensitic (F/M) steels with target operating temperatures up to 650 °C and higher are being developed in order to further increase thermal efficiency so as to reduce coal consumption and air pollution. An 11% Cr F/M steel was prepared by reference to the nominal chemical composition of SAVE12 steel with an expected maximum use temperature of 650 °C. The precipitate phases of the 11% Cr F/M steel normalized at 1050 °C for 0.5 h and tempered at 780 °C for 1.5 h were investigated by transmission electron microscopy. Except for Cr-/Cr-Fe-Co-rich M{sub 23}C{sub 6},more » Nb-/V-/Ta-Nb-/Nd-rich MX, Fe-rich M{sub 5}C{sub 2}, Co-rich M{sub 3}C and Fe-Co-rich M{sub 6}C phases previously identified in the steel, two types of sigma phases consisting of σ-FeCr and σ-FeCrW were found to be also present in the normalized and tempered steel. Identified σ-FeCr and σ-FeCrW phases have a simple tetragonal crystal structure with estimated lattice parameters a/c = 0.8713/0.4986 and 0.9119/0.5053 nm, respectively. The compositions in atomic pct of the observed sigma phases were determined to be approximately 50Fe-50Cr for the σ-FeCr, and 30Fe-55Cr-10W in addition to a small amount of Ta, Co and Mn for the σ-FeCrW. The sigma phases in the steel exhibit various blocky morphologies, and appear to have a smaller amount compared with the dominant phases Cr-rich M{sub 23}C{sub 6} and Nb-/V-/Ta-Nb-rich MX of the steel. The σ-FeCr phase in the steel was found to precipitate at δ-ferrite/martensite boundaries, suggesting that δ-ferrite may rapidly induce the formation of sigma phase at δ-ferrite/martensite boundaries in high Cr F/M steels containing δ-ferrite. The formation mechanism of sigma phases in the steel is also discussed in terms of the presence of δ-ferrite, M{sub 23}C{sub 6} precipitation, precipitation/dissolution of M{sub 2}X, and steel composition. - Highlights: •Precipitate phases in normalized and tempered 11%Cr F/M steel are presented in detail. • σ-FeCr phase, 50Fe50Cr (in at.%), was identified in normalized and tempered 11%Cr F/M steel. • σ-FeCrW phase, 30Fe55Cr10W (in at.%), was identified in normalized and tempered 11%Cr F/M steel. • Sigma phase in the 11%Cr F/M steel was found to precipitate at δ-ferrite/martensite boundaries. • δ-ferrite may rapidly induce the sigma phase formation at δ-ferrite/martensite boundaries.« less

A simple process to obtain anisotropic self-biased magnets constituted of stacked barium ferrite single domain particles

NASA Astrophysics Data System (ADS)

Mattei, Jean-Luc; Le, Cong Nha; Chevalier, Alexis; Maalouf, Azar; Noutehou, Nathan; Queffelec, Patrick; Laur, Vincent

2018-04-01

An efficient and inexpensive process is presented that produces highly oriented bulk compacts made of BaM particles. Barium hexaferrite particles (BaM, nominal composition BaFe11O19) were prepared by a chemical coprecipitation method, using different rates and types of precipitating agents (NaOH and Na2CO3). It was demonstrated that when a large excess of Na2CO3 is used, a noteworthy packing of hexagonal BaM platelets is obtained, after mechanical compaction and firing at moderate temperature (1140 °C), without including any more steps than those required for a conventional sintering process. The hysteresis loop displays a very competitive squareness of 0.88 (normalized remanent magnetization) and a coercivity of 215 kA/m, which make this BaM bulk ferrite suitable for self-biased applications.

Dielectric properties of Ti4+ substituted BaFe12O19 nanoparticles

NASA Astrophysics Data System (ADS)

Ghoneim, A. I.; Amer, M. A.; Meaz, T. M.; Attalah, S. S.

2017-02-01

Series of nanocrystalline BaTixFe12-(4/3)xO19 hexagonal ferrites, 0≤x≤1, was prepared using the chemical co-precipitation method. As-prepared samples were heated at 1200 °C for 20 h and slowly cooled to room temperature (RT). XRD studies proved that the samples have single phase M-type hexagonal nanostructure, where their grain size lies in the range of 42.4 - 61.3 nm. Their dielectric properties were studied against temperature (T) and frequency (F). DC conductivity showed increase against T, whereas AC conductivity showed increase with increasing both T and F. This proved the semiconducting behavior of the samples. Activation energies were found to lie in the range of 0.054-0.169 eV for temperature range of RT 373 K and of 0.114-0.274 eV for higher temperatures up to 473 K. Variation of the dielectric constant and AC conductivity against F revealed dispersion in all these hexagonal nanostructures, which was assigned to Maxwell-Wagner type of interfacial polarization. Variation of the dielectric loss tangent against F showed a relaxation spectrum for all samples, whereas the dielectric constant and loss tangent showed an increasing trend against T. The relative magnetic permeability μr showed an increasing trend with temperature.

Influence of nickel substitution on crystal structure and magnetic properties of strontium ferrite preparation via sol-gel auto-combustion route

NASA Astrophysics Data System (ADS)

Roohani, Ebrahim; Arabi, Hadi; Sarhaddi, Reza

2018-01-01

In this research, SrFe12-xNixO19 (x = 0 - 1) hexagonal ferrites were prepared by sol-gel auto-combustion method. Effect of Ni substitution on structural, morphological and magnetic properties of nanoparticles was investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM), respectively. The XRD results confirmed that all samples with x ≤ 0.5 have single phase M-type strontium ferrite structure, whereas for the SrFe12-xNixO19 samples with x > 0.5, the spinel NiFe2O4 phase has also appeared. The lattice parameters and crystallite sizes of the powders were concluded from the XRD data and Williamson-Hall method. Magnetic analyses showed that the coercivity of powders decreased from 5672 Oe to 639 Oe while the saturation magnetization increased from 74 emu/g to 81 emu/g with nickel substitution. The results of this study suggest that the strontium hexaferrites doped with Ni are suitable for applications in high density magnetic recording media as well as microwave devices because of their promising magnetic properties.

Enhanced microwave absorption properties of CTAB assisted Pr-Cu substituted nanomaterial

NASA Astrophysics Data System (ADS)

Sadiq, Imran; Naseem, Shahzad; Riaz, Saira; Khan, Hasan M.; Ashiq, Muhammad Naeem; Hussain, S. Sajjad; Rana, Mazhar

2016-09-01

In this study, the rare earth Pr3+and divalent Cu2+ elements substituted Sr1-xPrxMn2Fe16-yCuyO27 (x=0, 0.02, 0.06, 0.1 and y=0, 0.1, 0.3, 0.5) W-type hexagonal ferrites were prepared by Sol-Gel method. TGA and DSC analysis of as prepared material was carried out to confirm the temperature at which required phase can be obtained. The XRD patterns exhibit the single phase for all the samples and the lattice parameters were changed with the additives. The absorption bands at wave number 636 and 554 cm-1 in FTIR spectrum indicate the stretching vibration of metal-oxygen ions which also ratifies the single phase for the prepared material. Microstructural analysis confirms the agglomeration of nanograins which leads to formation of platelet like structure which cause in the enhancement of the microwave absorption properties of material. The minimum reflection loss of -59.8 dB at 9.34 GHz frequency was observed makes the prepared material good candidate to be used in super high frequency application. The attenuation constant and reflectivity results are also in good agreement with minimum reflection losses results.

Influence of Sn-Mg co-substitution on the microstructural and magnetic characteristics of M-type SrCaLa hexagonal ferrites

NASA Astrophysics Data System (ADS)

Yang, Yujie; Wang, Fanhou; Huang, Duohui; Shao, Juxiang; Tang, Jin; Ur Rehman, Khalid Mehmood; Wu, Zhen

2018-04-01

Sn-Mg co-substituted M-type SrCaLa hexaferrites Sr0.5Ca0.2La0.3Fe12.0-2x(SnMg)xO19 (0.0 ≤ x ≤ 0.5) have been synthesized by ball milling and calcining. The results of X-ray diffraction show that a single magnetoplumbite phase is exhibited in all the samples and no impurity phase is observed in the structure. Lattice constants (c and a) increase with increasing Sn-Mg content (x) from 0.0 to 0.5. Platelet like structure exhibited by FE-SEM micrographs confirms the hexagonal structure of the synthesized samples. The saturation magnetization (Ms) first increases with increasing SnMg content (x) from 0.0 to 0.1, and then decreases when Sn-Mg content (x) ≥ 0.1. The remanent magnetization (Mr), Mr/Ms ratio, coercivity (Hc), magnetic anisotropy field (Ha) and first anisotropy constant (K1) decrease with increasing Sn-Mg content (x) from 0.0 to 0.5.

Microwave and millimeter wave dielectric permittivity and magnetic permeability of epsilon-gallium-iron-oxide nano-powders

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

Chao, Liu, E-mail: liu.chao@tufts.edu; Afsar, Mohammed N.; Ohkoshi, Shin-ichi

2015-05-07

In millimeter wave frequency range, hexagonal ferrites with high uniaxial anisotropic magnetic fields are used as absorbers. These ferrites include M-type barium ferrite (BaFe{sub 12}O{sub 19}) and strontium ferrite (SrFe{sub 12}O{sub 19}), which have natural ferromagnetic resonant frequency range from 40 GHz to 60 GHz. However, the higher frequency range lacks suitable materials that support the higher frequency ferromagnetic resonance. A series of gallium-substituted ε-iron oxides (ε-Ga{sub x}Fe{sub 2−x}O{sub 3}) are synthesized, which have ferromagnetic resonant frequencies appearing over the frequency range of 30 GHz to 150 GHz. The ε-Ga{sub x}Fe{sub 2−x}O{sub 3} is synthesized by the sol-gel method. The particlemore » sizes are observed to be smaller than 100 nm. In this paper, in-waveguide transmission and reflection method and the free space magneto-optical approach have been employed to study these newly developed ε-Ga{sub x}Fe{sub 2−x}O{sub 3} particles in millimeter waves. These techniques enable to obtain precise transmission spectra to determine the dielectric and magnetic properties of both isotropic and anisotropic ferrites in the microwave and millimeter wave frequency range from single set of direct measurements. The complex dielectric permittivity and magnetic permeability spectra of ε-Ga{sub x}Fe{sub 2−x}O{sub 3} are shown in this paper. Strong ferromagnetic resonances at different frequencies determined by the x parameter are found.« less

Structural, electrical and magnetic study of Nd-Ni substituted W-type Hexaferrite

NASA Astrophysics Data System (ADS)

Khan, Imran; Sadiq, Imran; Ali, Irshad; Rana, Mazhar-Ud-Din; Najam-Ul-Haq, Muhammad; Shah, Afzal; Shakir, Imran; Naeem Ashiq, Muhammad

2016-01-01

A series of Nd-Ni substituted W-type hexaferrites with composition Sr1-xNdxCo2NiyFe16-yO27 (where x=0.0, 0.025, 0.050, 0.075, 0.1 and y=0.0, 0.25, 0.50, 0.75, 1) has been prepared by the chemical co-precipitation method. The effect of rare earth Nd substitution at strontium site while Ni at iron site on microstructure, electrical and magnetic properties has been investigated. All the XRD patterns of the synthesized materials show single W-type hexagonal phase without any other intermediate phases. SEM images show that the particles are homogeneous and hexagonal platelet-like shape. DC electrical resistivity measurements were carried out in temperature range of 298-673 K showing metal-to-semiconductor transition when doped with Nd-Ni. The magnetic properties such as saturation magnetization, remanence, squareness ratio and coercivity were calculated from hysteresis loops and were observed to increase with the increase in Nd-Ni concentration up to a certain substitution level which is beneficial for high density recording media.

Microstructure, magnetic and microwave absorptive behavior of doped W-type hexaferrite nanoparticles prepared by co-precipitation method

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

Gordani, Gholam Reza, E-mail: gordani@gmail.com; Mohseni, Marzieh; Ghasemi, Ali

2016-04-15

Highlights: • High frequency properties of substituted W-type Sr-hexaferrite. • Saturation magnetization of samples is decreased with increasing of dopants content. • The ferrite sample covers about 6 GHz of bandwidth in K{sub u} band. • The optimum substituted samples can be used as a potential magnetic loss material. • Sample contain x = 0.4 of dopants have shown greater than 90% of reflection loss. - Abstract: Substituted W-type hexaferrite nanoparticles of SrZn{sub 2−x}Co{sub x/2}Ni{sub x/2}Fe{sub 16}O{sub 27} were synthesized by a chemical co-precipitation method. The X-ray diffraction results confirmed that W-type ferrite was identified as the main phase inmore » whole samples in the range of x = 0–0.4. According to magnetic hysteresis loops, with increasing of substituted cations, saturation of magnetization increased and coercivity decreased due to crystalline site occupation of Zn with Ni and Co cations. The microwave reflection loss analysis results in the K{sub u} band (12–18 GHz) show that the highest value of reflection loss of samples was −29.11 dB at frequency of 14.57 GHz with an absorption bandwidth of more than 6 GHz by choosing reflection loss value of −10 dB as a reference. The results indicate that, the sample with appropriate amount of substituted cations hold great promise for microwave device applications.« less

Pb(core)/ZnO(shell) nanowires obtained by microwave-assisted method

PubMed Central

2011-01-01

In this study, Pb-filled ZnO nanowires [Pb(core)/ZnO(shell)] were synthesized by a simple and novel one-step vapor transport and condensation method by microwave-assisted decomposition of zinc ferrite. The synthesis was performed using a conventional oven at 1000 W and 5 min of treatment. After synthesis, a spongy white cotton-like material was obtained in the condensation zone of the reaction system. HRTEM analysis revealed that product consists of a Pb-(core) with (fcc) cubic structure that preferentially grows in the [111] direction and a hexagonal wurtzite ZnO-(Shell) that grows in the [001] direction. Nanowire length was more than 5 μm and a statistical analysis determined that the shell and core diameters were 21.00 ± 3.00 and 4.00 ± 1.00 nm, respectively. Experimental, structural details, and synthesis mechanism are discussed in this study. PMID:21985637

Crystal growth of hexaferrite architecture for magnetoelectrically tunable microwave semiconductor integrated devices

NASA Astrophysics Data System (ADS)

Hu, Bolin

Hexaferrites (i.e., hexagonal ferrites), discovered in 1950s, exist as any one of six crystallographic structural variants (i.e., M-, X-, Y-, W-, U-, and Z-type). Over the past six decades, the hexaferrites have received much attention owing to their important properties that lend use as permanent magnets, magnetic data storage materials, as well as components in electrical devices, particularly those operating at RF frequencies. Moreover, there has been increasing interest in hexaferrites for new fundamental and emerging applications. Among those, electronic components for mobile and wireless communications especially incorporated with semiconductor integrated circuits at microwave frequencies, electromagnetic wave absorbers for electromagnetic compatibility, random-access memory (RAM) and low observable technology, and as composite materials having low dimensions. However, of particular interest is the magnetoelectric (ME) effect discovered recently in the hexaferrites such as SrScxFe12-xO19 (SrScM), Ba2--xSrxZn 2Fe12O22 (Zn2Y), Sr4Co2Fe 36O60 (Co2U) and Sr3Co2Fe 24O41 (Co2Z), demonstrating ferroelectricity induced by the complex internal alignment of magnetic moments. Further, both Co 2Z and Co2U have revealed observable magnetoelectric effects at room temperature, representing a step toward practical applications using the ME effect. These materials hold great potential for applications, since strong magnetoelectric coupling allows switching of the FE polarization with a magnetic field (H) and vice versa. These features could lead to a new type of storage devices, such as an electric field-controlled magnetic memory. A nanoscale-driven crystal growth of magnetic hexaferrites was successfully demonstrated at low growth temperatures (25--40% lower than the temperatures required often for crystal growth). This outcome exhibits thermodynamic processes of crystal growth, allowing ease in fabrication of advanced multifunctional materials. Most importantly, the crystal growth technique is considered theoretically and experimentally to be universal and suitable for the growth of a wide range of diverse crystals. In the present experiment, the conical spin structure of Co2Y ferrite crystals were a found to give rise to an intrinsic magnetoelectric effect. Our experiment reveals a remarkable increase in the conical phase transition temperature by ~150 K for Co 2Y ferrite, compared to 5--10 K of Zn2Y ferrites recently reported. The high quality Co2Y ferrite crystals, having low microwave loss and magnetoelectricity, were successfully grown on wide bandgap semiconductor GaN. The demonstration of the nanostructure materials-based "system on a wafer" architecture is a critical milestone to next generation microwave integrated systems. It is also practical that future microwave integrated systems and their magnetic performances could be tuned by an electric field because of the magnetoelectricity of hexaferrites.

Sensitization Behavior of Type 409 Ferritic Stainless Steel: Confronting DL-EPR Test and Practice W of ASTM A763

NASA Astrophysics Data System (ADS)

Scalise, Taís Campos; de Oliveira, Mara Cristina Lopes; Sayeg, Isaac Jamil; Antunes, Renato Altobelli

2014-06-01

Stainless steels employed for manufacturing automotive exhaust systems must withstand severe thermal cycles, corrosive environment due to urea decomposition, and welding operations. AISI 409 ferritic stainless steel can be considered a low-cost alternative for this application. However, depending on the manufacturing conditions during welding cycles, this material can be sensitized due to the precipitation of chromium carbides at grain boundaries. In this work, the intergranular corrosion resistances of the AISI 409 ferritic stainless steel were evaluated after annealing at 300, 500, and 700 °C for 2, 4, and 6 h. Solution-annealed samples were also tested for comparison purposes. Two methodologies were used to assess the sensitization behavior of the 409 stainless steel samples: the first one was based on the ASTM A763 (practice W), while the second one was based on the double-loop electrochemical potentiodynamic reactivation test. It was possible to identify that the annealing treatment performed at 500 °C was more critical to the occurrence of intergranular corrosion.

Fabrication of thin bulk ceramics for microwave circulator applications

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

Ings, J.B.; Simmins, J.J.; May, J.L.

1995-09-01

Planer MMIC circulator applications require the production of thin, flat garnet, spinel, and hexagonal ferrite circulator elements. Fabrication of cira 250 {mu}m circulator elements was done by tape casting and roll compaction. For the garnet, tape cast gave equivalent results to roll compaction. For the spinel and hexaferrite materials, which undergo magnetic flocculation, roll compaction was found to be the preferred fabrication method. Roll compacted lithium ferrite resulted in higher densities and lower {triangle}H and tan{delta} than did the tape case material. Roll compacted barium hexaferrite resulted in higher densities and remanent magnetization than did the tape cast material.

Enhanced antibactericidal function of W4+-doped titania-coated nickel ferrite composite nanoparticles: a biomaterial system.

PubMed

Sunkara, B K; Misra, R D K

2008-03-01

The study demonstrates a distinct enhancement of antimicrobial activity of W4+-doped titania that is coated on nickel ferrite nanoparticles in comparison to undoped titania. The composite nanoparticles were synthesized by uniquely combining reverse micelle and chemical hydrolysis synthesis methods [Rana S, Rawat J, Misra RDK, Acta Biomater 2005;1:691]. The superior antimicrobial activity of W4+-doped titania is related to the inhibition of electron-hole recombination and decrease in the band gap energy of titania. The function of the ferrite is to facilitate the removal of nanoparticles from the sprayed surface using a small magnetic field. The coating of ferrite nanoparticles with titania retains superparamagnetic character and magnetic strength of composite nanoparticles signifying non-deterioration of magnetic properties and promoting their use as removable antimicrobial photocatalyst nanoparticles.

High temperature phase chemistries and solidification mode prediction in nitrogen-strengthened austenitic stainless steels

NASA Astrophysics Data System (ADS)

Ritter, Ann M.; Henry, Michael F.; Savage, Warren F.

1984-07-01

Nitronic 50 and Nitronic 50W, two nitrogen-strengthened stainless steels, were heat treated over a wide range of temperatures, and the compositions of the ferrite and austenite at each temperature were measured with analytical electron microscopy techniques. The compositional data were used to generate the (γ + δ phase field on a 58 pct Fe vertical section. Volume fractions of ferrite and austenite were calculated from phase chemistries and compared with volume fractions determined from optical micrographs. Weld solidification modes were predicted by reference to the Cr and Ni contents of each alloy, and the results were compared with predictions based on the ratios of calculated Cr and Ni equivalents for the alloys. Nitronic 50, which contained ferrite and austenite at the solidus temperature of 1370 °C, solidified through the eutectic triangle, and the weld microstructure was similar to that of austenitic-ferritic solidification. Nitronic 50W was totally ferritic at 1340 °C and solidified as primary delta ferrite. During heat treatments, Nitronic 50 and Nitronic 50W precipitated secondary phases, notably Z-phase (NbCrN), sigma phase, and stringered phases rich in Mn and Cr.

Structural elucidation and magnetic behavior evaluation of Cu-Cr doped BaCo-X hexagonal ferrites

NASA Astrophysics Data System (ADS)

Azhar Khan, Muhammad; Hussain, Farhat; Rashid, Muhammad; Mahmood, Asif; Ramay, Shahid M.; Majeed, Abdul

2018-04-01

Ba2-xCuxCo2CryFe28-yO46 (x = 0.0, 0.1, 0.2, 0.3, 0.4, y = 0.0, 0.2, 0.4, 0.6, 0.8) X-type hexagonal ferrites were synthesized via micro-emulsion route. The techniques which were applied to characterize the prepared samples are as follows: X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Dielectric measurements and vibrating sample magnetometer (VSM). The structural parameters i.e. lattice constant (a, c), cell volume (V), X-ray density, bulk density and crystallite size of all the prepared samples were obtained using XRD analysis. The lattice parameters 'a' and 'c' increase from 5.875 Å to 5.934 Å and 83.367 Å to 83.990 Å respectively. The crystallite size of investigated samples lies in the range of 28-32 nm. The magnetic properties of all samples have been calculated by vibrating sample magnetometer (VSM) analysis. The increase in coercivity (Hc) was observed with the increase of doping contents. It was observed that the coercivity (Hc) of all prepared samples is inversely related to the crystalline size which reflects that all materials are super-paramagnetic. The dielectric parameters i.e. dielectric constant, dielectric loss, tangent loss etc were obtained in the frequency range of 1 MHz-3 GHz and followed the Maxwell-Wagner's model. The significant variation the dielectric parameters are observed with increasing frequency. The maximum Q value is obtained at ∼2 GHz due to which these materials are used for high frequency multilayer chip inductors.

Phase composition and magnetism of sol-gel synthesized Ga-Fe-O nanograins

NASA Astrophysics Data System (ADS)

Rećko, K.; Waliszewski, J.; Klekotka, U.; Soloviov, D.; Ostapczuk, G.; Satuła, D.; Biernacka, M.; Balasoiu, M.; Basa, A.; Kalska-Szostko, B.; Szymański, K.

2018-02-01

We have succeeded in synthesizing orthorhombic Ga(1-x)Fe(1+x)O3 (-0.05? x?0.5), hexagonal GayFe(2-y)O3 (0?y?1.8) and cubic Ga(1+z)Fe(2-z)O4 (-0.1?z?0.8) nanograins of gallium ferrites using conventional precursors and an organic environment of Pechini scenario under atmospheric-pressure conditions (SG method). Phase composition and homogeneity were analyzed using X-ray diffraction. Small angle neutron scattering disclosed ellipsoidal particle shapes of gallium iron oxides (GFO) crystallizing in orthorhombic (o-GFO) and hexagonal (h-GFO) symmetry and parallelepiped shapes of Ga(1+y)Fe(2-y)O4 (c-GFO) grains. Despite local agglomeration among the magnetic grains, the scanning electron microscopy and transmission electron microscopy images point to faced-elliptical shapes. The Mössbauer spectroscopy with magnetization measurements was carried out in the temperature range of 5-295 K. The analysis of gallium ferrites magnetism demonstrates that iron atoms locate with various probabilities in crystallographic positions and the spontaneous magnetization preserves up to room temperature (RT).

Tunable microwave absorbing nano-material for X-band applications

NASA Astrophysics Data System (ADS)

Sadiq, Imran; Naseem, Shahzad; Ashiq, Muhammad Naeem; Khan, M. A.; Niaz, Shanawer; Rana, M. U.

2016-03-01

The effect of rare earth elements substitution in Sr1.96RE0.04Co2Fe27.80Mn0.2O46 (RE=Ce, Gd, Nd, La and Sm) X-type hexagonal ferrites prepared by using sol gel autocombustion method was studied. The XRD and FTIR analysis show the single phase of the prepared material. The lattice constants a (Å) and c (Å) varies with the additives. The particle size measured by Scherer formula for all the samples varies in the range of 54-100 nm and confirmed by the TEM analysis. The average grain size measured by SEM analysis lies in the range of 0.672-1.01 μm for all the samples. The Gd-substituted ferrite has higher value of coercivity (526.06 G) among all the samples which could be a good material for longitudinal recording media. The results also indicate that the Gd-substituted sample has maximum reflection loss of -25.2 dB at 11.878 GHz, can exhibit the best microwave absorption properties among all the substituted samples. Furthermore, the minimum value of reflection loss shifts towards the lower and higher frequencies with the substitution of rare earth elements which confirms that the microwave absorption properties can be tuned with the substitution of rare earth elements in pure ferrites. The peak value of attenuation constant at higher frequency agrees well the reflection loss data.

Optical Sensing And Imaging Opportunities

DTIC Science & Technology

2016-02-12

Functional Materials Workshops, supported by AFOSR.Potentially Useful New Research Areas.- Plasmonics - Infrared antennae- IV-VI (lead salt) Infrared Photo...Potentially Useful New Research Areas. - Plasmonics - Infrared antennae - IV-VI (lead salt) Infrared Photo Detectors and Focal Plane Arrays...Hexagonal Ferrite Thin Films for Q-Band Signal Processing Devices Plasmonics New techniques for transmitting optical signals through nano-scale

Distributed Ferrite Isolation in Traveling-Wave Tubes.

DTIC Science & Technology

coupling to broadband edge modes of ferrite slabs. Evidence of coupling to the lower branch of edge mode, i.e., magnetostatic, has been obtained with L...band helix . Cold tests and analysis suggest coupling to ferrite edge modes from helix is easier at higher microwave frequencies. Plans for a hot...test at the 1-2 kW power level is an L-band TWT incorporating such distributed ferrites are described.

MnZn-ferrites: Targeted Material Design for New Emerging Application Products

NASA Astrophysics Data System (ADS)

Zaspalis, V. T.; Tsakaloudi, V.; Kogias, G.

2014-07-01

In this article the main characteristics for emerging MnZn-ferrite applications are described on the basis of the new demands they possess on the ferrite material development. A number of recently developed MnZn-ferrite materials is presented together with the main scientific principles lying behind their development. These include: (i) high saturation flux density MnZn-ferrites (i.e. Bsat=550 mT at 10 kHz, 1200 A/m, 100°C), (ii) low power losses MnZn-ferrites (i.e. Pv~210 mW cm-3 at 100 kHz, 200mT, 100°C), (iii) MnZn-ferrites with broad temperature stability (i.e. PV<375 mW cm-3 for 25°C

Development and Testing of Shingle-type Solar Cell Modules

NASA Technical Reports Server (NTRS)

Shepard, N. F., Jr.

1979-01-01

The design, development, fabrication and testing of a shingle-type terrestrial solar cell module which produces 98 watts/sq m of exposed module area at 1 kW/sq m insolation and 61 C are reported. These modules make it possible to easily incorporate photovoltaic power generation into the sloping roofs of residential or commercial buildings by simply nailing the modules to the plywood roof sheathing. This design consists of nineteen series-connected 53 mm diameter solar cells arranged in a closely packed hexagon configuration. These cells are individually bonded to the embossed surface of a 3 mm thick thermally tempered hexagon-shaped piece of glass. Polyvinyl butyral is used as the laminating adhesive.

Microwave assisted scalable synthesis of titanium ferrite nanomaterials

NASA Astrophysics Data System (ADS)

Shukla, Abhishek; Bhardwaj, Abhishek K.; Singh, S. C.; Uttam, K. N.; Gautam, Nisha; Himanshu, A. K.; Shah, Jyoti; Kotnala, R. K.; Gopal, R.

2018-04-01

Titanium ferrite magnetic nanomaterials are synthesized by one-step, one pot, and scalable method assisted by microwave radiation. Effects of titanium content and microwave exposure time on size, shape, morphology, yield, bonding nature, crystalline structure, and magnetic properties of titanium ferrite nanomaterials are studied. As-synthesized nanomaterials are characterized by X-ray diffraction (XRD), ultraviolet-visible absorption spectroscopy (UV-Vis), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, transmission electron microscopy (TEM), and vibrating sample magnetometer measurements. XRD measurements depict the presence of two phases of titanium ferrite into the same sample, where crystallite size increases from ˜33 nm to 37 nm with the increase in titanium concentration. UV-Vis measurement showed broad spectrum in the spectral range of 250-600 nm which reveals that its characteristic peaks lie between ultraviolet and visible region; ATR-FTIR and Raman measurements predict iron-titanium oxide structures that are consistent with XRD results. The micrographs of TEM and selected area electron diffraction patterns show formation of hexagonal shaped particles with a high degree of crystallinity and presence of multi-phase. Energy dispersive spectroscopy measurements confirm that Ti:Fe compositional mass ratio can be controlled by tuning synthesis conditions. Increase of Ti defects into titanium ferrite lattice, either by increasing titanium precursor or by increasing exposure time, enhances its magnetic properties.

Coexistence of ferromagnetism and unconventional spin-glass freezing in the site-disordered kagome ferrite SrS n2F e4O11

NASA Astrophysics Data System (ADS)

Shlyk, L.; Strobel, S.; Farmer, B.; De Long, L. E.; Niewa, R.

2018-02-01

Single-crystal x-ray diffraction refinements indicate SrS n2F e4O11 crystallizes in the hexagonal R -type ferrite structure with noncentrosymmetric space group P 63m c and lattice parameters a =5.9541 (2 )Å , c =13.5761 (5 )Å , Z =2 (R (F )=0.034 ). Octahedrally coordinated 2 a [M (1) and M (1a)] and 6 c sites [M (2 )] have random, mixed occupation by Sn and Fe; whereas the tetrahedrally coordinated 2 b sites [Fe(3) and Fe(3a)] are exclusively occupied by Fe, whose displacement from the ideal position with trigonal-bipyramidal coordination causes the loss of inversion symmetry. Our dc and ac magnetization data indicate SrS n2F e4O11 single crystals undergo a ferro- or ferri-magnetic transition below a temperature TC=630 K with very low coercive fields μoHc ⊥=0.27 Oe and μoHc ∥=1.5 Oe at 300 K, for applied field perpendicular and parallel to the c axis, respectively. The value for TC is exceptionally high, and the coercive fields exceptionally low, among the known R-type ferrites. Time-dependent dc magnetization and frequency-dependent ac magnetization data indicate the onset of short-range, spin-glass freezing below Tf=35.8 K , which results from crystallographic disorder of magnetic F e3 + and nonmagnetic S n4 + ions on a frustrated Kagome sublattice. Anomalous ac susceptibility and thermomagnetic relaxation behavior in the short-range-ordered state differs from that of conventional spin glasses. Optical measurements in the ultraviolet to visible frequency range in a diffuse reflectance geometry indicate an overall optical band gap of 0.8 eV, consistent with observed semiconducting properties.

Microstructural characterization of high-carbon ferrochromium

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

Lesko, A.; Navara, E.

1996-04-01

Light optical and scanning electron microscopy techniques were used for high-carbon ferrochromium microstructural analysis. Different microstructures were observed for industrially and laboratory-produced ferroalloys. Primary carbides of M{sub 7}C{sub 3} with chromium ferrite were found in the industrially produced, slowly solidified, and cooled ferroalloy, while primary M{sub 7}C{sub 3} carbides accompanied a eutectic mixture of M{sub 7}C{sub 3} carbides and chromium ferrite in the laboratory-melted and in the water-solidified and water-cooled materials. Different microstructural arrangements are directly related to the friability properties of this material, which characterizes its resistance to abrasion on handling and impact. In ferrochromium upgraded by carbon contentmore » reduction, the eutectic M{sub 7}C{sub 3} hexagonal carbides are partly replaced by M{sub 23}C{sub 6} dendritic carbides. The presence of dendritic carbides in the ferrochromium eutectic microstructure can be interpreted as a proof of a lower carbon content, raising the commercial value of the ferroalloy. The hexagonal M{sub 7}C{sub 3} carbides exhibited a central hollow along the longitudinal axis, and on metallographic samples they looked like screw nuts. A model of the solidification mechanism for such crystals is proposed.« less

Hydrothermal synthesis and structural characterization of an organic–inorganic hybrid sandwich-type tungstoantimonate [Cu(en){sub 2}(H{sub 2}O)]{sub 4}[Cu(en){sub 2}(H{sub 2}O){sub 2}][Cu{sub 2}Na{sub 4}(α-SbW{sub 9}O{sub 33}){sub 2}]·6H{sub 2}O

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

Liu, Yingjie; College of Medicine, Henan University, Kaifeng, Henan 475004; Cao, Jing

An organic–inorganic hybrid sandwich-type tungstoantimonate [Cu(en){sub 2}(H{sub 2}O)]{sub 4}[Cu(en){sub 2}(H{sub 2}O){sub 2}][Cu{sub 2}Na{sub 4}(α-SbW{sub 9}O{sub 33}){sub 2}]·6H{sub 2}O (1) has been synthesized by reaction of Sb{sub 2}O{sub 3}, Na{sub 2}WO{sub 4}·2H{sub 2}O, CuCl{sub 2}·2H{sub 2}O with en (en=ethanediamine) under hydrothermal conditions and structurally characterized by elemental analysis, inductively coupled plasma atomic emission spectrometry, IR spectrum and single-crystal X-ray diffraction. 1 displays a centric dimeric structure formed by two equivalent trivacant Keggin [α-SbW{sub 9}O{sub 33}]{sup 9−} subunits sandwiching a hexagonal (Cu{sub 2}Na{sub 4}) cluster. Moreover, those related hexagonal hexa-metal cluster sandwiched tungstoantimonates have been also summarized and compared. The variable-temperature magneticmore » measurements of 1 exhibit the weak ferromagnetic exchange interactions within the hexagonal (Cu{sub 2}Na{sub 4}) cluster mediated by the oxygen bridges. - Graphical abstract: An organic–inorganic hybrid (Cu{sub 2}Na{sub 4}) sandwiched tungstoantimonate [Cu(en){sub 2}(H{sub 2}O)]{sub 4}[Cu (en){sub 2}(H{sub 2}O){sub 2}][Cu{sub 2}Na{sub 4}(α-SbW{sub 9}O{sub 33}){sub 2}]·6H{sub 2}O was synthesized and magnetic properties was investigated. Display Omitted - Highlights: • Organic–inorganic hybrid sandwich-type tungstoantimonate. • (Cu{sub 2}Na{sub 4} sandwiched) tungstoantimonate [Cu{sub 2}Na{sub 4}(α-SbW{sub 9}O{sub 33}){sub 2}]{sup 10−}. • Ferromagnetic tungstoantimonate.« less

The influence of Cr content on the mechanical properties of ODS ferritic steels

NASA Astrophysics Data System (ADS)

Li, Shaofu; Zhou, Zhangjian; Jang, Jinsung; Wang, Man; Hu, Helong; Sun, Hongying; Zou, Lei; Zhang, Guangming; Zhang, Liwei

2014-12-01

The present investigation aimed at researching the mechanical properties of the oxide dispersion strengthened (ODS) ferritic steels with different Cr content, which were fabricated through a consolidation of mechanical alloyed (MA) powders of 0.35 wt.% nano Y2O3 dispersed Fe-12.0Cr-0.5Ti-1.0W (alloy A), Fe-16.0Cr-0.5Ti-1.0W (alloy B), and Fe-18.0Cr-0.5Ti-1.0W (alloy C) alloys (all in wt.%) by hot isostatic pressing (HIP) with 100 MPa pressure at 1150 °C for 3 h. The mechanical properties, including the tensile strength, hardness, and impact fracture toughness were tested by universal testers, while Young's modulus was determined by ultrasonic wave non-destructive tester. It was found that the relationship between Cr content and the strength of ODS ferritic steels was not a proportional relationship. However, too high a Cr content will cause the precipitation of Cr-enriched segregation phase, which is detrimental to the ductility of ODS ferritic steels.

Rare earth doped M-type hexaferrites; ferromagnetic resonance and magnetization dynamics

NASA Astrophysics Data System (ADS)

Sharma, Vipul; Kumari, Shweta; Kuanr, Bijoy K.

2018-05-01

M-type hexagonal barium ferrites come in the category of magnetic material that plays a key role in electromagnetic wave propagation in various microwave devices. Due to their large magnetic anisotropy and large magnetization, their operating frequency exceeds above 50 GHz. Doping is a way to vary its magnetic properties to such an extent that its ferromagnetic resonance (FMR) response can be tuned over a broad frequency band. We have done a complete FMR study of rare earth elements neodymium (Nd) and samarium (Sm), with cobalt (Co) as base, doped hexaferrite nanoparticles (NPs). X-ray diffractometry, vibrating sample magnetometer (VSM), and ferromagnetic resonance (FMR) techniques were used to characterize the microstructure and magnetic properties of doped hexaferrite nanoparticles. Using proper theoretical electromagnetic models, various parameters are extracted from FMR data which play important role in designing and fabricating high-frequency microwave devices.

Fabrication and integrity test preparation of HIP-joined W and ferritic-martensitic steel mockups for fusion reactor development

NASA Astrophysics Data System (ADS)

Lee, Dong Won; Shin, Kyu In; Kim, Suk Kwon; Jin, Hyung Gon; Lee, Eo Hwak; Yoon, Jae Sung; Choi, Bo Guen; Moon, Se Youn; Hong, Bong Guen

2014-10-01

Tungsten (W) and ferritic-martensitic steel (FMS) as armor and structural materials, respectively, are the major candidates for plasma-facing components (PFCs) such as the blanket first wall (BFW) and the divertor, in a fusion reactor. In the present study, three W/FMS mockups were successfully fabricated using a hot isostatic pressing (HIP, 900 °C, 100 MPa, 1.5 hrs) with a following post-HIP heat treatment (PHHT, tempering, 750 °C, 70 MPa, 2 hrs), and the W/FMS joining method was developed based on the ITER BFW and the test blanket module (TBM) development project from 2004 to the present. Using a 10-MHz-frequency flat-type probe to ultrasonically test of the joint, we found no defects in the fabricated mockups. For confirmation of the joint integrity, a high heat flux test will be performed up to the thermal lifetime of the mockup under the proper test conditions. These conditions were determined through a preliminary analysis with conventional codes such as ANSYS-CFX for thermal-hydraulic conditions considering the test facility, the Korea heat load test facility with an electron beam (KoHLT-EB), and its water coolant system at the Korea Atomic Energy Research Institute (KAERI).

Quantitative determination of occupation sites of trace Co substituted for multiple Fe sites in M-type hexagonal ferrite using statistical beam-rocking TEM-EDXS analysis.

PubMed

Ohtsuka, Masahiro; Muto, Shunsuke; Tatsumi, Kazuyoshi; Kobayashi, Yoshinori; Kawata, Tsunehiro

2016-04-01

The occupation sites and the occupancies of trace dopants in La/Co co-doped Sr-M-type ferrite, SrFe12O19, were quantitatively and precisely determined by beam-rocking energy-dispersive X-ray spectroscopy (EDXS) on the basis of electron-channeling effects. Because the Co atoms, in particular, should be partially substituted for the five crystallographically inequivalent sites, which could be key parameters in improving the magneto-crystalline anisotropy, it is difficult yet intriguing to discover their occupation sites and occupancies without using the methods of large-scale facilities, such as neutron diffraction and synchrotron radiation. In the present study, we tackled this problem by applying an extended statistical atom location by channeling enhanced microanalysis method, using conventional transmission electron microscopy, EDXS and dynamical electron elastic/inelastic scattering theories. The results show that the key occupation sites of Co were the 2a, 4f1 and 12k sites. The quantified occupancies of Co were consistent with those of the previous study, which involved a combination of neutron diffraction and extended X-ray absorption fine structure analysis, as well as energetics considerations based on by first-principles calculations. © The Author 2015. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Comparative Wide Temperature Core Loss Characteristics of Two Candidate Ferrites for the NASA/TRW 1500 W PEBB Converter

NASA Technical Reports Server (NTRS)

Niedra, Janis M.

1999-01-01

High frequency core loss and magnetization properties of commercial type MN8CX and PC40, high resistivity, MnZn based, power ferrites are presented over the temperature range of -l50 C to 150 C, at selected values of peak flux density (B (sub p)). Most of the data is at 100 kHz, with some data extended to 200 and 300 kHz for the MN8CX. Plots of the specific Core loss against temperature exhibit the minimal characteristic of such ferrites. These plots show that the MN8CX is optimized for minimum loss at about 25 C, whereas the PC40 is optimized at about 80 C. At the points of minimum loss and for the same B (sub p), the MN8CX has roughly half the losses of the PC40 at the lower flux densities. This loss ratio continues down to cryogenic temperatures. However, above about 80 C the losses are practically equal. The lowest 100 kHz loss recorded, 50 mW/cm3 for the MNGCX at a B (sub p) of 0.1T, equals that of a very low loss, Co based, transverse magnetically annealed, amorphous ribbon material. Except possibly at lower B (sub p) or much higher frequencies, these ferrites are not competitive for low losses over a wide temperature range with certain specialty amorphous materials. Permeability is computed from a linear model, plots against temperature are presented and again compared to the specialty amorphous materials.

Five-parameter crystallographic characteristics of the interfaces formed during ferrite to austenite transformation in a duplex stainless steel

NASA Astrophysics Data System (ADS)

Haghdadi, N.; Cizek, P.; Hodgson, P. D.; Tari, V.; Rohrer, G. S.; Beladi, H.

2018-05-01

The crystallography of interfaces in a duplex stainless steel having an equiaxed microstructure produced through the ferrite to austenite diffusive phase transformation has been studied. The five-parameter interface character distribution revealed a high anisotropy in habit planes for the austenite-ferrite and austenite-austenite interfaces for different lattice misorientations. The austenite and ferrite habit planes largely terminated on (1 1 1) and (1 1 0) planes, respectively, for the austenite-ferrite interfaces associated with Kurdjumov-Sachs (K-S) and Nishiyama-Wasserman (N-W) orientation relationships. This was mostly attributed to the crystallographic preference associated with the phase transformation. For the austenite-ferrite interfaces with orientation relationships which are neither K-S nor N-W, both austenite and ferrite habit planes had (1 1 1) orientations. Σ3 twin boundaries comprised the majority of austenite-austenite interfaces, mostly showing a pure twist character and terminating on (1 1 1) planes due to the minimum energy configuration. The second highest populated austenite-austenite boundary was Σ9, which tended to have grain boundary planes in the tilt zone due to the geometrical constraints. Furthermore, the intervariant crystallographic plane distribution associated with the K-S orientation relationship displayed a general tendency for the austenite habit planes to terminate with the (1 1 1) orientation, mainly due to the crystallographic preference associated with the phase transformation.

Development of a shingle-type solar cell module

NASA Technical Reports Server (NTRS)

Shepard, N. F., Jr.; Sanchez, L. E.

1978-01-01

The development of a solar cell module, which is suitable for use in place of shingles on the sloping roofs of residental or commercial buildings, is reported. The design consists of nineteen series-connected 53 mm diameter solar cells arranged in a closely packed hexagon configuration. The shingle solar cell module consists of two basic functional parts: an exposed rigid portion which contains the solar cell assembly, and a semi-flexible portion which is overlapped by the higher courses of the roof installation. Consideration is given to the semi-flexible substrate configuration and solar cell and module-to-module interconnectors. The results of an electrical performance analysis are given and it is noted that high specific power output can be attributed to the efficient packing of the circular cells within the hexagon shape. The shingle should function for at least 15 years, with a specific power output of 98 W/sq w.

Cr-W-V bainitic/ferritic steel with improved strength and toughness and method of making

DOEpatents

Klueh, Ronald L.; Maziasz, Philip J.

1994-01-01

A high strength, high toughness Cr-W-V ferritic steel composition suitable for fast induced-radioactivity (FIRD) decay after irradiation in a fusion reactor comprises 2.5-3.5 wt % Cr, 2. This invention was made with Government support under contract DE-AC05-840R21400 awarded by the U.S. Department of Energy to Martin Marietta Energy Systems, Inc. and the Government has certain rights in this invention.

Quantum percolation phase transition and magnetoelectric dipole glass in hexagonal ferrites

NASA Astrophysics Data System (ADS)

Rowley, S. E.; Vojta, T.; Jones, A. T.; Guo, W.; Oliveira, J.; Morrison, F. D.; Lindfield, N.; Baggio Saitovitch, E.; Watts, B. E.; Scott, J. F.

2017-07-01

Hexagonal ferrites not only have enormous commercial impact (£2 billion/year in sales) due to applications that include ultrahigh-density memories, credit-card stripes, magnetic bar codes, small motors, and low-loss microwave devices, they also have fascinating magnetic and ferroelectric quantum properties at low temperatures. Here we report the results of tuning the magnetic ordering temperature in PbF e12 -xG axO19 to zero by chemical substitution x . The phase transition boundary is found to vary as TN˜(1-x /xc ) 2 /3 with xc very close to the calculated spin percolation threshold, which we determine by Monte Carlo simulations, indicating that the zero-temperature phase transition is geometrically driven. We find that this produces a form of compositionally tuned, insulating, ferrimagnetic quantum criticality. Close to the zero-temperature phase transition, we observe the emergence of an electric dipole glass induced by magnetoelectric coupling. The strong frequency behavior of the glass freezing temperature Tm has a Vogel-Fulcher dependence with Tm finite, or suppressed below zero in the zero-frequency limit, depending on composition x . These quantum-mechanical properties, along with the multiplicity of low-lying modes near the zero-temperature phase transition, are likely to greatly extend applications of hexaferrites into the realm of quantum and cryogenic technologies.

Surfactant assisted synthesis of aluminum doped SrFe{sub 10}Al{sub 2}O{sub 19} hexagonal ferrite

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

Neupane, D., E-mail: dneupane@memphis.edu; Wang, L.; Mishra, S. R.

2015-05-07

M-type aluminum doped SrFe{sub 10}Al{sub 2}O{sub 19} were synthesized via co-precipitation method using cetyltrimethyl ammonium bromide (CTAB) as a surfactant. The effects of CTAB content (x = 0, 1, 3, and 9 wt. %) on the formation, structure, morphology, magnetic, and dielectric properties of the SrFe{sub 10}Al{sub 2}O{sub 19} nanoparticles were investigated. X-ray diffraction results show elimination of α-Fe{sub 2}O{sub 3} phase from samples prepared using CTAB. Morphological changes including grain and crystallite size was noticed with the increase in the CTAB content. With the increase in CTAB, powder particles grew in hexagonal plates. A linear increase in saturation magnetization, Ms, with CTABmore » content was observed from 56.5 emu/g at 0% CTAB to 66.4 emu/g at 9% CTAB. This is a net increase of 17.5% in Ms. The coercivity (Hc ∼ 5700 Oe) of sample reached maximum at 1% CTAB and reduced with further CTAB content reaching to a minimum value of 4488 Oe at 9% CTAB. A slight increase in Curie temperature (735 K) was also observed for samples synthesized using CTAB as compared to that of sample prepared in the absence of CTAB (729 K). Samples synthesized with CTAB show higher dielectric constants as compared to samples prepared without CTAB, while dielectric constant for all samples show decrease in value with the increase in frequency. These results imply that CTAB may act as a crystallization master, controlling the nucleation and growth of SrFe{sub 10}Al{sub 2}O{sub 19} crystal. The study delineates the scope of improving magnetic properties of ferrites without substitution of metal ions.« less

Enhanced stability of magnetoelectric gyrators under high power conditions

NASA Astrophysics Data System (ADS)

Leung, Chung Ming; Zhuang, Xin; Gao, Min; Tang, Xiao; Xu, Junran; Li, Jiefang; Zhang, Jitao; Srinivasan, G.; Viehland, D.

2017-10-01

In this study, three different coil-based magnetoelectric (ME) gyrators of different geometries, including gyrators with high power output, have been designed and characterized. These included two magnetostrictive/piezoelectric/magnetostrictive (M-P-M) and one piezoelectric/magnetostrictive/piezoelectric (P-M-P) type ME gyrators, which consisted of nickel zinc ferrite (NZFO) and lead zirconate titanate (PZT) ceramic plates. Compared with M-P-M ME gyrators, the P-M-P ones exhibited a higher power efficiency (η) of 85% when operated at resonance under an optimal magnetic bias field (HBias) of 40 Oe at low power conditions. It retained a relatively high efficiency of η = 79% under a high input power density of 2.87 W/cm3. A low reduction in the magnetomechanical coupling and mechanical quality (k33,m and Qm) factors of the NZFO ferrite layer in the ME gyrator explains the resilience of the P-M-P type structure with increasing power drive. The findings open the possibility of using ME gyrators in high power applications.

Thermal conductivity of ultra-thin chemical vapor deposited hexagonal boron nitride films

NASA Astrophysics Data System (ADS)

Alam, M. T.; Bresnehan, M. S.; Robinson, J. A.; Haque, M. A.

2014-01-01

Thermal conductivity of freestanding 10 nm and 20 nm thick chemical vapor deposited hexagonal boron nitride films was measured using both steady state and transient techniques. The measured value for both thicknesses, about 100 ± 10 W m-1 K-1, is lower than the bulk basal plane value (390 W m-1 K-1) due to the imperfections in the specimen microstructure. Impressively, this value is still 100 times higher than conventional dielectrics. Considering scalability and ease of integration, hexagonal boron nitride grown over large area is an excellent candidate for thermal management in two dimensional materials-based nanoelectronics.

Structure and magnetic properties of iron-based soft magnetic composite with Ni-Cu-Zn ferrite-silicone insulation coating

NASA Astrophysics Data System (ADS)

Li, Wangchang; Wang, Wei; Lv, Junjun; Ying, Yao; Yu, Jing; Zheng, Jingwu; Qiao, Liang; Che, Shenglei

2018-06-01

This paper investigates the structure and magnetic properties of Ni-Cu-Zn ferrite-silicone coated iron-based soft magnetic composites (SMCs). Scanning electron microscopy coupled with a energy-dispersive spectroscopy (EDS) analysis revealed that the Ni-Cu-Zn ferrite and silicone resin were uniformly coated on the surface of iron powders. By controlling the composition of the coating layer, low total core loss of 97.7 mW/cm3 (eddy current loss of 48 mW/cm3, hysteresis loss of 49.7 mW/cm3, measured at 100 kHz and 0.02 T) and relatively high effective permeability of 72.5 (measured at 100 kHz) were achieved. In addition, the as-prepared SMCs displayed higher electrical resistivity, good magnetic characteristics over a wide range of frequencies (20-200 kHz) and ideal the D-C bias properties (more than 75% at H = 50 Oe). Furthermore, higher elastic modulus and hardness of SMCs, which means that the coating layer has good mechanical properties and is not easily damaged during the pressing process, were obtained in this paper. The results of this work indicate that the Ni-Cu-Zn ferrite-silicone coated SMCs have desirable properties which would make them suitable for application in the fields of the electric-magnetic switching devices, such as inductance coils, transformer cores, synchronous electric motors and resonant inductors.

Spin-Orbit Torque-Assisted Switching in Magnetic Insulator Thin Films with Perpendicular Magnetic Anisotropy

NASA Astrophysics Data System (ADS)

Wu, Mingzhong

As an in-plane charge current flows in a heavy metal film with spin-orbit coupling, it produces a torque that can induce magnetization switching in a neighboring ferromagnetic metal film. Such spin-orbit torque (SOT)-induced switching has been studied extensively in recent years and has shown higher efficiency than switching using conventional spin-transfer torque. This presentation reports the SOT-assisted switching in heavy metal/magnetic insulator systems.1 The experiments made use of Pt/BaFe12O19 bi-layered structures. Thanks to its strong spin-orbit coupling, Pt has been widely used to produce pure spin currents in previous studies. BaFe12O19 is an M-type barium hexagonal ferrite and is often referred as BaM. It is one of the few magnetic insulators with strong magneto-crystalline anisotropy and shows an effective uniaxial anisotropy field of about 17 kOe. It's found that the switching response in the BaM film strongly depends on the charge current applied to the Pt film. When a constant magnetic field is applied in the film plane, the charge current in the Pt film can switch the normal component of the magnetization (M⊥) in the BaM film between the up and down states. The current also dictates the up and down states of the remnant magnetization when the in-plane field is reduced to zero. When M⊥ is measured by sweeping an in-plane field, the response manifests itself as a hysteresis loop, which evolves in a completely opposite manner if the sign of the charge current is flipped. When the coercivity is measured by sweeping an out-of-plane field, its value can be reduced or increased by as much as about 500 Oe if an appropriate charge current is applied. 1. P. Li, T. Liu, H. Chang, A. Kalitsov, W. Zhang, G. Csaba, W. Li, D. Richardson, A. Demann, G. Rimal, H. Dey, J. S. Jiang, W. Porod, S. Field, J. Tang, M. C. Marconi, A. Hoffmann, O. Mryasov, and M. Wu, Nature Commun. 7:12688 doi: 10.1038/ncomms12688 (2016).

Development of low loss hexaferrite materials for microwave applications

NASA Astrophysics Data System (ADS)

Su, Zhijuan

Hexaferrites have been widely used in microwave and millimeter wave devices as permanent magnets and as gyromagnetic materials, e.g., in circulators, filters, isolators, inductors, and phase shifters. As a critical component in radar and modern wireless communication systems, it is the microwave circulator that has drawn much attention. Many efforts have been made to design light and miniature circulators with self-biased ferrite materials. We report the magnetic and structural properties of a series of W-type barium hexaferrites of composition BaZn2-xCoxFe16O27 where x=0.15, 0.20, and 0.25. The anisotropy field of these BaW ferrites decreased with the substitution of divalent Co ions, while, they maintained crystallographic c-axis texture. The measured anisotropy field was ~10 kOe, and a hysteresis loop squareness Mr/Ms=79% was obtained due to well-controlled grain size within the range of single domain scale. U-type barium hexaferrite thin films were deposited on (0001) sapphire substrates by pulsed laser deposition. The results indicate a measured anisotropy field of ~8 kOe, and the saturation magnetization (4piMs) of 3.6 kG. More interestingly, an optimal post-deposition annealing of the films results in a strong (0, 0, n) crystallographic texture and a high squareness (Mr/Ms= 92%) out of the film plane. Furthermore, the highly self-biased ferrite films exhibited low FMR linewidth of ~200 Oe. Improved performance and miniaturization are needed to meet the ever-increasing demands of devices used in ultra-high frequency (UHF), L-band, and S-band, which are of particular interest in a variety of commercial and defense related applications. Utilizing materials possessing high permeability and permittivity with low magnetic losses is a promising solution. As a critical component in radar and modern wireless communication systems, antenna elements with compact size are constantly sought. Ferrite composites of the nominal composition Ba3Co2+xIrxFe24-2xO41 were studied in order to achieve low magnetic and dielectric losses and equivalent permittivity and permeability over a frequency range of 0.3-1 GHz. Crystallographic structure was characterized by X-ray diffraction, which revealed a Z-type phase accompanied by increasing amounts of Y-type phase as the iridium amount was increased. The measured microwave dielectric and magnetic properties showed that the loss tandeltaepsilon and loss tandeltamicro were decreased by 80% and 90% at 0.8 GHz with the addition of iridium having x =0.12 and 0.15, respectively. An effective medium approximation was adopted to analyze the composite ferrites having mixed phase structures. Moreover, adding Bi2O3 resulted in equivalent values of real permittivity and real permeability over the studied frequency range. The resultant data gives rise to low loss factors (i.e., tandeltaepsilon/epsilon' = 0.008 and tandelta micro/micro'=0.037 at 0.8 GHz) while characteristic impedance was the same as that of free space impedance.

Synthesis, microstructure, and magnetic properties of monosized Mn x Zn y Fe3 − x − y O4 ferrite nanocrystals

PubMed Central

2013-01-01

We report the synthesis and characterization of ferrite nanocrystals which exhibit high crystallinity and narrow size distributions. The three types of samples including Zn ferrite, Mn ferrite, and Mn-Zn ferrite were prepared via a non-aqueous nanoemulsion method. The structural, chemical, and magnetic properties of the nanocrystals are analyzed by transmission electron microscopy, X-ray diffraction, X-ray fluorescence, and physical property measurement system. The characterization indicates that the three types of ferrite nanocrystals were successfully produced, which show well-behaved magnetic properties, ferrimagnetism at 5 K and superparamagnetism at 300 K, respectively. In addition, the magnetization value of the ferrites increases with the increasing concentration of Mn. PMID:24344630

Structural and magnetic properties of La–Co substituted Sr–Ca hexaferrites synthesized by the solid state reaction method

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

Yang, Yujie; Liu, Xiansong, E-mail: xiansongliu@ahu.edu.cn; Jin, Dali

2014-11-15

Graphical abstract: The change of the remanence (B{sub r}) and intrinsic coercivity (H{sub cj}) with La content (x) and Co content (y) of hexagonal ferrite Sr{sub 0.7−x}Ca{sub 0.3}La{sub x}Fe{sub 12−y}Co{sub y}O{sub 19} magnets. - Highlights: • Sr{sub 0.7−x}Ca{sub 0.3}La{sub x}Fe{sub 12−y}Co{sub y}O{sub 19} hexaferrites were synthesized by the solid state reaction method. • B{sub r} continuously increases with increasing dopant contents. • H{sub cb}, H{sub cj} and (BH){sub max} for the magnets first increases and then decreases with an increase in the La–Co contents. - Abstract: Hexagonal ferrite Sr{sub 0.7−x}Ca{sub 0.3}La{sub x}Fe{sub 12−y}Co{sub y}O{sub 19} (x = 0.05–0.50; y =more » 0.04–0.40) magnetic powders and magnets were synthesized by the solid state reaction method. X-ray diffraction was employed to determine the phase compositions of the magnetic powders. There is a single magnetoplumbite phase in the magnetic powders with the substitution of La (0.05 ≤ x ≤ 0.15) and Co (0.04 ≤ y ≤ 0.12) contents. For the magnetic powders containing La (x ≥ 0.20) and Co (y ≥ 0.16), magnetic impurities begin to appear in the structure. A field emission scanning electron microscope was used to characterize the micrographs of the magnets. The magnets have formed hexagonal structures. Magnetic properties of the magnets were measured by a magnetic properties test instrument. The remanence continuously increases with increasing dopant contents. Whereas, the magnetic induction coercivity, intrinsic coercivity and maximum energy product for the magnets first increases and then decreases with an increase in the La–Co contents.« less

Hole polarons and p -type doping in boron nitride polymorphs

NASA Astrophysics Data System (ADS)

Weston, L.; Wickramaratne, D.; Van de Walle, C. G.

2017-09-01

Boron nitride polymorphs hold great promise for integration into electronic and optoelectronic devices requiring ultrawide band gaps. We use first-principles calculations to examine the prospects for p -type doping of hexagonal (h -BN ), wurtzite (w z -BN ), and cubic (c -BN ) boron nitride. Group-IV elements (C, Si) substituting on the N site result in a deep acceptor, as the atomic levels of the impurity species lie above the BN valence-band maximum. On the other hand, group-II elements (Be, Mg) substituting on the B site do not give impurity states in the band gap; however, these dopants lead to the formation of small hole polarons. The tendency for polaron formation is far more pronounced in h -BN compared to w z -BN or c -BN . Despite forming small hole polarons, Be acceptors enable p -type doping, with ionization energies of 0.31 eV for w z -BN and 0.24 eV for c -BN ; these values are comparable to the Mg ionization energy in GaN.

High Temperature Strengthening in 12Cr-W-Mo Steels by Controlling the Formation of Delta Ferrite

NASA Astrophysics Data System (ADS)

Wang, Shushen; Chang, Li; Lin, Deye; Chen, Xiaohua; Hui, Xidong

2014-09-01

Novel 12Cr-W-Mo-Co heat resistance steels (HRSs) with excellent mechanical properties have been developed for ultra-supercritical (USC) applications above 923 K (650 °C). The thermal analysis of the present steels indicates that the remelting temperature of secondary phases is increased by Co alloying, resulting in the improvement of microstructural stability. Delta ferrite in these HRSs is completely suppressed as the content of Co is increased up to 5 pct. The room temperature tensile strength (TS), yield strength (YS), and the elongation (EL) of the HRS with 5 pct Co reach 887.9, 652.6 MPa, and 21.07 pct, respectively. At 948 K (675 °C), the TS and YS of the HRS with 5 pct Co attain 360 and 290 MPa, respectively, which are higher than those of T/P122 steel by 27.4 and 22.1 pct, respectively. TEM study of the microstructure confirmed that the strengthening effects for these 12Cr-W-Mo-Co HRSs are attributed to the suppression of delta ferrite, the formation of fine martensitic laths with substructure, dislocation networks and walls, and the precipitation of second nanoscale phases.

Vertical MoSe2-MoO x p-n heterojunction and its application in optoelectronics.

PubMed

Chen, Xiaoshuang; Liu, Guangbo; Hu, Yunxia; Cao, Wenwu; Hu, PingAn; Hu, Wenping

2018-01-26

The hybrid n-type 2D transition-metal dichalcogenide (TMD)/p-type oxide van der Waals (vdW) heterojunction nanosheets consist of 2D layered MoSe 2 (the n-type 2D material) and MoO x (the p-type oxide) which are grown on SiO 2 /Si substrates for the first time via chemical vapor deposition technique, displaying the regular hexagon structures with the average length dimension of sides of ∼8 μm. Vertical MoSe 2 -MoO x p-n heterojunctions demonstrate obviously current-rectifying characteristic, and it can be tuned via gate voltage. What is more, the photodetector based on vertical MoSe 2 -MoO x heterojunctions displays optimal photoresponse behavior, generating the responsivity, detectivity, and external quantum efficiency to 3.4 A W -1 , 0.85 × 10 8 Jones, and 1665.6%, respectively, at V ds  = 5 V with the light wavelength of 254 nm under 0.29 mW cm -2 . These results furnish a building block on investigating the flexible and transparent properties of vdW and further optimizing the structure of the devices for better optoelectronic and electronic performance.

Vertical MoSe2-MoO x p-n heterojunction and its application in optoelectronics

NASA Astrophysics Data System (ADS)

Chen, Xiaoshuang; Liu, Guangbo; Hu, Yunxia; Cao, Wenwu; Hu, PingAn; Hu, Wenping

2018-01-01

The hybrid n-type 2D transition-metal dichalcogenide (TMD)/p-type oxide van der Waals (vdW) heterojunction nanosheets consist of 2D layered MoSe2 (the n-type 2D material) and MoO x (the p-type oxide) which are grown on SiO2/Si substrates for the first time via chemical vapor deposition technique, displaying the regular hexagon structures with the average length dimension of sides of ˜8 μm. Vertical MoSe2-MoO x p-n heterojunctions demonstrate obviously current-rectifying characteristic, and it can be tuned via gate voltage. What is more, the photodetector based on vertical MoSe2-MoO x heterojunctions displays optimal photoresponse behavior, generating the responsivity, detectivity, and external quantum efficiency to 3.4 A W-1, 0.85 × 108 Jones, and 1665.6%, respectively, at V ds = 5 V with the light wavelength of 254 nm under 0.29 mW cm-2. These results furnish a building block on investigating the flexible and transparent properties of vdW and further optimizing the structure of the devices for better optoelectronic and electronic performance.

Epitaxial growth of 100-μm thick M-type hexaferrite crystals on wide bandgap semiconductor GaN/Al{sub 2}O{sub 3} substrates

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

Hu, Bolin; Su, Zhijuan; Bennett, Steve

2014-05-07

Thick barium hexaferrite BaFe{sub 12}O{sub 19} (BaM) films having thicknesses of ∼100 μm were epitaxially grown on GaN/Al{sub 2}O{sub 3} substrates from a molten-salt solution by vaporizing the solvent. X-ray diffraction measurement verified the growth of BaM (001) textured growth of thick films. Saturation magnetization, 4πM{sub s}, was measured for as-grown films to be 4.6 ± 0.2 kG and ferromagnetic resonance measurements revealed a microwave linewidth of ∼100 Oe at X-band. Scanning electron microscopy indicated clear hexagonal crystals distributed on the semiconductor substrate. These results demonstrate feasibility of growing M-type hexaferrite crystal films on wide bandgap semiconductor substrates by using a simplemore » powder melting method. It also presents a potential pathway for the integration of ferrite microwave passive devices with active semiconductor circuit elements creating system-on-a-wafer architectures.« less

Synthesis of ferrite and nickel ferrite nanoparticles using radio-frequency thermal plasma torch

NASA Astrophysics Data System (ADS)

Son, S.; Taheri, M.; Carpenter, E.; Harris, V. G.; McHenry, M. E.

2002-05-01

Nanocrystalline (NC) ferrite powders have been synthesized using a 50 kW-3 MHz rf thermal plasma torch for high-frequency soft magnet applications. A mixed powder of Ni and Fe (Ni:Fe=1:2), a NiFe permalloy powder with additional Fe powder (Ni:Fe=1:2), and a NiFe permalloy powder (Ni:Fe=1:1) were used as precursors for synthesis. Airflow into the reactor chamber was the source of oxygen for oxide formation. XRD patterns clearly show that the precursor powders were transformed into NC ferrite particles with an average particle size of 20-30 nm. SEM and TEM studies indicated that NC ferrite particles had well-defined polygonal growth forms with some exhibiting (111) faceting and many with truncated octahedral and truncated cubic shapes. The Ni content in the ferrite particles was observed to increase in going from mixed Ni and Fe to mixed permalloy and iron and finally to only permalloy starting precursor. The plasma-torch synthesized ferrite materials using exclusively the NiFe permalloy precursor had 40%-48% Ni content in the Ni-ferrite particle, differing from the NiFe2O4 ideal stoichiometry. EXAFS was used to probe the cation coordination in low Ni magnetite species. The coercivity and Neel temperature of the high Ni content ferrite sample were 58 Oe and ˜590 °C, respectively.

Design of lightweight broadband microwave absorbers in the X-band based on (polyaniline/MnNiZn ferrite) nanocomposites

NASA Astrophysics Data System (ADS)

Ali, Nassim Nasser; Al-Qassar Bani Al-Marjeh, Rama; Atassi, Yomen; Salloum, Akil; Malki, Adnan; Jafarian, Mojtaba

2018-05-01

We present the design of novel, lightweight, broadband microwave absorbers based on polyaniline/Mn0.1Ni0.45Zn0.45Fe2O4 (PANI/MnNiZn ferrite) nanocomposites. The ferrite is synthesized by sol-gel technique. Then, the polymer is deposited by in-situ chemical oxidative polymerization. The structural and morphological characterizations of the composites are investigated by SEM, XRD, FT-IR and UV-vis spectroscopy. The functional characterization is performed by measuring the dc-conductivity and microwave absorption characteristics in the X-band. The absorbers exhibit broad bandwidths under -10 dB ranging from 2.60 to 3.74 GHz and low surface density ranging from 2.5 to 3.1 kg/m2. The absorber of 3.74 GHz bandwidth has a minimum reflection loss of -31.32 dB at 11.13 GHz with a matching thickness of 3 mm and a low loading in paraffin of only 25% w/w.

Influence of thermo-mechanical treatment in ferritic phase field on microstructure and mechanical properties of reduced activation ferritic-martensitic steel

NASA Astrophysics Data System (ADS)

Prakash; Vanaja, J.; Laha, K.; Nageswara Rao, G. V. S.

2018-03-01

The present study focuses on the evaluation of microstructure and mechanical properties of reduced activation ferritic-martensitic (RAFM) steel (9Cr-1W-0.06Ta) subjected to thermo-mechanical treatment (TMT) in ferritic phase field. The results obtained were compared with the steel in conventional normalised plus tempered (N+T) condition. The microstructure of the steel in N+T and TMT conditions was assessed by optical and scanning electron microscopes. Hardness, tensile and creep studies were carried out and the results were correlated with the microstructural studies. While the TMT processed steel resulted in coarser prior austenite grains and exhibited ferritic microstructure with large distribution of fine M23C6 and MX precipitates, the N+T steel reveals tempered martensitic structure with finer prior austenitic grains with coarser M23C6 and MX precipitates. Although ferritic structure is present in TMT processed steel, it exhibits better tensile and creep rupture strengths than N+T steel due to the presence of increased dislocation density and finer distribution of precipitates.

Articles comprising ferritic stainless steels

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

Rakowski, James M.

An article of manufacture comprises a ferritic stainless steel that includes a near-surface region depleted of silicon relative to a remainder of the ferritic stainless steel. The article has a reduced tendency to form an electrically resistive silica layer including silicon derived from the steel when the article is subjected to high temperature oxidizing conditions. The ferritic stainless steel is selected from the group comprising AISI Type 430 stainless steel, AISI Type 439 stainless steel, AISI Type 441 stainless steel, AISI Type 444 stainless steel, and E-BRITE.RTM. alloy, also known as UNS 44627 stainless steel. In certain embodiments, the articlemore » of manufacture is a fuel cell interconnect for a solid oxide fuel cell.« less

Evolution of Moiré Profiles from van der Waals Superstructures of Boron Nitride Nanosheets

PubMed Central

Liao, Yunlong; Cao, Wei; Connell, John W.; Chen, Zhongfang; Lin, Yi

2016-01-01

Two-dimensional (2D) van der Waals (vdW) superstructures, or vdW solids, are formed by the precise restacking of 2D nanosheet lattices, which can lead to unique physical and electronic properties that are not available in the parent nanosheets. Moiré patterns formed by the crystalline mismatch between adjacent nanosheets are the most direct features for vdW superstructures under microscopic imaging. In this article, transmission electron microscopy (TEM) observation of hexagonal Moiré patterns with unusually large micrometer-sized lateral areas (up to ~1 μm2) and periodicities (up to ~50 nm) from restacking of liquid exfoliated hexagonal boron nitride nanosheets (BNNSs) is reported. This observation was attributed to the long range crystallinity and the contaminant-free surfaces of these chemically inert nanosheets. Parallel-line-like Moiré fringes with similarly large periodicities were also observed. The simulations and experiments unambiguously revealed that the hexagonal patterns and the parallel fringes originated from the same rotationally mismatched vdW stacking of BNNSs and can be inter-converted by simply tilting the TEM specimen following designated directions. This finding may pave the way for further structural decoding of other 2D vdW superstructure systems with more complex Moiré images. PMID:27188697

A SURVEY OF THE CORROSION OF MARTENSITIC AND FERRITIC STAINLESS STEELS IN PRESSURIZED WATER

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

Beaver, R.J.; Leitten, C.F. Jr.

1963-07-16

>The corrosion resistance of mantensitic and ferritic austenitic stainless steels and carbon steels in pressurized water at 500 to 600 deg F is compared. Included are specific out-of-pile data for austenitic stainless steels, AISI types types 410, 420, 431, and 440C; the ferritic AISI types 430, 442, and 446; the precipitation-hardening type 17-4PH; and carbon steels, ASTM 212 A and B. Available corrosion results obtained under irradiation at exposures in the range of 7 x 10/sup 16/ to 3 x 10/sup 19/ nvt are also included for types 304, types of martensitic and ferritic stainless steels which were evaluated domore » not contain nickel. For application where it is desirable to minimize Co/sup 58/ activity produced from nickel, selection of a martensitic or ferritic stainless steel may be more appropriate than choosing the more popular nickel-bearing austenitic stainless steel or a fuel-element cladding material. Interpretation of the data indicates that, on the average, martensitic and ferritic stainless steels corrode more rapidly than austenitic alloys but more slowly than carbon and low-alloy steels. Under selected controlled water conditions or under irradiation, the corrosion of the nickel-free stainless steels appears to differ little from the austenitics. The corrosion of martensitic and ferritic stainless steels in pressurized-water systems therefore does not appear of such magnitude as to rule out development of these materials as the cladding fuel elements for specific applications. (auth)« less

Ternary manganese ferrite/graphene/polyaniline nanostructure with enhanced electrochemical capacitance performance

NASA Astrophysics Data System (ADS)

Xiong, Pan; Hu, Chenyao; Fan, Ye; Zhang, Wenyao; Zhu, Junwu; Wang, Xin

2014-11-01

A ternary manganese ferrite/graphene/polyaniline (MGP) nanostructure is designed and synthesized via a facile two-step approach. This nanostructure exhibits outstanding electrochemical performances, such as high specific capacitance (454.8 F g-1 at 0.2 A g-1), excellent rate capability (75.8% capacity retention at 5 A g-1), and good cycling stability (76.4% capacity retention after 5000 cycles at 2 A g-1), which are superior to those of its individual components (manganese ferrite, reduced-graphene oxide, polyaniline) and corresponding binary hybrids (manganese ferrite/graphene (MG), manganese ferrite/polyaniline (MP), and graphene/polyaniline (GP)). A symmetric supercapacitor device using the as-obtained hybrid has been fabricated and tested. The device exhibits a high specific capacitance of 307.2 F g-1 at 0.1 A g-1 with a maximum energy density of 13.5 W h kg-1. The high electrochemical performance of ternary MGP can be attributed to its well-designed nanostructure and the synergistic effect of the individual components.

Thermal expansion characteristics of Fe-9Cr-0.12C-0.56Mn-0.24V-1.38W-0.06Ta (wt.%) reduced activation ferritic-martensitic steel

NASA Astrophysics Data System (ADS)

Subramanian, Raju; Tripathy, Haraprasanna; Rai, Arun Kumar; Hajra, Raj Narayan; Saibaba, Saroja; Jayakumar, Tammana; Rajendra Kumar, Ellappan

2015-04-01

The lattice and bulk thermal expansion behavior of an Indian version of reduced activation ferritic-martensitic (INRAFM) steel has been quantified using high temperature X-ray diffraction and dilatometry. The lattice parameter of tempered α-ferrite phase exhibited a smooth quadratic increase with temperature, while that of γ-austenite remained fairly linear up to 1273 K. The results suggest that α-ferrite + Carbides → γ-austenite transformation occurs upon continuous heating in the temperature range, 1146 ⩽ T ⩽ 1173 K. Further, this transformation is found to be accompanied by a reduction in average atomic volume. The mean linear thermal expansion coefficients of tempered α-ferrite and γ-austenite phases are estimated to be about 1.48 × 10-5 and 2.4 × 10-5 K-1 respectively. The magnetic contribution to relative thermal dilatation (Δl/l298)mag is found to be small and negative, as compared to phonon contribution.

Quantitative LIBS analysis of vanadium in samples of hexagonal mesoporous silica catalysts.

PubMed

Pouzar, Miloslav; Kratochvíl, Tomás; Capek, Libor; Smoláková, Lucie; Cernohorský, Tomás; Krejcová, Anna; Hromádko, Ludek

2011-02-15

The method for the analysis of vanadium in hexagonal mesoporous silica (V-HMS) catalysts using Laser Induced Breakdown Spectrometry (LIBS) was suggested. Commercially available LIBS spectrometer was calibrated with the aid of authentic V-HMS samples previously analyzed by ICP OES after microwave digestion. Deposition of the sample on the surface of adhesive tape was adopted as a sample preparation method. Strong matrix effect connected with the catalyst preparation technique (1st vanadium added in the process of HMS synthesis, 2nd already synthesised silica matrix was impregnated by vanadium) was observed. The concentration range of V in the set of nine calibration standards was 1.3-4.5% (w/w). Limit of detection was 0.13% (w/w) and it was calculated as a triple standard deviation from five replicated determinations of vanadium in the real sample with a very low vanadium concentration. Comparable results of LIBS and ED XRF were obtained if the same set of standards was used for calibration of both methods and vanadium was measured in the same type of real samples. LIBS calibration constructed using V-HMS-impregnated samples failed for measuring of V-HMS-synthesized samples. LIBS measurements seem to be strongly influenced with different chemical forms of vanadium in impregnated and synthesised samples. The combination of LIBS and ED XRF is able to provide new information about measured samples (in our case for example about procedure of catalyst preparation). Copyright © 2010 Elsevier B.V. All rights reserved.

Comparative cytotoxic response of nickel ferrite nanoparticles in human liver HepG2 and breast MFC-7 cancer cells.

PubMed

Ahamed, Maqusood; Akhtar, Mohd Javed; Alhadlaq, Hisham A; Khan, M A Majeed; Alrokayan, Salman A

2015-09-01

Nickel ferrite nanoparticles (NPs) have received much attention for their potential applications in biomedical fields such as magnetic resonance imaging, drug delivery and cancer hyperthermia. However, little is known about the toxicity of nickel ferrite NPs at the cellular and molecular levels. In this study, we investigated the cytotoxic responses of nickel ferrite NPs in two different types of human cells (i.e., liver HepG2 and breast MCF-7). Nickel ferrite NPs induced dose-dependent cytotoxicity in both types of cells, which was demonstrated by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazoliumbromide (MTT), neutral red uptake (NRU) and lactate dehydrogenase (LDH) assays. Nickel ferrite NPs were also found to induce oxidative stress, which was evident by the depletion of glutathione and the induction of reactive oxygen species (ROS) and lipid peroxidation. The mitochondrial membrane potential due to nickel ferrite NP exposure was also observed. The mRNA levels for the tumor suppressor gene p53 and the apoptotic genes bax, CASP3 and CASP9 were up-regulated, while the anti-apoptotic gene bcl-2 was down-regulated following nickel ferrite NP exposure. Furthermore, the activities of apoptotic enzymes (caspase-3 and caspase-9) were also higher in both types of cells treated with nickel ferrite NPs. Cytotoxicity induced by nickel ferrite was efficiently prevented by N-acetyl cysteine (ROS scavenger) treatment, which suggested that oxidative stress might be one of the possible mechanisms of nickel ferrite NP toxicity. We also observed that MCF-7 cells were slightly more susceptible to nickel ferrite NP exposure than HepG2 cells. This study warrants further investigation to explore the potential mechanisms of different cytotoxic responses of nickel ferrite NPs in different cell lines. Copyright © 2015 Elsevier Ltd. All rights reserved.

Tube manufacturing and characterization of oxide dispersion strengthened ferritic steels

NASA Astrophysics Data System (ADS)

Ukai, Shigeharu; Mizuta, Shunji; Yoshitake, Tunemitsu; Okuda, Takanari; Fujiwara, Masayuki; Hagi, Shigeki; Kobayashi, Toshimi

2000-12-01

Oxide dispersion strengthened (ODS) ferritic steels have an advantage in radiation resistance and superior creep rupture strength at elevated temperature due to finely distributed Y2O3 particles in the ferritic matrix. Using a basic composition of low activation ferritic steel (Fe-12Cr-2W-0.05C), cladding tube manufacturing by means of pilger mill rolling and subsequent recrystallization heat-treatment was conducted while varying titanium and yttria contents. The recrystallization heat-treatment, to soften the tubes hardened due to cold-rolling and to subsequently improve the degraded mechanical properties, was demonstrated to be effective in the course of tube manufacturing. For a titanium content of 0.3 wt% and yttria of 0.25 wt%, improvement of the creep rupture strength can be attained for the manufactured cladding tubes. The ductility is also adequately maintained.

Effect of van der Waals interactions on the stability of SiC polytypes

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

Kawanishi, Sakiko, E-mail: s-kawa@tagen.tohoku.ac.jp; Mizoguchi, Teruyasu

2016-05-07

Density functional theory calculations with a correction of the long-range dispersion force, namely, the van der Waals (vdW) force, are performed for SiC polytypes. The lattice parameters are in good agreement with those obtained from the experiments. Furthermore, the stability of the polytypes in the experiments, which show 3C-SiC as the most stable, is reproduced by the present calculations. The effects of the vdW force on the electronic structure and the stability of polytypes are discussed. We observe that the vdW interaction is more sensitive to the cubic site than the hexagonal site. Thus, the influence of the vdW forcemore » increases with decreasing the hexagonality of the polytype, which results in the confirmation that the most stable polytype is 3C-SiC.« less

The effect of Bi substitution on the microstructure and magnetic properties of the Sr0.4Ba0.3La0.3Fe12-xBixO19 hexagonal ferrites

NASA Astrophysics Data System (ADS)

Yang, Yujie; Wang, Fanhou; Liu, Xiansong; Shao, Juxiang; Feng, Shuangjiu; Huang, Duohui; Li, Mingling

2017-01-01

Bi3+ ions doped M-type hexaferrites, Sr0.4Ba0.3La0.3Fe12-xBixO19 (0≤x≤0.7), were prepared by the ceramic process. The phase components of the magnetic powders were investigated by X-ray diffraction. The results show that a single magnetoplumbite phase is obtained for the magnetic powders with x from 0 to 0.2, and BiFeO3 as a second phase appears when Bi content (x)≥0.3. The micrographs of the sintered magnets were observed by a field emission scanning electron microscopy. The sintered magnets are formed of hexagonal-shaped crystals. The magnetic properties of the sintered magnets were measured at room temperature by a permanent magnetic measuring system. The remanence (Br) first increases with x from 0 to 0.2, and then decreases when Bi content (x)≥0.2. The intrinsic coercivity (Hcj) and magnetic induction coercivity (Hcb) firstly decrease quickly with x from 0 to 0.1, and then increase linearly when Bi content (x)≥0.1. The maximum energy product [(BH)max] increases with x from 0 to 0.3, and then decreases when Bi content (x)≥0.3. The ratio Hk/Hcj ratio first increases with Bi content (x) from 0 to 0.4. And the Hk/Hcj ratio decreases when x≥0.4.

Development of high strength ferritic steel for interconnect application in SOFCs

NASA Astrophysics Data System (ADS)

Froitzheim, J.; Meier, G. H.; Niewolak, L.; Ennis, P. J.; Hattendorf, H.; Singheiser, L.; Quadakkers, W. J.

High-Cr ferritic model steels containing various additions of the refractory elements Nb and/or W were studied with respect to oxidation behaviour (hot) tensile properties, creep behaviour and high-temperature electrical conductivity of the surface oxide scales. Whereas W additions of around 2 wt.% had hardly any effect on the oxidation rates at 800 and 900 °C, Nb additions of 1% led to a substantially enhanced growth rate of the protective surface oxide scale. It was found that this adverse effect can be alleviated by suitable Si additions. This is related to the incorporation of Si and Nb into Laves phase precipitates which also contribute to increased creep and hot tensile strength. The dispersion of Laves phase precipitates was greatly refined by combined additions of Nb and W. The high-temperature electrical conductivity of the surface oxide scales was similar to that of the Nb/W-free alloys. Thus the combined additions of Nb, W and Si resulted in an alloy with oxidation resistance, ASR contribution and thermal expansion comparable to the commercial alloy Crofer 22 APU, but with creep strength far greater than that of Crofer 22 APU.

Investigation of Barium Ferrite, Searching for Soft Magnetic Materials in High Frequency Applications

NASA Astrophysics Data System (ADS)

Wu, Shuang; Kanada, Isao; Mewes, Tim; Mewes, Claudia; Mankey, Gary; Ariake, Yusuke; Suzuki, Takao

Soft ferrites have been extensively and intensively applied for high frequency device applications. Among them, Ba-ferrites substituted by Mn and Ti are particularly attractive as future soft magnetic material candidates for advanced high frequency device applications. However, very little has been known as to the intrinsic magnetic properties, such as damping parameter, which is crucial to develop high frequency devices. In the present study, much effort has been focused on fabrication of single crystal Ba-ferrites and measurements of damping parameter by FMR. Ba-ferrite samples consisted of many grains with various sizes have been prepared. The saturation magnetization and the magnetic anisotropy field of the sample are in reasonable agreement with the values in literature. The resonances positions in the FMR spectra over a wide frequency range also comply with theoretical predictions. However, the complex resonance shapes observed makes it difficult to extract dynamic magnetic property. Possible reasons are the demagnetization field originating from irregular sample shape or existence of multiple grains in the samples. S.W. acknowledges the support under the TDK Scholar Program.

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

Han,W.Q.

Boron nitride (BN) is a synthetic binary compound located between III and V group elements in the Periodic Table. However, its properties, in terms of polymorphism and mechanical characteristics, are rather close to those of carbon compared with other III-V compounds, such as gallium nitride. BN crystallizes into a layered or a tetrahedrally linked structure, like those of graphite and diamond, respectively, depending on the conditions of its preparation, especially the pressure applied. Such correspondence between BN and carbon readily can be understood from their isoelectronic structures [1, 2]. On the other hand, in contrast to graphite, layered BN ismore » transparent and is an insulator. This material has attracted great interest because, similar to carbon, it exists in various polymorphic forms exhibiting very different properties; however, these forms do not correspond strictly to those of carbon. Crystallographically, BN is classified into four polymorphic forms: Hexagonal BN (h-BN) (Figure 1(b)); rhombohedral BN (r-BN); cubic BN (c-BN); and wurtzite BN (w-BN). BN does not occur in nature. In 1842, Balmain [3] obtained BN as a reaction product between molten boric oxide and potassium cyanide under atmospheric pressure. Thereafter, many methods for its synthesis were reported. h-BN and r-BN are formed under ambient pressure. c-BN is synthesized from h-BN under high pressure at high temperature while w-BN is prepared from h-BN under high pressure at room temperature [1]. Each BN layer consists of stacks of hexagonal plate-like units of boron and nitrogen atoms linked by SP{sup 2} hybridized orbits and held together mainly by Van der Waals force (Fig 1(b)). The hexagonal polymorph has two-layered repeating units: AA'AA'... that differ from those in graphite: ABAB... (Figure 1(a)). Within the layers of h-BN there is coincidence between the same phases of the hexagons, although the boron atoms and nitrogen atoms are alternatively located along the c-axis. The rhombohedral system consists of three-layered units: ABCABC..., whose honeycomb layers are arranged in a shifted phase, like as those of graphite. Reflecting its weak interlayer bond, the h-BN can be cleaved easily along its layers, and hence, is widely used as a lubricant material. The material is stable up to a high temperature of 2300 C before decomposition sets in [2] does not fuse a nitrogen atmosphere of 1 atm, and thus, is applicable as a refractory material. Besides having such properties, similar to those of graphite, the material is transparent, and acts as a good electric insulator, especially at high temperatures (10{sup 6} {Omega}m at 1000 C) [1]. c-BN and w-BN are tetrahedrally linked BN. The former has a cubic sphalerite-type structure, and the latter has a hexagonal wurtzite-type structure. c-BN is the second hardest known material (the hardest is diamond), the so-called white diamond. It is used mainly for grinding and cutting industrial ferrous materials because it does not react with molten iron, nickel, and related alloys at high temperatures whereas diamond does [1]. It displays the second highest thermal conductivity (6-9 W/cm.deg) after diamond. This chapter focuses principally upon information about h-BN nanomaterials, mainly BN nanotubes (BNNTs), porous BN, mono- and few-layer-BN sheets. There are good reviews book chapters about c-BN in [1, 4-6].« less

Delta-Ferrite Distribution in a Continuous Casting Slab of Fe-Cr-Mn Austenitic Stainless Steel

NASA Astrophysics Data System (ADS)

Chen, Chao; Cheng, Guoguang

2017-10-01

The delta-ferrite distribution in a continuous casting slab of Fe-Cr-Mn stainless steel grade (200 series J4) was analyzed. The results showed that the ferrite fraction was less than 3 pct. The "M" type distribution was observed in the thickness direction. For the distribution at the centerline, the maximum ferrite content was found in the triangular zone of the macrostructure. In addition, in this zone, the carbon and sulfur were severely segregated. Furthermore, an equilibrium solidification calculation by Thermo-Calc® software indicates that the solidification mode of the composition in this triangular zone is the same as the solidification mode of the averaged composition, i.e., the FA (ferrite-austenite) mode. None of the nickel-chromium equivalent formulas combined with the Schaeffler-type diagram could predict the ferrite fraction of the Cr-Mn stainless steel grade in a reasonable manner. The authors propose that more attention should be paid to the development of prediction models for the ferrite fraction of stainless steels under continuous casting conditions.

Morphology and properties of low-carbon bainite

NASA Astrophysics Data System (ADS)

Ohtani, H.; Okaguchi, S.; Fujishiro, Y.; Ohmori, Y.

1990-03-01

Morphology of low-carbon bainite in commercial-grade high-tensile-strength steels in both isothermal transformation and continuous cooling transformation is lathlike ferrite elongated in the <11l>b direction. Based on carbide distribution, three types of bainites are classified: Type I, is carbide-free, Type II has fine carbide platelets lying between laths, and Type III has carbides parallel to a specific ferrite plane. At the initial stage of transformation, upper bainitic ferrite forms a subunit elongated in the [-101]f which is nearly parallel to the [lll]b direction with the cross section a parallelogram shape. Coalescence of the subunit yields the lathlike bainite with the [-101]f growth direction and the habit plane between (232)f and (lll)f. Cementite particles precipitate on the sidewise growth tips of the Type II bainitic ferrite subunit. This results in the cementite platelet aligning parallel to a specific ferrite plane in the laths after coalescence. These morphologies of bainites are the same in various kinds of low-carbon high-strength steels. The lowest brittle-ductile transition temperature and the highest strength were obtained either by Type III bainite or bainite/martensite duplex structure because of the crack path limited by fine unit microstructure. It should also be noted that the tempered duplex structure has higher strength than the tempered martensite in the tempering temperature range between 200 °C and 500 °C. In the case of controlled rolling, the accelerated cooling afterward produces a complex structure comprised of ferrite, cementite, and martensite as well as BI-type bainite. Type I bainite in this structure is refined by controlled rolling and plays a very important role in improving the strength and toughness of low-carbon steels.

Development of a low-cost double rotor axial flux motor with soft magnetic composite and ferrite permanent magnet materials

NASA Astrophysics Data System (ADS)

Liu, Chengcheng; Zhu, Jianguo; Wang, Youhua; Guo, Youguang; Lei, Gang; Liu, Xiaojing

2015-05-01

This paper proposes a low-cost double rotor axial flux motor (DRAFM) with low cost soft magnetic composite (SMC) core and ferrite permanent magnets (PMs). The topology and operating principle of DRAFM and design considerations for best use of magnetic materials are presented. A 905 W 4800 rpm DRAFM is designed for replacing the high cost NdFeB permanent magnet synchronous motor (PMSM) in a refrigerator compressor. By using the finite element method, the electromagnetic parameters and performance of the DRAFM operated under the field oriented control scheme are calculated. Through the analysis, it is shown that that the SMC and ferrite PM materials can be good candidates for low-cost electric motor applications.

Highly efficient solid state magnetoelectric gyrators

NASA Astrophysics Data System (ADS)

Leung, Chung Ming; Zhuang, Xin; Friedrichs, Daniel; Li, Jiefang; Erickson, Robert W.; Laletin, V.; Popov, M.; Srinivasan, G.; Viehland, D.

2017-09-01

An enhancement in the power-conversion-efficiency (η) of a magneto-electric (ME) gyrator has been found by the use of Mn-substituted nickel zinc ferrite. A trilayer gyrator of Mn-doped Ni0.8Zn0.2Fe2O3 and Pb(Zr,Ti)O3 has η = 85% at low power conditions (˜20 mW/in3) and η ≥ 80% at high power conditions (˜5 W/in3). It works close to fundamental electromechanical resonance in both direct and converse modes. The value of η is by far the highest reported so far, which is due to the high mechanical quality factor (Qm) of the magnetostrictive ferrite. Such highly efficient ME gyrators with a significant power density could become important elements in power electronics, potentially replacing electromagnetic and piezoelectric transformers.

Microstructural and thermal properties of pure BaFe{sub 12}O{sub 19} and Sr doped barium ferrite (Ba{sub 0.9}Sr{sub 0.1}Fe{sub 12}O{sub 19}) synthesized by auto combustion method

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

Taufeeq, Saba, E-mail: sabataufeeq23@gmail.com; Parveen, Azra; Agrawal, Shraddha

2016-05-23

Nanoparticles (NPs) of Pure BaFe{sub 12}O{sub 19} and Strontium doped Barium Ferrite (Ba{sub 0.9}Sr{sub 0.1}Fe{sub 12}O{sub 19}) have been successfully synthesized by Auto combustion method using citric acid as a chelating agent and calcined at 450°C for 3 hrs and 850°C for 4 hrs. Microstructural studies were carried by XRD and SEM techniques. Structural studies suggest that the crystal system remains hexagonal even with the doping of Strontium. The XRD analysis confirms the formation of the structures in the nanometer regime and the peaks are the evidence of the crystalline phase. The SEM images shows the morphology of surface ofmore » the samples. The thermal property studied by TGA shows the weight loss which is with varying the temperature and weight loss also varies with Sr doping. The TGA analysis exhibits the loss of weight at different temperatures.« less

Method for preparing spherical ferrite beads and use thereof

DOEpatents

Lauf, Robert J.; Anderson, Kimberly K.; Montgomery, Frederick C.; Collins, Jack L.

2002-01-01

The invention allows the fabrication of small, dense, highly polished spherical beads of hexagonal ferrites with selected compositions for use in nonreciprocal microwave and mm-wave devices as well as in microwave absorbent or reflective coatings, composites, and the like. A porous, generally spherical bead of hydrous iron oxide is made by a sol-gel process to form a substantially rigid bead having a generally fine crystallite size and correspondingly finely distributed internal porosity. The resulting gel bead is washed and hydrothermally reacted with a soluble alkaline earth salt (typically Ba or Sr) under conditions of elevated temperature and pressure to convert the bead into a mixed hydrous iron-alkaline earth oxide while retaining the generally spherical shape. This mixed oxide bead is then washed, dried, and calcined to produce the desired (BaFe.sub.12 O.sub.19 or SrFe.sub.12 O.sub.19) crystal structure. The calcined bead is then sintered to form a dense bead of the BaFe.sub.12 O.sub.19 and SrFe.sub.12 O.sub.19 phase suitable for polishing and incorporation into various microwave devices and components.

Colloidal approach to dispersion and enhanced deaggregation of aqueous ferrite suspensions

NASA Astrophysics Data System (ADS)

Mandanas, Michael Patrick M.

The role of solution and surface chemistry on deaggregation of calcined ferrites during attrition (stirred-media) milling of aqueous suspensions were investigated. Suspensions of commercially calcined Fe2O 3 powder (d50 ˜ 5.0 mum) were milled at different solid loadings and suspension pH. The drift of suspension pH, from pH 2.5 to pH 7.0, during solid loading experiments accounted for the observed reagglomeration with milling time. The observed deaggregation rates during pH stat milling, in the acidic region, can be related to (i) elevated solubility and (ii) enhanced dispersion via surface charge. Proton adsorption density during pH stat milling at different pH values is also comparable to existing potentiometric titration plots and can be related to deaggregation rates. A passivation-dispersion approach for dispersing manganese zinc ferrite (MnxZn(1 - x)Fe2O4) powder is presented. Addition of oxalic acid can help control dissolution reactions from particle surfaces and is subsequently dispersed with polyethyleneimine (PEI). Fully dissociated oxalic acid (pK1 = 1.2, pK2 = 4.3) solutions reacted with MnxZn(1 - x)Fe 2O4 leads to the formation of a uniform negative charge on the particle surface, resulting from the sparingly soluble salt formed on the surface. The resulting rheological data for passivation/dispersion of relatively high solid MnxZn(1 - x)Fe2O 4 suspensions (˜80 w/o, (˜40 v/o)) demonstrate improved colloid stability with improved rheological properties. Using the passivation dispersion scheme developed, deaggregation of commercially calcined MnxZn(1 - x)Fe2O4 powders during attrition milling was investigated. Reagglomeration is apparent when using a typical treatment, 2 w/w of a sulfonated based naphthalene condensate, during deaggregation of the calcined MnxZn(1 - x)Fe 2O4. However, is not observed for select oxalate/PEI treatments. The determined ideal treatment is 2 w/w oxalate and 3 w/w PEI based on the particle size and rheological characteristics of the suspensions during milling. (Abstract shortened by UMI.)

Performance of ferritic stainless steels for automobile muffler corrosion

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

Tarutani, Y.; Hashizume, T.

1995-11-01

Corrosion behavior of ferritic stainless steels was studied in artificial exhaust gas condensates containing corrosive ions such as Cl{sup {minus}} and SO{sub 3}{sup 2{minus}}. Continuous immersion tests in flasks and Dip and Dry tests by using the alternate corrosion tester with a heating system clarified the effects of chromium and molybdenum additions on the corrosion resistance of a ferritic stainless steel in the artificial exhaust gas condensates. Effects of surface oxidation on the corrosion behavior were investigated in a temperature range of 573K to 673K. Oxidation of 673K reduced the corrosion resistance of the ferritic stainless steels in the artificialmore » environment of the automobile muffler. Particulate matter deposited on the muffler inner shell from the automobile exhaust gas was also examined. Deposited particulate matter increased the corrosion rate of the ferritic stainless steel. Finally, the authors also investigated the corrosion of the automobile mufflers made of Type 436L ferritic stainless steel with 18% chromium-1.2% molybdenum after 24 months, in Japan. The sets of results clarified that Type 436L ferritic stainless steel as the material for the automobile muffler exhibited acceptable corrosion resistance.« less

A preliminary ferritic-martensitic stainless steel constitution diagram

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

Balmforth, M.C.; Lippold, J.C.

1998-01-01

This paper describes preliminary research to develop a constitution diagram that will more accurately predict the microstructure of ferritic and martensitic stainless steel weld deposits. A button melting technique was used to produce a wide range of compositions using mixtures of conventional ferritic and martensitic stainless steels, including types 403, 409, 410, 430, 439 and 444. These samples were prepared metallographically, and the vol-% ferrite and martensite was determined quantitatively. In addition, the hardness and ferrite number (FN) were measured. Using this data, a preliminary constitution diagram is proposed that provides a more accurate method for predicting the microstructures ofmore » arc welds in ferritic and martensitic stainless steels.« less

Cr-W-V bainitic/ferritic steel with improved strength and toughness and method of making

DOEpatents

Klueh, R.L.; Maziasz, P.J.

1994-03-08

This work describes a high strength, high toughness bainitic/ferritic steel alloy comprising about 2.75% to 4.0% chromium, about 2.0% to 3.5% tungsten, about 0.10% to 0.30% vanadium, and about 0.1% to 0.15% carbon with the balance iron, wherein the percentages are by total weight of the composition, wherein the alloy having been heated to an austenitizing temperature and then cooled at a rate sufficient to produce carbide-free acicular bainite. 15 figures.

Tritium Effects on Fracture Toughness of Stainless Steel Weldments

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

MORGAN, MICHAEL; CHAPMAN, G. K.; TOSTEN, M. H.

2005-05-12

The effects of tritium on the fracture toughness properties of Type 304L and Type 21-6-9 stainless steel weldments were measured. Weldments were tritium-charged-and-aged and then tested in order to measure the effect of the increasing decay helium content on toughness. The results were compared to uncharged and hydrogen-charged samples. For unexposed weldments having 8-12 volume percent retained delta ferrite, fracture toughness was higher than base metal toughness. At higher levels of weld ferrite, the fracture toughness decreased to values below that of the base metal. Hydrogen-charged and tritium-charged weldments had lower toughness values than similarly charged base metals and toughnessmore » decreased further with increasing weld ferrite content. The effect of decay helium content was inconclusive because of tritium off-gassing losses during handling, storage and testing. Fracture modes were dominated by the dimpled rupture process in unexposed weldments. In hydrogen and tritium-exposed weldments, the fracture modes depended on the weld ferrite content. At high ferrite contents, hydrogen-induced transgranular fracture of the weld ferrite phase was observed.« less

Self-Association Process of a Peptide in Solution: From β-Sheet Filaments to Large Embedded Nanotubes

PubMed Central

Valéry, C.; Artzner, F.; Robert, B.; Gulick, T.; Keller, G.; Grabielle-Madelmont, C.; Torres, M.-L.; Cherif-Cheikh, R.; Paternostre, M.

2004-01-01

Lanreotide is a synthetic octapeptide used in the therapy against acromegaly. When mixed with pure water at 10% (w/w), Lanreotide (acetate salt) forms liquid crystalline and monodisperse nanotubes with a radius of 120 Å. The molecular and supramolecular organization of these structures has been determined in a previous work as relying on the lateral association of 26 β-sheet filaments made of peptide noncovalent dimers, the basic building blocks. The work presented here has been devoted to the corresponding self-association mechanisms, through the characterization of the Lanreotide structures formed in water, as a function of peptide (acetate salt) concentration (from 2% to 70% (w/w)) and temperature (from 15°C to 70°C). The corresponding states of water were also identified and quantified from the thermal behavior of water in the Lanreotide mixtures. At room temperature and below 3% (w/w) Lanreotide acetate in water, soluble aggregates were detected. From 3% to 20% (w/w) long individual and monodisperse nanotubes crystallized in a hexagonal lattice were evidenced. Their molecular and supramolecular organizations are identical to the ones characterized for the 10% (w/w) sample. Heating induces the dissolution of the nanotubes into soluble aggregates of the same structural characteristics as the room temperature ones. The solubilization temperature increases from 20°C to 70°C with the peptide concentration and reaches a plateau between 15% and 25% (w/w) in peptide. These aggregates are proposed to be the β-sheet filaments that self-associate to build the walls of the nanotubes. Above 20% (w/w) of Lanreotide acetate in water, polydisperse embedded nanotubes are formed and the hexagonal lattice is lost. These embedded nanotubes exhibit the same molecular and supramolecular organizations as the individual monodisperse nanotubes formed at lower peptide concentration. The embedded nanotubes do not melt in the range of temperature studied indicating a higher thermodynamic stability than individual nanotubes. In parallel, the thermal behaviors of water in mixtures containing 2–80% (w/w) in peptide have been studied by differential scanning calorimetry, and three different types of water were characterized: 1), bulk water melting at 0°C, 2), nonfreezing water, and 3), interfacial water melting below 0°C. The domains of existence and coexistence of these different water states are related to the different Lanreotide supramolecular structures. All these results were compiled into a binary Lanreotide-water phase diagram and allowed to propose a self-association mechanism of Lanreotide filaments into monodisperse individual nanotubes and embedded nanotubes. PMID:15041685

Tungsten - Yttrium Based Nuclear Structural Materials

NASA Astrophysics Data System (ADS)

Ramana, Chintalapalle; Chessa, Jack; Martinenz, Gustavo

2013-04-01

The challenging problem currently facing the nuclear science community in this 21st century is design and development of novel structural materials, which will have an impact on the next-generation nuclear reactors. The materials available at present include reduced activation ferritic/martensitic steels, dispersion strengthened reduced activation ferritic steels, and vanadium- or tungsten-based alloys. These materials exhibit one or more specific problems, which are either intrinsic or caused by reactors. This work is focussed towards tungsten-yttrium (W-Y) based alloys and oxide ceramics, which can be utilized in nuclear applications. The goal is to derive a fundamental scientific understanding of W-Y-based materials. In collaboration with University of Califonia -- Davis, the project is designated to demonstrate the W-Y based alloys, ceramics and composites with enhanced physical, mechanical, thermo-chemical properties and higher radiation resistance. Efforts are focussed on understanding the microstructure, manipulating materials behavior under charged-particle and neutron irradiation, and create a knowledge database of defects, elemental diffusion/segregation, and defect trapping along grain boundaries and interfaces. Preliminary results will be discussed.

Dynamic strain aging behavior of modified 9Cr-1Mo and reduced activation ferritic martensitic steels under low cycle fatigue

NASA Astrophysics Data System (ADS)

Mariappan, K.; Shankar, Vani; Sandhya, R.; Prasad Reddy, G. V.; Mathew, M. D.

2013-04-01

Influence of temperature and strain rate on low cycle fatigue (LCF) behavior of modified 9Cr-1Mo ferritic martensitic steel and 1.4W-0.06Ta reduced activation ferritic martensitic (RAFM) steel in normalized and tempered conditions was studied. Total strain controlled LCF tests between 300 and 873 K on modified 9Cr-1Mo steel and RAFM steel and at various strain rates on modified 9Cr-1Mo steel were performed at total strain amplitude of ±0.6%. Both the steels showed continuous cyclic softening at all temperatures. Whereas manifestations of dynamic strain aging (DSA) were observed in both the steels which decreased fatigue life at intermediate temperatures, at higher temperatures, oxidation played a crucial role in decreasing fatigue life.

High-pressure Phase Relation In The MgAl2O4-Mg2SiO4 System

NASA Astrophysics Data System (ADS)

Kojitani, H.; Hisatomi, R.; Akaogi, M.

2005-12-01

High-pressure and high-temperature experiments indicate that high-pressure phases of oceanic basalts contain Al-rich phases. MgAl2O4 with calcium ferrite-type crystal structure is considered as a main component of such the Al-rich phases. Since the calcium ferrite-type MgAl2O4 can be synthesized at only the maximum pressure of a Kawai-type high-pressure apparatus with tungsten carbide (WC) anvils, the amount of a synthesized sample is very limited. Therefore, the crystal structure of the calcium ferrite-type MgAl2O4 has been hardly known in detail due to these difficulties in sample synthesis. In our high-pressure experiments in the MgO-Al2O3-SiO2 system, it was shown that Mg2SiO4 component could be dissolved in the MgAl2O4 calcium ferrite. In this study, we tried to synthesize a single phase MgAl2O4 calcium ferrite sample and to make the Rietveld refinement of the XRD pattern of the sample. The high-pressure phase relations in the MgAl2O4-Mg2SiO4 system were studied to know the stability field of the MgAl2O4-Mg2SiO4 calcium ferrite solid solutions. Lattice parameters-composition relation of the MgAl2O4-Mg2SiO4 calcium ferrite solid solutions was also determined. High-pressure and high-temperature experiments were performed by using a Kawai-type high-pressure apparatus at Gakushuin University. WC anvils with truncated edge length of 1.5 mm were used. Heating was made by a Re heater. Temperature was measured by a Pt/Pt-13%Rh thermocouple. Starting materials for the phase relation experiments were the mixture of MgO, Al2O3 and SiO2 with bulk compositions of MgAl2O4:Mg2SiO4 = 90:10, 78:22, 70:30 and 50:50. The starting materials were held at 21-27 GPa and 1600 °C for 3 hours and then were recovered by the quenching method. The MgAl2O4 calcium ferrite sample for the Rietveld analysis was prepared by heating MgAl2O4 spinel at 27 GPa and about 2200 °C for one hour. Powder X-ray diffraction (XRD) profiles of obtained samples were measured by using a X-ray diffractometer at Gakushuin University (RINT 2500V, Cr Kα, 45 kV, 250 mA). Composition analysis of the recovered samples was made using SEM-DES. The RIETAN-2000 program was used to perform the Rietveld refinement. The results of the high-pressure phase relation experiments show that stability field of single phase of MgAl2O4-Mg2SiO4 solid solutions spreads at lower pressure than that of pure MgAl2O4 calcium ferrite. The lowest pressure at which the calcium ferrite solid solution can be synthesized is about 23 GPa. The maximum solubility of Mg2SiO4 component is about 35%. Lattice parameters of pure MgAl2O4 calcium ferrite were determined as a = 9.9495(6) Å, b = 8.6466(5) Å, c = 2.7901(2) Å ( Pbnm space group) by the Rietveld refinement. Obtained atomic positions for calcium ferrite-type MgAl2O4 are very similar to those of CaFe2O4 calcium ferrite. Lattice parameters of MgAl2O4-Mg2SiO4 calcium ferrite solid solutions with various compositions indicate that c-axis does not change with the composition and that a- and b-axes have a linear increase and decrease trend with increasing Mg2SiO4 component, respectively.

The Influence of Al+++ Substitution for Fe+++ in M-Type Ba Ferrite Powder on the Intrinsic Coercivity HcJ

NASA Astrophysics Data System (ADS)

Zheng, Zong-Yu; Feng, Jie; Mei, Xue-Ming; Guo, Bi-Jun; Zhang,

1990-05-01

The influence of Al+++ Substitution for Fe+++ in M-type Ba ferrite on the magnetocrystalline anisotropy field HA and the critical single-domain radius Rc has been studied by Haneda and Kojima. It is difficult to obtain HcJ values agreeing with theoretical results for the reason that the HcJ is very sensitive to the preparation method. We have been developing a new method called “coprecipitation combined with high-temperature melting.” It offers a suitable condition for studying the rule of HcJ of Ba Fe12-xAlxO19. Our results conformed to the effects calculated by Haneda and Kojima. The highest level of HcJ in our experiment reached 16000 Oe. We have fabricated plastic sheet magnets from the superhigh HcJ ferrite powder and padded the soft ferrite core with this sheet magnet to adjust the bias magnetic field. This ferrite core can be improved and the weight and size of the device can be reduced.

Effect of Heat Input on Microstructure Evolution and Mechanical Properties in the Weld Heat-Affected Zone of 9Cr-2W-VTa Reduced Activation Ferritic-Martensitic Steel for Fusion Reactor

NASA Astrophysics Data System (ADS)

Moon, Joonoh; Lee, Chang-Hoon; Lee, Tae-Ho; Kim, Hyoung Chan

2015-01-01

The phase transformation and mechanical properties in the weld heat-affected zone (HAZ) of a reduced activation ferritic/martensitic steel were explored. The samples for HAZs were prepared using a Gleeble simulator at different heat inputs. The base steel consisted of tempered martensite and carbides through quenching and tempering treatment, whereas the HAZs consisted of martensite, δ-ferrite, and a small volume of autotempered martensite. The prior austenite grain size, lath width of martensite, and δ-ferrite fraction in the HAZs increased with increase in the heat input. The mechanical properties were evaluated using Vickers hardness and Charpy V-notch impact test. The Vickers hardness in the HAZs was higher than that in the base steel but did not change noticeably with increase in the heat input. The HAZs showed poor impact property due to the formation of martensite and δ-ferrite as compared to the base steel. In addition, the impact property of the HAZs deteriorated more with the increase in the heat input. Post weld heat treatment contributed to improve the impact property of the HAZs through the formation of tempered martensite, but the impact property of the HAZs remained lower than that of base steel.

van der Waals heterostructures of germanene, stanene, and silicene with hexagonal boron nitride and their topological domain walls

NASA Astrophysics Data System (ADS)

Wang, Maoyuan; Liu, Liping; Liu, Cheng-Cheng; Yao, Yugui

2016-04-01

We investigate van der Waals (vdW) heterostructures made of germanene, stanene, or silicene with hexagonal boron nitride (h-BN). The intriguing topological properties of these buckled honeycomb materials can be maintained and further engineered in the heterostructures, where the competition between the substrate effect and external electric fields can be used to control the tunable topological phase transitions. Using such heterostructures as building blocks, various vdW topological domain walls (DW) are designed, along which there exist valley polarized quantum spin Hall edge states or valley-contrasting edge states which are protected by valley(spin)- resolved topological charges and can be tailored by the patterning of the heterojunctions and by external fields.

Crystallization and preliminary characterization of a highly thermostable lectin from Trichosanthes dioica and comparison with other Trichosanthes lectins

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

Dharkar, Poorva D.; Anuradha, P.; Gaikwad, Sushama M.

2006-03-01

A lectin from Trichosanthes dioica seeds has been purified and crystallized using 25%(w/v) PEG 2K MME, 0.2 M ammonium acetate, 0.1 M Tris–HCl pH 8.5 and 50 µl 0.5%(w/v) n-octyl β-d-glucopyranoside as thick needles belonging to hexagonal space group P6{sub 4}. A lectin from Trichosanthes dioica seeds has been purified and crystallized using 25%(w/v) PEG 2K MME, 0.2 M ammonium acetate, 0.1 M Tris–HCl pH 8.5 and 50 µl 0.5%(w/v) n-octyl β-d-glucopyranoside as thick needles belonging to hexagonal space group P6{sub 4}. Unit-cell parameters were a = b = 167.54, c = 77.42 Å. The crystals diffracted to a Braggmore » spacing of 2.8 Å. Both the structures of abrin-a and T. kirilowii lectin could be used as a model in structure determination using the molecular-replacement method; however, T. kirilowii lectin coordinates gave better values of reliability and correlation parameters. The thermal, chemical and pH stability of this lectin have also been studied. When heated, its haemagglutination activity remained unaffected up to 363 K. Other stability studies show that 4 M guanidinium hydrochloride (Gdn–HCl) initiates unfolding and that the protein is completely unfolded at 6 M Gdn–HCl. Treatment with urea resulted in a total loss of activity at higher concentrations of denaturant with no major structural changes. The protein remained stable over a wide pH range, from pH 6 to pH 12, except for partial unfolding at extremely alkaline pH. The role of disulfide bonds in the protein stability was found to be insignificant. Rayleigh light-scattering studies showed no molecular aggregation in any of the extreme treated conditions. The unusual stability of this lectin resembles that of type II ribosome-inactivating proteins (type II RIPs), which is also supported by structure determination. The structural features observed in a preliminary electron-density map were compared with the other two available Trichosanthes lectin structures.« less

Emulation of reactor irradiation damage using ion beams

DOE PAGES

Was, G. S.; Jiao, Z.; Getto, E.; ...

2014-06-14

The continued operation of existing light water nuclear reactors and the development of advanced nuclear reactor depend heavily on understanding how damage by radiation to levels degrades materials that serve as the structural components in reactor cores. The first high dose ion irradiation experiments on a ferritic-martensitic steel showing that ion irradiation closely emulates the full radiation damage microstructure created in-reactor are described. Ferritic-martensitic alloy HT9 (heat 84425) in the form of a hexagonal fuel bundle duct (ACO-3) accumulated 155 dpa at an average temperature of 443°C in the Fast Flux Test Facility (FFTF). Using invariance theory as a guide,more » irradiation of the same heat was conducted using self-ions (Fe++) at 5 MeV at a temperature of 460°C and to a dose of 188 displacements per atom. The void swelling was nearly identical between the two irradiation and the size and density of precipitates and loops following ion irradiation are within a factor of two of those for neutron irradiation. The level of agreement across all of the principal microstructure changes between ion and reactor irradiation establishes the capability of tailoring ion irradiation to emulate the reactor-irradiated microstructure.« less

Low-Temperature Aging Characteristics of Type 316L Stainless Steel Welds: Dependence on Solidification Mode

NASA Astrophysics Data System (ADS)

Abe, Hiroshi; Watanabe, Yutaka

2008-06-01

Thermal aging embrittlement of light water reactor (LWR) components made of stainless steel cast has been recognized as a potential degradation issue, and careful attention has been paid to it. Although welds of austenitic stainless steels have γ-δ duplex microstructure, which is similar to that of the stainless steel cast, examination of the thermal aging characteristics of the stainless steel welds is very limited. In this investigation, two types of type 316L stainless steel weld metal with different solidification modes were prepared using two kinds of filler metals having tailored Ni equivalent and Cr equivalent. Differences between the two weld metals in the morphology of microstructure, in the composition of δ-ferrite, and in hardening behaviors with isothermal aging at 335 °C have been investigated. The hardness of the ferrite phase has increased with aging time, while the hardness of austenite phase has stayed the same. The mottled aspect has been observed in δ-ferrite of aged samples by transmission electron microscopy (TEM) observation. These characteristics suggest that spinodal decomposition has occurred in δ-ferrite by aging at 335 °C. The age-hardening rate of δ-ferrite was faster for the primary austenite solidification mode (AF mode) sample than the primary ferrite solidification mode (FA mode) sample in the initial stage of the aging up to 2000 hours. It has been suggested that the solidification mode can affect the kinetics of spinodal decomposition.

Effect of Proeutectoid Ferrite Morphology on the Microstructure and Mechanical Properties of Hot Rolled 60Si2MnA Spring Steel

NASA Astrophysics Data System (ADS)

Yang, Hu; Wei-qing, Chen; Huai-bin, Han; Rui-juan, Bai

2017-02-01

The hot rolled 60Si2MnA spring steel was transformed to obtain different proeutectoid ferrite morphologies by different cooling rates after finish rolling through dynamic thermal simulation test. The coexistence relationship between proeutectoid ferrite and pearlite, and the effect of proeutectoid ferrite morphology on mechanical properties were systematically investigated. Results showed that the reticular proeutectoid ferrite could be formed by the cooling rates of 0.5-2 °C/s; the small, dispersed and blocky proeutectoid ferrite could be formed by the increased cooling rates of 3-5 °C/s; and the bulk content of proeutectoid ferrite decreased. The pearlitic colony and interlamellar spacing also decreased, the reciprocal of them both followed a linear relationship with the reciprocal of proeutectoid ferrite bulk content. Besides, the tensile strength, percentage of area reduction, impact energy and microhardness increased, which all follow a Hall-Petch-type relationship with the inverse of square root of proeutectoid ferrite bulk content. The fracture morphologies of tensile and impact tests transformed from intergranular fracture to cleavage and dimple fracture, and the strength and plasticity of spring steel were both improved. The results have been explained on the basis of proeutectoid ferrite morphologies-microstructures-mechanical properties relationship effectively.

Hydrothermally formed three-dimensional hexagon-like P doped Ni(OH)2 rod arrays for high performance all-solid-state asymmetric supercapacitors

NASA Astrophysics Data System (ADS)

Li, Kunzhen; Li, Shikuo; Huang, Fangzhi; Lu, Yan; Wang, Lei; Chen, Hong; Zhang, Hui

2018-01-01

Three dimensional hexagon-like phosphrous (P) doped Ni(OH)2 rod arrays grown on Ni foam (NF) are fabricated by a facile and green one-step hydrothermal process. Ni foam is only reacted in a certain concentration of P containing H2O2 aqueous solution. The possible growth mechanism of the P doped Ni(OH)2 rod arrays is discussed. As a battery-type electrode material in situ formed on Ni foam, the binder-free P doped Ni(OH)2 rod arrays electrode displays a ultrahigh specific areal capacitance of 2.11C cm-2 (3.51 F cm-2) at 2 mA cm-2, and excellent cycling stability (95.5% capacitance retention after 7500 cycles). The assembled all-solid-state asymmetric supercapacitor (AAS) based on such P doped Ni(OH)2 rod arrays as the positive electrode and activated carbon as the negative electrode achieves an energy density of 81.3 Wh kg-1 at the power density of 635 W kg-1. The AAS device also exhibits excellent practical performance, which can easily drive an electric fan (3 W rated power) when two AAS devices are assembled in series. Thus, our synthesized P doped Ni(OH)2 rod arrays has a lot of potential applications in future energy storage prospects.

Optical Temperature Sensor Based on Infrared Excited Green Upconversion Emission in Hexagonal Phase NaLuF4:Yb3+/Er3+ Nanorods.

PubMed

Li, Dongyu; Tian, Linlin; Huang, Zhen; Shao, Lexi; Quan, Jun; Wang, Yuxiao

2016-04-01

Hexagonal phase NaLuF4:Yb3+/Er3+ nanorods were synthesized hydrothermally. An analysis of the intense green upconversion emissions at 525 nm and 550 nm in hexagonal phase NaLuF4:Yb3/+Er3+ nanorods under excitation power density of 4.2 W/cm2 available from a diode laser emitting at 976 nm, have been undertaken. Fluorescence intensity ratio (FIR) variation of temperature-sensitive green upconversion emissions at 525 nm and 550 nm in this material was recorded in the physiological range from 295 to 343 K. The maximum sensitivity derived from the FIR technique of the green upconversion emissions is approximately 0.0044 K-1. Experimental results implied that hexagonal phase NaLuF4:Yb3/+Er3+ nanorods was a potential candidate for optical temperature sensor.

Structural investigation of chemically synthesized ferrite magnetic nanomaterials

NASA Astrophysics Data System (ADS)

Uyanga, E.; Sangaa, D.; Hirazawa, H.; Tsogbadrakh, N.; Jargalan, N.; Bobrikov, I. A.; Balagurov, A. M.

2018-05-01

In recent times, interest in ferrite magnetic nanomaterials has considerably grown, mainly due to their highly promising medical and biological applications. Spinel ferrite powder samples, with high heat generation abilities in AC magnetic fields, were studied for their application to the hyperthermia treatment of cancer tumors. These properties of ferrites strongly depend on their chemical composition, ion distribution between crystallographic positions, magnetic structure and method of preparation. In this study, crystal and magnetic structures of several magnetic spinels were investigated by neutron diffraction. The explanation of the mechanism triggering the heat generation ability in the magnetic materials, and the electronic and magnetic states of ferrite-spinel type structures, were theoretically defined by a first-principles method. Ferrites with the composition of CuxMg1-xFe2O4 have been investigated as a heat generating magnetic nanomaterial. Atomic fraction of copper in ferrite was varied between 0 and 100% (that is, x between 0 and 1.0 with 0.2 steps), with the copper dope limit corresponding to appear a tetragonal phase.

Structural and Magnetic Properties Evolution of Co-Nd Substituted M-type Hexagonal Strontium Ferrites Synthesized by Ball-Milling-Assisted Ceramic Process

NASA Astrophysics Data System (ADS)

Chen, Wen; Wu, Wenwei; Zhou, Chong; Zhou, Shifang; Li, Miaoyu; Ning, Yu

2018-03-01

M-type hexagonal Sr1- x Co x Nd x Fe12- x O19 ( x = 0, 0.08, 0.16, and 0.24) has been synthesized by ball milling, followed by calcination in air. The calcined products have been characterized by x-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectra, and vibrating sample magnetometry. XRD and SEM analyses confirm the formation of M-type Sr hexaferrite with platelet-like morphology when Sr1- x Co x Nd x Fe12- x O19 ( x = 0, 0.08, 0.16, and 0.24) precursors are calcined at 950°C in air for 2.5 h. Lattice parameters " a" and " c" values of Sr1- x Co x Nd x Fe12- x O19 reflect a very small variation after doping of Nd3+ and Co2+ ions. Average crystallite size of Sr1- x Co x Nd x Fe12- x O19 sample, calcined at 1150°C, decreased obviously after doping of Co2+ and Nd3+ ions. This is because the bond energy of Nd3+-O2- is much larger than that of Sr2+-O2-. Magnetic characterization indicates that all the samples exhibit good magnetic properties. Substitution of Sr2+ and Fe3+ ions by Nd3+ and Co2+ ions can improve the specific saturation magnetizations and remanence of Sr1- x Co x Nd x Fe12- x O19. Sr0.84Co0.16Nd0.16Fe11.84O19, calcined at 1050°C, has the highest specific saturation magnetization value (74.75 ± 0.60 emu/g), remanence (45.15 ± 0.32 emu/g), and magnetic moment (14.34 ± 0.11 μ B); SrFe12O19, calcined at 1150°C, has the highest coercivity value (4037.01 ± 42.39 Oe). These magnetic parameters make this material a promising candidate for applications such as high-density magnetic recording and microwave absorbing materials.

Heat-Resistant Alloys for Ordnance Materiel and Aircraft and Naval Engine Parts (N-102): Part 1 - Heat Resistant Alloys of the 21%Cr:9%Ni Type

DTIC Science & Technology

1945-06-29

10.555Ni Alloy 22 Sigma and Ferrite In 22.3#r:7.7*Ni Alloy 23 Ferrite Mosaic In 22.3#r:7.7#Ni Alloy 24 Precipitated Carbides In 21.2*Cr:8.7*Ni... ferritic steels and heat resistant cast irons are widely applied. Where plasticity is essential,steels must be used. The irons exhibit some...ductility above 900°F, but they are seldom able to survive sudden thermal or mechanical stresses that exceed their elastic strength. Ferritic steels, of

Microstructure and Charpy impact properties of 12 14Cr oxide dispersion-strengthened ferritic steels

NASA Astrophysics Data System (ADS)

Oksiuta, Z.; Baluc, N.

2008-02-01

This paper describes the microstructure and Charpy impact properties of 12-14 Cr ODS ferritic steels fabricated by mechanical alloying of pure Fe, Cr, W, Ti and Y 2O 3 powders in a Retsch ball mill in argon atmosphere, followed by hot isostatic pressing at 1100 °C under 200 MPa for 4 h and heat treatment at 850 °C for 1 h. Weak Charpy impact properties were obtained in the case of both types of as-hipped materials. In the case of 14Cr materials, the weak Charpy properties appeared related to a bimodal grain size distribution and a heterogeneous dislocation density between the coarse and fine grains. No changes in microstructure were evidenced after heat treatment at 850 °C. Significant improvement in the transition temperature and upper shelf energy of 12Cr materials was obtained by heat treatment at 850 °C for 1 h, which was attributed to the formation of smaller grains, homogenous in size and containing fewer dislocations, with respect to the as-hipped microstructure. This modified microstructure results in a good compromise between strength and Charpy impact properties.

Control of magnetization reversal in oriented strontium ferrite thin films

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

Roy, Debangsu, E-mail: debangsu@physics.iisc.ernet.in; Anil Kumar, P. S.

2014-02-21

Oriented Strontium Ferrite films with the c axis orientation were deposited with varying oxygen partial pressure on Al{sub 2}O{sub 3}(0001) substrate using Pulsed Laser Deposition technique. The angle dependent magnetic hysteresis, remanent coercivity, and temperature dependent coercivity had been employed to understand the magnetization reversal of these films. It was found that the Strontium Ferrite thin film grown at lower (higher) oxygen partial pressure shows Stoner-Wohlfarth type (Kondorsky like) reversal. The relative importance of pinning and nucleation processes during magnetization reversal is used to explain the type of the magnetization reversal with different oxygen partial pressure during growth.

Modulation of magnetic interaction in Bismuth ferrite through strain and spin cycloid engineering

NASA Astrophysics Data System (ADS)

Yadav, Rama Shanker; Reshi, Hilal Ahmad; Pillai, Shreeja; Rana, D. S.; Shelke, Vilas

2016-12-01

Bismuth ferrite, a widely studied room temperature multiferroic, provides new horizons of multifunctional behavior in phase transited bulk and thin film forms. Bismuth ferrite thin films were deposited on lattice mismatched LaAlO3 substrate using pulsed laser deposition technique. X-ray diffraction confirmed nearly tetragonal (T-type) phase of thin film involving role of substrate induced strain. The film thickness of 56 nm was determined by X-ray reflectivity measurement. The perfect coherence and epitaxial nature of T- type film was observed through reciprocal space mapping. The room temperature Raman measurement of T-type bismuth ferrite thin film also verified phase transition with appearance of only few modes. In parallel, concomitant La and Al substituted Bi1-xLaxFe0.95Al0.05O3 (x = 0.1, 0.2, 0.3) bulk samples were synthesized using solid state reaction method. A structural phase transition into orthorhombic (Pnma) phase at x = 0.3 was observed. The structural distortion at x = 0.1, 0.2 and phase transition at x = 0.3 substituted samples were also confirmed by changes in Raman active modes. The remnant magnetization moment of 0.199 emu/gm and 0.28 emu/gm were observed for x = 0.2 and 0.3 bulk sample respectively. The T-type bismuth ferrite thin film also showed high remnant magnetization of around 20emu/cc. The parallelism in magnetic behavior between T-type thin film and concomitant La and Al substituted bulk samples is indication of modulation, frustration and break in continuity of spiral spin cycloid.

Voltage gain optimization of transmission line transformers

NASA Astrophysics Data System (ADS)

Pécastaing, L.; Reess, T.; Paillol, J.; Gibert, A.; Domens, P.

2003-06-01

Transmission Line Transformers (TLT) based on the use of ferrite beads are presented. This work aims at optimising the performance of the voltage gain and the compactness of the TLT according to the position, the type and the number of ferrites used. The ferrites have been selected taking into account two main parameters: the maximum currents flowing through the outer conductor of the lines of a TLT without ferrite beads and the current frequencies. The function of these ferrites is to decrease the effect of parasitic short-circuit transmission lines between the outer conductors of the coaxial cables of the TLT. Voltages and secondary currents are measured on each cable. The voltage gain achieved reaches the optimum theoretical value thanks to the use of ferrites for a 2, 4 and 10-stage transmission line transformer. Each cable is shorter than 1.5 meter in length which provides an unquestionable advantage of compactness.

Enhanced Switchable Ferroelectric Photovoltaic Effects in Hexagonal Ferrite Thin Films via Strain Engineering.

PubMed

Han, Hyeon; Kim, Donghoon; Chu, Kanghyun; Park, Jucheol; Nam, Sang Yeol; Heo, Seungyang; Yang, Chan-Ho; Jang, Hyun Myung

2018-01-17

Ferroelectric photovoltaics (FPVs) are being extensively investigated by virtue of switchable photovoltaic responses and anomalously high photovoltages of ∼10 4 V. However, FPVs suffer from extremely low photocurrents due to their wide band gaps (E g ). Here, we present a promising FPV based on hexagonal YbFeO 3 (h-YbFO) thin-film heterostructure by exploiting its narrow E g . More importantly, we demonstrate enhanced FPV effects by suitably exploiting the substrate-induced film strain in these h-YbFO-based photovoltaics. A compressive-strained h-YbFO/Pt/MgO heterojunction device shows ∼3 times enhanced photovoltaic efficiency than that of a tensile-strained h-YbFO/Pt/Al 2 O 3 device. We have shown that the enhanced photovoltaic efficiency mainly stems from the enhanced photon absorption over a wide range of the photon energy, coupled with the enhanced polarization under a compressive strain. Density functional theory studies indicate that the compressive strain reduces E g substantially and enhances the strength of d-d transitions. This study will set a new standard for determining substrates toward thin-film photovoltaics and optoelectronic devices.

Oil/water nano-emulsion loaded with cobalt ferrite oxide nanocubes for photo-acoustic and magnetic resonance dual imaging in cancer: in vitro and preclinical studies.

PubMed

Vecchione, Raffaele; Quagliariello, Vincenzo; Giustetto, Pierangela; Calabria, Dominic; Sathya, Ayyappan; Marotta, Roberto; Profeta, Martina; Nitti, Simone; Silvestri, Niccolò; Pellegrino, Teresa; Iaffaioli, Rosario V; Netti, Paolo Antonio

2017-01-01

Dual imaging dramatically improves detection and early diagnosis of cancer. In this work we present an oil in water (O/W) nano-emulsion stabilized with lecithin and loaded with cobalt ferrite oxide (Co 0.5 Fe 2.5 O 4 ) nanocubes for photo-acoustic and magnetic resonance dual imaging. The nanocarrier is responsive in in vitro photo-acoustic and magnetic resonance imaging (MRI) tests. A clear and significant time-dependent accumulation in tumor tissue is shown in in vivo photo-acoustic studies on a murine melanoma xenograft model. The proposed O/W nano-emulsion exhibits also high values of r 2 /r 1 (ranging from 45 to 85, depending on the magnetic field) suggesting a possible use as T 2 weighted image contrast agents. In addition, viability and cellular uptake studies show no significant cytotoxicity on the fibroblast cell line. We also tested the O/W nano-emulsion loaded with curcumin against melanoma cancer cells demonstrating a significant cytotoxicity and thus showing possible therapeutic effects in addition to the in vivo imaging. Copyright © 2016 Elsevier Inc. All rights reserved.

Radiation damage studies of ion-irradiated low-activation developmental martensitic steel alloys for fusion applications

NASA Astrophysics Data System (ADS)

Mazey, D. J.; Hanks, W.; Lurcook, O. K.

1990-09-01

Five martensitic, nominally 9 and 11% Cr-W-V-Mn-Ta stainless steels which have been developed as low-activation alloys for fusion-reactor structural applications have been irradiated with 52 MeV Cr 6+ ions to 20 dpa at 475°C in the Harwell Variable Energy Cyclotron (VEC). Four of the alloys contained additions of 0.1 wt% Ta and these had been shown in prior tests to have mechanical properties comparable with the conventional FV 448 alloy. Examinations by TEM showed that irradiation-induced precipitates were present on a fine-scale in all of the alloys. These comprised Cr-rich lath-like defects in the 9Cr, Ta-free alloy; small Cr-rich particles in the 9Cr-3W-0.1Ta alloy and Cr-rich planar precipitates in the remaining alloys. Little or no irradiation-induced cavitation was observed. The other important irradiation-induced response was in the dislocation structure in the Ta-containing alloys which comprised an extensive rafted array of elongated a <100> type dislocation loops having major axes aligned in <100> directions. A significant fraction of the presumed a <100> loops contained stacking-fault fringes and analysis suggested that these were Cr 2N or Fe 4N nitride phase which it is known can form on {001} habit planes. Such nitrides are observed frequently under thermal-annealing conditions in ferritic steels, but less frequently under irradiation. Their formation in relation to the void swelling resistance of ferritic-martensitic alloys is discussed.

Deposition of Lanthanum Strontium Cobalt Ferrite (LSCF) Using Suspension Plasma Spraying for Oxygen Transport Membrane Applications

NASA Astrophysics Data System (ADS)

Fan, E. S. C.; Kesler, O.

2015-08-01

Suspension plasma spray deposition was utilized to fabricate dense lanthanum strontium cobalt ferrite oxygen separation membranes (OSMs) on porous metal substrates for mechanical support. The as-sprayed membranes had negligible and/or reversible material decomposition. At the longer stand-off distance (80 mm), smooth and dense membranes could be manufactured using a plasma with power below approximately 81 kW. Moreover, a membrane of 55 μm was observed to have very low gas leakage rates desirable for OSM applications. This thickness could potentially be decreased further to improve oxygen diffusion by using metal substrates with finer surface pores.

USSR and Eastern Europe Scientific Abstracts Engineering and Equipment No.29

DTIC Science & Technology

1977-02-08

Perlite (12CrlMoV and 12Cr2MoVSib), ferrite - martensite (lCrllW2MoV), and austentite (Crl8Nil2Ti) steels are discussed for use in the heat-transfer...620°C. Other austentite steels have been developed, including EI695R, EP184, EP17, 45Crl0Mnl4Al-2 (which has a 20-40% ferrite phase ), 0Crl3Mnl2Ni2NSi2...middle zone of 10 mm and at the corners -- up to 40 mm. The shell was reinforced with a grid having square meshes of low -carbon steel wire, 1 mm in diam

Investigation of Ta-MX/Z-Phase and Laves Phase as Precipitation Hardening Particles in a 12 Pct Cr Heat-Resistant Steel

NASA Astrophysics Data System (ADS)

Sanhueza, J. P.; Rojas, D.; Prat, O.; García, J.; Meléndrez, M. F.; Suarez, S.

2018-07-01

A 12 pct Cr martensitic/ferritic steel was designed and produced to study Laves and Z-phase as precipitation hardening particles under creep conditions (650 °C). According to thermodynamic calculations, W and Cu additions were selected to ensure the precipitation of Laves after tempering. It is known that Z-phase formation does not follow the classical nucleation theory. Indeed, MX particles are transformed into Z-phase by Cr diffusion from the matrix to the precipitate. Therefore, to promote fast Z-phase formation, Ta, Co, and N additions were used to produce Ta-MX, which will be transformed into Z-phase. The main result achieved was the precipitation of Laves after tempering, with a particle size of 196 nm. As regards to Z-phase, the transformation of Ta-MX into Z-phase after tempering was confirmed by the formation of hybrid nanoparticles of 30 nm. Although W and Ta have a low diffusion in the martensitic/ferritic matrix, characterization of the precipitates after isothermal aging revealed that Laves and Z-phase have fast growth kinetics, reaching 400 and 143 nm, respectively, at 8760 hours. Consequently, creep test at 650 °C showed premature failures after few thousand hours. Therefore, it is expected that future research in the field of martensitic/ferritic steels will focus on the growth and coarsening behavior of Laves and Z-phase.

TEM and HRTEM study of oxide particles in an Al-alloyed high-Cr oxide dispersion strengthened ferritic steel with Hf addition

NASA Astrophysics Data System (ADS)

Dou, Peng; Kimura, Akihiko; Kasada, Ryuta; Okuda, Takanari; Inoue, Masaki; Ukai, Shigeharu; Ohnuki, Somei; Fujisawa, Toshiharu; Abe, Fujio; Jiang, Shan; Yang, Zhigang

2017-03-01

The nanoparticles in an Al-alloyed high-Cr oxide dispersion strengthened (ODS) ferritic steel with Hf addition, i.e., SOC-16 (Fe-15Cr-2W-0.1Ti-4Al-0.62Hf-0.35Y2O3), have been examined by transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). Relative to an Al-alloyed high-Cr ODS ferritic steel without Hf addition, i.e., SOC-9 (Fe-15.5Cr-2W-0.1Ti-4Al-0.35Y2O3), the dispersion morphology and coherency of the oxide nanoparticles in SOC-16 were significantly improved. Almost all the small nanoparticles (diameter <10 nm) in SOC-16 were found to be consistent with cubic Y2Hf2O7 oxides with the anion-deficient fluorite structure and coherent with the bcc steel matrix. The larger particles (diameter >10 nm) were also mainly identified as cubic Y2Hf2O7 oxides with the anion-deficient fluorite structure. The results presented here are compared with those of SOC-9 with a brief discussion of the underlying mechanisms of the unusual thermal and irradiation stabilities of the oxides as well as the superior strength, excellent irradiation tolerance and extraordinary corrosion resistance of SOC-16.

Investigation of Ta-MX/Z-Phase and Laves Phase as Precipitation Hardening Particles in a 12 Pct Cr Heat-Resistant Steel

NASA Astrophysics Data System (ADS)

Sanhueza, J. P.; Rojas, D.; Prat, O.; García, J.; Meléndrez, M. F.; Suarez, S.

2018-05-01

A 12 pct Cr martensitic/ferritic steel was designed and produced to study Laves and Z-phase as precipitation hardening particles under creep conditions (650 °C). According to thermodynamic calculations, W and Cu additions were selected to ensure the precipitation of Laves after tempering. It is known that Z-phase formation does not follow the classical nucleation theory. Indeed, MX particles are transformed into Z-phase by Cr diffusion from the matrix to the precipitate. Therefore, to promote fast Z-phase formation, Ta, Co, and N additions were used to produce Ta-MX, which will be transformed into Z-phase. The main result achieved was the precipitation of Laves after tempering, with a particle size of 196 nm. As regards to Z-phase, the transformation of Ta-MX into Z-phase after tempering was confirmed by the formation of hybrid nanoparticles of 30 nm. Although W and Ta have a low diffusion in the martensitic/ferritic matrix, characterization of the precipitates after isothermal aging revealed that Laves and Z-phase have fast growth kinetics, reaching 400 and 143 nm, respectively, at 8760 hours. Consequently, creep test at 650 °C showed premature failures after few thousand hours. Therefore, it is expected that future research in the field of martensitic/ferritic steels will focus on the growth and coarsening behavior of Laves and Z-phase.

IMPROVED TYPE OF FUEL ELEMENT

DOEpatents

Monson, H.O.

1961-01-24

A radiator-type fuel block assembly is described. It has a hexagonal body of neutron fissionable material having a plurality of longitudinal equal- spaced coolant channels therein aligned in rows parallel to each face of the hexagonal body. Each of these coolant channels is hexagonally shaped with the corners rounded and enlarged and the assembly has a maximum temperature isothermal line around each channel which is approximately straight and equidistant between adjacent channels.

Chain hexagonal cacti with the extremal eccentric distance sum.

PubMed

Qu, Hui; Yu, Guihai

2014-01-01

Eccentric distance sum (EDS), which can predict biological and physical properties, is a topological index based on the eccentricity of a graph. In this paper we characterize the chain hexagonal cactus with the minimal and the maximal eccentric distance sum among all chain hexagonal cacti of length n, respectively. Moreover, we present exact formulas for EDS of two types of hexagonal cacti.

Structural and magnetic properties of Ni-Zn doped BaM nanocomposite via citrate precursor

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

Rana, Kush; Thakur, Preeti; Thakur, Atul, E-mail: atulphysics@gmail.com

2016-05-23

Ni-Zn substituted M-type barium ferrite nanocomposite has been prepared via citrate precursor method. Nanocomposite having composition BaNi{sub 0.5}Zn{sub 0.5}Fe{sub 11}O{sub 19} was sintered at 900°C for 3hrs and characterized by using different characterization techniques. X-ray diffraction (XRD) confirmed the formation of double phase with most prominent peak at (114). Average crystallite size for pure BaM and BNZFO were found to be 36 nm & 45 nm. Field emission scanning electron microscopy (FESEM) confirmed the formation of hexagonal platelets with a layered structure. Magnetic properties of these samples were investigated by using vibrating sample magnetometer (VSM). Magnetic parameters like saturation magnetization (M{sub s}),more » coericivity (H{sub c}) and squareness ratio (SQR) of nanocomposite were found to be 60 emu/g, 3663 Oe and 0.6163 respectively. These values were noticed to be higher as compared to pure BaM. Enhanced magnetic properties of nanocomposite were strongly dependent on exchange coupling. Therefore these properties make this nanocomposite a suitable candidate for magnetic recording and high frequency applications.« less

Ternary nitrogen-doped graphene/nickel ferrite/polyaniline nanocomposites for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Wang, Wenjuan; Hao, Qingli; Lei, Wu; Xia, Xifeng; Wang, Xin

2014-12-01

The electrochemical property of graphene can be significantly enhanced due to the incorporating of heteroatoms into graphene. In this article, the ternary nitrogen-doped graphene/nickel ferrite/polyaniline (NGNP) nanocomposite is synthesized by a facile two-step approach and its electrochemical properties as electrodes for supercapacitors are studied by various electrochemical measurements. The specific capacitance of NGNP is 645.0 F g-1 at 1 mV s-1 and 667.0 F g-1 at 0.1 A g-1 in a three- and two-electrode system, respectively, much higher than other binary electrodes. In a two-electrode symmetric system, the energy density of the NGNP electrode is 92.7 W h kg-1 at a power density of 110.8 W kg-1, moreover, that of the supercapacitor based on NGNP can also reach 23.2 W h kg-1 at a power density of 27.7 W kg-1. In addition, the capacitance loses only 5% after repeating test for 5000 cycles, and about 10% after 10,000 cycles at a high current density 5 A g-1. The results demonstrate the novel ternary NGNP electrode produced by the current economical method will gain promising applications in supercapacitors and other devices by virtue of its outstanding characteristics (high specific capacitance, high power and energy density, excellent cycle life).

Tantalum modified ferritic iron base alloys

NASA Technical Reports Server (NTRS)

Oldrieve, R. E.; Blankenship, C. P. (Inventor)

1977-01-01

Strong ferritic alloys of the Fe-CR-Al type containing 0.4% to 2% tantalum were developed. These alloys have improved fabricability without sacrificing high temperature strength and oxidation resistance in the 800 C (1475 F) to 1040 C (1900 F) range.

Evidence for W=0 pairing in repulsive Hubbard square and hexagonal geometries

NASA Astrophysics Data System (ADS)

Perfetto, Enrico; Stefanucci, Gianluca; Callegari, Agnese; Cini, Michele

2004-08-01

Square and hexagonal lattices with purely repulsive on-site interactions on all sites and appropriate fillings show W=0 pairing, and the effective attractive interaction is due to a symmetry driven correlation effect; the W=0 pairs are two-body singlet eigenstates of the Hamiltonian with vanishing on-site repulsion. We can set up gedanken experiments with these bound pairs. Chains of CuO 4 units connected by weak links provide a test case which displays bound pair hopping and superconducting flux quantization (SFQ). Focusing on the low-energy sector, one obtains an accurate description in terms of an effective hard-core boson Hamiltonian which naturally describes itinerant pairs and SFQ in mesoscopic rings. For the numerical calculations, we take advantage of a recently proposed exact spin-disentangled diagonalization technique which can be generally applied to many-fermion problems and drastically reduces the size of the matrices to be handled. Remarkably, the very same pairing mechanism also works neatly with the wrapped honeycomb lattice, suitable for armchair carbon nanotubes; the binding energy of W=0 pairs depends strongly on the filling and decreases towards a small but non-zero value in the graphite limit.

Studies on Electrical and Magnetic Properties of Mg-Substituted Nickel Ferrites

NASA Astrophysics Data System (ADS)

Chavan, Pradeep; Naik, L. R.; Belavi, P. B.; Chavan, Geeta; Ramesha, C. K.; Kotnala, R. K.

2017-01-01

The semiconducting polycrystalline ferrite materials with the general formula Ni1- x Mg x Fe2O4 were synthesized by using the solid state reaction method. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrographs, and atomic force microscopy techniques were utilized to study the structural parameters. XRD confirms the formation of single phase cubic spinel structure of the ferrites. The crystallite sizes of ferrites determined using the Debye-Scherer formula ranges from 0.963 μm to 1.069 μm. The cation distribution of ferrite shows that Mg2+ ions occupy a tetrahedral site ( A-site) and the Ni2+ ion occupy an octahedral site ( B-site) whereas Fe3+ ions occupies an octahedral as well as a tetrahedral site. The study of elastic parameters such as the longitudinal modulus, rigidity modulus, Young's modulus, bulk modulus, and Debye temperature were estimated using the FTIR technique. The decrease of direct current (DC) resistivity with increase in temperature indicates the semiconducting nature of ferrites. The dielectric constant as well as loss tangent decreases with increase in frequency, and at still higher frequencies, they are almost constant. This shows usual dielectric dispersion behavior attributed to the Maxwell-Wagner type of interfacial polarization and is in accordance with Koop's phenomenological theory. The linear increase of alternating current conductivity with increase of frequency shows the small polaron hopping type of conduction mechanism in all the ferrites. The magnetic properties such as saturation magnetization ( M s ), magnetic moment, coercivity, remnant magnetization ( M r ), and the ratio of M r /M s was estimated using the M-H loop.

Development of Anode-Supported Single Cells and Small Stacks for Intermediate Temperature Sofc at Kepri

NASA Astrophysics Data System (ADS)

Yoo, Y.-S.; Park, J.-W.; Park, J.-K.; Lim, H.-C.; Oh, J.-M.; Bae, J.-M.

Recent results on intermediate temperature-operating solid oxide fuel cells (IT-SOFC) are mainly focused on getting the higher performance of single cell at lower operating temperature, especially using planar type. We have started a project to develop 1 kW-class SOFC system for Residential Power Generation(RPG) application. For a 1 kW-class SOFC stack that can be operated at intermediate temperatures, we have developed anode-supported, planar type SOFC to have advantages for commercialization of SOFCs considering mass production and using cost-effective interconnects such as ferritic stainless steels. At higher temperature, performance of SOFC can be increased due to higher electrochemical activity of electrodes and lower ohmic losses, but the surface of metallic interconnects at cathode side is rapidly oxidized into resistive oxide scale. For efficient operation of SOFC at reduced temperature at, firstly we have developed alternative cathode materials of LSCF instead of LSM to get higher performance of electrodes, and secondly introduced functional-layered structure at anode side. The I-V and AC impedance characteristics of improved single cells and small stacks were evaluated at intermediate temperatures (650°C and 750°C) using hydrogen gas as a fuel.

Atom probe study of vanadium interphase precipitates and randomly distributed vanadium precipitates in ferrite.

PubMed

Nöhrer, M; Zamberger, S; Primig, S; Leitner, H

2013-01-01

Atom probe tomography and transmission electron microscopy were used to examine the precipitation reaction in the austenite and ferrite phases in vanadium micro-alloyed steel after a thermo-mechanical process. It was observed that only in the ferrite phase precipitates could be found, whereupon two different types were detected. Thus, the aim was to reveal the difference between these two types. The first type was randomly distributed precipitates from V supersaturated ferrite and the second type V interphase precipitates. Not only the arrangement of the particles was different also the chemical composition. The randomly distributed precipitates consisted of V, C and N in contrast to that the interphase precipitates showed a composition of V, C and Mn. Furthermore the randomly distributed precipitates had maximum size of 20 nm and the interphase precipitates a maximum size of 15 nm. It was assumed that the reason for these differences is caused by the site in which they were formed. The randomly distributed precipitates were formed in a matrix consisting mainly of 0.05 at% C, 0.68 at% Si, 0.03 at% N, 0.145 at% V and 1.51 at% Mn. The interphase precipitates were formed in a region with a much higher C, Mn and V content. Copyright © 2013 Elsevier Ltd. All rights reserved.

Temperature and frequency characteristics of low-loss MnZn ferrite in a wide temperature range

NASA Astrophysics Data System (ADS)

Sun, Ke; Lan, Zhongwen; Yu, Zhong; Xu, Zhiyong; Jiang, Xiaona; Wang, Zihui; Liu, Zhi; Luo, Ming

2011-05-01

A low-loss Mn0.7Zn0.24Fe2.06O4 ferrite has been prepared by a solid-state reaction method. The MnZn ferrite has a high initial permeability, μi (3097), a high saturation induction, Bs (526 mT), a high Curie temperature, Tc (220 °C), and a low core loss, PL (≤ 415 kW/m3) in a wide temperature (25-120 °C) and frequency (10-100 kHz) range. As the temperature increases, an initial decrease followed by a subsequent increase of hysteresis loss, Ph, and eddy current loss, Pe is observed. Both Ph and Pe increase with increasing frequency. When f ≥ 300 kHz, a residual loss, Pr, appears. Pe increases with increasing temperature and frequency. The temperature and frequency dependence of Ph can be explained by irreversible domain wall movements, Pe by the skin effect, and Pr by domain wall resonance, respectively.

Development oxide dispersion strengthened ferritic steels for fusion

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

Mukhopadhyay, D.K.; Froes, F.H.; Gelles, D.S.

1997-04-01

Uniaxial tension creep response is reported for an oxide dispersion strengthened (ODS) steel, Fe-13.5Cr-2W-0.5Ti-0.25 Y{sub 2}O{sub 3} (in weight percent) manufactured using the mechanical alloying process. Acceptable creep response is obtained at 900{degrees}C.

The Microstructure and Pitting Resistance of Weld Joints of 2205 Duplex Stainless Steel

NASA Astrophysics Data System (ADS)

Wu, Mingfang; Liu, Fei; Pu, Juan; Anderson, Neil E.; Li, Leijun; Liu, Dashuang

2017-11-01

2205 duplex stainless steel (DSS) was welded by submerged arc welding. The effects of both heat input and groove type on the ferrite/austenite ratio and elemental diffusion of weld joints were investigated. The relationships among welding joint preparation, ferrite/austenite ratio, elemental diffusion, and pitting corrosion resistance of weld joints were analyzed. When the Ni content of the weld wire deposit was at minimum 2-4% higher than that of 2205 DSS base metal, the desired ratio of ferrite/austenite and elemental partitioning between the austenite and ferrite phases were obtained. While the pitting sensitivity of weld metal was higher than that of base metal, the self-healing capability of the passive film of weld metal was better than that of the base metal when a single V-type groove was used. Furthermore, the heat input should be carefully controlled since pitting corrosion occurred readily in the coarse-grained heat-affected zone near the fusion line of welded joints.

Effect of Cu-doping on structural and electrical properties of Ni0.4-xCu0.3+xMg0.3Fe2O4 ferrites prepared using sol-gel method

NASA Astrophysics Data System (ADS)

Dhaou, Mohamed Houcine

2018-06-01

Ni0.4-xCu0.3+xMg0.3Fe2O4 spinel ferrites were prepared by sol-gel technique. X-ray diffraction results indicate that ferrite samples have a cubic spinel-type structure with ? space group. The electrical properties of the studied samples using complex impedance spectroscopy technique have been investigated as a function of frequency at different temperatures. We found that the addition of copper in Ni0.4-xCu0.3+xMg0.3Fe2O4 ferrite system can improve its conductivity. Dielectric properties have been discussed in terms of hopping of charge carriers between Fe2+ and Fe3+ ions. For all samples, frequency dependence of the imaginary part of impedance (Z") shows the existence of relaxation phenomenon. The appropriate equivalent circuit configuration for modeling the Nyquist plots of impedance is of the type of (Rg + Rgb//Cgb).

Prospects and limitations for p-type doping in boron nitride polymorphs

NASA Astrophysics Data System (ADS)

Weston, Leigh; van de Walle, Chris G.

Using first-principles calculations, we examine the potential for p-type doping of BN polymorphs via substitutional impurities. Based on density functional theory with a hybrid functional, our calculations reveal that group-IV elements (C, Si) substituting at the N site result in acceptor levels that are more than 1 eV above the valence-band maximum in all of the BN polymorphs, and hence far too deep to allow for p-type doping. On the other hand, group-II elements (Be, Mg) substituting at the B site lead to shallower acceptor levels. However, for the ground-state hexagonal phase (h-BN), we show that p-type doping at the B site is inhibited by the formation of hole polarons. Our calculations reveal that hole localization is intrinsic to sp2 bonded h-BN, and this places fundamental limits on hole conduction in this material. In contrast, the sp3 bonded wurtzite (w-BN) and cubic (c-BN) polymorphs are capable of forming shallow acceptor levels. For Be dopants, the acceptor ionization energies are 0.31 eV and 0.24 eV for w-BN and c-BN, respectively; these values are only slightly larger than the ionization energy of the Mg acceptor in GaN. This work was supported by NSF.

Low resolution crystal structure of Arenicola erythrocruorin: influence of coiled coils on the architecture of a megadalton respiratory protein.

PubMed

Royer, William E; Omartian, Michael N; Knapp, James E

2007-01-05

Annelid erythrocruorins are extracellular respiratory complexes assembled from 180 subunits into hexagonal bilayers. Cryo-electron microscopic experiments have identified two different architectural classes. In one, designated type I, the vertices of the two hexagonal layers are partially staggered, with one hexagonal layer rotated by about 16 degrees relative to the other layer, whereas in the other class, termed type II, the vertices are essentially eclipsed. We report here the first crystal structure of a type II erythrocruorin, that from Arenicola marina, at 6.2 A resolution. The structure reveals the presence of long continuous triple-stranded coiled-coil "spokes" projecting towards the molecular center from each one-twelfth unit; interdigitation of these spokes provides the only contacts between the two hexagonal layers of the complex. This arrangement contrasts with that of a type I erythrocruorin from Lumbricus terrestris in which the spokes are broken into two triple-stranded coiled coils with a disjointed connection. The disjointed connection allows formation of a more compact structure in the type I architecture, with the two hexagonal layers closer together and additional extensive contacts between the layers. Comparison of sequences of the coiled-coil regions of various linker subunits shows that the linker subunits from type II erythrocruorins possess continuous heptad repeats, whereas a sequence gap places these repeats out of register in the type I linker subunits, consistent with a disjointed coiled-coil arrangement.

Phase composition and microstructure of WC-Co alloys obtained by selective laser melting

NASA Astrophysics Data System (ADS)

Khmyrov, Roman S.; Shevchukov, Alexandr P.; Gusarov, Andrey V.; Tarasova, Tatyana V.

2018-03-01

Phase composition and microstructure of initial WC, BK8 (powder alloy 92 wt.% WC-8 wt.% Co), Co powders, ball-milled powders with four different compositions (1) 25 wt.% WC-75 wt.% Co, (2) 30 wt.% BK8-70 wt.% Co, (3) 50 wt.% WC-50 wt.% Co, (4) 94 wt.% WC-6 wt.% Co, and bulk alloys obtained by selective laser melting (SLM) from as-milled powders in as-melted state and after heat treatment were investigated by scanning electron microscopy and X-ray diffraction analysis. Initial and ball-milled powders consist of WC, hexagonal α-Co and face-centered cubic β-Co. The SLM leads to the formation of major new phases W3Co3C, W4Co2C and face-centered cubic β-Co-based solid solution. During the heat treatment, there occurs partial decomposition of the face-centered cubic β-Co-based solid solution with the formation of W2C and hexagonal α-Co solid solution. The microstructure of obtained bulk samples, in general, corresponds to the observed phase composition.

Effect of W and N on mechanical properties of reduced activation ferritic/martensitic EUROFER-based steel grades

NASA Astrophysics Data System (ADS)

Puype, A.; Malerba, L.; De Wispelaere, N.; Petrov, R.; Sietsma, J.

2018-04-01

The C, N, and W content in EUROFER97, a 9CrWVTa reduced-activation ferritic/martensitic (RAFM) steel, was varied to obtain an experimental assessment of the main effects of the compositional variation on the mechanical properties and microstructural characteristics of six different experimental grades. Light optical microscopy (LOM) and electron back-scattered diffraction (EBSD) revealed in almost all cases a fine tempered lath martensite structure. Analyses of transmission electron micrographs, together with inductively coupled plasma mass spectrometry (ICPMS) and energy-dispersive x-ray spectroscopy (EDS) data, shows the precipitation state and spatial distribution of MxCy (M = Cr, W and Fe) and MX (M = V and/or Ta, X = C or N) carbonitrides within the matrix. The mechanical characterization of the six different steel grades was carried out by means of A50 tensile testing and Charpy tests on standard specimens (55 × 10 × 10 mm3). Lowering the carbon content and keeping the nitrogen content higher than 0.02 wt%, leads to a reduction of the ductile-to-brittle-transition-temperature (DBTT) in comparison with EUROFER97-2. The addition of tungsten further reduces the DBTT to - 94 °C, while maintaining good tensile strength and elongation.

Effects of biaxial strains on electronic and elastic properties of hexagonal XSi2 (X = Cr, Mo, W) from first-principles

NASA Astrophysics Data System (ADS)

Zhu, Haiyan; Shi, Liwei; Li, Shuaiqi; Zhang, Shaobo; Xia, Wangsuo

2018-02-01

Structural, electronic properties and elastic anisotropy of hexagonal C40 XSi2 (X = Cr, Mo, W) under equibiaxial in-plane strains are systematically studied using first-principle calculations. The energy gaps show significant changes with biaxial strains, whereas they are always indirect band-gap materials for -6% <ɛxx < 6%. All elastic constants, bulk modulus, shear modulus, Young's modulus increase (decrease) almost linearly with increasing compressive (tensile) strains. The evolutions of BH /GH ratio and Poisson's ratio indicate that these compounds have a better (worse) ductile behaviour under compressive (tensile) strains. A set of 3D plots show a larger directional variability in the Young's modulus E and shear modulus G at different strains for the three compounds, which is consist with the values of anisotropy factors. Moreover, the evolution of Debye temperature and anisotropy of sound velocities with biaxial strains are discussed.

Effect of Austenitic and Austeno-Ferritic Electrodes on 2205 Duplex and 316L Austenitic Stainless Steel Dissimilar Welds

NASA Astrophysics Data System (ADS)

Verma, Jagesvar; Taiwade, Ravindra V.

2016-11-01

This study addresses the effect of different types of austenitic and austeno-ferritic electrodes (E309L, E309LMo and E2209) on the relationship between weldability, microstructure, mechanical properties and corrosion resistance of shielded metal arc welded duplex/austenitic (2205/316L) stainless steel dissimilar joints using the combined techniques of optical, scanning electron microscope, energy-dispersive spectrometer and electrochemical. The results indicated that the change in electrode composition led to microstructural variations in the welds with the development of different complex phases such as vermicular ferrite, lathy ferrite, widmanstatten and intragranular austenite. Mechanical properties of welded joints were diverged based on compositions and solidification modes; it was observed that ferritic mode solidified weld dominated property wise. However, the pitting corrosion resistance of all welds showed different behavior in chloride solution; moreover, weld with E2209 was superior, whereas E309L exhibited lower resistance. Higher degree of sensitization was observed in E2209 weld, while lesser in E309L weld. Optimum ferrite content was achieved in all welds.

Oleate Coated Magnetic Cores Based on Magnetite, Zn Ferrite and Co Ferrite Nanoparticles - Preparation, Physical Characterization and Biological Impact on Helianthus Annuus Photosynthesis

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

Ursache-Oprisan, Manuela; Foca-nici, Ecaterina; Cirlescu, Aurelian

2010-12-02

Sodium oleate was used as coating shell for magnetite, Zn ferrite and Co ferrite powders to stabilize them in the form of aqueous magnetic suspensions. The physical characterization was carried out by applying X-ray diffraction and magnetization measurements. Both crystallite size and magnetic core diameter ranged between 7 and 11 nm. The influence of magnetic nanoparticle suspensions (corresponding to magnetic nanoparticle levels of 10{sup -14}-10{sup -15}/cm{sup 3}) on sunflower seedlings was studied considering the changes in the photosynthesis pigment levels. Similar responses were obtained for magnetite and cobalt ferrite nanoparticle treatment consisting in the apparent inhibition of chlorophyll biosynthesis whilemore » for zinc ferrite nanoparticles some concentrations seemed to have stimulatory effects on the chlorophylls as well as on the carotene levels. But the chlorophyll ratio was diminished in the case of all three types of magnetic nanoparticles meaning their slight negative effect on the light harvesting complex II (LHC II) from the chloroplast membranes and consequently on the photosynthesis efficiency.« less

Oleate Coated Magnetic Cores Based on Magnetite, Zn Ferrite and Co Ferrite Nanoparticles—Preparation, Physical Characterization and Biological Impact on Helianthus Annuus Photosynthesis

NASA Astrophysics Data System (ADS)

Ursache-Oprisan, Manuela; Foca-nici, Ecaterina; Cirlescu, Aurelian; Caltun, Ovidiu; Creanga, Dorina

2010-12-01

Sodium oleate was used as coating shell for magnetite, Zn ferrite and Co ferrite powders to stabilize them in the form of aqueous magnetic suspensions. The physical characterization was carried out by applying X-ray diffraction and magnetization measurements. Both crystallite size and magnetic core diameter ranged between 7 and 11 nm. The influence of magnetic nanoparticle suspensions (corresponding to magnetic nanoparticle levels of 10-14-10-15/cm3) on sunflower seedlings was studied considering the changes in the photosynthesis pigment levels. Similar responses were obtained for magnetite and cobalt ferrite nanoparticle treatment consisting in the apparent inhibition of chlorophyll biosynthesis while for zinc ferrite nanoparticles some concentrations seemed to have stimulatory effects on the chlorophylls as well as on the carotene levels. But the chlorophyll ratio was diminished in the case of all three types of magnetic nanoparticles meaning their slight negative effect on the light harvesting complex II (LHC II) from the chloroplast membranes and consequently on the photosynthesis efficiency.

Studies on magnetic properties of chemically synthesized crystalline calcium ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Debnath, A.; Bera, A.; Chattopadhyay, K. K.; Saha, B.

2016-05-01

Spinel-type ferrites have taken a very important role for modern electronic industry. Most of these ferrites exhibit low-loss dielectric properties, high resistivity, low eddy current and also high temperature ferromagnetism. Calcium ferrite is one such important metal oxide which is environmentally safe, chemically stable, low cost and greatly abundant. This outstanding material of calcium ferrite is synthesized by a simple chemical precipitation method using NaOH as the precipitating agent. Ferric chloride anhydrous (FeCl3) and Calcium chloride dihydrate (CaCl2.2H2O) were used as iron and calcium sources respectively. The samples were heated at 200°C for 8h to obtain homogeneous powder of Calcium ferrite. The powders were characterized by using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), Transmission electrical microscopy (TEM), and Fourier transform infrared spectroscopic (FTIR) measurements. The polycrystalline nature of the sample was confirmed by X-ray diffraction study. The magnetic properties of the sample were investigated by vibrating sample magnetometer (VSM) measurements. Magnetization curve of the prepared sample depicts that as synthesized calcium ferrite nanoparticles have saturation magnetic moment of 1.74 emu/g and the coercivity of 35.08 Oe with superparamagnetic behavior. The synthesized calcium ferrite nanoparticles with such magnetic properties will be a candidate material for different applications in electronics and exploring its functionality in the field of recently developing semiconductor device physics and spintronics.

Improved Rotary Transformer For Shaft-Position Indicator

NASA Technical Reports Server (NTRS)

Mclyman, W. T.

1991-01-01

Improved rotary transformer for Inductosyn (or equivalent) shaft-position-indicating circuit has pair of ferrite cores instead of the solid-iron cores. Designed with view toward decreasing excitation power (to maximum allowable 2 W) supplied to shaft-position-indicating circuit to increase its output signal and make tracking system less vulnerable to electromagnetic interference.

PARTICLE ACCELERATOR DIVISION SUMMARY REPORT FOR NOVEMBER 1958 THROUGH MAY 1959

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

None

Work in the division is summarized in the areas of theoretical studies, model magnet studies, ring magnet vacuum chamber, vacuum pumping system, ring magnet power supply, radio-frequency system, injection system, theoretical studies on radial motion through the linac, outgassing, and ferrite bonding. (For preceding period see ANL-5956.) (W.D.M.)

Mechanical properties of welded joints of the reduced-activation ferritic steel: 8% Cr-2% W-0.2% V-0.04% Ta-Fe

NASA Astrophysics Data System (ADS)

Hayakawa, H.; Yoshitake, A.; Tamura, M.; Natsume, S.; Gotoh, A.; Hishinuma, A.

1991-03-01

A reduced-activation ferritic steel, 8Cr-2W-0.2V-0.04Ta-Fe (F-82H) has been developed by JAERI and NKK to improve creep properties and toughness as compared with HT9. The mechanical properties and phase stability of the steel were reported at the previous conferences, ICFRM-2 and 3. This paper is concerned with the mechanical properties of weld metal and welded joints using a newly-developed filler wire of F-82H which contains less C and Ta than the base metal. The design concept of chemical composition of the filler wire was based on as much reduction of activity after irradiation as possible and considerations of the hardenability and toughness of the weld metal. Mechanical properties, such as tensile strength and toughness, of the weld metal and welded joints produced by GTAW after stress-relieving heat treatment were investigated. The results showed that this welding material has almost the same properties as the base metal.

Hexagonal CeO2 nanostructures: an efficient electrode material for supercapacitors.

PubMed

Maheswari, Nallappan; Muralidharan, Gopalan

2016-09-28

Cerium oxide (CeO2) has emerged as a new and promising pseudocapacitive material due to its prominent valance states and extensive applications in various fields. In the present study, hexagonal CeO2 nanostructures have been prepared via the hydrothermal method employing cationic surfactant cetyl trimethyl ammonium bromide (CTAB). CTAB ensures a slow rate of hydrolysis to form small sized CeO2 nanostructures. The role of calcination temperature on the morphological, structural, electrochemical properties and cyclic stability has been assessed for supercapacitor applications. The mesoscopic hexagonal architecture endows the CeO2 with not only a higher specific capacity, but also with an excellent rate capability and cyclability. When the charge/discharge current density is increased from 2 to 10 A g(-1) the reversible charge capacity decreased from 927 F g(-1) to 475 F g(-1) while 100% capacity retention at a high current density of 20 A g(-1) even after 1500 cycles could be achieved. Furthermore, the asymmetric supercapacitor based on CeO2 exhibited a significantly higher energy density of 45.6 W h kg(-1) at a power density of 187.5 W kg(-1) with good cyclic stability. The electrochemical richness of the CeO2 nanostructure makes it a suitable electrode material for supercapacitor applications.

His-Tag-Mediated Dimerization of Chemoreceptors Leads to Assembly of Functional Nanoarrays.

PubMed

Haglin, Elizabeth R; Yang, Wen; Briegel, Ariane; Thompson, Lynmarie K

2017-11-07

Transmembrane chemotaxis receptors are found in bacteria in extended hexagonal arrays stabilized by the membrane and by cytosolic binding partners, the kinase CheA and coupling protein CheW. Models of array architecture and assembly propose receptors cluster into trimers of dimers that associate with one CheA dimer and two CheW monomers to form the minimal "core unit" necessary for signal transduction. Reconstructing in vitro chemoreceptor ternary complexes that are homogeneous and functional and exhibit native architecture remains a challenge. Here we report that His-tag-mediated receptor dimerization with divalent metals is sufficient to drive assembly of nativelike functional arrays of a receptor cytoplasmic fragment. Our results indicate receptor dimerization initiates assembly and precedes formation of ternary complexes with partial kinase activity. Restoration of maximal kinase activity coincides with a shift to larger complexes, suggesting that kinase activity depends on interactions beyond the core unit. We hypothesize that achieving maximal activity requires building core units into hexagons and/or coalescing hexagons into the extended lattice. Overall, the minimally perturbing His-tag-mediated dimerization leads to assembly of chemoreceptor arrays with native architecture and thus serves as a powerful tool for studying the assembly and mechanism of this complex and other multiprotein complexes.

Preparation of Magnesium, Cobalt and Nickel Ferrite Nanoparticles from Metal Oxides using Deep Eutectic Solvents.

PubMed

Söldner, Anika; Zach, Julia; Iwanow, Melanie; Gärtner, Tobias; Schlosser, Marc; Pfitzner, Arno; König, Burkhard

2016-09-05

Natural deep eutectic solvents (DESs) dissolve simple metal oxides and are used as a reaction medium to synthesize spinel-type ferrite nanoparticles MFe2 O4 (M=Mg, Zn, Co, Ni). The best results for phase-pure spinel ferrites are obtained with the DES consisting of choline chloride (ChCl) and maleic acid. By employing DESs, the reactions proceed at much lower temperatures than usual for the respective solid-phase reactions of the metal oxides and at the same temperatures as synthesis with comparable calcination processes using metal salts. The method therefore reduces the overall required energy for the nanoparticle synthesis. Thermogravimetric analysis shows that the thermolysis process of the eutectic melts in air occurs in one major step. The phase-pure spinel-type ferrite particles are thoroughly characterized by X-ray diffraction, diffuse-reflectance UV/Vis spectroscopy, and scanning electron microscopy. The properties of the obtained nanoparticles are shown to be comparable to those obtained by other methods, illustrating the potential of natural DESs for processing metal oxides. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hydrogen interaction with ferrite/cementite interface: ab initio calculations and thermodynamics

NASA Astrophysics Data System (ADS)

Mirzoev, A. A.; Verkhovykh, A. V.; Okishev, K. Yu.; Mirzaev, D. A.

2018-02-01

The paper presents the results of ab initio modelling of the interaction of hydrogen atoms with ferrite/cementite interfaces in steels and thermodynamic assessment of the ability of interfaces to trap hydrogen atoms. Modelling was performed using the density functional theory with generalised gradient approximation (GGA'96), as implemented in WIEN2k package. An Isaichev-type orientation relationship between the two phases was accepted, with a habit plane (101)c ∥ (112)α. The supercell contained 64 atoms (56 Fe and 8 C). The calculated formation energies of ferrite/cementite interface were 0.594 J/m2. The calculated trapping energy at cementite interstitial was 0.18 eV, and at the ferrite/cementite interface - 0.30 eV. Considering calculated zero-point energy, the trapping energies at cementite interstitial and ferrite/cementite interface become 0.26 eV and 0.39 eV, respectively. The values are close to other researchers' data. These results were used to construct a thermodynamic description of ferrite/cementite interface-hydrogen interaction. Absorption calculations using the obtained trapping energy values showed that even thin lamellar ferrite/cementite mixture with an interlamellar spacing smaller than 0.1 μm has noticeable hydrogen trapping ability at a temperature below 400 K.

Fabrication, characterization and comparison of composite magnetic materials for high efficiency integrated voltage regulators with embedded magnetic core micro-inductors

NASA Astrophysics Data System (ADS)

Bellaredj, Mohamed L. F.; Mueller, Sebastian; Davis, Anto K.; Mano, Yasuhiko; Kohl, Paul A.; Swaminathan, Madhavan

2017-11-01

High-efficiency integrated voltage regulators (IVRs) require the integration of power inductors, which have low loss and reduced size at very high frequency. The use of a magnetic material core can reduce significantly the inductor area and simultaneously increase the inductance. This paper focuses on the fabrication, characterization and modeling of nickel zinc (NiZn) ferrite and carbonyl iron powder (CIP)-epoxy magnetic composite materials, which are used as the magnetic core materials of embedded inductors in a printed wiring board (PWB) for a system in package (SIP) based buck type IVR. The fabricated composite materials and process are fully compatible with FR4 epoxy resin prepreg and laminate. For 85% weight loading of the magnetic powder (around 100 MHz at room temperature), the composite materials show a relative permeability of 7.5-8.1 for the NiZn ferrite composite and 5.2-5.6 for the CIP composite and a loss tangent value of 0.24-0.28 for the NiZn ferrite composite and 0.09-0.1 for the CIP-composite. The room temperature saturation flux density values are 0.1351 T and 0.5280 T for the NiZn ferrite and the CIP composites, respectively. The frequency dispersion parameters of the magnetic composites are modeled using a simplified Lorentz and Landau-Lifshitz-Gilbert equation for a Debye type relaxation. Embedded magnetic core solenoid inductors were designed based on the composite materials for the output filter of a high-efficiency SIP based buck type IVR. Evaluation of a SIP based buck type IVR with the designed inductors shows that it can reach peak efficiencies of 91.7% at 11 MHz for the NiZn ferrite-composite, 91.6% at 14 MHz for CIP-composite and 87.5% (NiZn ferrite-composite) and 87.3% (CIP-composite) efficiency at 100 MHz for a 1.7 V:1.05 V conversion. For a direct 5 V:1 V conversion using a stacked topology, a peak efficiency of 82% at 10 MHz and 72% efficiency at 100 MHz can be achieved for both materials.

Barriers to the Migration of Interphase Boundaries.

DTIC Science & Technology

1984-01-06

and G.W. Lorimer, "Considerations on a Martensitic Mechanism for the F.C.C.->B.C.C. Transformation in a Cu-0.33 W/O Cr Alloy ," Scripta Met., 9, 533...Plate-Shaped Precipitates in Aluminum- Copper and Aluminum-Gold Alloys ’ by Y.H. Chen and R.D. Doherty," Scripta Met., 11, 731 (1977). 19. H.I. Aaronson...34A Re-examination of the Thermodynamics of the Proeutectoid Ferrite Transformation in Fe-C Alloys ," Met. V" Trans., 9A, 999 (1978). 24. J.M. Rigsbee

Structural materials issues for the next generation fission reactors

NASA Astrophysics Data System (ADS)

Chant, I.; Murty, K. L.

2010-09-01

Generation-IV reactor design concepts envisioned thus far cater to a common goal of providing safer, longer lasting, proliferation-resistant, and economically viable nuclear power plants. The foremost consideration in the successful development and deployment of Gen-W reactor systems is the performance and reliability issues involving structural materials for both in-core and out-of-core applications. The structural materials need to endure much higher temperatures, higher neutron doses, and extremely corrosive environments, which are beyond the experience of the current nuclear power plants. Materials under active consideration for use in different reactor components include various ferritic/martensitic steels, austenitic stainless steels, nickel-base superalloys, ceramics, composites, etc. This article addresses the material requirements for these advanced fission reactor types, specifically addressing structural materials issues depending on the specific application areas.

Discovery of a hexagonal ultradense hydrous phase in (Fe,Al)OOH

NASA Astrophysics Data System (ADS)

Zhang, Li; Yuan, Hongsheng; Meng, Yue; Mao, Ho-kwang

2018-03-01

A deep lower-mantle (DLM) water reservoir depends on availability of hydrous minerals which can store and transport water into the DLM without dehydration. Recent discoveries found hydrous phases AlOOH (Z = 2) with a CaCl2-type structure and FeOOH (Z = 4) with a cubic pyrite-type structure stable under the high-pressure–temperature (P-T) conditions of the DLM. Our experiments at 107–136 GPa and 2,400 K have further demonstrated that (Fe,Al)OOH is stabilized in a hexagonal lattice. By combining powder X-ray-diffraction techniques with multigrain indexation, we are able to determine this hexagonal hydrous phase with a = 10.5803(6) Å and c = 2.5897(3) Å at 110 GPa. Hexagonal (Fe,Al)OOH can transform to the cubic pyrite structure at low T with the same density. The hexagonal phase can be formed when δ-AlOOH incorporates FeOOH produced by reaction between water and Fe, which may store a substantial quantity of water in the DLM.

K-band high power latching switch. [communication satellite system

NASA Technical Reports Server (NTRS)

Mlinar, M. J.; Piotrowski, W. S.; Raue, J. E.

1980-01-01

A 19 GHz waveguide latching switch with a bandwidth of 1400 MHz and an exceptionally low insertion loss of 0.25 dB was demonstrated. The RF and driver ferrites are separate structures and can be optimized individually. This analysis for each structure is separately detailed. Basically, the RF section features a dual turnstile junction. The circulator consists of a dielectric tube which contains two ferrite rods, and a dielectric spacer separating the ferrite parts along the center of symmetry of the waveguide to form two turnstiles. This subassembly is indexed and locked in the center of symmetry of a uniform junction of three waveguides by the metallic transformers installed in the top and bottom walls of the housing. The switching junction and its actuating circuitry met all RF performance objectives and all shock and vibration requirements with no physical damage or performance degradation. It exceeds thermal requirements by operating over a 100 C temperature range (-44 C to +56 C) and has a high power handling capability allowing up to 100 W of CW input power.

Studies on magnetic properties of chemically synthesized crystalline calcium ferrite nanoparticles

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

Debnath, A., E-mail: debnathanimesh@gmail.com; Bera, A.; Saha, B.

Spinel-type ferrites have taken a very important role for modern electronic industry. Most of these ferrites exhibit low-loss dielectric properties, high resistivity, low eddy current and also high temperature ferromagnetism. Calcium ferrite is one such important metal oxide which is environmentally safe, chemically stable, low cost and greatly abundant. This outstanding material of calcium ferrite is synthesized by a simple chemical precipitation method using NaOH as the precipitating agent. Ferric chloride anhydrous (FeCl{sub 3}) and Calcium chloride dihydrate (CaCl{sub 2}.2H{sub 2}O) were used as iron and calcium sources respectively. The samples were heated at 200°C for 8h to obtain homogeneousmore » powder of Calcium ferrite. The powders were characterized by using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), Transmission electrical microscopy (TEM), and Fourier transform infrared spectroscopic (FTIR) measurements. The polycrystalline nature of the sample was confirmed by X-ray diffraction study. The magnetic properties of the sample were investigated by vibrating sample magnetometer (VSM) measurements. Magnetization curve of the prepared sample depicts that as synthesized calcium ferrite nanoparticles have saturation magnetic moment of 1.74 emu/g and the coercivity of 35.08 Oe with superparamagnetic behavior. The synthesized calcium ferrite nanoparticles with such magnetic properties will be a candidate material for different applications in electronics and exploring its functionality in the field of recently developing semiconductor device physics and spintronics.« less

Assessment of delta ferrite in multipass TIG welds of 40 mm thick SS 316L: A comparative study of ferrite number (FN) prediction and measurements

NASA Astrophysics Data System (ADS)

Buddu, Ramesh Kumar; Raole, P. M.; Sarkar, B.

2017-04-01

Austenitic stainless steels are widely used in the fabrication of fusion reactor major systems like vacuum vessel, divertor, cryostat and other structural components development. Multipass welding is used for the development of thick plates for the structural components fabrication. Due to the repeated weld thermal cycles, the microstructure adversely alters owing to the presence of complex phases like austenite, ferrite and delta ferrite and subsequently influences the mechanical properties like tensile and impact toughness of joints. The present paper reports the detail analysis of delta ferrite phase in welded region of 40 mm thick SS316L plates welded by special design multipass narrow groove TIG welding process under three different heat input conditions. The correlation of delta ferrite microstructure of different type structures acicular and vermicular is observed. The chemical composition of weld samples was used to predict the Ferrite Number (FN), which is representative form of delta ferrite in welds, with Schaeffler’s, WRC-1992 diagram and DeLong techniques by calculating the Creq and Nieq ratios and compared with experimental data of FN from Feritescope measurements. The low heat input conditions (1.67 kJ/mm) have produced higher FN (7.28), medium heat input (1.72 kJ/mm) shown FN (7.04) where as high heat input (1.87 kJ/mm) conditions has shown FN (6.68) decreasing trend and FN data is compared with the prediction methods.

Hexagon solar power panel

NASA Technical Reports Server (NTRS)

Rubin, I. (Inventor)

1978-01-01

A solar energy panel support is described upon which silicon cells are arrayed. The cells are wafer thin and of two geometrical types, both of the same area and electrical rating, namely hexagon cells and hourglass cells. The hourglass cells are composites of half hexagons. A near perfect nesting relationship of the cells achieves a high density packing whereby optimum energy production per panel area is achieved.

Hexagon solar power panel

DOEpatents

Rubin, Irwin

1978-01-01

A solar energy panel comprises a support upon which silicon cells are arrayed. The cells are wafer thin and of two geometrical types, both of the same area and electrical rating, namely hexagon cells and hourglass cells. The hourglass cells are composites of half hexagons. A near perfect nesting relationship of the cells achieves a high density packing whereby optimum energy production per panel area is achieved.

Isolation of genomic DNA using magnetic cobalt ferrite and silica particles.

PubMed

Prodelalová, Jana; Rittich, Bohuslav; Spanová, Alena; Petrová, Katerina; Benes, Milan J

2004-11-12

Adsorption separation techniques as an alternative to laborious traditional methods (e.g., based on phenol extraction procedure) have been applied for DNA purification. In this work we used two types of particles: silica and cobalt ferrite (unmodified or modified with a reagent containing weakly basic aminoethyl groups, aminophenyl groups, or alginic acid). DNA from chicken erythrocytes and DNA isolated from bacteria Lactococcus lactis were used for testing of adsorption/desorption properties of particles. The cobalt ferrite particles modified with different reagents were used for isolation of PCR-ready bacterial DNA from different dairy products.

Improving soft magnetic properties of Mn-Zn ferrite by rare earth ions doping

NASA Astrophysics Data System (ADS)

Zhong, X. C.; Guo, X. J.; Zou, S. Y.; Yu, H. Y.; Liu, Z. W.; Zhang, Y. F.; Wang, K. X.

2018-04-01

Mn-Zn ferrites doped with different Sm2O3, Gd2O3, Ce2O3 or Y2O3 were prepared by traditional ceramic technology using industrial pre-sintered powders. A small amount of Sm2O3, Gd2O3, Ce2O3 or Y2O3 can significantly improve the microstructure and magnetic properties. The single spinel phase structure can be maintained with the doping amount up to 0.07 wt.%. A refined grain structure and uniform grain size distribution can be obtained by doping. For all rare earth oxides, a small amount of doping can significantly increase the permeability and reduce the coercivity and magnetic core loss. The optimized doping amount for Sm2O3 or Gd2O3 is 0.01 wt.%, while for Ce2O3 or Y2O3 is 0.03 wt.%. A further increase of the doping content will lead to reduced soft magnetic properties. The ferrite sample with 0.01 wt.% Sm2O3 exhibits the good magnetic properties with permeability, loss, and coercivity of 2586, 316 W/kg, and 24A/m, respectively, at 200 mT and 100 kHz. The present results indicate that rare earth doping can be suggested to be one of the effective ways to improve the performance of soft ferrites.

Transition of dislocation glide to shear transformation in shocked tantalum

DOE PAGES

Hsiung, Luke L.; Campbell, Geoffrey H.

2017-02-28

A TEM study of pure tantalum and tantalum-tungsten alloys explosively shocked at a peak pressure of 30 GPa (strain rate: ~1 x 10 4 sec -1) is presented. While no ω (hexagonal) phase was found in shock-recovered pure Ta and Ta-5W that contain mainly a low-energy cellular dislocation structure, shock-induced ω phase was found to form in Ta-10W that contains evenly distributed dislocations with a stored dislocation density higher than 1 x 10 12 cm -2. The TEM results clearly reveal that shock-induced α (bcc) → ω (hexagonal) shear transformation occurs when dynamic recovery reactions which lead the formation low-energymore » cellular dislocation structure become largely suppressed in Ta-10W shocked under dynamic (i.e., high strain-rate and high-pressure) conditions. A novel dislocation-based mechanism is proposed to rationalize the transition of dislocation glide to twinning and/or shear transformation in shock-deformed tantalum. Lastly, twinning and/or shear transformation take place as an alternative deformation mechanism to accommodate high-strain-rate straining when the shear stress required for dislocation multiplication exceeds the threshold shear stresses for twinning and/or shear transformation.« less

Evolution of weld metal microstructure in shielded metal arc welding of X70 HSLA steel with cellulosic electrodes: A case study

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

Ghomashchi, Reza, E-mail: reza.ghomashchi@adelaide.edu.au; Costin, Walter; Kurji, Rahim

2015-09-15

The microstructure of weld joint in X70 line pipe steel resulted from shielded metal arc welding with E6010 cellulosic electrodes is characterized using optical and electron microscopy. A range of ferritic morphologies have been identified ranging from polygonal inter- and intra-prior austenite grains allotriomorphic, idiomorphic ferrites to Widmanstätten, acicular and bainitic ferrites. Electron Backscatter Diffraction (EBSD) analysis using Image Quality (IQ) and Inverse Pole Figure (IPF) maps through superimposition of IQ and IPF maps and measurement of percentages of high and low angle grain boundaries was identified to assist in differentiation of acicular ferrite from Widmanstätten and bainitic ferrite morphologies.more » In addition two types of pearlitic structures were identified. There was no martensite detected in this weld structure. The morphology, size and chemistry of non-metallic inclusions are also discussed briefly. - Highlights: • Application of EBSD reveals orientation relationships in a range of phases for shielded metal arc welding of HSLA steel. • Nucleation sites of various ferrite morphologies identified • Formation of upper and lower bainite and their morphologies.« less

Design of a fuel element for a lead-cooled fast reactor

NASA Astrophysics Data System (ADS)

Sobolev, V.; Malambu, E.; Abderrahim, H. Aït

2009-03-01

The options of a lead-cooled fast reactor (LFR) of the fourth generation (GEN-IV) reactor with the electric power of 600 MW are investigated in the ELSY Project. The fuel selection, design and optimization are important steps of the project. Three types of fuel are considered as candidates: highly enriched Pu-U mixed oxide (MOX) fuel for the first core, the MOX containing between 2.5% and 5.0% of the minor actinides (MA) for next core and Pu-U-MA nitride fuel as an advanced option. Reference fuel rods with claddings made of T91 ferrite-martensitic steel and two alternative fuel assembly designs (one uses a closed hexagonal wrapper and the other is an open square variant without wrapper) have been assessed. This study focuses on the core variant with the closed hexagonal fuel assemblies. Based on the neutronic parameters provided by Monte-Carlo modeling with MCNP5 and ALEPH codes, simulations have been carried out to assess the long-term thermal-mechanical behaviour of the hottest fuel rods. A modified version of the fuel performance code FEMAXI-SCK-1, adapted for fast neutron spectrum, new fuels, cladding materials and coolant, was utilized for these calculations. The obtained results show that the fuel rods can withstand more than four effective full power years under the normal operation conditions without pellet-cladding mechanical interaction (PCMI). In a variant with solid fuel pellets, a mild PCMI can appear during the fifth year, however, it remains at an acceptable level up to the end of operation when the peak fuel pellet burnup ∼80 MW d kg-1 of heavy metal (HM) and the maximum clad damage of about 82 displacements per atom (dpa) are reached. Annular pellets permit to delay PCMI for about 1 year. Based on the results of this simulation, further steps are envisioned for the optimization of the fuel rod design, aiming at achieving the fuel burnup of 100 MW d kg-1 of HM.

Design of 1 MHz Solid State High Frequency Power Supply

NASA Astrophysics Data System (ADS)

Parmar, Darshan; Singh, N. P.; Gajjar, Sandip; Thakar, Aruna; Patel, Amit; Raval, Bhavin; Dhola, Hitesh; Dave, Rasesh; Upadhay, Dishang; Gupta, Vikrant; Goswami, Niranjan; Mehta, Kush; Baruah, Ujjwal

2017-04-01

High Frequency Power supply (HFPS) is used for various applications like AM Transmitters, metallurgical applications, Wireless Power Transfer, RF Ion Sources etc. The Ion Source for a Neutral beam Injector at ITER-India uses inductively coupled power source at High Frequency (∼1 MHz). Switching converter based topology used to generate 1 MHz sinusoidal output is expected to have advantages on efficiency and reliability as compared to traditional RF Tetrode tubes based oscillators. In terms of Power Electronics, thermal and power coupling issues are major challenges at such a high frequency. A conceptual design for a 200 kW, 1 MHz power supply and a prototype design for a 600 W source been done. The prototype design is attempted with Class-E amplifier topology where a MOSFET is switched resonantly. The prototype uses two low power modules and a ferrite combiner to add the voltage and power at the output. Subsequently solution with Class-D H-Bridge configuration have been evaluated through simulation where module design is stable as switching device do not participate in resonance, further switching device voltage rating is substantially reduced. The rating of the modules is essentially driven by the maximum power handling capacity of the MOSFETs and ferrites in the combiner circuit. The output passive network including resonance tuned network and impedance matching network caters for soft switching and matches the load impedance to 50ohm respectively. This paper describes the conceptual design of a 200 kW high frequency power supply and experimental results of the prototype 600 W, 1 MHz source.

W-Sb-Te phase-change material: A candidate for the trade-off between programming speed and data retention

NASA Astrophysics Data System (ADS)

Peng, Cheng; Wu, Liangcai; Rao, Feng; Song, Zhitang; Yang, Pingxiong; Song, Hongjia; Ren, Kun; Zhou, Xilin; Zhu, Min; Liu, Bo; Chu, Junhao

2012-09-01

W-Sb-Te phase-change material has been proposed to improve the performance of phase-change memory (PCM). Crystallization temperature, crystalline resistance, and 10-year data retention of Sb2Te increase markedly by W doping. The Wx(Sb2Te)1-x films crystallize quickly into a stable hexagonal phase with W uniformly distributing in the crystal lattice, which ensures faster SET speed and better operation stability for the application in practical device. PCM device based on W0.07(Sb2Te)0.93 shows ultrafast SET operation (6 ns) and good endurance (1.8 × 105 cycles). W-Sb-Te material is a promising candidate for the trade-off between programming speed and data retention.

Hexagonal nanorods of tungsten trioxide: Synthesis, structure, electrochemical properties and activity as supporting material in electrocatalysis

NASA Astrophysics Data System (ADS)

Salmaoui, Samiha; Sediri, Faouzi; Gharbi, Néji; Perruchot, Christian; Aeiyach, Salah; Rutkowska, Iwona A.; Kulesza, Pawel J.; Jouini, Mohamed

2011-07-01

Tungsten trioxide, unhydrated with hexagonal structure (h-WO 3), has been prepared by hydrothermal method at a temperature of 180 °C in acidified sodium tungstate solution. Thus prepared h-WO 3 has been characterized by X-ray diffraction (XRD) method and using electrochemical techniques. The morphology has been examined by scanning and transmission electron microscopies (SEM and TEM) and it is consistent with existence of nanorods of 50-70 nm diameter and up to 5 μm length. Cyclic voltammetric characterization of thin films of h-WO 3 nanorods has revealed reversible redox behaviour with charge-discharge cycling corresponding to the reversible lithium intercalation/deintercalation into the crystal lattice of the h-WO 3 nanorods. In propylene carbonate containing LiClO 4, two successive redox processes of hexagonal WO 3 nanorods are observed at the scan rate of 50 mV/s. Such behaviour shall be attributed to the presence of at least two W atoms of different surroundings in the lattice structure of h-WO 3 nanorods. On the other hand, in aqueous LiClO 4 solution, only one redox process is observed at the scan rate of 10 mV/s. The above observations can be explained in terms of differences in the diffusion of ions inside two types of channel cavities existing in the structure of the h-WO 3 nanorods. Moreover, the material can be applied as active support for the catalytic bi-metallic Pt-Ru nanoparticles during electrooxidation of ethanol in acid medium (0.5 mol dm -3 H 2SO 4).

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

Wiengmoon, A., E-mail: ampornw@nu.ac.th

The effects of Si on microstructure and phase transformation at elevated temperature of ferritic 31wt.%Cr-1.1wt.%C white cast irons with up to 3wt.%Si have been studied. Applications of these irons include parts requiring heat resistance at elevated temperature. The irons were produced by sand casting. The microstructure in as-cast condition and after being subjected to high temperature (700 to 1000 °C) was investigated by light microscopy, X-ray diffraction, and electron microscopy. The results revealed that the as-cast microstructure consisted mainly of primary ferrite dendrites and eutectic (ferrite + M{sub 7}C{sub 3}). Si promotes M{sub 7}C{sub 3}-to-M{sub 23}C{sub 6} transformation in themore » irons subjected to transformation at elevated temperature, but no sigma phase was found. The extent of M{sub 7}C{sub 3}-to-M{sub 23}C{sub 6} transformation increases proportional to the increasing transformation temperature, holding time and Si content in the irons. For the iron with 1.0wt.%Si content after holding at elevated temperatures, martensite was also found, which could be attributed to carbon accretion effects in eutectic ferrite. Si was incorporated in M{sub 23}C{sub 6} such that M{sub 23}C{sub 6} containing Si can show darker contrast under SEM-BEI as compared to M{sub 7}C{sub 3}; this is the opposite to what has been observed for the cases of typical M{sub 23}C{sub 6} and M{sub 23}C{sub 6} containing Mo or W. The results obtained are important to understand the change in properties of ferritic, high chromium irons containing Si subjected to elevated temperature.« less

Properties of solar generators with reflectors and radiators

NASA Astrophysics Data System (ADS)

Ebeling, W. D.; Rex, D.; Bierfischer, U.

1980-06-01

Radiation cooled concentrator systems using silicon and GaAs cells were studied. The principle of radiation cooling by the reflector surfaces is discussed for cylindrical parabolic reflectors (SARA), truncated hexagonal pyramids, and a small trough configuration. Beam paths, collection properties for imperfect orientation, and thermal optimization parameters were analyzed. The three concentrating systems with radiation cooling offer advantages over the plane panel and over the large trough. With silicon solar cells they exhibit considerably lower solar cell consumption per Kw and also lower mass per kW. With GaAs cells the SARA system reduces the number of solar cells needed per kW to less than 10%. Also in all other cases SARA offers the best values for alpha and F sub sol, as long as narrow angular tolerances of the panel orientation can be met. Analysis of the energy collecting properties for imperfect orientation shows the superiority of the hexagonal concentrator. This device can produce power for even large angles between the sun and the panel normal.

Fabrication and Characterization of Quinoa Protein Nanoparticle-Stabilized Food-Grade Pickering Emulsions with Ultrasound Treatment: Interfacial Adsorption/Arrangement Properties.

PubMed

Qin, Xin-Sheng; Luo, Zhi-Gang; Peng, Xi-Chun

2018-05-02

The natural quinoa protein isolate (QPI) was largely reflected in the nanoparticle form at pH 7.0 (∼401 nm), and the ultrasound at 20 min progressively improved the contact angle (wettability) and surface hydrophobicity of the nanoparticles. Ultrasound process also modified the type of intraparticle interaction, and the internal forces of sonicated particles were largely maintained by both disulfide bonds and hydrophobic interaction forces. In emulsion system, the ultrasound progressively increased the emulsification efficiency of the QPI nanoparticles, particularly at high protein concentration ( c > 1%, w/ v) and higher emulsion stability against coalescence. As compared with the natural QPI-stabilized emulsions, the 20 min sonicated emulsions exhibited higher packing and adsorption at the protein interface. The microstructure of emulsions that occurs is bridging flocculation of droplets at low c (≤1%, w/ v), while the amount of protein particles could be high enough to cover the droplet surface at high c ( >1%, w/ v) with hexagonal array model arrangement. Thus these results illustrated that both natural and sonicated QPI nanoparticles could be performed as effective food-grade stabilizer for Pickering emulsion; however, the sonicated QPI nanoparticles exhibited much better emulsifying and interfacial properties.

On the novel double perovskites A2Fe(Mn0.5W0.5)O6 (A= Ca, Sr, Ba). Structural evolution and magnetism from neutron diffraction data

NASA Astrophysics Data System (ADS)

García-Ramos, Crisanto A.; Larrégola, Sebastián; Retuerto, María; Fernández-Díaz, María Teresa; Krezhov, Kiril; Alonso, José Antonio

2018-06-01

New A2Fe(Mn0.5W0.5)O6 (A = Ca, Sr, Ba) double perovskite oxides have been prepared by ceramic techniques. X-ray diffraction (XRD) complemented with neutron powder diffraction (NPD) indicate a structural evolution from monoclinic (space group P21/n) for A = Ca to cubic (Fm-3m) for A = Sr and finally to hexagonal (P63/mmc) for A = Ba as the perovskite tolerance factor increases with the A2+ ionic size. The three oxides present different tilting schemes of the FeO6 and (Mn,W)O6 octahedra. NPD data also show evidence in all cases of a considerable anti-site disordering, involving the partial occupancy of Fe positions by Mn atoms, and vice-versa. Magnetic susceptibility data show magnetic transitions below 50 K characterized by a strong irreversibility between ZFC and FC susceptibility curves. The A = Ca perovskite shows a G-type magnetic structure, with weak ordered magnetic moments due to the mentioned antisite disordering. Interesting magnetostrictive effects are observed for the Sr perovskite below 10 K.

Influence of CaCO3 and SiO2 additives on magnetic properties of M-type Sr ferrites

NASA Astrophysics Data System (ADS)

Huang, Ching-Chien; Jiang, Ai-Hua; Hung, Yung-Hsiung; Liou, Ching-Hsuan; Wang, Yi-Chen; Lee, Chi-Ping; Hung, Tong-Yin; Shaw, Chun-Chung; Kuo, Ming-Feng; Cheng, Chun-Hu

2018-04-01

An experiment was carried out to investigate the influence of CaCO3 and SiO2 additives on the magnetic and physical properties of M-type Sr ferrites by changing experimental parameters such as the additive composition and Ca/Si ratio. Specimens were prepared by conventional ceramic techniques. It was found that the magnetic properties (Br = 4.42 kG, iHc = 3.32 kOe and (BH)max = 4.863 MGOe) were considerably improved upon adding CaCO3 = 1.1% and SiO2 = 0.4 wt% together with Co3O4, and the mechanical properties thereof were acceptable for motor applications. It was revealed that CaCO3 and SiO2 additives led to an upswing in the magnetic properties via the enhancement of uniform grain growth, particle alignment, and the densification of Sr ferrite.

Influence of Alloy Content and Prior Microstructure on Evolution of Secondary Phases in Weldments of 9Cr-Reduced Activation Ferritic-Martensitic Steel

NASA Astrophysics Data System (ADS)

Thomas Paul, V.; Sudha, C.; Saroja, S.

2015-08-01

9Cr-Reduced Activation Ferritic-Martensitic steels with 1 and 1.4 wt pct tungsten are materials of choice for the test blanket module in fusion reactors. The steels possess a tempered martensite microstructure with a decoration of inter- and intra-lath carbides, which undergoes extensive modification on application of heat. The change in substructure and precipitation behavior on welding and subsequent thermal exposure has been studied using both experimental and computational techniques. Changes i.e., formation of various phases, their volume fraction, size, and morphology in different regions of the weldment due to prolonged thermal exposure was influenced not only by the time and temperature of exposure but also the prior microstructure. Laves phase of type Fe2W was formed in the high tungsten steel, on aging the weldment at 823 K (550 °C). It formed in the fine-grained heat-affected zone (HAZ) at much shorter durations than in the base metal. The accelerated kinetics has been understood in terms of enhanced precipitation of carbides at lath/grain boundaries during aging and the concomitant depletion of carbon and chromium and enrichment of tungsten in the vicinity of the carbides. Therefore, the fine-grained HAZ in the weldment was identified as a region susceptible for failure during service.

Loss of preload in screwed implant joints as a function of time and tightening/untightening sequences.

PubMed

Bernardes, Sérgio Rocha; da Gloria Chiarello de Mattos, Maria; Hobkirk, John; Ribeiro, Ricardo Faria

2014-01-01

The purpose of this study was to determine whether abutment screw tightening and untightening influenced loss of preload in three different implant/abutment interfaces, or on the implant body. Five custom-fabricated machined titanium implants were used, each with its respective abutment, with different connection types, retention screws, and torque values (external hexagon with titanium screw/32 Ncm, external hexagon with coated screw/32 Ncm, internal hexagon/20 Ncm and internal conical/20 and 32 Ncm). Each implant tested had two strain gauges attached and was submitted to five tightening/untightening sequences. External hexagons resulted in the lowest preload values generated in the implant cervical third (mean of 27.75 N), while the internal hexagon had the highest values (mean of 219.61 N). There was no immediate significant loss of preload after screw tightening. Tightening/untightening sequences, regardless of the implant/abutment interface design or type of screw used in the study, did not result in any significant loss of initial preload. Conical implant connections demonstrated greater structural reinforcement within the internal connections.

Main types of optical beams giving predominant contributions to the light backscatter for the irregular hexagonal columns

NASA Astrophysics Data System (ADS)

Shishko, Victor A.; Konoshonkin, Alexander V.; Kustova, Natalia V.; Borovoi, Anatoli G.

2017-11-01

This work presents the estimation of contribution of the main types of optical beams to the light backscatter for randomly oriented hexagonal ice column, the right dihedral angle of which was distorted within the range of 0° (regular particle) to 10°. Calculations were obtained within the physical optics approximation. The wavelength was 532 nm and the refractive index was 1.3116. The results showed that the total contribution of the main types of optical beams to the total backscattering cross section reach the value of 85% at small distortion angle of the hexagonal column and at substantial distortion angle the total contribution of the main types of optical beams decrease up to 55% of the total backscattering cross section. The obtained conclusions can significantly reduce the calculation time in the case when there is no need for high accuracy of the calculation.

Growth of Nanoscale Nickel Ferrite on Carbonaceous Matrix- A Novel Method of Turning Harmful Particulates into a Functional Nanocomposite: An XAFS Study

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

Pattanaik, S.; Huggins, F; Huffman, G

2010-01-01

Particulate matter (PM) emission from residual oil combustion typically consists of carbonaceous material accompanied by inorganic matter notably transition metal sulfates. Often a minor sulfide form is found in the coarse fraction while an oxide form is more common in the fine and ultrafine fractions. A composite comprising of nanoscale nickel ferrite dispersed on carbonaceous matrix has been obtained following liberation of metal sulfates from the fine PM - a novel method of turning harmful particulates into a functional nanocomposite without the need for elaborate preparation using expensive precursors. The nickel ferrite content in the composite varies with the Fe/Nimore » ratio in particulate, fuel type, and combustion condition. Such variation may lead to the composite exhibiting diverse physical behaviors. Detailed structure and cation distribution in dispersed ferrite have been studied using Fe and Ni K-edges XAFS spectroscopy. Peaks are identified in the radial structure function with specific atom pair correlations within the spinel ferrite from which the relative occupancy of the cations in the octahedral and tetrahedral sites can be discerned. The results show that Ni(II) has strong preference for the octahedral site, while Fe(III) prefers both sites which is consistent with that of an inverted spinel ferrite.« less

Growth of nanoscale nickel ferrite on carbonaceous matrix--A novel method of turning harmful particulates into a functional nanocomposite: An XAFS study.

PubMed

Pattanaik, Sidhartha; Huggins, Frank E; Huffman, Gerald P

2010-06-15

Particulate matter (PM) emission from residual oil combustion typically consists of carbonaceous material accompanied by inorganic matter notably transition metal sulfates. Often a minor sulfide form is found in the coarse fraction while an oxide form is more common in the fine and ultrafine fractions. A composite comprising of nanoscale nickel ferrite dispersed on carbonaceous matrix has been obtained following liberation of metal sulfates from the fine PM--a novel method of turning harmful particulates into a functional nanocomposite without the need for elaborate preparation using expensive precursors. The nickel ferrite content in the composite varies with the Fe/Ni ratio in particulate, fuel type, and combustion condition. Such variation may lead to the composite exhibiting diverse physical behaviors. Detailed structure and cation distribution in dispersed ferrite have been studied using Fe and Ni K-edges XAFS spectroscopy. Peaks are identified in the radial structure function with specific atom pair correlations within the spinel ferrite from which the relative occupancy of the cations in the octahedral and tetrahedral sites can be discerned. The results show that Ni(II) has strong preference for the octahedral site, while Fe(III) prefers both sites which is consistent with that of an inverted spinel ferrite. Copyright 2010 Elsevier B.V. All rights reserved.

Design and Fabrication of Millimeter Wave Hexagonal Nano-Ferrite Circulator on Silicon CMOS Substrate

NASA Astrophysics Data System (ADS)

Oukacha, Hassan

The rapid advancement of Complementary Metal Oxide Semiconductor (CMOS) technology has formed the backbone of the modern computing revolution enabling the development of computationally intensive electronic devices that are smaller, faster, less expensive, and consume less power. This well-established technology has transformed the mobile computing and communications industries by providing high levels of system integration on a single substrate, high reliability and low manufacturing cost. The driving force behind this computing revolution is the scaling of semiconductor devices to smaller geometries which has resulted in faster switching speeds and the promise of replacing traditional, bulky radio frequency (RF) components with miniaturized devices. Such devices play an important role in our society enabling ubiquitous computing and on-demand data access. This thesis presents the design and development of a magnetic circulator component in a standard 180 nm CMOS process. The design approach involves integration of nanoscale ferrite materials on a CMOS chip to avoid using bulky magnetic materials employed in conventional circulators. This device constitutes the next generation broadband millimeter-wave circulator integrated in CMOS using ferrite materials operating in the 60GHz frequency band. The unlicensed ultra-high frequency spectrum around 60GHz offers many benefits: very high immunity to interference, high security, and frequency re-use. Results of both simulations and measurements are presented in this thesis. The presented results show the benefits of this technique and the potential that it has in incorporating a complete system-on-chip (SoC) that includes low noise amplifier, power amplier, and antenna. This system-on-chip can be used in the same applications where the conventional circulator has been employed, including communication systems, radar systems, navigation and air traffic control, and military equipment. This set of applications of circulator shows how crucial this device is to many industries and the need for smaller, cost effective RF components.

Co2+Ti4+ substituted Z-type barium ferrite with enhanced imaginary permeability and resonance frequency

NASA Astrophysics Data System (ADS)

Li, Z. W.; Guoqing, Lin; Chen, Linfeng; Yuping, Wu; Ong, C. K.

2006-03-01

Co2+Ti4+ substitution for Fe3+ in Co2Z (Ba3Co2Fe24O41) has been prepared. The crystal structure and static and high-frequency magnetic properties have been studied for Ba3Co2+xTixFe24-2xO41 and the corresponding ferrite/polymer composites. As compared to the general Co2Z ferrite/polymer composite, the CoTi substituted ferrite/polymer composite with x=1.0 has a high natural resonance frequency (4.5 GHz), due to its large out-of-plane anisotropy fields Hθ. Furthermore, the maximum imaginary permeability μmax'' is increased by about 50%. The increase is attributed to a decreased damping coefficient, based on the curve-fitted results to the complex permeability spectra. The composites are good electromagnetic attenuation materials with low reflectivity and broad bandwidth at microwave frequencies.

Development and testing of shingle-type solar cell modules. Final report

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

Shepard, N.F.

1979-02-28

The design, development, fabrication and testing of a shingle-type terrestrial solar cell module which produces 98 watts/m/sup 2/ of exposed module area at 1 kW/m/sup 2/ insolation and 61/sup 0/C are reported. These modules make it possible to easily incorporate photovoltaic power generation into the sloping roofs of residential or commercial buildings by simply nailing the modules to the plywood roof sheathing. This design consists of nineteen series-connected 53 mm diameter solar cells arranged in a closely packaged hexagon configuration. These cells are individually bonded to the embossed surface of a 3 mm thick thermally tempered hexagon-shaped piece of ASGmore » SUNADEX glass. Monsanto SAFLEX polyvinyl butyral is used as the laminating adhesive. RTVII functions as the encapsulant between the underside of the glass superstrate and a rear protective sheet of 0.8 mm thick TEXTOLITE. The semi-flexible portion of each shingle module is a composite laminate construction consisting of outer layers of B.F. Goodrich FLEXSEAL and an epichlorohydrin closed cell foam core. The module design has satisfactorily survived the JPL-defined qualification testing program which includes 50 thermal cycles between -40 and +90/sup 0/C, a seven-day temperature-humidity exposure test and a mechanical integrity test consisting of a bidirectional cyclic loading at 2390 Pa (50 lb/ft/sup 2/) which is intended to simulate loads due to a 45 m/s (100 mph) wind.« less

Star cell type core configuration for structural sandwich materials

DOEpatents

Christensen, Richard M.

1995-01-01

A new pattern for cellular core material used in sandwich type structural materials. The new pattern involves star shaped cells intermixed with hexagonal shaped cells. The new patterned cellular core material includes star shaped cells interconnected at points thereof and having hexagonal shape cells positioned adjacent the star points. The new pattern allows more flexibility and can conform more easily to curved shapes.

A first-principles study on polar hexagonal Cs2TeM3O12 (M = W, Mo): New visible-light responsive photocatalyst

NASA Astrophysics Data System (ADS)

Zahedi, Ehsan; Hojamberdiev, Mirabbos

2017-08-01

The crystal structures, electro-optical properties, and charge carrier effective masses of Cs2TeW3O12 and Cs2TeMo3O12 with hexagonal, polar and non-centrosymmetric crystal structure were investigated based on density functional theory. Cs2TeW3O12 and Cs2TeMo3O12 are found to be indirect K (1/3, 1/3, 0) → G (0, 0, 0) band gap semiconductors (Eg > 3 eV) with small effective masses of photogenerated charge carriers. The mixing of octahedrally coordinated d° transition metal cations (W6+ and Mo6+) with the filled p orbitals of the oxygen ligands leads to the formation of some W5+/Mo5+ sites and splitting of d orbitals into the partially filled t2g (dxy, dyz, and dzx) orbitals and empty eg (dz2 and dx2-y2) orbitals. The top of the valence bond is mainly contributed by O 2p orbital of the oxygen ligands mixed with the partially filled t2g orbitals of W 5d/Mo 4d, while the conduction band mainly consists of empty eg orbitals of W 5d/Mo 4d with a little contribution of O 2p orbitals. The dielectric function exhibits a slight anisotropic behavior and optical absorption peak for Cs2TeW3O12 and Cs2TeMo3O12 belonging to the strong electronic transition O 2p → W 5d/Mo 4d within the octahedral units. According to the estimated valence band and conduction band edges, Cs2TeW3O12 and Cs2TeMo3O12 can be applied as visible-light-responsive photocatalysts for the decomposition of organic pollutants and dye molecules. Also, Cs2TeMo3O12 can be used in water splitting for hydrogen generation but Cs2TeW3O12 requires further experimental studies to confirm its ability for water splitting.

Helium sequestration at nanoparticle-matrix interfaces in helium + heavy ion irradiated nanostructured ferritic alloys

DOE PAGES

Parish, Chad M.; Unocic, Kinga A.; Tan, Lizhen; ...

2016-10-24

Here we irradiated four ferritic alloys with energetic Fe and He ions: one castable nanostructured alloy (CNA) containing Ti-W-Ta-carbides, and three nanostructured ferritic alloys (NFAs). The NFAs were: 9Cr containing Y-Ti-O nanoclusters, and two Fe-12Cr-5Al NFAs containing Y-Zr-O or Y-Hf-O clusters. All four were subjected to simultaneous dual-beam Fe + He ion implantation (650 °C, ~50 dpa, ~15 appm He/dpa), simulating fusion-reactor conditions. Examination using scanning/transmission electron microscopy (STEM) revealed high-number-density helium bubbles of ~8 nm, ~10 21 m -3 (CNA), and of ~3 nm, 10 23 m -3 (NFAs). STEM combined with multivariate statistical analysis data mining suggests thatmore » the precipitate-matrix interfaces in all alloys survived ~50 dpa at 650 °C and serve as effective helium trapping sites. All alloys appear viable structural material candidates for fusion or advanced fission energy systems. Finally, among these developmental alloys the NFAs appear to sequester the helium into smaller bubbles and away from the grain boundaries more effectively than the early-generation CNA.« less

Microwave combustion synthesis of Co1-xZnxFe2O4 (0⩽x⩽0.5): Structural, magnetic, optical and vibrational spectroscopic studies.

PubMed

Sundararajan, M; Kennedy, L John; Vijaya, J Judith; Aruldoss, Udaya

2015-04-05

Nanostructured pure and zinc doped cobalt ferrites (Co1-xZnxFe2O4 where x fraction ranging from 0 to 0.5) were prepared by microwave combustion method employing urea as a fuel. The nanostructured samples were characterized by using various instrumental techniques such as X-ray powder diffractometry, high resolution scanning electron microscopy, energy dispersive X-ray analysis, UV-visible diffuse reflectance spectroscopy, photoluminescence spectroscopy and Fourier transformed infrared (FT-IR) spectroscopy. Vibrating sample magnetometry at room temperature was recorded to study the magnetic behavior of the samples. X-ray analysis and the FT-IR spectroscopy revealed the formation of cobalt ferrite cubic spinel-type structure. The average crystallite sizes for the samples were in the range of 3.07-11.30 nm. The direct band gap (Eg) was estimated using Kubelka-Munk method and is obtained from the UV-vis spectra. The band gap value decreased with an increase in zinc fraction (2.56-2.17 eV). The violet and green emission observed in the photoluminescence spectra revealed that cobalt ferrites are governed by defect controlled processes. The elemental analysis of zinc doped cobalt ferrites were obtained from energy dispersive X-ray (EDX) analysis. From the magnetic measurements, it is observed that cobalt ferrite and zinc doped cobalt ferrite systems fall under the soft ferrite category. The saturation magnetization (Ms) value of undoped cobalt ferrite is 14.26 emu/g, and it has reached a maximum of 29.61 emu/g for Co0.7Zn0.3Fe2O4. Copyright © 2014 Elsevier B.V. All rights reserved.

Effects of Ti and Ta addition on microstructure stability and tensile properties of reduced activation ferritic/martensitic steel for nuclear fusion reactors

NASA Astrophysics Data System (ADS)

Kim, Han Kyu; Lee, Ji Won; Moon, Joonoh; Lee, Chang Hoon; Hong, Hyun Uk

2018-03-01

The effects of Ti and Ta addition on microstructure stability and tensile properties of a reduced activation ferritic/martensitic (RAFM) steel have been investigated. Ti addition of 0.06 wt% to conventional RAFM reference base steel (Fe-9.3Cr-0.93W-0.22V-0.094Ta-0.1C) was intended to promote the precipitation of nano-sized (Ti,W) carbides with a high resistance to coarsening. In addition, the Ti addition was substituted for 0.094 wt% Ta. The Ti-added RAFM steel (Ti-RAFM) exhibited a higher yield strength (ΔYS = 32 MPa) at 600 °C than the reference base steel due to additional precipitation hardening by (Ti,W)-rich MX with an average size of 6.1 nm and the area fraction of 2.39%. However, after thermal exposure at 600 °C for 1000 h, this Ti-RAFM was more susceptible to degradation than the reference base steel; the block width increased by 77.6% in Ti-RAFM after thermal exposure while the reference base steel showed only 9.1% increase. In order to suppress diffusion rate during thermal exposure, the large-sized Ta element with low activation was added to Ti-RAFM. The Ta-added Ti-RAFM steel exhibited good properties with outstanding microstructure stability. Quantitative comparison in microstructures was discussed with a consideration of Ti and Ta addition.

Surface cracking and melting of different tungsten grades under transient heat and particle loads in a magnetized coaxial plasma gun

NASA Astrophysics Data System (ADS)

Kikuchi, Y.; Sakuma, I.; Iwamoto, D.; Kitagawa, Y.; Fukumoto, N.; Nagata, M.; Ueda, Y.

2013-07-01

Surface damage of pure tungsten (W), W alloys with 2 wt.% tantalum (W-Ta) and vacuum plasma spray (VPS) W coating on a reduced activation material of ferritic steel (F82H) due to repetitive ELM-like pulsed (˜0.3 ms) deuterium plasma irradiation has been investigated by using a magnetized coaxial plasma gun. Surface cracks appeared on a pure W sample exposed to 10 plasma pulses of ˜0.3 MJ m-2, while a W-Ta sample did not show surface cracks with similar pulsed plasma irradiation. The energy density threshold for surface cracking was significantly increased by the existence of the alloying element of tantalum. No surface morphology change of a VPS W coated F82H sample was observed under 10 plasma pulses of ˜0.3 MJ m-2, although surface melting and cracks in the resolidification layer occurred at higher energy density of ˜0.9 MJ m-2. There was no indication of exfoliation of the W coating from the substrate of F82H after the pulsed plasma exposures.

Recent progress of tungsten R&D for fusion application in Japan

NASA Astrophysics Data System (ADS)

Ueda, Y.; Lee, H. T.; Ohno, N.; Kajita, S.; Kimura, A.; Kasada, R.; Nagasaka, T.; Hatano, Y.; Hasegawa, A.; Kurishita, H.; Oya, Y.

2011-12-01

The status of ongoing research projects of tungsten R&D in Japan is summarized in this paper. For tungsten material development, a new improved fabrication technique, the so-called superplasticity-based microstructural modification, is described. This technique successfully improved fracture strength and ductility at room temperature. Recent results on vacuum plasma spray W coating and W brazing on ferritic steels and vanadium alloys are explained. Feasibility of these techniques for the manufacture of the blanket is successfully demonstrated. The latest findings on the effect of neutron damage in tungsten on T retention and on the change in mechanical and electrical properties are described. Retention characteristics for neutron-damaged W were different compared to those for ion-damaged W. Upon neutron irradiation, tungsten alloys containing transmutation elements of W (Re and Os) show changes in properties that are different compared with those shown by pure W. The effects of mixed plasma exposure (D/He/C) are described. Both D/He and D/C mixed ion irradiations significantly affect ion-driven permeation in W. He bubble dynamics play a key role in nano-structure formation on the W surface.

Primary and secondary precipitates in a hierarchical-precipitate-strengthened ferritic alloy

DOE PAGES

Song, Gian; Sun, Zhiqian; Poplawsky, Jonathan D.; ...

2017-02-27

The microstructures of a hierarchical-precipitate-strengthened ferritic alloy are characterized, using transmission-electron microscopy (TEM) and atom-probe tomography (APT). The alloy shows duplex precipitates. The primary precipitate with an average edge length of 90 nm consists of NiAl- and Ni2TiAl-type phases, while the secondary precipitate with an average radius of 2 nm is a NiAl-type phase. Based on the APT results, the volume fractions of the primary and secondary precipitates were calculated, using the lever rule to be 17.3 and 2.3 %, respectively.

Modification of the electronic properties of hexagonal boron-nitride in BN/graphene vertical heterostructures

DOE PAGES

Pan, Minghu; Liang, Liangbo; Lin, Wenzhi; ...

2016-09-28

Van der Waals (vdW) heterostructures consist of isolated atomic planar structures, assembled layer- by-layer into desired structures in a well-defined sequence. Graphene deposited on hexagonal boron nitride (h-BN) has been first considered as a testbed system for vdW heterostructures, and many others have been demonstrated both theoretically and experimentally, revealing many attractive properties and phenomena. However, much less emphasis has been placed on how graphene actively affects h-BN properties. Here, we perform local probe measurements on single-layer h-BN grown over graphene and highlight the manifestation of a proximity effect that significantly affects the electronic properties of h-BN due to itsmore » coupling with the underlying graphene. We find electronic states originating from the graphene layer and the Cu substrate to be injected into the wide electronic gap of the h-BN top layer. Such proximity effect is further confirmed in a study of the variation of h-BN in-gap states with interlayer couplings, elucidated using a combination of topographical/ spectroscopic measurements and first-principles density functional theory calculations. In conclusion, the findings of this work indicate the potential of mutually engineering electronic properties of the components of vdW heterostructures.« less

Eutectic equilibria in the quaternary system Fe-Cr-Mn-C

NASA Technical Reports Server (NTRS)

Nowotny, H.; Wayne, S.; Schuster, J. C.

1982-01-01

The constitution of the quaternary system, Fe-Cr-Mn-C and to a lesser extent of the quinary system, Fe-Cr-Mn-Al-C were examined for in situ composite alloy candidates. Multivariant eutectic compositions were determined from phase equilibria studies wherein M7C3 carbides (approximately 30% by volume) formed from the melt within gamma iron. An extended field of the hexagonal carbide, (Cr, Fe, Mn)7 C3, was found without undergoing transformation to the orthorhombic structure. Increasing stability for this carbide was found for higher ratios of Cr/Fe(+) Cr + Mn. Aluminum additions promoted a ferritic matrix while manganese favored the desired gamma austenitic matrix. In coexistence with the matrix phase, chromium enters preferentially the carbide phase while manganese distributes equally between the gamma matrix and the M7C3 carbide. The composition and lattice parameters of the carbide and matrix phases were determined to establish their respective stabilities.

Chemically stabilized epitaxial wurtzite-BN thin film

NASA Astrophysics Data System (ADS)

Vishal, Badri; Singh, Rajendra; Chaturvedi, Abhishek; Sharma, Ankit; Sreedhara, M. B.; Sahu, Rajib; Bhat, Usha; Ramamurty, Upadrasta; Datta, Ranjan

2018-03-01

We report on the chemically stabilized epitaxial w-BN thin film grown on c-plane sapphire by pulsed laser deposition under slow kinetic condition. Traces of no other allotropes such as cubic (c) or hexagonal (h) BN phases are present. Sapphire substrate plays a significant role in stabilizing the metastable w-BN from h-BN target under unusual PLD growth condition involving low temperature and pressure and is explained based on density functional theory calculation. The hardness and the elastic modulus of the w-BN film are 37 & 339 GPa, respectively measured by indentation along <0001> direction. The results are extremely promising in advancing the microelectronic and mechanical tooling industry.

The effect of solution pH on the electrochemical performance of nanocrystalline metal ferrites MFe2O4 (M=Cu, Zn, and Ni) thin films

NASA Astrophysics Data System (ADS)

Elsayed, E. M.; Rashad, M. M.; Khalil, H. F. Y.; Ibrahim, I. A.; Hussein, M. R.; El-Sabbah, M. M. B.

2016-04-01

Nanocrystalline metal ferrite MFe2O4 (M=Cu, Zn, and Ni) thin films have been synthesized via electrodeposition-anodization process. Electrodeposited (M)Fe2 alloys were obtained from aqueous sulfate bath. The formed alloys were electrochemically oxidized (anodized) in aqueous (1 M KOH) solution, at room temperature, to the corresponding hydroxides. The parameters controlling the current efficiency of the electrodeposition of (M)Fe2 alloys such as the bath composition and the current density were studied and optimized. The anodized (M)Fe2 alloy films were annealed in air at 400 °C for 2 h. The results revealed the formation of three ferrite thin films were formed. The crystallite sizes of the produced films were in the range between 45 and 60 nm. The microstructure of the formed film was ferrite type dependent. The corrosion behavior of ferrite thin films in different pH solutions was investigated using open circuit potential (OCP) and potentiodynamic polarization measurements. The open circuit potential indicates that the initial potential E im of ZnFe2O4 thin films remained constant for a short time, then sharply increased in the less negative direction in acidic and alkaline medium compared with Ni and Cu ferrite films. The values of the corrosion current density I corr were higher for the ZnFe2O4 films at pH values of 1 and 12 compared with that of NiFe2O4 and CuFe2O4 which were higher only at pH value 1. The corrosion rate was very low for the three ferrite films when immersion in the neutral medium. The surface morphology recommended that Ni and Cu ferrite films were safely used in neutral and alkaline medium, whereas Zn ferrite film was only used in neutral atmospheres.

Crystalline phase transformation of colloidal cadmium sulfide nanocrystals

NASA Astrophysics Data System (ADS)

Ghali, M.; Eissa, A. M.; Mosaad, M. M.

2017-03-01

In this paper, we give a microscopic view concerning influence of the growth conditions on the physical properties of nanocrystals (NCs) thin films made of CdS, prepared using chemical bath deposition CBD technique. We show a crystalline phase transformation of CdS NCs from hexagonal wurtzite (W) structure to cubic zincblende (ZB) when the growth conditions change, particularly the solution pH values. This effect was confirmed using X-ray diffraction (XRD), transmission electron microscopy (TEM), optical absorption and photoluminescence (PL) measurements. The optical absorption spectra allow calculation of the bandgap value, Eg, where significant increase ˜200 meV in the CdS bandgap when transforming from Hexagonal to Cubic phase was found.

Interlocking egg-crate type grid assembly

DOEpatents

Kast, Steven J.

1987-01-01

Disclosed is an interlocking egg-crate hexagonal grid for supporting a nuclear fuel pin in a hexagonal array. The grid is formed from strips bent at an angle of about 120.degree. at each vertex. Over some faces of each hexagonal cell the strips are coplanar but are arranged, by stacking and interlocking, to avoid any double thickness of metal in that plane. Springs and dimples are formed in the faces of each cell to hold the fuel pin substantially centered.

Interlocking egg-crate type grid assembly

DOEpatents

Kast, S.J.

1985-03-15

Disclosed is an interlocking egg-crate hexagonal grid for supporting a nuclear fuel pin in a hexagonal array. The grid is formed from strips bent at an angle of about 120/sup 0/ at each vertex. Over some faces of each hexagonal cell the strips are coplanar but are arranged, by stacking interlocking, to avoid any double thickness of metal in that plane. Springs and dimples are formed in the faces of each cell to hold the fuel pin substantially centered.

New magnetic rails with double-layer Halbach structure by employing NdFeB and ferrite magnets for HTS maglev

NASA Astrophysics Data System (ADS)

Sun, Ruixue; Zheng, Jun; Zheng, Botian; Qian, Nan; Li, Jipeng; Deng, Zigang

2018-01-01

In the high temperature superconducting (HTS) maglev system, the magnetic rail as an essential infrastructure is needed all along the route to carry passengers and goods to the destinations. Thus, large amount of rare earth magnetic materials are required in the magnetic rail construction. In order to decrease the dependence of magnetic rails on rare earth elements, the ferrite magnet is employed to replace part of the NdFeB magnets containing rare earth elements. Consequently, a new type rail with double-layer Halbach structure is presented, which is consisted of NdFeB and ferrite magnets. In this paper, we designed and fabricated the proposed rail, and further measured its magnetic flux density distribution and electromagnetic force interacting with HTS bulks. Experimental results indicate that, this new type rail, in double-layer Halbach structure, can achieve an equivalent distribution of magnetic flux density and levitation performance as the pure NdFeB Halbach rail, while a 10% reduction in NdFeB magnet consumption can be realized at the same time. In addition this work explores another magnetic material selection for HTS maglev applications. The dependence on rare earth element and the cost of magnetic rails can be further reduced, as the coercive force of ferrite magnets improved.

Star cell type core configuration for structural sandwich materials

DOEpatents

Christensen, R.M.

1995-08-01

A new pattern for cellular core material used in sandwich type structural materials is disclosed. The new pattern involves star shaped cells intermixed with hexagonal shaped cells. The new patterned cellular core material includes star shaped cells interconnected at points thereof and having hexagonal shape cells positioned adjacent the star points. The new pattern allows more flexibility and can conform more easily to curved shapes. 3 figs.

Computational design and performance prediction of creep-resistant ferritic superalloys

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

Liaw, Peter K.; Wang, Shao-Yu; Dunand, David C.

Ferritic superalloys containing the B2 phase with the parent L21 phase precipitates in a disordered solid-solution matrix, also known as a hierarchical-precipitate-strengthened ferritic alloy (HPSFA), had been developed for high-temperature structural applications in fossil-energy power plants. These alloys were designed by adding Ti into a previously-studied NiAl-strengthened ferritic alloy (denoted as FBB8 in this study). Following with the concept of HPSFAs, in the present research, a systematic investigation on adding other elements, such as Hf and Zr, and optimizing the Ti content within the alloy system, has been conducted, in order to further improve the creep resistance of the modelmore » alloys. Studies include advanced experimental techniques, first-principles calculations on thermodynamic and mechanical properties, and numerical simulations on precipitation hardening, have been integrated and conducted to characterize the complex microstructures and excellent creep resistance of alloys. The experimental techniques include transmission-electron microscopy (TEM), scanning-electron microscopy (SEM), neutron diffraction (ND), and atom-probe tomography (APT), which provide the detailed microstructural information of the model alloys. Systematic tension/compression creep tests have also been conducted in order to verify the creep resistance of the potential alloy compositions. The results show that when replacing Ti with Hf and Zr, it does not form the L21 phase. Instead, the hexagonal Laves phase forms and distributes majorly along the grain boundary, or large segregation within grains. Since the Laves phase does not form parent to the B2-phase precipitates, it cannot bring the strengthening effect of HPSFAs. As a result, the FBB8 + 2 wt. % Hf and FBB8 + 2 wt. % Zr alloys have similar mechanical properties to the original FBB8. The FBB8 + Ti series alloys had also been studied, from the creep tests and microstructural characterizations, the FBB8 + 3.5 wt.% Ti possesses the greatest creep resistance, with the L21/B2 phase ratio of 4 (80% of the precipitates is the L21 phase, and 20% is the B2 phase). First-principles calculations include thermodynamics, elastic properties, and interfacial properties, which have been conducted for the understanding of the thermodynamic and mechanical properties of HPSFAs. In addition to the systematic experimental approach and first-principles calculations, a series of numerical tools and algorithms, which assist in the optimization of creep properties of ferritic superalloys, are utilized and developed. These numerical simulation results are compared with the available experimental data and previous first-principles calculations, providing the deep insight of creep mechanisms of the creep-resistant ferritic superalloys. To conclude the present research, we’ve found that (1) only FBB8 + Ti alloys have the potential of forming HPSFA, and FBB8 + Hf and FBB8 + Zr do not work. Therefore, only FBB8 + Ti alloys have desirable creep resistance, (2) the optimum composition for the FBB8 + Ti alloys is FBB8 + 3.5% Ti, which has the greatest creep resistance (218.8 MPa as the threshold stress at 700 oC), (3) first-principle calculations obtained results that could not be obtained in experiments, which are relevant to develop ferritic superalloys with the improved creep resistance, and (4) two-dimensional dislocation-dynamics simulations investigate effects of factors like precipitate volume fractions and precipitate radii in the alloy systems, which helps in developing the most desirable microstructure with greatest strengthening.« less

Biodiesel production from waste cooking oil using copper doped zinc oxide nanocomposite as heterogeneous catalyst.

PubMed

Gurunathan, Baskar; Ravi, Aiswarya

2015-01-01

A novel CZO nanocomposite was synthesized and used as heterogeneous catalyst for transesterification of waste cooking oil into biodiesel using methanol as acyl acceptor. The synthesized CZO nanocomposite was characterized in FESEM with an average size of 80 nm as nanorods. The XRD patterns indicated the substitution of ZnO in the hexagonal lattice of Cu nanoparticles. The 12% (w/w) nanocatalyst concentration, 1:8 (v:v) O:M ratio, 55 °C temperature and 50 min of reaction time were found as optimum for maximum biodiesel yield of 97.71% (w/w). Hence, the use of CZO nanocomposite can be used as heterogeneous catalyst for biodiesel production from waste cooking oil. Copyright © 2015 Elsevier Ltd. All rights reserved.

Postirradiation thermocyclic loading of ferritic-martensitic structural materials

NASA Astrophysics Data System (ADS)

Belyaeva, L.; Orychtchenko, A.; Petersen, C.; Rybin, V.

Thermonuclear fusion reactors of the Tokamak-type will be unique power engineering plants to operate in thermocyclic mode only. Ferritic-martensitic stainless steels are prime candidate structural materials for test blankets of the ITER fusion reactor. Beyond the radiation damage, thermomechanical cyclic loading is considered as the most detrimental lifetime limiting phenomenon for the above structure. With a Russian and a German facility for thermal fatigue testing of neutron irradiated materials a cooperation has been undertaken. Ampule devices to irradiate specimens for postirradiation thermal fatigue tests have been developed by the Russian partner. The irradiation of these ampule devices loaded with specimens of ferritic-martensitic steels, like the European MANET-II, the Russian 05K12N2M and the Japanese Low Activation Material F82H-mod, in a WWR-M-type reactor just started. A description of the irradiation facility, the qualification of the ampule device and the modification of the German thermal fatigue facility will be presented.

Microstructural characterization and electron backscatter diffraction analysis across the welded interface of duplex stainless steel

NASA Astrophysics Data System (ADS)

Zhang, Zhiqiang; Jing, Hongyang; Xu, Lianyong; Han, Yongdian; Gao, Zhanqi; Zhao, Lei; Zhang, Jianli

2017-08-01

The microstructural evolution, orientation relationships, boundary characteristics, grain type, local deformation, and microhardness across the welded interface of duplex stainless steel (DSS) were investigated. The DSS welded joint consisted of four typical zones: base metal (BM), low-temperature heat-affected zone (LTHAZ), high-temperature heat-affected zone (HTHAZ), and weld metal (WM). The apparent microstructural changes in the HTHAZ and LTHAZ were secondary austenite and Cr2N precipitation. A modified cooperative precipitation mechanism of secondary austenite and Cr2N at the interface was proposed. Furthermore, the ferrite in both the HTHAZ and LTHAZ maintained the same distribution as the ferrite texture in the BM, while this ferrite texture disappeared completely in the WM. Different austenite grains in the different zones exhibited different orientation relationships with the ferrite matrix. Special grain boundaries were mainly distributed between the austenite grains, while the ferrite grains primarily contained random grain boundaries. Austenite twins constituted the largest proportion of the special boundaries. The special austenite grain boundaries in the BM and LTHAZ were higher in relative frequency than those in the HTHAZ and WM. The ferrite grains in the HTHAZ and WM mainly consisted of substructured grains. In the BM, the recrystallization degree of ferrite was significantly lower than that of austenite grains. The local deformations were mainly generated in the grain boundaries and within the deformed grains. The HTHAZ exhibited the highest hardness, while the BM had the lowest hardness. The LTHAZ had a lower hardness than the HTHAZ and higher hardness than the BM.

WE-DE-201-12: Thermal and Dosimetric Properties of a Ferrite-Based Thermo-Brachytherapy Seed

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

Warrell, G; Shvydka, D; Parsai, E I

Purpose: The novel thermo-brachytherapy (TB) seed provides a simple means of adding hyperthermia to LDR prostate permanent implant brachytherapy. The high blood perfusion rate (BPR) within the prostate motivates the use of the ferrite and conductive outer layer design for the seed cores. We describe the results of computational analyses of the thermal properties of this ferrite-based TB seed in modelled patient-specific anatomy, as well as studies of the interseed and scatter (ISA) effect. Methods: The anatomies (including the thermophysical properties of the main tissue types) and seed distributions of 6 prostate patients who had been treated with LDR brachytherapymore » seeds were modelled in the finite element analysis software COMSOL, using ferrite-based TB and additional hyperthermia-only (HT-only) seeds. The resulting temperature distributions were compared to those computed for patient-specific seed distributions, but in uniform anatomy with a constant blood perfusion rate. The ISA effect was quantified in the Monte Carlo software package MCNP5. Results: Compared with temperature distributions calculated in modelled uniform tissue, temperature distributions in the patient-specific anatomy were higher and more heterogeneous. Moreover, the maximum temperature to the rectal wall was typically ∼1 °C greater for patient-specific anatomy than for uniform anatomy. The ISA effect of the TB and HT-only seeds caused a reduction in D90 similar to that found for previously-investigated NiCu-based seeds, but of a slightly smaller magnitude. Conclusion: The differences between temperature distributions computed for uniform and patient-specific anatomy for ferrite-based seeds are significant enough that heterogeneous anatomy should be considered. Both types of modelling indicate that ferrite-based seeds provide sufficiently high and uniform hyperthermia to the prostate, without excessively heating surrounding tissues. The ISA effect of these seeds is slightly less than that for the previously-presented NiCu-based seeds.« less

Effect of Eu–Ni substitution on electrical and dielectric properties of Co–Sr–Y-type hexagonal ferrite

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

Ali, Irshad, E-mail: irshadalibzu@gmail.com; Islam, M.U.; Ashiq, Muhammad Naeem, E-mail: naeemashiqqau@yahoo.com

2014-01-01

Graphical abstract: - Highlights: • Single phase nanostructured Sr{sub 2}Co{sub 2−x}Ni{sub x} Eu{sub y}Fe{sub 12−y}O{sub 22} were synthesized by the microemulsion method. • The materials show semiconducting behavior. • The high resistivity makes these materials useful for high frequency applications. • The Curie temperature decreases with the substituents. - Abstract: Single phase nanostructured Eu–Ni substituted Y-type hexaferrites with nominal composition Sr{sub 2}Co{sub 2−x}Ni{sub x} Eu{sub y}Fe{sub 12−y}O{sub 22} (x = 0.0–1, y = 0.0–0.1) were synthesized by the normal microemulsion method. X-ray diffraction (XRD) technique was employed for phase analysis and indexing of each pattern corroborates that well defined Y-typemore » crystalline phase is formed. It is observed that DC resistivity enhanced which is accredited to room temperature resistivity differences of dopant and host ions. The hopping of electrons and jumping of holes are responsible for conduction below Curie temperature (T{sub C}), whereas above Curie temperature is due to polaron hopping. The decrease in T{sub C} may be due to the fact that Eu–Fe interactions on the B sites are weaker than Fe–Fe interaction. The dispersion in the dielectric constant ε′(f) favor the occurrence of peaks in the tan δ(f). The extraordinary values of resistivity and small dielectric loss make these materials pre-eminent contestant for high frequency applications.« less

An Anionic Phospholipid Enables the Hydrophobic Surfactant Proteins to Alter Spontaneous Curvature

PubMed Central

Chavarha, Mariya; Loney, Ryan W.; Rananavare, Shankar B.; Hall, Stephen B.

2013-01-01

The hydrophobic surfactant proteins, SP-B and SP-C, greatly accelerate the adsorption of the surfactant lipids to an air/water interface. Previous studies of factors that affect curvature suggest that vesicles may adsorb via a rate-limiting structure with prominent negative curvature, in which the hydrophilic face of the lipid leaflets is concave. To determine if SP-B and SP-C might promote adsorption by inducing negative curvature, we used small-angle x-ray scattering to test whether the physiological mixture of the two proteins affects the radius of cylindrical monolayers in the inverse hexagonal phase. With dioleoyl phosphatidylethanolamine alone, the proteins had no effect on the hexagonal lattice constant, suggesting that the proteins fail to insert into the cylindrical monolayers. The surfactant lipids also contain ∼10% anionic phospholipids, which might allow incorporation of the cationic proteins. With 10% of the anionic dioleoyl phosphatidylglycerol added to dioleoyl phosphatidylethanolamine, the proteins induced a dose-related decrease in the hexagonal lattice constant. At 30°C, the reduction reached a maximum of 8% relative to the lipids alone at ∼1% (w/w) protein. Variation of NaCl concentration tested whether the effect of the protein represented a strictly electrostatic effect that screening by electrolyte would eliminate. With concentrations up to 3 M NaCl, the dose-related change in the hexagonal lattice constant decreased but persisted. Measurements at different hydrations determined the location of the pivotal plane and proved that the change in the lattice constant produced by the proteins resulted from a shift in spontaneous curvature. These results provide the most direct evidence yet that the surfactant proteins can induce negative curvature in lipid leaflets. This finding supports the model in which the proteins promote adsorption by facilitating the formation of a negatively curved, rate-limiting structure. PMID:23442910

Sound velocities of Na0.4Mg0.6Al1.6Si0.4O4 NAL and CF phases to 73 GPa determined by Brillouin scattering method

NASA Astrophysics Data System (ADS)

Dai, Lidong; Kudo, Yuki; Hirose, Kei; Murakami, Motohiko; Asahara, Yuki; Ozawa, Haruka; Ohishi, Yasuo; Hirao, Naohisa

2013-03-01

The sound velocities of two aluminum-rich phases in the lower mantle, hexagonal new Al-rich phase (NAL) and its corresponding high-pressure polymorph orthorhombic Ca-ferrite-type phase (CF), were determined with the Brillouin scattering method in a pressure range from 9 to 73 GPa at room temperature. Both NAL and CF samples have identical chemical composition of Na0.4Mg0.6Al1.6Si0.4O4 (40 % NaAlSiO4-60 % MgAl2O4). Infrared laser annealing in the diamond anvil cell was performed to minimize the stress state of the sample and obtain the high-quality Brillouin spectra. The results show shear modulus at zero pressure G 0 = 121.960 ± 0.087 GPa and its pressure derivative G' = 1.961 ± 0.009 for the NAL phase, and G 0 = 129.653 ± 0.059 GPa and G' = 2.340 ± 0.004 for the CF phase. The zero-pressure shear velocities of the NAL and CF phases are obtained to be 5.601 ± 0.005 km/sec and 5.741 ± 0.001 km/sec, respectively. We also found that shear velocity increases by 2.5 % upon phase transition from NAL to CF at around 40 GPa.

Structural phase transition of as-synthesized Sr-Mn nanoferrites by annealing temperature

NASA Astrophysics Data System (ADS)

Amer, M. A.; Meaz, T. M.; Attalah, S. S.; Ghoneim, A. I.

2015-11-01

The Sr0.2Mn0.8Fe2O4 nanoparticle ferrites were synthesized by the co-precipitation method and annealed at different temperatures T. XRD, TEM, FT-IR, VSM and Mössbauer techniques were used to characterize the samples. This study proved that the structural phase of nanoferrites was transformed from cubic spinel for T≤500 °C to Z-type hexagonal for T≥700 °C. The structural transformation was attributed to Jahn-Teller effect of the Mn3+ ions and/or atomic disorder existed in the crystal lattice. The obtained spectra and parameters for the samples were affected by the transformation process. The lattice constant a showed a splitting to a and c for T>500 °C. The lattice constant c, grain and crystallite size R, strain, octahedral B-site band position and force constant, Debye temperature, coercivity Hc, remnant magnetization, squareness and magnetic moment, spontaneous magnetization and hyperfine magnetic fields showed increase against T. The lattice constant a, distortion and dislocation parameters, specific surface area, tetrahedral A-site band position and force constant, threshold frequency, Young's and bulk moduli, saturation magnetization Ms, area ratio of B-/A-sites, A-site line width were decreased with T. Experimental and theoretical densities, porosity, Poison ratio, stiffness constants, rigidity modulus, B-site line width and spontaneous magnetization showed dependence on T, whereas Ms and Hc proved dependence on R.

Subgrain refinement strengthening. Second quarterly progress report, January 1, 1975-March 31, 1975. [Epsilon-Brite 26-1

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

Klundt, R.; Walser, B.; Monma, Y.

During the past quarter (January-March 1975) we have initiated mechanical properties studies on type 304 stainless steel and on a ferritic alloy, E-Brite 26-1. Purpose of these studies was to establish a sound data base from which the alloys specifically chosen for this program can be evaluated (namely, ferritic steel, precipitation hardening austenitic stainless steel and a nickel rich austenitic alloy).

Characterization of the secondary flow in hexagonal ducts

NASA Astrophysics Data System (ADS)

Marin, O.; Vinuesa, R.; Obabko, A. V.; Schlatter, P.

2016-12-01

In this work we report the results of DNSs and LESs of the turbulent flow through hexagonal ducts at friction Reynolds numbers based on centerplane wall shear and duct half-height Reτ,c ≃ 180, 360, and 550. The evolution of the Fanning friction factor f with Re is in very good agreement with experimental measurements. A significant disagreement between the DNS and previous RANS simulations was found in the prediction of the in-plane velocity, and is explained through the inability of the RANS model to properly reproduce the secondary flow present in the hexagon. The kinetic energy of the secondary flow integrated over the cross-sectional area yz decreases with Re in the hexagon, whereas it remains constant with Re in square ducts at comparable Reynolds numbers. Close connection between the values of Reynolds stress u w ¯ on the horizontal wall close to the corner and the interaction of bursting events between the horizontal and inclined walls is found. This interaction leads to the formation of the secondary flow, and is less frequent in the hexagon as Re increases due to the 120∘ aperture of its vertex, whereas in the square duct the 90∘ corner leads to the same level of interaction with increasing Re. Analysis of turbulence statistics at the centerplane and the azimuthal variance of the mean flow and the fluctuations shows a close connection between hexagonal ducts and pipe flows, since the hexagon exhibits near-axisymmetric conditions up to a distance of around 0.15DH measured from its center. Spanwise distributions of wall-shear stress show that in square ducts the 90∘ corner sets the location of a high-speed streak at a distance zv+≃50 from it, whereas in hexagons the 120∘ aperture leads to a shorter distance of zv+≃38 . At these locations the root mean square of the wall-shear stresses exhibits an inflection point, which further shows the connections between the near-wall structures and the large-scale motions in the outer flow.

Study on microstructural changes in thermally-aged stainless steel weld-overlay cladding of nuclear reactor pressure vessels by atom probe tomography

NASA Astrophysics Data System (ADS)

Takeuchi, T.; Kameda, J.; Nagai, Y.; Toyama, T.; Nishiyama, Y.; Onizawa, K.

2011-08-01

The effect of thermal aging on microstructural changes was investigated in stainless steel weld-overlay cladding composed of 90% austenite and 10% δ-ferrite phases using atom probe tomography (APT). In as-received materials subjected to cooling process after post-welding heat treatments (PWHT), a slight fluctuation of the Cr concentration was already observed due to spinodal decomposition in the ferrite phase but not in the austenitic phase. Thermal aging at 400 °C for 10,000 h caused not only an increase in the amplitude of spinodal decomposition but also the precipitation of G phases with composition ratios of Ni:Si:Mn = 16:7:6 in the ferrite phase. The chemical compositions of M 23C 6 type carbides seemed to be formed at the austenite/ferrite interface were analyzed. The analyses of the magnitude of the spinodal decomposition and the hardness implied that the spinodal decomposition was the main cause of the hardening.

Development of W-composites/EUROFER brazed joints for the first wall component of future fusion reactors

NASA Astrophysics Data System (ADS)

de Prado, J.; Sánchez, M.; Antusch, S.; Ureña, A.

2017-12-01

The present work describes a joining procedure between two different tungsten composite materials (W-2Y2O3 and W-1TiC) with reduced activation ferritic-martensitic steel (Eurofer). The results indicated the achievement, in both cases, of high quality W-composites/Eurofer joints using 80Cu-20Ti as filler material. The braze is constituted by several ternary Cu-Ti-Fe phases distributed along a Cu-matrix, which acts as ductile phase capable of relieving the residual stresses, which could be produced during the service life of the component. Some cracks growing from W-braze interface into the base material have been detected. They are originated by the stresses produced during the cooling stage of the brazing cycle. Regarding the strength of the joints, similar shear strengths of both joints were obtained (˜105 MPa). These values were slightly lower than the ones obtained when pure tungsten was used as the base metal.

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

Su, Zhijuan; Hu, Bolin; Chen, Yajie, E-mail: y.chen@neu.edu

A series of Z-type and Y-type ferrite composites with various phase fractions were studied for their RF properties including the measurement of permittivity to permeability spectra over a frequency range of 0.1–10 GHz. Phase identification of the ferrite composites' constituents was determined by X-ray diffraction. An effective medium approximation was used to predict the magnetic and dielectric behavior of the composites. The experiments indicated that the composite having 75 vol. % of Z-type ferrite demonstrated a permeability of ∼12 with a nearly equivalent permittivity, yielding a ratio (μ′/ε′) of 0.91 at a frequency range from 0.55 to 0.75 GHz. The dielectric loss (i.e.,more » tan δ{sub ε}) and magnetic loss (i.e., tan δ{sub μ}) were measured to be lower than 0.08 at f = 0.1–1 GHz and 0.29 at f = 0.1–0.7 GHz, respectively. Furthermore, the loss factors, as tan δ{sub ε}/ε′ and tan δ{sub μ}/μ′, were calculated to be 0.003 and 0.02 at 0.65 GHz, respectively.« less

The fatigue evaluation method for a structural stainless steel using the magnetic sensor composed of three pancake coils

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

Oka, M.; Tsuchida, Y.; Enokizono, M.

May metallic structural materials, such as stainless steels, are currently used in our surroundings. If external force is repeatedly added for many years, it is thought that fatigue damage accumulates in stainless steels. When excessive fatigue damage accumulates in these metals, there is a possibility that they are destroyed by fatigue damage accumulation. Therefore, it is important to know the amount of the fatigue damage they have suffered in order to prevent them from being destroyed. We are developing the fatigue evaluation method for stainless steels with a magnetic sensor composed of three pancake type coils. In this research, themore » inspection object is ferritic stainless steels such as SUS430. The method of fatigue evaluation for ferritic stainless steels uses the three coil type sensor, and shows a good correlation between the number of stress cycles and the output signal of the sensor, even though the correlation between the output signal and an added stress is not completely accurate. This paper describes the evaluation method of fatigue damage in ferritic stainless steel using a magnetic sensor composed of three pancake-type coils.« less

A study of the suitability of ferrite for use in low-field insertion devices

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

Johnson, K.; Hassenzahl, W.V.

1995-02-01

Most insertion devices built to date use rare-earth permanent-magnet materials, which have a high remanent field and are more expensive than many other permanent-magnet materials. Low-field insertion devices could use less-expensive, lower performance magnetic materials if they had suitable magnetic characteristics. These materials must be resistant to demagnetization during construction and operation of the insertion device, have uniform magnetization, possess low minor-axis magnetic moments, and have small minor field components on the surfaces. This paper describes an investigation to determine if ferrite possesses magnetic qualities suitable for insertion device applications. The type of ferrite investigated, MMPA Ceramic 8 from Stackpolemore » Inc., was found to be acceptable for insertion device applications.« less

Region-wide glacier mass budgets and area changes for the Central Tien Shan between ~ 1975 and 1999 using Hexagon KH-9 imagery

NASA Astrophysics Data System (ADS)

Pieczonka, Tino; Bolch, Tobias

2015-05-01

The meltwater released by the glaciers in the Central Tien Shan feeds in particular the Tarim River which is the main artery for the oases at the northern margin of the Taklamakan desert. The correct assessment of the contribution of the glaciers' meltwater to the total runoff is hampered by the lack of long-term measurements of glacier mass budgets. Digital terrain models (DTMs) for the different regions in the Central Tien Shan were generated based on ~ 1975 KH-9 Hexagon imagery and compared to the SRTM3 DTM acquired in February 2000. Moreover, glacier area changes for the period ~ 1975-2008 have been measured by means of multi-temporal optical satellite imagery. The geodetic mass budget estimates for a glacierized area of 5000 km2 revealed increasing mass loss east to west and from the inner to the outer ranges. Highest mass loss accompanied by the most pronounced glacier retreat was found for the Ak-Shirak massif with a region-wide mass balance of - 0.51 ± 0.36 m w.e. a- 1 and a rate of area change of - 0.27 ± 0.15% a- 1, whilst moderate mass loss was observed for the Inylchek (0.20 ± 0.44 m w.e. a- 1) and Tomur area (0.33 ± 0.30 m w.e. a- 1) despite partly debris cover. These latter regions also revealed the lowest glacier shrinkage within the entire Central Tien Shan. The total glacier mass loss of 0.35 ± 0.34 m w.e. a- 1 is, however, within the global average whilst the glacier area shrinkage is comparatively low. On average, the investigated glacierized area of ~ 6600 km2 shrank by 0.11 ± 0.15% a- 1 only. We could also identify several surge-type glaciers. The results are consistent with in-situ mass balance measurements for Karabatkak Glacier and previously published results of the Ak-Shirak range proving the suitability of declassified imagery for glacier change investigations. The contribution to the runoff of Aksu River, the largest tributary of the Tarim River, due to glacier imbalance has been determined at ~ 20% for the 1975-2000 period.

High Temperature Elastic Properties of Reduced Activation Ferritic-Martensitic (RAFM) Steel Using Impulse Excitation Technique

NASA Astrophysics Data System (ADS)

Tripathy, Haraprasanna; Raju, Subramanian; Hajra, Raj Narayan; Saibaba, Saroja

2018-03-01

The polycrystalline elastic constants of an indigenous variant of 9Cr-1W-based reduced activation ferritic-martensitic (RAFM) steel have been determined as a function of temperature from 298 K to 1323 K (25 °C to 1000 °C), using impulse excitation technique (IET). The three elastic constants namely, Young's modulus E, shear modulus G, and bulk modulus B, exhibited significant softening with increasing temperature, in a pronounced non-linear fashion. In addition, clearly marked discontinuities in their temperature variations are noticed in the region, where ferrite + carbides → austenite phase transformation occurred upon heating. Further, the incidence of austenite → martensite transformation upon cooling has also been marked by a step-like jump in both elastic E and shear moduli G. The martensite start M s and M f finish temperatures estimated from this study are, M s = 652 K (379 °C) and M f =580 K (307 °C). Similarly, the measured ferrite + carbide → austenite transformation onset ( Ac 1) and completion ( Ac 3) temperatures are found to be 1126 K and 1143 K (853 °C and 870 °C), respectively. The Poisson ratio μ exhibited distinct discontinuities at phase transformation temperatures; but however, is found to vary in the range 0.27 to 0.29. The room temperature estimates of E, G, and μ for normalized and tempered microstructure are found to be 219 GPa, 86.65 GPa, and 0.27, respectively. For the metastable austenite phase, the corresponding values are: 197 GPa, 76.5 GPa, and 0.29, respectively. The measured elastic properties as well as their temperature dependencies are found to be in good accord with reported estimates for other 9Cr-based ferritic-martensitic steel grades. Estimates of θ D el , the elastic Debye temperature and γ G, the thermal Grüneisen parameter obtained from measured bulk elastic properties are found to be θ D el = 465 K (192 °C) and γ G = 1.57.

Electronic structure and direct observation of ferrimagnetism in multiferroic hexagonal YbFeO 3

DOE PAGES

Cao, Shi; Sinha, Kishan; Zhang, Xin; ...

2017-06-26

Here, the magnetic interactions between rare-earth and Fe ions in hexagonal rare-earth ferrites (h–RFeO 3), may amplify the weak ferromagnetic moment on Fe, making these materials more appealing as multiferroics. To elucidate the interaction strength between the rare-earth and Fe ions as well as the magnetic moment of the rare-earth ions, element-specific magnetic characterization is needed. Using x-ray magnetic circular dichroism, we have studied the ferrimagnetism in h–YbFeO 3 by measuring the magnetization of Fe and Yb separately. The results directly show antialignment of magnetization of Yb and Fe ions in h–YbFeO 3 at low temperature, with an exchange fieldmore » on Yb of about 17 kOe. The magnetic moment of Yb is about 1.6μ B at low temperature, significantly reduced compared with the 4.5μ B moment of a free Yb 3+. In addition, the saturation magnetization of Fe in h–YbFeO 3 has a sizable enhancement compared with that in h–LuFeO 3. These findings directly demonstrate that ferrimagnetic order exists in h–YbFeO 3; they also account for the enhancement of magnetization and the reduction of coercivity in h–YbFeO 3 compared with those in h–LuFeO 3 at low temperature, suggesting an important role for the rare-earth ions in tuning the multiferroic properties of h–RFeO 3.« less

Effect of growth parameters on crystallinity and properties of ZnO films grown by plasma assisted MOCVD

NASA Astrophysics Data System (ADS)

Losurdo, M.; Giangregorio, M. M.; Sacchetti, A.; Capezzuto, P.; Bruno, G.; Malandrino, G.; Fragalà, I. L.

2007-07-01

Thin films of ZnO have been grown by plasma assisted metal-organic chemical vapour deposition (PA-MOCVD) using a 13.56 MHz O 2 plasma and the Zn(TTA)•tmed (HTTA=2-thenoyltrifluoroacetone, TMED=N,N,N',N'-tetramethylethylendiamine) precursor. The effects of growth parameters such as the plasma activation, the substrate, the surface temperature, and the ratio of fluxes of precursors on the structure, morphology, and optical and electrical properties of ZnO thin films have been studied. Under a very low plasma power of 20 W, c-axis oriented hexagonal ZnO thin films are grown on hexagonal sapphire (0001), cubic Si(001) and amorphous quartz substrates. The substrate temperature mainly controls grain size.

Development of Oxide Dispersion Strengthened (ODS) Ferritic Steel Through Powder Forging

NASA Astrophysics Data System (ADS)

Kumar, Deepak; Prakash, Ujjwal; Dabhade, Vikram V.; Laha, K.; Sakthivel, T.

2017-04-01

Oxide dispersion strengthened (ODS) ferritic steels are candidates for cladding tubes in fast breeder nuclear reactors. In this study, an 18%Cr ODS ferritic steel was prepared through powder forging route. Elemental powders with a nominal composition of Fe-18Cr-2 W-0.2Ti (composition in wt.%) with 0 and 0.35% yttria were prepared by mechanical alloying in a Simoloyer attritor under argon atmosphere. The alloyed powders were heated in a mild steel can to 1473 K under flowing hydrogen atmosphere. The can was then hot forged. Steps of sealing, degassing and evacuation are eliminated by using powder forging. Heating ODS powder in hydrogen atmosphere ensures good bonding between alloy powders. A dense ODS alloy with an attractive combination of strength and ductility was obtained after re-forging. On testing at 973 K, a loss in ductility was observed in yttria-containing alloy. The strength and ductility increased with increase in strain rate at 973 K. Reasons for this are discussed. The ODS alloy exhibited a recrystallized microstructure which is difficult to achieve by extrusion. No prior particle boundaries were observed after forging. The forged compacts exhibited isotropic mechanical properties. It is suggested that powder forging may offer several advantages over the traditional extrusion/HIP routes for fabrication of ODS alloys.

Influence of the Heterogeneous Nucleation Sites on the Kinetics of Intermetallic Phase Formation in Aged Duplex Stainless Steel

NASA Astrophysics Data System (ADS)

Melo, Elis Almeida; Magnabosco, Rodrigo

2017-11-01

The aim of this work is to study the influence of the heterogeneous nucleation site quantity, observed in different ferrite and austenite grain size samples, on the phase transformations that result in intermetallic phases in a UNS S31803 duplex stainless steel (DSS). Solution treatment was conducted for 1, 24, 96, or 192 hours at 1373 K (1100 °C) to obtain different ferrite and austenite grain sizes. After solution treatment, isothermal aging treatments for 5, 8, 10, 20, 30, or 60 minutes at 1123 K (850 °C) were performed to verify the influence of different amounts of heterogeneous nucleation sites in the kinetics of intermetallic phase formation. The sample solution treated for 1 hour, with the highest surface area between matrix phases, was the one that presented, after 60 minutes at 1123 K (850 °C), the smaller volume fraction of ferrite (indicative of greater intermetallic phase formation), higher volume of sigma (that was present in coral-like and compact morphologies), and chi phase. It was not possible to identify which was the first nucleated phase, sigma or chi. It was also observed that the phase formation kinetics is higher for the sample solution treated for 1 hour. It was evidenced that, from a certain moment on, the chi phase begins to be consumed due to the sigma phase formation, and the austenite/ferrite interface presents higher S V for all solution treatment times. It was also observed that intermetallic phases form preferably in austenite-ferrite interfaces, although the higher occupation rate occurs at triple junction ferrite-ferrite-ferrite. It was verified that there was no saturation of nucleation sites in any interface type nor triple junction, and the equilibrium after 1 hour of aging at 1123 K (850 °C) was not achieved. It was then concluded that sigma phase formation is possibly controlled by diffusional processes, without saturation of nucleation sites.

Influence of iron substitution by selected rare-earth ions on the properties of NiZn ferrite fillers and PVC magneto-polymer composites

NASA Astrophysics Data System (ADS)

Ušák, Elemír; Ušáková, Mariana; Dosoudil, Rastislav; Šoka, Martin; Dobročka, Edmund

2018-04-01

Nickel-zinc ferrites are very important soft magnetic materials from the point of view of diverse technical applications (such as, e.g., various electronic devices and components) for their high magnetic permeability and permittivity, low core loss, high resistivity, high Curie temperature as well as mechanical strength and chemical stability. Due to their good absorbing properties, they can be used as microwave absorbing and shielding materials with the aim of decreasing the environmental pollution caused by non-ionizing microwave radiation. The ferrite material incorporated into the polymer matrix creates qualitatively new magneto-polymer composite material taking benefits from both components. The properties typical for polymers (elasticity, mouldability, etc.) are combined with good high-frequency magnetic parameters, thus allowing to utilize these materials, e.g., in high-frequency applications where especially flexibility of composite materials plays a key role. Small amounts of selected rare-earth (RE) ions, in particular Y3+, La3+, Eu3+ and Gd3+ have been embedded into the nickel-zinc ferrite that has been used as the magnetic filler in magnetic polymer composites with polyvinylchloride (PVC) acting as the polymeric matrix. The effect of various types of rare-earth ions on the structural as well as quasi-static and dynamic (electro)magnetic properties of the ferrite fillers as well as ferrite/PVC composites, in particular the frequency dispersion of the complex permeability, has been studied.

Laser weldability of 21Cr-6Ni-9Mn stainless steel: Part I - Impurity effects and solidifcation mode

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

Tate, Stephen B.; Javernick, Daniel Anthony; Lienert, Thomas J.

For laser welded type 21Cr-6Ni-9Mn (21-6-9) stainless steels, the relationship between solidification cracking susceptibility and chemical composition was examined, and primary solidification mode (PSM) diagrams were developed to predict solidification mode. Sigmajig testing was used with experimental heats of type 21-6-9 to determine the effect of P and S on solidification cracking w hen primary austenite solidification occurred. Phosphorus showed a larger influence on solidification cracking relative to S, and a relationship of (P+0.2S ) was found for total impurity content. PSM diagrams to predict solidification mode were developed by analyzing welds made at three travel speeds for a widemore » range of 21-6-9 alloys and some other similar alloys. The minimum Cr eq/Ni eq required for primary ferrite solidification increased as travel speed increased, with more alloys showing primary austenite solidification at higher travel rates. Furthermore, as travel speed increased from 21 to 85 mm/s, the average solidification rate increased from 6 to 25 mm/s.« less

Laser weldability of 21Cr-6Ni-9Mn stainless steel: Part I - Impurity effects and solidifcation mode

DOE PAGES

Tate, Stephen B.; Javernick, Daniel Anthony; Lienert, Thomas J.; ...

2016-11-02

For laser welded type 21Cr-6Ni-9Mn (21-6-9) stainless steels, the relationship between solidification cracking susceptibility and chemical composition was examined, and primary solidification mode (PSM) diagrams were developed to predict solidification mode. Sigmajig testing was used with experimental heats of type 21-6-9 to determine the effect of P and S on solidification cracking w hen primary austenite solidification occurred. Phosphorus showed a larger influence on solidification cracking relative to S, and a relationship of (P+0.2S ) was found for total impurity content. PSM diagrams to predict solidification mode were developed by analyzing welds made at three travel speeds for a widemore » range of 21-6-9 alloys and some other similar alloys. The minimum Cr eq/Ni eq required for primary ferrite solidification increased as travel speed increased, with more alloys showing primary austenite solidification at higher travel rates. Furthermore, as travel speed increased from 21 to 85 mm/s, the average solidification rate increased from 6 to 25 mm/s.« less

Wrought Cr--W--V bainitic/ferritic steel compositions

DOEpatents

Klueh, Ronald L.; Maziasz, Philip J.; Sikka, Vinod Kumar; Santella, Michael L.; Babu, Sudarsanam Suresh; Jawad, Maan H.

2006-07-11

A high-strength, high-toughness steel alloy includes, generally, about 2.5% to about 4% chromium, about 1.5% to about 3.5% tungsten, about 0.1% to about 0.5% vanadium, and about 0.05% to 0.25% carbon with the balance iron, wherein the percentages are by total weight of the composition, wherein the alloy is heated to an austenitizing temperature and then cooled to produce an austenite transformation product.

Stress Corrosion Cracking and Hydrogen Embrittlement of Thick Section High Strength Low Alloy Steel

DTIC Science & Technology

1986-06-01

copper and especially molybdenum. Dual phase HSLA steels are comprised of islands of martensite or bainite in a ferrite matrix. The... Copper Steels", TransactionN AIME, Volume 105, pp. 133-166, 1933. 60. Creswick, W. E., "Commercial Development of a Rimmed Low Alloy Precipitation ... precipitates all serve to minimize the aggregate effects of hydrogen. 82 - ------- ------ - 3. MATERIAL 3.1 bSLA STEELS High strength low alloy

Phase equilibria and crystal chemistry of rubidium niobates and rubidium tantalates

NASA Technical Reports Server (NTRS)

Minor, D. B.; Roth, R. S.; Parker, H. S.; Brower, W. S.

1977-01-01

The phase equilibria relations and crystal chemistry of portions of the Rb2O-Nb2O5 and Rb2O-Ta2O5 systems were investigated for structures potentially useful as ionic conductors. A hexagonal tungsten bronze-type (HTB) structure was found in both systems as well as three hexagonal phases with mixed HTB-pyrochlore type structures. Ion exchange experiments between various alkali ions are described for several phases. Unit cell dimensions and X-ray diffraction powder patterns are reported.

The source of high signal cooperativity in bacterial chemosensory arrays

PubMed Central

Piñas, Germán E.; Frank, Vered; Vaknin, Ady; Parkinson, John S.

2016-01-01

The Escherichia coli chemosensory system consists of large arrays of transmembrane chemoreceptors associated with a dedicated histidine kinase, CheA, and a linker protein, CheW, that couples CheA activity to receptor control. The kinase activity responses to receptor ligand occupancy changes can be highly cooperative, reflecting allosteric coupling of multiple CheA and receptor molecules. Recent structural and functional studies have led to a working model in which receptor core complexes, the minimal units of signaling, are linked into hexagonal arrays through a unique interface 2 interaction between CheW and the P5 domain of CheA. To test this array model, we constructed and characterized CheA and CheW mutants with amino acid replacements at key interface 2 residues. The mutant proteins proved defective in interface 2-specific in vivo cross-linking assays, and formed signaling complexes that were dispersed around the cell membrane rather than clustered at the cell poles as in wild type chemosensory arrays. Interface 2 mutants down-regulated CheA activity in response to attractant stimuli in vivo, but with much less cooperativity than the wild type. Moreover, mutant cells containing fluorophore-tagged receptors exhibited greater basal anisotropy that changed rapidly in response to attractant stimuli, consistent with facile changes in loosely packed receptors. We conclude that interface 2 lesions disrupt important network connections between core complexes, preventing receptors from operating in large, allosteric teams. This work confirms the critical role of interface 2 in organizing the chemosensory array, in directing the clustered array to the cell poles, and in producing its highly cooperative signaling properties. PMID:26951681

Mesoporous Silica Matrix as a Tool for Minimizing Dipolar Interactions in NiFe2O4 and ZnFe2O4 Nanoparticles

PubMed Central

Virumbrales, Maider; Saez-Puche, Regino; Torralvo, María José; Blanco-Gutierrez, Veronica

2017-01-01

NiFe2O4 and ZnFe2O4 nanoparticles have been prepared encased in the MCM (Mobile Composition of Matter) type matrix. Their magnetic behavior has been studied and compared with that corresponding to particles of the same composition and of a similar size (prepared and embedded in amorphous silica or as bare particles). This study has allowed elucidation of the role exerted by the matrix and interparticle interactions in the magnetic behavior of each ferrite system. Thus, very different superparamagnetic behavior has been found in ferrite particles of similar size depending on the surrounding media. Also, the obtained results clearly provide evidence of the vastly different magnetic behavior for each ferrite system. PMID:28640197

Thermal annealing effect on structural and thermoelectric properties of hexagonal Bi2Te3 nanoplate thin films by drop-casting technique

NASA Astrophysics Data System (ADS)

Hosokawa, Yuichi; Wada, Kodai; Tanaka, Masaki; Tomita, Koji; Takashiri, Masayuki

2018-02-01

High-purity hexagonal bismuth telluride (Bi2Te3) nanoplates were prepared by a solvothermal synthesis method, followed by the fabrication of nanoplate thin films by the drop-casting technique. The Bi2Te3 nanoplates exhibited a single-crystalline phase with a rhombohedral crystal structure. The nanoplates had a flat surface with edge sizes ranging from 500 to 2000 nm (average size of 1000 nm) and a thickness of less than 50 nm. The resulting Bi2Te3 nanoplate thin films were composed of well-aligned hexagonal nanoplates along the surface direction with an approximate film thickness of 40 µm. To tightly connect the nanoplates together within the thin films, thermal annealing was performed at different temperatures. We found that the thermoelectric properties, especially the Seebeck coefficient, were very sensitive to the annealing temperature. Finally, the optimum annealing temperature was determined to be 250 °C and the Seebeck coefficient and power factor were -300 µV/K and 3.5 µW/(cm·K2), respectively.

Structural characterization of a new vacancy ordered perovskite modification found for Ba{sub 3}Fe{sub 3}O{sub 7}F (BaFeO{sub 2.333}F{sub 0.333}): Towards understanding of vacancy ordering for different perovskite-type ferrites

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

Clemens, Oliver, E-mail: oliver.clemens@kit.edu; Karlsruher Institut für Technologie, Institut für Nanotechnologie, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen

2015-05-15

The new vacancy ordered perovskite-type compound Ba{sub 3}Fe{sub 3}O{sub 7}F (BaFeO{sub 2.33}F{sub 0.33}) was prepared by topochemical low-temperature fluorination of Ba{sub 2}Fe{sub 2}O{sub 5} (BaFeO{sub 2.5}) using stoichiometric amounts of polyvinylidene difluoride (PVDF). The vacancy order was found to be unique so far for perovskite compounds, and the connectivity pattern can be explained by the formula Ba{sub 3}(FeX{sub 6/2}) (FeX{sub 5/2}) (FeX{sub 3/2}X{sub 1/1}), with X=O/F. Mössbauer measurements were used to confirm the structural analysis and agree with the presence of Fe{sup 3+} in the above mentioned coordination environments. Group–subgroup relationships were used to build a starting model for themore » structure solution and to understand the relationship to the cubic perovskite structure. Furthermore, a comparison of a variety of vacancy-ordered iron-containing perovskite-type structures is given, highlighting the factors which favour one structure type over the other depending on the composition. - Graphical abstract: The crystal structure of Ba{sub 3}Fe{sub 3}O{sub 7}F in comparison to other perovskite type ferrites. - Highlights: • The crystal structure of Ba{sub 3}Fe{sub 3}O{sub 7}F in comparison to other perovskite type ferrites. • Ba{sub 3}Fe{sub 3}O{sub 7}F was synthesized by low temperature fluorination of Ba{sub 2}Fe{sub 2}O{sub 5}. • Ba{sub 3}Fe{sub 3}O{sub 7}F shows a unique vacancy order not found for other perovskite type compounds. • The structure of Ba{sub 3}Fe{sub 3}O{sub 7}F was solved using group–subgroup relationships. • A systematic comparison to other ferrite type compounds reveals structural similarities and differences. • The A-site coordination of the cation is shown to play an important role for the type of vacancy order found.« less

Ultra-Low Carbon Bainitic Steels for Heavy Plate Applications

DTIC Science & Technology

1990-12-01

these steels. The CCT diagrams 7 of steels typical of the HY grades indicate that the nose of the proeutectoid ferrite/pearlite reactions is located...austenite, carbides, and martensite. An example of the type of CCT diagram for one of the steels used in this investigation is presented in Figure 12...introduce a "bay" of unstable austenite which acts to separate the ferrite "nose" from the bainite/martensite regions on TTT or CCT diagrams , see Figure

Fullerene-derivative PC61BM forms three types of phase-pure monolayer on the surface of Au(111)

NASA Astrophysics Data System (ADS)

Li, Wen-Jie; Du, Ying-Ying; Zhang, Han-Jie; Chen, Guang-Hua; Sheng, Chun-Qi; Wu, Rui; Wang, Jia-Ou; Qian, Hai-Jie; Ibrahim, Kurash; He, Pi-Mo; Li, Hong-Nian

2016-12-01

We have studied the packing structures of C60-derivative PC61BM on the surface of Au(111) in ultrahigh vacuum using scanning tunneling microscopy. The Au(111) has a triangle-like reconstructed surface, which results in some packing structures different from those reported for low coverages. PC61BM can form three types of phase-pure monolayer, namely, the compact straight molecular double-row monolayer, the hexagonal-packing monolayer and the glassy monolayer. The different types of monolayer form for different molecular densities and different annealing temperatures. In addition to the already known inter-molecular interactions (Van de Waals interaction and hydrogen bond), the steric effect of the phenyl-butyric-acid-methyl-ester side tail plays conspicuous role in the molecular self-assembly at high coverages. The steric effect makes it difficult to prepare a hexagonal-packing monolayer at room temperature and decides the instability of the hexagonal-packing monolayer prepared by thermal annealing.

Steady-State Thermal-Hydraulics Analyses for the Conversion of the BR2 Reactor to LEU

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

Licht, J. R.; Bergeron, A.; Dionne, B.

2015-12-01

BR2 is a research reactor used for radioisotope production and materials testing. It’s a tank-in-pool type reactor cooled by light water and moderated by beryllium and light water (Figure 1). The reactor core consists of a beryllium moderator forming a matrix of 79 hexagonal prisms in a hyperboloid configuration; each having a central bore that can contain a variety of different components such as a fuel assembly, a control or regulating rod, an experimental device, or a beryllium or aluminum plug. Based on a series of tests, the BR2 operation is currently limited to a maximum allowable heat flux ofmore » 470 W/cm2 to ensure fuel plate integrity during steady-state operation and after a loss-of-flow/loss-of-pressure accident.« less

Perpendicularly oriented barium ferrite thin films with low microwave loss, prepared by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Da-Ming, Chen; Yuan-Xun, Li; Li-Kun, Han; Chao, Long; Huai-Wu, Zhang

2016-06-01

Barium ferrite (BaM) thin films are deposited on platinum coated silicon wafers by pulsed laser deposition (PLD). The effects of deposition substrate temperature on the microstructure, magnetic and microwave properties of BaM thin films are investigated in detail. It is found that microstructure, magnetic and microwave properties of BaM thin film are very sensitive to deposition substrate temperature, and excellent BaM thin film is obtained when deposition temperature is 910 °C and oxygen pressure is 300 mTorr (1 Torr = 1.3332 × 102 Pa). X-ray diffraction patterns and atomic force microscopy images show that the best thin film has perpendicular orientation and hexagonal morphology, and the crystallographic alignment degree can be calculated to be 0.94. Hysteresis loops reveal that the squareness ratio (M r/M s) is as high as 0.93, the saturated magnetization is 4004 Gs (1 Gs = 104 T), and the anisotropy field is 16.5 kOe (1 Oe = 79.5775 A·m-1). Ferromagnetic resonance measurements reveal that the gyromagnetic ratio is 2.8 GHz/kOe, and the ferromagnetic resonance linewith is 108 Oe at 50 GHz, which means that this thin film has low microwave loss. These properties make the BaM thin films have potential applications in microwave devices. Project supported by the Open Foundation of State Key Laboratory of Electronic Thin Films and Integrated Devices (Grant No. KFJJ201506), the Scientific Research Starting Foundation of Hainan University (Grant No. kyqd1539), and the Natural Science Foundation of Hainan Province (Grant No. 20165187).

Non-noble catalysts and catalyst supports for phosphoric acid fuel cells

NASA Technical Reports Server (NTRS)

Mcalister, A. J.

1981-01-01

Tungsten carbide, which is active for hydrogen oxidation, is CO tolerant and has a hexagonal structure is discussed. Titanium carbide is inactive and has a cubic structure. Four different samples of the cubic alloys W sub x-1Ti sub XC sub 1-y were found to be active and CO tolerant. When the activities of these cubic alloys are weighted by the reciprocal of the square to those of highly forms of WC. They offer important insight into the nature of the active sites on W-C anode catalysts for use in phosphoric acid fuel cells.

Theoretical study of cathode surfaces and high-temperature superconductors

NASA Technical Reports Server (NTRS)

Mueller, Wolfgang

1995-01-01

Calculations are presented for the work functions of BaO on W, Os, Pt, and alloys of Re-W, Os-W, and Ir-W that are in excellent agreement with experiment. The observed emission enhancement for alloy relative to tungsten dispenser cathodes is attributed to properties of the substrate crystal structure and explained by the smaller depolarization of the surface dipole on hexagonal as compared to cubic substrates. For Ba and BaO on W(100), the geometry of the adsorbates has been determined by a comparison of inverse photoemission spectra with calculated densities of unoccupied states based on the fully relativistic embedded cluster approach. Results are also discussed for models of scandate cathodes and the electronic structure of oxygen on W(100) at room and elevated temperatures. A detailed comparison is made for the surface electronic structure of the high-temperature superconductor YBa2Cu3O7 as obtained with non-, quasi-, and fully relativistic cluster calculations.

Characterization of microstructure of A508III/309L/308L weld and oxide films formed in deaerated high-temperature water

NASA Astrophysics Data System (ADS)

Xiong, Qi; Li, Hongjuan; Lu, Zhanpeng; Chen, Junjie; Xiao, Qian; Ma, Jiarong; Ru, Xiangkun

2018-01-01

The microstructure of A508III/309L/308L weld clad and the properties of the oxide films formed in simulated pressurized water reactor primary water at 290 °C were characterized. The A508III heat-affected zone (HAZ) consisted primarily of a decarburization zone with ferrite near the fusion line and a following pearlite structure with fine grains. A high hardness region in the HAZ could be the result of C-enrichment. M23C6 and M7C3 precipitates were observed in element transition zone. 308L stainless steel (SS) containing ∼ 12% ferrites exhibited both ferritic-austenitic solidification mode (FA mode, δ→γ) and austenitic-ferritic solidification mode (AF mode, γ→δ), whereas 309L SS containing ∼ 9% ferrites exhibited only FA mode. The A508III surface oxide film was mainly Fe3O4 in deaerated high-temperature water. The coarse grain zone covered with few oxide particles was different from other types of film on the other region of HAZ and the bulk zone. More pitting appears on 309L SS after immersion in deaerated high-temperature water due to the dissolution of inclusions. SS surface oxide films consisted primarily of spinels. The oxide film on SS was divided into two layers. Ni was concentrated mainly at the oxide/substrate interface. The oxide film formed on 309L was thicker than that on the 308L. The ferrite in the stainless steel could improve the oxidation resistance.

Orientation dependence of microfracture behavior in a dual-phase high-strength low-alloy steel

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

Suh, D.; Lee, S.; Kim, N.J.

1997-02-01

In selecting the processing conditions and evaluating the reliability of structural materials, microscopic observations and identification of the fracture mechanisms in local cracking behavior are required. An important instance in the failure of the local brittle zone (LBZ) in the welding zone. The LBZ, which is very brittle, is the coarse-grained heat-affected zone near the fusion line, a zone known to be critical to the fracture toughness of welded parts. Thus, maintaining stable fracture resistance by predicting the microfracture behavior is important when using high-strength low-alloy (HSLA) steels in offshore structural steel welds. Depending on the thermal cycles involved duringmore » welding, the ferrite/martensite structure can have various morphologies of martensite particles, for example, fibrous and blocky martensite. In summary, in situ SEM fracture tests reveal that in the L-oriented IQ DCB specimen, a microcrack tends to propagate relatively uniformly throughout the ferrite and well-distributed fine fibrous martensite, yielding good elongation with high strength level. Also, the IQ structure in the T orientation shows similar microfracture behavior. On the other hand, in the SQ structure, where blocky-type martensite is mixed with ferrite, strain is localized into shear bands mostly in the ferrite region, and a local microcrack propagates along the strain-localized band formed in the ferrite, resulting in the SQ structure in the T orientation, where the ferrite-martensite bands are parallel to the notch direction, the martensite cannot act as an efficient barrier to microcrack advance, and thus the tensile ductility is decreased.« less

Temperature-dependent phase transition and comparative investigation on enhanced magnetic and optical properties between sillenite and perovskite bismuth ferrite-rGO nanocomposites

NASA Astrophysics Data System (ADS)

Jalil, M. A.; Chowdhury, Sayeed Shafayet; Alam Sakib, Mashnoon; Enamul Hoque Yousuf, S. M.; Khan Ashik, Emran; Firoz, Shakhawat H.; Basith, M. A.

2017-08-01

The manuscript reports the synthesis as well as a comparative investigation of the structural, magnetic, and optical properties between sillenite and perovskite type bismuth ferrite-reduced graphene oxide nanocomposites. Graphite oxide is prepared using the modified Hummers' method, followed by hydrothermal synthesis of bismuth ferrite-reduced graphene oxide nanocomposites at different reaction temperatures. The X-ray diffraction measurements confirm the formation of perovskite type BiFeO3-rGO nanocomposites at a reaction temperature of 200 °C. This is the lowest temperature to obtain perovskite type BiFeO3-rGO nanocomposites under the reaction procedure adopted, however, a structural transition to sillenite type Bi25FeO40-rGO is observed at 180 °C. The FESEM images demonstrate that the particle size of the perovskite nanocomposite is 25-60 nm, and for the sillenite phase nanocomposite it is 10-30 nm. The as-synthesized nanocomposites exhibit significantly enhanced saturation magnetization over pure BiFeO3 nanoparticles, with the sillenite Bi25FeO40-rGO nanocomposite having higher saturation magnetization than perovskite BiFeO3-rGO. The optical characteristics of the as-synthesized nanocomposites demonstrate considerably higher absorbance in the visible range with significantly lower band gap in comparison to undoped BiFeO3. Again, the sillenite Bi25FeO40-rGO nanocomposite is shown to have a lower band gap compared to the perovskite counterpart. Our investigation provides a means of selective phase formation as desired between sillenite Bi25FeO40-rGO and perovskite BiFeO3-rGO by controlling the hydrothermal reaction temperature. The outcome of our investigation suggests that the formation of nanocomposite of sillenite bismuth ferrite with reduced graphene oxide is promising to improve the magnetic and optical properties for potential technological applications.

Design considerations for quasi-phase-matching in doubly resonant lithium niobate hexagonal micro-resonators

NASA Astrophysics Data System (ADS)

Sono, Tleyane J.; Riziotis, Christos; Mailis, Sakellaris; Eason, Robert W.

2017-09-01

Fabrication capabilities of high optical quality hexagonal superstructures by chemical etching of inverted ferroelectric domains in lithium niobate platform suggests a route for efficient implementation of compact hexagonal microcavities. Such nonlinear optical hexagonal micro-resonators are proposed as a platform for second harmonic generation (SHG) by the combined mechanisms of total internal reflection (TIR) and quasi-phase-matching (QPM). The proposed scheme for SHG via TIR-QPM in a hexagonal microcavity can improve the efficiency and also the compactness of SHG devices compared to traditional linear-type based devices. A simple theoretical model based on six-bounce trajectory and phase matching conditions was capable for obtaining the optimal cavity size. Furthermore numerical simulation results based on finite difference time domain beam propagation method analysis confirmed the solutions obtained by demonstrating resonant operation of the microcavity for the second harmonic wave produced by TIR-QPM. Design aspects, optimization issues and characteristics of the proposed nonlinear device are presented.

Proposal of Magnetic Circuit using Magnetic Shielding with Bulk-Type High Tc Superconductors

NASA Astrophysics Data System (ADS)

Fukuoka, Katsuhiro; Hashimoto, Mitsuo; Tomita, Masaru; Murakami, Masato

Recently, bulk-type high Tc superconductors having a characteristic of critical current density over 104 A/cm2 in liquid nitrogen temperature (77K) on 1T, can be produced. They are promising for many practical applications such as a magnetic bearing, a magnetic levitation, a flywheel, a magnetic shielding and others. In this research, we propose a magnetic circuit that is able to use for the magnetic shield of plural superconductors as an application of bulk-type high Tc superconductors. It is a closed magnetic circuit by means of a toroidal core. Characteristics of the magnetic circuit surrounded with superconductors are evaluated and the possibility is examined. As the magnetic circuit of the ferrite core is surrounded with superconductors, the magnetic flux is shielded even if it leaked from the ferrite core.

CSMP (Continuous System Modeling Program) Modeling of Brushless DC Motors.

DTIC Science & Technology

1984-09-01

Characteristics of Fifteen HP Samarium Cobalt and Ferrite Based brushless DC Ictcrs j. Operated by the Same Power Conditioner ," IEEE Transactions on Pcwer stenM...paratus and Systeis, v. P -Ii-- -ry Demerdash, N.A. and Nehl.T.W., Dynamic Modeling cf Brushless DC Motor-Power Conditioner U if-- fo -- Iec tro me...III _J- _ o 0 NAVAL POSTGRADUATE SCHOOL Monterey, California •S THETIS CSMP MODEL{ING OF BRUSHLESS DC MOTORS by DTIC

Effects of Tensile Loading on Upper Shelf Fracture Toughness

DTIC Science & Technology

1994-06-01

applicability of this technique in the lower shelf ductile-brittle transition regime of ferritic steels has been demonstrated by Sorem, Dodds and Rolfe ...correct the load for the effect of rotation (Loss 1977; Merkle , 198x). The objective of the first correction is to correct the measured displacement...Testing and Materials, Philadelphia, pp. 114-132. Sorem, W.A., Dodds, R H., and Rolfe , S.T. (1991) "Effects of Crack Depth on Elastic Plastic Fracture

A Correlation Between the Heat Affected Zone Microstructure and the Thermal History During Welding of HY-130 Steel.

DTIC Science & Technology

1981-09-01

Engineers, Vol. 162, n 223, 1945. 16. Grange, R. A. and Baughman, R. W., "Hardness of Tempered Martensite in Carbon and Low Alloy Steels ," Transactions...One possible explanation is the forma- tion of the delta ferrite phase (with its attendant very low carbon solubility) in the vicinity of the fusion...32 18. isothermal Transformation Diagram for HY-130 (T) Steel -------------------------------------------- 3 19. Peak Temperature vs

Nonlinear surface waves at ferrite-metamaterial waveguide structure

NASA Astrophysics Data System (ADS)

Hissi, Nour El Houda; Mokhtari, Bouchra; Eddeqaqi, Noureddine Cherkaoui; Shabat, Mohammed Musa; Atangana, Jacques

2016-09-01

A new ferrite slab made of a metamaterial (MTM), surrounded by a nonlinear cover cladding and a ferrite substrate, was shown to support unusual types of electromagnetic surface waves. We impose the boundary conditions to derive the dispersion relation and others necessary to formulate the proposed structure. We analyse the dispersion properties of the nonlinear surface waves and we calculate the associated propagation index and the film-cover interface nonlinearity. In the calculation, several sets of the permeability of the MTM are considered. Results show that the waves behaviour depends on the values of the permeability of the MTM, the thickness of the waveguide and the film-cover interface nonlinearity. It is also shown that the use of the singular solutions to the electric field equation allows to identify several new properties of surface waves which do not exist in conventional waveguide.

Vector MO magnetometry for mapping microwave currents

NASA Astrophysics Data System (ADS)

Višňovský, Š.; Lišková-Jakubisová, E.; Harward, I.; Celinski, Z.

2018-05-01

Magneto-optic (MO) effects in magnetic multilayers (MML) can be employed in non-invasive 2D mapping of microwave (mw) radiation on the surface of semiconductor chips. A typical sensor configuration consists of Fe nanolayers sandwiched with dielectrics on a thin Si substrate transparent to mw radiation. To extend the observation bandwidth, Δf, up to 100 GHz range the sensor works at ferromagnetic resonance (FMR) frequency in applied magnetic flux density, Bappl. The mw currents excite the precession of magnetization, M, in magnetic nanolayers proportional to their amplitude. The MO component reflected on the sensor surface is proportional to the amplitude of M component, M⊥. The laser source operates at the wavelength of 410 nm. Its plane of incidence is oriented perpendicular to the M⊥ plane. M⊥ oscillates between polar and transverse configurations. A substantial improvement of MO figure of merit takes place in aperiodic MML. More favorable Δf vs. Bappl dependence and MO response can potentially be achieved in MML imbedding hexagonal ferrite or Co nanolayers with in-plane magnetic anisotropy.

Thermal relaxation and collective dynamics of interacting aerosol-generated hexagonal NiFe2O4 nanoparticles.

PubMed

Ortega, D; Kuznetsov, M V; Morozov, Yu G; Belousova, O V; Parkin, I P

2013-12-28

This article reports on the magnetic properties of interacting uncoated nickel ferrite (NiFe2O4) nanoparticles synthesized through an aerosol levitation-jet technique. A comprehensive set of samples with different compositions of background gas and metal precursors, as well as applied electric field intensities, has been studied. Nanoparticles prepared under a field of 210 kV m(-1) show moderately high-field irreversibility and shifted hysteresis loops after field-cooling, also exhibiting a joint temperature decrease of the exchange field and coercivity. The appearance of memory effects has been checked using the genuine ZFC protocol and the observed behavior cannot be fully explained in terms of thermal relaxation. Although dipolar interactions prevail, exchange interactions occur to a certain extent within a narrow range of applied fields. The origin of the slow dynamics in the system is found to be given by the interplay of the distribution of energy barriers due to size dispersion and the cooperative dynamics associated with frustrated interactions.

Role of stacking disorder in ice nucleation

NASA Astrophysics Data System (ADS)

Lupi, Laura; Hudait, Arpa; Peters, Baron; Grünwald, Michael; Gotchy Mullen, Ryan; Nguyen, Andrew H.; Molinero, Valeria

2017-11-01

The freezing of water affects the processes that determine Earth’s climate. Therefore, accurate weather and climate forecasts hinge on good predictions of ice nucleation rates. Such rate predictions are based on extrapolations using classical nucleation theory, which assumes that the structure of nanometre-sized ice crystallites corresponds to that of hexagonal ice, the thermodynamically stable form of bulk ice. However, simulations with various water models find that ice nucleated and grown under atmospheric temperatures is at all sizes stacking-disordered, consisting of random sequences of cubic and hexagonal ice layers. This implies that stacking-disordered ice crystallites either are more stable than hexagonal ice crystallites or form because of non-equilibrium dynamical effects. Both scenarios challenge central tenets of classical nucleation theory. Here we use rare-event sampling and free energy calculations with the mW water model to show that the entropy of mixing cubic and hexagonal layers makes stacking-disordered ice the stable phase for crystallites up to a size of at least 100,000 molecules. We find that stacking-disordered critical crystallites at 230 kelvin are about 14 kilojoules per mole of crystallite more stable than hexagonal crystallites, making their ice nucleation rates more than three orders of magnitude higher than predicted by classical nucleation theory. This effect on nucleation rates is temperature dependent, being the most pronounced at the warmest conditions, and should affect the modelling of cloud formation and ice particle numbers, which are very sensitive to the temperature dependence of ice nucleation rates. We conclude that classical nucleation theory needs to be corrected to include the dependence of the crystallization driving force on the size of the ice crystallite when interpreting and extrapolating ice nucleation rates from experimental laboratory conditions to the temperatures that occur in clouds.

Rotating non-Boussinesq Rayleigh-Benard convection

NASA Astrophysics Data System (ADS)

Moroz, Vadim Vladimir

This thesis makes quantitative predictions about the formation and stability of hexagonal and roll patterns in convecting system unbounded in horizontal direction. Starting from the Navier-Stokes, heat and continuity equations, the convection problem is then reduced to normal form equations using equivariant bifurcation theory. The relative stabilities of patterns lying on a hexagonal lattice in Fourier space are then determined using appropriate amplitude equations, with coefficients obtained via asymptotic expansion of the governing partial differential equations, with the conducting state being the base state, and the control parameter and the non-Boussinesq effects being small. The software package Mathematica was used to calculate amplitude coefficients of the appropriate coupled Ginzburg-Landau equations for the rigid-rigid and free-free case. A Galerkin code (initial version of which was written by W. Pesch et al.) is used to determine pattern stability further from onset and for strongly non-Boussinesq fluids. Specific predictions about the stability of hexagon and roll patterns for realistic experimental conditions are made. The dependence of the stability of the convective patterns on the Rayleigh number, planform wavenumber and the rotation rate is studied. Long- and shortwave instabilities, both steady and oscillatory, are identified. For small Prandtl numbers oscillatory sideband instabilities are found already very close to onset. A resonant mode interaction in hexagonal patterns arising in non-Boussinesq Rayleigh-Benard convection is studied using symmetry group methods. The lowest-order coupling terms for interacting patterns are identified. A bifurcation analysis of the resulting system of equations shows that the bifurcation is transcritical. Stability properties of resulting patterns are discussed. It is found that for some fluid properties the traditional hexagon convection solution does not exist. Analytical results are supported by numerical solutions of the convection equations using the Galerkin procedure and a Floquet analysis.

Role of stacking disorder in ice nucleation.

PubMed

Lupi, Laura; Hudait, Arpa; Peters, Baron; Grünwald, Michael; Gotchy Mullen, Ryan; Nguyen, Andrew H; Molinero, Valeria

2017-11-08

The freezing of water affects the processes that determine Earth's climate. Therefore, accurate weather and climate forecasts hinge on good predictions of ice nucleation rates. Such rate predictions are based on extrapolations using classical nucleation theory, which assumes that the structure of nanometre-sized ice crystallites corresponds to that of hexagonal ice, the thermodynamically stable form of bulk ice. However, simulations with various water models find that ice nucleated and grown under atmospheric temperatures is at all sizes stacking-disordered, consisting of random sequences of cubic and hexagonal ice layers. This implies that stacking-disordered ice crystallites either are more stable than hexagonal ice crystallites or form because of non-equilibrium dynamical effects. Both scenarios challenge central tenets of classical nucleation theory. Here we use rare-event sampling and free energy calculations with the mW water model to show that the entropy of mixing cubic and hexagonal layers makes stacking-disordered ice the stable phase for crystallites up to a size of at least 100,000 molecules. We find that stacking-disordered critical crystallites at 230 kelvin are about 14 kilojoules per mole of crystallite more stable than hexagonal crystallites, making their ice nucleation rates more than three orders of magnitude higher than predicted by classical nucleation theory. This effect on nucleation rates is temperature dependent, being the most pronounced at the warmest conditions, and should affect the modelling of cloud formation and ice particle numbers, which are very sensitive to the temperature dependence of ice nucleation rates. We conclude that classical nucleation theory needs to be corrected to include the dependence of the crystallization driving force on the size of the ice crystallite when interpreting and extrapolating ice nucleation rates from experimental laboratory conditions to the temperatures that occur in clouds.

Study of mixed ternary transition metal ferrites as potential electrodes for supercapacitor applications

NASA Astrophysics Data System (ADS)

Bhujun, Bhamini; Tan, Michelle T. T.; Shanmugam, Anandan S.

Nanocrystallites of three mixed ternary transition metal ferrite (MTTMF) were prepared by a facile sol-gel method and adopted as electrode material for supercapacitors. The phase development of the samples was determined using Fourier transform infrared (FT-IR) and thermal gravimetric analysis (TG). X-ray diffraction (XRD) analysis revealed the formation of a single-phase spinel ferrite in CuCoFe2O4 (CuCoF), NiCoFe2O4 (NiCoF) and NiCuFe2O4 (NiCuF). The surface characteristics and elemental composition of the nanocomposites have been studied by means of field emission scanning electron microscopy (FESEM), as well as energy dispersive spectroscopy (EDS). The electrochemical performance of the nanomaterials was evaluated using a two-electrode configuration by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic technique in 1 M KOH electrolyte and was found to be in the order of: CuCoF > NiCoF > NiCuF. A maximum specific capacitance of 221 Fg-1 was obtained with CuCoF at a scan rate of 5 mV s-1. In addition to an excellent cycling stability, an energy density of 7.9 kW kg-1 was obtained at a current density of 1 Ag-1. The high electrochemical performance of the MTTMF nanocomposites obtained indicates that these materials are promising electrodes for supercapacitors.

Crystallographic characterizations of eutectic and secondary carbides in a Fe-12Cr-2.5Mo-1.5W-3V-1.25C alloy

NASA Astrophysics Data System (ADS)

Guo, Jing; Liu, Ligang; Feng, Yunli; Liu, Sha; Ren, Xuejun; Yang, Qingxiang

2017-03-01

In this work, the morphology and structures of the eutectic and secondary carbides in a new high chromium Fe-12Cr-2.5Mo-1.5W-3V-1.25C designed for cold-rolling work roll were systematically studied. The precipitated carbides inside the grains and along the grain boundaries were investigated with optical microscope, scanning electron microscopy with energy dispersive spectroscopy, transmission electron microscopy and X-Ray diffraction. Selected area diffraction patterns have been successfully used to identify the crystal formation and lattice constants of the carbides with different alloying elements. The results show that the eutectic carbides precipitated contain MC and M2C distributed along the grain boundaries with dendrite feature. The composition and crystal structure analysis shows that the eutectic MC carbides contain VC and WC with a cubic and hexagonal crystal lattice structures respectively, while the eutectic M2C carbides predominantly contain V2C and Mo2C with orthorhombic and hexagonal crystal lattices respectively. The secondary carbides contain MC, M2C, M7C3 formed along the grain boundaries and their sizes are much larger than the eutectic carbides ones. The secondary M23C6 is much small (0.3-0.5μm) and is distributed dispersively inside the grain. Similar to the eutectic carbides, the secondary carbides also contain VC, WC, V2C, and Mo2C. M7C3 is hexagonal (Fe,Cr)7C3, while M23C6 is indexed to be in a cubic crystal form.

Assessment of off-stoichiometric Zr33-xFe52+xSi15 C14 Laves phase compounds as permanent magnet materials

NASA Astrophysics Data System (ADS)

Gabay, A. M.; Hadjipanayis, G. C.

2018-05-01

Recently, Fe-based rare-earth-free compounds with non-cubic crystal structures were proposed as a base for permanent magnets which would not rely on critical elements. In this work, two series of alloys, Zr27Fe73-wSiw (0 ≤ w ≤ 15) and Zr33-xFe52+xSi15 (0 ≤ x ≤ 11), were prepared and characterized after annealing at 1538 K in order to determine the fundamental magnetic properties of the C36 and C14 hexagonal Laves phase compounds. A mixture of the cubic C15 and Zr6Fe23 structures was observed instead of the expected C36 structure. The hexagonal C14 was found in all Zr33-xFe52+xSi15 alloys with its lattice parameters linearly decreasing as the Fe(Si) atoms occupy the Zr sites in the Laves phase crystal structure. The solubility limit of Fe in the C14 structure at 1538 K corresponds to x = 9.5. The Curie temperature of the C14 compounds increases with deviation from the Laves phase stoichiometry from 290 K to 530 K. The room-temperature spontaneous magnetization also increases reaching, after correcting for the non-magnetic impurities, a value of 6.7 kG. The magnetocrystalline anisotropy of the off-stoichiometric C14 Laves phase was found to be uniaxial with the easy magnetization direction parallel to the hexagonal axis. Unfortunately, the anisotropy field, which does not exceed 10 kOe, is not sufficiently high to make the compounds interesting as permanent magnet materials.

A hexagonal orthogonal-oriented pyramid as a model of image representation in visual cortex

NASA Technical Reports Server (NTRS)

Watson, Andrew B.; Ahumada, Albert J., Jr.

1989-01-01

Retinal ganglion cells represent the visual image with a spatial code, in which each cell conveys information about a small region in the image. In contrast, cells of the primary visual cortex use a hybrid space-frequency code in which each cell conveys information about a region that is local in space, spatial frequency, and orientation. A mathematical model for this transformation is described. The hexagonal orthogonal-oriented quadrature pyramid (HOP) transform, which operates on a hexagonal input lattice, uses basis functions that are orthogonal, self-similar, and localized in space, spatial frequency, orientation, and phase. The basis functions, which are generated from seven basic types through a recursive process, form an image code of the pyramid type. The seven basis functions, six bandpass and one low-pass, occupy a point and a hexagon of six nearest neighbors on a hexagonal lattice. The six bandpass basis functions consist of three with even symmetry, and three with odd symmetry. At the lowest level, the inputs are image samples. At each higher level, the input lattice is provided by the low-pass coefficients computed at the previous level. At each level, the output is subsampled in such a way as to yield a new hexagonal lattice with a spacing square root of 7 larger than the previous level, so that the number of coefficients is reduced by a factor of seven at each level. In the biological model, the input lattice is the retinal ganglion cell array. The resulting scheme provides a compact, efficient code of the image and generates receptive fields that resemble those of the primary visual cortex.

In-situ X-ray diffraction study of phase transformations in the Am-O system

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

Lebreton, Florent, E-mail: florent.lebreton@cea.fr; GEMH, ENSCI, 87065 Limoges; Belin, Renaud C., E-mail: renaud.belin@cea.fr

2012-12-15

In the frame of minor actinides recycling, americium can be transmuted by adding it in UO{sub 2} or (U, Pu)O{sub 2} fuels. Americium oxides exhibiting a higher oxygen potential than U or Pu oxides, its addition alters the fuel properties. To comprehend its influence, a thorough knowledge of the Am-O phase equilibria diagram and of thermal expansion behavior is of main interest. Due to americium scarcity and high radiotoxicity, few experimental reports on this topic are available. Here we present in-situ high-temperature XRD results on the reduction from AmO{sub 2} to Am{sub 2}O{sub 3}. We show that fluorite (Fm-3m) AmO{submore » 2} is reduced to cubic (Ia-3) C Prime -type Am{sub 2}O{sub 3+{delta}}, and then into hexagonal (P6{sub 3}/mmc) A-type Am{sub 2}O{sub 3}, which remains stable up to 1840 K. We also demonstrate the transitional existence of the monoclinic (C2/m) B-type Am{sub 2}O{sub 3}. At last, we describe, for the first time, the thermal expansion behavior of the hexagonal Am{sub 2}O{sub 3} between room temperature and 1840 K. - Graphical abstract: Americium dioxide was in situ studied by high-temperature X-ray diffraction. First, fluorite AmO{sub 2} is reduced to cubic C Prime -type Am{sub 2}O{sub 3+{delta}} and then transforms into hexagonal A-type Am{sub 2}O{sub 3}, which remains stable up to 1840 K. Then, we demonstrate the transitional existence of monoclinic B-type Am{sub 2}O{sub 3}. At last, we describe, for the first time, the thermal expansion of A-type Am{sub 2}O{sub 3} between room temperature and 1840 K. This work may contribute to a better understanding of Am oxide behavior. Highlights: Black-Right-Pointing-Pointer We realize an in-situ high-temperature X-ray diffraction study on an AmO{sub 2} sample. Black-Right-Pointing-Pointer Fluorite AmO{sub 2} transforms to cubic Am{sub 2}O{sub 3+{delta}} and then to hexagonal Am{sub 2}O{sub 3}. Black-Right-Pointing-Pointer Little-known monoclinic Am{sub 2}O{sub 3} is observed during the cubic-to-hexagonal transition. Black-Right-Pointing-Pointer Lattice parameter thermal expansion of hexagonal Am{sub 2}O{sub 3} is given up to 1840 K. Black-Right-Pointing-Pointer We give additional data on AmO{sub 2} lattice parameter expansion under self-irradiation.« less

Synthesis and characterization of the pseudo-hexagonal hollandites ALi{sub 2}Ru{sub 6}O{sub 12} (A=Na, K)

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

Foo, M.L.; He, T.; Huang, Q.

The crystal structures, synthesis and physical properties of ruthenium hollandites ALi{sub 2}Ru{sub 6}O{sub 12} (A=Na, K) with a new pseudo-hexagonal structure type are described. Analogous to tetragonal hollandites, the framework is made of MO{sub 6} octahedra in double chains that share corner oxygens with each other to create interstitial tunnels. The tunnels are either hexagonal or triangular in cross-section. Magnetic susceptibilities, low temperature specific heat, and electrical resistivities are reported. The data indicate that these materials are normal, low density of states metals. This new structure type can be extended from A=Group I to A=Group II ions with the synthesismore » of CaLi{sub 2}Ru{sub 6}O{sub 12} and SrLi{sub 2}Ru{sub 6}O{sub 12}.« less

Influence of strain rate and temperature on tensile properties and flow behaviour of a reduced activation ferritic-martensitic steel

NASA Astrophysics Data System (ADS)

Vanaja, J.; Laha, K.; Sam, Shiju; Nandagopal, M.; Panneer Selvi, S.; Mathew, M. D.; Jayakumar, T.; Rajendra Kumar, E.

2012-05-01

Tensile strength and flow behaviour of a Reduced Activation Ferritic-Martensitic (RAFM) steel (9Cr-1W-0.06Ta-0.22V-0.08C) have been investigated over a temperature range of 300-873 K at different strain rates. Tensile strength of the steel decreased with temperature and increased with strain rate except at intermediate temperatures. Negative strain rate sensitivity of flow stress of the steel at intermediate temperatures revealed the occurrence of dynamic strain ageing in the steel, even though no serrated flow was observed. The tensile flow behaviour of the material was well represented by the Voce strain hardening equation for all the test conditions. Temperature and strain rate dependence of the various parameters of Voce equation were interpreted with the possible deformation mechanisms. The equivalence between the saturation stress at a given strain rate in tensile test and steady state deformation rate at a given stress in creep test was found to be satisfied by the RAFM steel.

Chemical Synthesis of Next Generation High Energy Product Hybrid SmCo Permanent Magnets for High Temperature Applications

DTIC Science & Technology

2010-08-01

among CoxC, AINiCo and Ba / Sr ferrite magnets. AINiCo is shown to exhibit high (BH)max, 35 kJmŗ, but a low intrinsic coercivity, mostly ə kOe...whereas Ba / Sr ferrite features high intrinsic coercivity, 3-4.5 kOe, but typical values of (BH)max below 25 kJm-3. However, the multiple...coercivity of cobalt carbide nanoparticles is compared with free powders of AINiCo and ceramic magnets of the Ba / Sr hexaferrite type. Curie temperatures near

Eddy current measurement of tube element spacing

DOEpatents

Latham, Wayne Meredith; Hancock, Jimmy Wade; Grut, Jayne Marie

1998-01-01

A method of electromagnetically measuring the distance between adjacent tube elements in a heat exchanger. A cylindrical, high magnetic permeability ferrite slug is placed in the tube adjacent the spacing to be measured. A bobbin or annular coil type probe operated in the absolute mode is inserted into a second tube adjacent the spacing to be measured. From prior calibrations on the response of the eddy current coil, the signals from the coil, when sensing the presence of the ferrite slug, are used to determine the spacing between the tubes.

The effect of tungsten on dislocation recovery and precipitation behavior of low-activation martensitic 9Cr steels

NASA Astrophysics Data System (ADS)

Abe, F.; Araki, H.; Noda, T.

1991-10-01

The effect of W on dislocation recovery and precipitation behavior was investigated for martensitic 9Cr-(0,l,2,4)W-0.1C (wt pct) steels after quenching, tempering, and subsequent prolonged aging. The steels were low induced-radioactivation martensitic steels for fusion reactor structures, intended as a possible replacement for conventional (7 to 12)Cr-Mo steels. During tempering after quenching, homogeneous precipitation of fine W2C occurred in martensite, causing secondary hardening between 673 and 823 K. The softening above the secondary hardening temperature shifted to higher temperatures with increasing W concentration, which was correlated with the decrease in self-diffusion rates with increasing W concentration. Carbides M23C6 and M7C3 were precipitated in the 9Cr steel without W after high-temperature tempering at 1023 K. With increasing W concentration, M7C3 was replaced by M23C6, and M6C formed in addition to M23C6. During subsequent aging at temperatures between 823 and 973 K after tempering, the recovery of dislocations, the agglomeration of carbides, and the growth of martensite lath subgrains occurred. Intermetallic Fe2W Laves also precipitated in the δ-ferrite grains of the 9Cr-4W steel. The effect of W on dislocation recovery and precipitation behavior is discussed in detail.

Alloy Design and Development of Cast Cr-W-V Ferritic Steels for Improved High-Temperature Strength for Power Generation Applications

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

Klueh, R L; Maziasz, P J; Vitek, J M

2006-09-23

Economic and environmental concerns demand that the power-generation industry seek increased efficiency for gas turbines. Higher efficiency requires higher operating temperatures, with the objective temperature for the hottest sections of new systems {approx} 593 C, and increasing to {approx} 650 C. Because of their good thermal properties, Cr-Mo-V cast ferritic steels are currently used for components such as rotors, casings, pipes, etc., but new steels are required for the new operating conditions. The Oak Ridge National Laboratory (ORNL) has developed new wrought Cr-W-V steels with 3-9% Cr, 2-3% W, 0.25% V (compositions are in wt.%), and minor amounts of additionalmore » elements. These steels have the strength and toughness required for turbine applications. Since cast alloys are expected to behave differently from wrought material, work was pursued to develop new cast steels based on the ORNL wrought compositions. Nine casting test blocks with 3, 9, and 11% Cr were obtained. Eight were Cr-W-V-Ta-type steels based on the ORNL wrought steels; the ninth was COST CB2, a 9Cr-Mo-Co-V-Nb cast steel, which was the most promising cast steel developed in a European alloy-development program. The COST CB2 was used as a control to which the new compositions were compared, and this also provided a comparison between Cr-W-V-Ta and Cr-Mo-V-Nb compositions. Heat treatment studies were carried out on the nine castings to determine normalizing-and-tempering treatments. Microstructures were characterized by both optical and transmission electron microscopy (TEM). Tensile, impact, and creep tests were conducted. Test results on the first nine cast steel compositions indicated that properties of the 9Cr-Mo-Co-V-Nb composition of COST CB2 were better than those of the 3Cr-, 9Cr-, and 11Cr-W-V-Ta steels. Analysis of the results of this first iteration using computational thermodynamics raised the question of the effectiveness in cast steels of the Cr-W-V-Ta combination versus the Cr-Mo-V-Nb combination in COST CB2. To explore this question, nine more casting test blocks, four 3Cr steels and five 11Cr steels were purchased, and microstructure and mechanical properties studies similar to those described above for the first iteration of test blocks were conducted. Experimental results from the second iteration indicated that 11 Cr steels with excellent properties are possible. The 11Cr-1.5Mo-V-Nb steels were superior to 11Cr-2W-V-Ta steels, and it appears the former class of steels can be developed to have tensile and creep properties exceeding those of COST CB2. The W-Nb combination in an 11Cr-2W-V-Nb steel had tensile and short-time creep properties at 650 C better than the 11Cr-1.5Mo-V-Nb steels, although long-time low-stress properties may not be as good because of Laves phase formation. Based on the results, the next step in the development of improved casting steels involves acquisition of 11Cr-1.5Mo-V-Nb-N-B-C and 11Cr-2W-V-Nb-N-B-C steels on which long-term creep-rupture tests (>10,000 h) be conducted. For better oxidation and corrosion resistance, development of 11Cr steels, as opposed to a 9Cr steels, such as COST CB2, are important for future turbine designs that envision operating temperatures of 650 C.« less

A study of transition from n- to p-type based on hexagonal WO3 nanorods sensor

NASA Astrophysics Data System (ADS)

Wu, Ya-Qiao; Hu, Ming; Wei, Xiao-Ying

2014-04-01

Hexagonal WO3 nanorods are fabricated by a facile hydrothermal process at 180 °C using sodium tungstate and sodium chloride as starting materials. The morphology, structure, and composition of the prepared nanorods are studied by scanning electron microscopy, X-ray diffraction spectroscopy, and energy dispersive spectroscopy. It is found that the agglomeration of the nanorods is strongly dependent on the PH value of the reaction solution. Uniform and isolated WO3 nanorods with diameters ranging from 100 nm-150 nm and lengths up to several micrometers are obtained at PH = 2.5 and the nanorods are identified as being hexagonal in phase structure. The sensing characteristics of the WO3 nanorod sensor are obtained by measuring the dynamic response to NO2 with concentrations in the range 0.5 ppm-5 ppm and at working temperatures in the range 25 °C-250 °C. The obtained WO3 nanorods sensors are found to exhibit opposite sensing behaviors, depending on the working temperature. When being exposed to oxidizing NO2 gas, the WO3 nanorod sensor behaves as an n-type semiconductor as expected when the working temperature is higher than 50 °C, whereas, it behaves as a p-type semiconductor below 50 °C. The origin of the n- to p-type transition is correlated with the formation of an inversion layer at the surface of the WO3 nanorod at room temperature. This finding is useful for making new room temperature NO2 sensors based on hexagonal WO3 nanorods.

Synchrotron-based XRD from rat bone of different age groups.

PubMed

Rao, D V; Gigante, G E; Cesareo, R; Brunetti, A; Schiavon, N; Akatsuka, T; Yuasa, T; Takeda, T

2017-05-01

Synchrotron-based XRD spectra from rat bone of different age groups (w, 56 w and 78w), lumber vertebra at early stages of bone formation, Calcium hydroxyapatite (HAp) [Ca 10 (PO 4 ) 6 (OH) 2 ] bone fill with varying composition (60% and 70%) and bone cream (35-48%), has been acquired with 15keV synchrotron X-rays. Experiments were performed at Desy, Hamburg, Germany, utilizing the Resonant and Diffraction beamline (P9), with 15keV X-rays (λ=0.82666 A 0 ). Diffraction data were quantitatively analyzed using the Rietveld refinement approach, which allowed us to characterize the structure of these samples in their early stages. Hydroxyapatite, received considerable attention in medical and materials sciences, since these materials are the hard tissues, such as bone and teeth. Higher bioactivity of these samples gained reasonable interest for biological application and for bone tissue repair in oral surgery and orthopedics. The results obtained from these samples, such as phase data, crystalline size of the phases, as well as the degree of crystallinity, confirm the apatite family crystallizing in a hexagonal system, space group P6 3 /m with the lattice parameters of a=9.4328Å and c=6.8842Å (JCPDS card #09-0432). Synchrotron-based XRD patterns are relatively sharp and well resolved and can be attributed to the hexagonal crystal form of hydroxyapatite. All the samples were examined with scanning electron microscope at an accelerating voltage of 15kV. The presence of large globules of different sizes is observed, in small age groups of the rat bone (8w) and lumber vertebra (LV), as distinguished from, large age groups (56 and 78w) in all samples with different magnification, reflects an amorphous phase without significant traces of crystalline phases. Scanning electron microscopy (SEM) was used to characterize the morphology and crystalline properties of Hap, for all the samples, from 2 to 100μm resolution. Copyright © 2017 Elsevier B.V. All rights reserved.

Isochronal annealing studies on 1.1 MeV Fe ion irradiated RAFM steel using variable energy slow positron beam

NASA Astrophysics Data System (ADS)

Ramachandran, Renjith; David, C.; Rajaraman, R.; Abhaya, S.; Panigrahi, B. K.; Amarendra, G.

2017-05-01

Indian Reduced Activation Ferritic Martensitic steel is irradiated with 1.1 MeV Fe ions to a dose of 0.1 dpa at room temperature. The positron annihilation study showed a decrease in S-parameter with annealing temperature due to vacancy annealing. A complete defect recovery is observed beyond 1073 K. The linear nature of (S, W) correlation plot shows that only one kind of defect is present throughout the annealing temperature.

Effects of heat input on pitting corrosion in super duplex stainless steel weld metals

NASA Astrophysics Data System (ADS)

Shin, Yong taek; Shin, Hak soo; Lee, Hae woo

2012-12-01

Due to the difference in reheating effects depending on the heat input of subsequent weld passes, the microstructure of the weld metal varies between acicular type austenite and a mixture of polygonal type and grain boundary mixed austenite. These microstructural changes may affect the corrosion properties of duplex stainless steel welds. This result indicates that the pitting resistance of the weld can be strongly influenced by the morphology of the secondary austenite phase. In particular, the ferrite phase adjacent to the acicular type austenite phase shows a lower Pitting Resistance Equivalent (PRE) value of 25.3, due to its lower chromium and molybdenum contents, whereas the secondary austenite phase maintains a higher PRE value of more than 38. Therefore, it can be inferred that the pitting corrosion is mainly due to the formation of ferrite phase with a much lower PRE value.

Nano-sized precipitate stability and its controlling factors in a NiAl-strengthened ferritic alloy

PubMed Central

Sun, Zhiqian; Song, Gian; Ilavsky, Jan; Ghosh, Gautam; Liaw, Peter K.

2015-01-01

Coherent B2-ordered NiAl-type precipitates have been used to reinforce solid-solution body-centered-cubic iron for high-temperature application in fossil-energy power plants. In this study, we investigate the stability of nano-sized precipitates in a NiAl-strengthened ferritic alloy at 700–950 °C using ultra-small angle X-ray scattering and electron microscopies. Here we show that the coarsening kinetics of NiAl-type precipitates is in excellent agreement with the ripening model in multicomponent alloys. We further demonstrate that the interfacial energy between the matrix and NiAl-type precipitates is strongly dependent on differences in the matrix/precipitate compositions. Our results profile the ripening process in multicomponent alloys by illustrating controlling factors of interfacial energy, diffusivities, and element partitioning. The study provides guidelines to design and develop high-temperature alloys with stable microstructures for long-term service. PMID:26537060

PERFORMANCE IMPROVEMENT OF CREEP-RESISTANT FERRITIC STEEL WELDMENTS THROUGH THERMO-MECHANICAL TREATMENT AND ALLOY DESIGN

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

Yamamoto, Yukinori; Babu, Prof. Sudarsanam Suresh; Shassere, Benjamin

Two different approaches have been proposed for improvement of cross-weld creep properties of the high temperature ferrous structural materials for fossil-fired energy applications. The traditional creep strength-enhanced ferritic (CSEF) steel weldments suffer from Type IV failures which occur at the fine-grained heat affected zone (FGHAZ). In order to minimize the premature failure at FGHAZ in the existing CSEF steels, such as modified 9Cr-1Mo ferritic-martensitic steels (Grade 91), a thermo-mechanical treatment consisting of aus-forging/rolling and subsequent aus-aging is proposed which promotes the formation of stable MX carbonitrides prior to martensitic transformation. Such MX remains undissolved during welding process, even in FGHAZ,more » which successfully improves the cross-weld creep properties. Another approach is to develop a new fully ferrtic, creep-resistant FeCrAl alloy which is essentially free from Type IV failure issues. Fe-30Cr-3Al base alloys with minor alloying additions were developed which achieved a combination of good oxidation/corrosion resistance and improved tensile and creep performance comparable or superior to Grade 92 steel.« less

Nd3+-doped soft glass double-clad fibers with a hexagonal inner cladding

NASA Astrophysics Data System (ADS)

Wang, Longfei; He, Dongbing; Hu, Lili; Chen, Danping

2015-04-01

The stack-and-draw technique was used to fabricate Nd3+-doped silicate and phosphate glass double-clad step-index fibers with a non-circular inner cladding. For the silicate fiber, a maximum output power of 7.7 W was obtained from a 94 cm fiber. An output power of 1.25 W was also realized with a short length fiber of 8 cm, confirming the application potential of this fiber in single frequency lasers and pulsed amplifiers where an efficient rare-earth-doped fiber with short length is desirable. For the phosphate fiber, a maximum output power of 2.78 W was obtained from a single-mode fiber with a core diameter of up to 35 μm.

Microtribological Mechanisms of Tungsten and Aluminum Nitride Films

NASA Astrophysics Data System (ADS)

Zhao, Hongjian; Mu, Chunyan; Ye, Fuxing

2016-04-01

Microtribology experiments were carried out on the W1- x Al x N films, deposited by radio frequency magnetron reactive sputtering on 304 stainless steel substrates and Si(100). Film wear mechanisms were investigated from the evolution of the friction coefficient and scanning electron microscopy observations. The results show that the WAlN films consist of a mixture of face-centered cubic W(Al)N and hexagonal wurtzite structure AlN phases and the preferred orientation changes from (111) to (200). The film damage after sliding test is mainly attributed to the composition and microstructure of the films. The amount of debris generated by friction is linked to the crack resistance. The better tribological properties for W1- x Al x N films ( x < 0.4) are mainly determined by the higher toughness.

Pressure induced structural phase transition of OsB 2: First-principles calculations

NASA Astrophysics Data System (ADS)

Ren, Fengzhu; Wang, Yuanxu; Lo, V. C.

2010-04-01

Orthorhombic OsB 2 was synthesized at 1000 °C and its compressibility was measured by using the high-pressure X-ray diffraction in a Diacell diamond anvil cell from ambient pressure to 32 GPa [R.W. Cumberland, et al. (2005)]. First-principles calculations were performed to study the possibility of the phase transition of OsB 2. An analysis of the calculated enthalpy shows that orthorhombic OsB 2 can transfer to the hexagonal phase at 10.8 GPa. The calculated results with the quasi-harmonic approximation indicate that this phase transition pressure is little affected by the thermal effect. The calculated phonon band structure shows that the hexagonal P 6 3/ mmc structure (high-pressure phase) is stable for OsB 2. We expect the phase transition can be further confirmed by the experimental work.

Catalyst effects in heterogeneous nucleation of acicular ferrite

NASA Astrophysics Data System (ADS)

Grong, Ø.; Kluken, A. O.; Nylund, H. K.; Dons, A. L.; Hjelen, J.

1995-03-01

The present investigation is concerned with basic studies of the mechanisms of acicular ferrite (AF)’formation in low-alloy steel weld metal. It is confirmed experimentally that different types of orientation relationships exist between AF and specific cubic inclusion constituent phases (i.e., γ-Al2 MnOAl2O3, and TiN). Since the majority of these falls within the Bain orientation region, it is concluded that the associated reduction of the energy barrier to nucleation is the primary cause for the ferrite nucleus to develop orientation relationships with both the substrate and the austenite. Theoretical calculations show that about 12 pct of the inclusions will contain a cubic phase that lies within the Bain region purely by chance if they are randomly orientated in space. This intrinsic density of heterogeneous nucleation sites is sufficiently high to promote the formation of fine, interlocking AF laths in the weld metal during the y- to- a transformation.

Highly Crystalline CVD-grown Multilayer MoSe2 Thin Film Transistor for Fast Photodetector

PubMed Central

Jung, Chulseung; Kim, Seung Min; Moon, Hyunseong; Han, Gyuchull; Kwon, Junyeon; Hong, Young Ki; Omkaram, Inturu; Yoon, Youngki; Kim, Sunkook; Park, Jozeph

2015-01-01

Hexagonal molybdenum diselenide (MoSe2) multilayers were grown by chemical vapor deposition (CVD). A relatively high pressure (>760 Torr) was used during the CVD growth to achieve multilayers by creating multiple nuclei based on the two-dimensional crystal growth model. Our CVD-grown multilayer MoSe2 thin-film transistors (TFTs) show p-type-dominant ambipolar behaviors, which are attributed to the formation of Se vacancies generated at the decomposition temperature (650 °C) after the CVD growth for 10 min. Our MoSe2 TFT with a reasonably high field-effect mobility (10 cm2/V · s) exhibits a high photoresponsivity (93.7 A/W) and a fast photoresponse time (τrise ~ 0.4 s) under the illumination of light, which demonstrates the practical feasibility of multilayer MoSe2 TFTs for photodetector applications. PMID:26477744

The preparation and degradation performance of CdS photocatalysts to methyl orange solution.

PubMed

Duan, Limei; Zhao, Weiqiang; Xu, Ling; Chen, Xiaohong; Lita, A; Liu, Zongrui

2013-03-01

In this paper, the CdS samples were prepared using thiourea or sodium sulfide as sulfur source by hydrothermal or solvothermal synthesis method, the results of XRD, TEM and SEM showed all the samples belong to hexagonal CdS nano-material with different morphologies. Using the degradation of methyl orange solution as a model reaction, the photocatalytic performance of different CdS samples was measured, and the samples prepared using thiourea as sulfur source exhibited better photocatalytic activity than those using sodium sulfide as sulfur source. The factors on degradation effect were discussed including the pH value of degradation system and the type of light source. The degradation effect of CdS samples increased with the pH value decreased, and the degradation effect was better when the methyl orange solution was irradiated under sunlight than under 250 W mercury lamp.

Crystallization of phycoerythrocyanin from the cyanobacterium Mastigocladus laminosus and preliminary characterization of two crystal forms.

PubMed

Rümbeli, R; Schirmer, T; Bode, W; Sidler, W; Zuber, H

1985-11-05

The light-harvesting protein phycoerythrocyanin from the cyanobacterium Mastigocladus laminosus Cohn has been crystallized in two different crystal forms by vapour diffusion. In 5% (w/v) polyethylene glycol at pH 8.5, hexagonal crystals of space group P63 with cell constants a = b = 158 A, c = 40.6 A were obtained, which turned out to be almost isomorphous with the hexagonal crystals of C-phycocyanin from the same organism. Consequently, the conformation of both phycobiliproteins must be very similar. From 1.5 M-ammonium sulfate (pH 8.5), orthorhombic crystals of space group P2221 with cell constants a = 60.5 A, b = 105 A, c = 188 A could be grown. Density measurements of these crystals indicate that the unit cell contains 18 (alpha beta)-units. A detailed packing scheme is proposed that is consistent with the observed pseudo-hexagonal X-ray intensity pattern and with the known size and shape of (alpha beta)3-trimers of C-phycocyanin. Accordingly, disc-like (alpha beta)3-trimers are associated face-to-face and stacked one upon another in rods with a period of 60.5 A, corresponding to the cell dimension a.

Freezing, melting and structure of ice in a hydrophilic nanopore.

PubMed

Moore, Emily B; de la Llave, Ezequiel; Welke, Kai; Scherlis, Damian A; Molinero, Valeria

2010-04-28

The nucleation, growth, structure and melting of ice in 3 nm diameter hydrophilic nanopores are studied through molecular dynamics simulations with the mW water model. The melting temperature of water in the pore was T(m)(pore) = 223 K, 51 K lower than the melting point of bulk water in the model and in excellent agreement with experimental determinations for 3 nm silica pores. Liquid and ice coexist in equilibrium at the melting point and down to temperatures as low as 180 K. Liquid water is located at the interface of the pore wall, increasing from one monolayer at the freezing temperature, T(f)(pore) = 195 K, to two monolayers a few degrees below T(m)(pore). Crystallization of ice in the pore occurs through homogeneous nucleation. At the freezing temperature, the critical nucleus contains approximately 75 to 100 molecules, with a radius of gyration similar to the radius of the pore. The critical nuclei contain features of both cubic and hexagonal ice, although stacking of hexagonal and cubic layers is not defined until the nuclei reach approximately 150 molecules. The structure of the confined ice is rich in stacking faults, in agreement with the interpretation of X-ray and neutron diffraction experiments. Though the presence of cubic layers is twice as prevalent as hexagonal ones, the crystals should not be considered defective Ic as sequences with more than three adjacent cubic (or hexagonal) layers are extremely rare in the confined ice.

Molecular magnetism of M6 hexagon ring in D(3d) symmetric [(MCl)6(XW9O33)2](12-) (M = Cu(II) and Mn(II), X = Sb(III) and As(III)).

PubMed

Yamase, Toshihiro; Ishikawa, Hirofumi; Abe, Hiroko; Fukaya, Keisuke; Nojiri, Hiroyuki; Takeuchi, Hideo

2012-04-16

Ferromagnetic [n-BuNH(3)](12)[(CuCl)(6)(SbW(9)O(33))(2)]·6H(2)O (1) and antiferromagnetic [n-BuNH(3)](12)[(MnCl)(6)(AsW(9)O(33))(2)]·6H(2)O (4) have been synthesized and structurally and magnetically characterized. Two complexes are structural analogues of [n-BuNH(3)](12)[(CuCl)(6)(AsW(9)O(33))(2)]·6H(2)O (2) and [n-BuNH(3)](12)[(MnCl)(6)(SbW(9)O(33))(2)]·6H(2)O (3) with their ferromagnetic interactions, first reported by us in 2006. (1) When variable temperature (T) direct current (dc) magnetic susceptibility (χ(M)) data are analyzed with the isotropic exchange Hamiltonian for the magnetic exchange interactions, χ(M)T vs T curves fitted by a full matrix diagonalization (for 1) and by the Kambe vector coupling method/Van Vleck's approximation (for 4) yield J = +29.5 and -0.09 cm(-1) and g = 2.3 and 1.9, respectively. These J values were significantly distinguished from +61.0 and +0.14 cm(-1) for 2 and 3, respectively. The magnetization under the pulsed field (up to 10(3) T/s) at 0.5 K exhibits hysteresis loops in the adiabatic process, and the differential magnetization (dM/dB) plots against the pulsed field display peaks characteristic of resonant quantum tunneling of magnetization (QTM) at Zeeman crossed fields, indicating single-molecule magnets for 1-3. High-frequency ESR (HFESR) spectroscopy on polycrystalline samples provides g(∥) = 2.30, g(⊥) = 2.19, and D = -0.147 cm(-1) for 1 (S = 3 ground state), g(∥) = 2.29, g(⊥) = 2.20, and D = -0.145 cm(-1) for 2 (S = 3), and g(∥) = 2.03 and D = -0.007 cm(-1) for 3 (S = 15). An attempt to rationalize the magnetostructural correlation among 1-4, the structurally and magnetically modified D(3d)-symmetric M (=Cu(II) and Mn(II))(6) hexagons sandwiched by two diamagnetic α-B-[XW(9)O(33)](9-) (X = Sb(III) and As(III)) ligands through M-(μ(3)-O)-W linkages, is made. The strongest ferromagnetic coupling for the Cu(6) hexagon of 2, the structure of which approximately provides the Cu(6)(μ(3)-O)(12) cylindrical geometry, is demonstrated by the polarization mechanism based on the point-dipole approximation, which provides a decrease of the ferromagnetic interaction due to the out-of-cylinder deviation of the Cu atoms for 1. The different nature of the magnetic exchange interaction in 3 and 4 is understood by the combined effect of the out-of plane deviation (the largest for 4) of the Mn atoms from the Mn(μ(3)-O)(2)Mn least-squares plane and the antiferromagnetic contribution arising from the large Mn-O-Mn bond angle. The primary contribution to D is discussed in terms of the magnetic dipole-dipole interaction between the electrons located on the magnetic sites in the M(6) hexagon. © 2012 American Chemical Society

Oxygen interaction with hexagonal OsB 2 at high temperature

DOE PAGES

Xie, Zhilin; Blair, Richard G.; Orlovskaya, Nina; ...

2016-08-10

The stability of ReB 2-type hexagonal OsB 2 powder at high temperature with oxygen presence has been studied by thermogravimetric analysis, differential scanning calorimetry, SEM, EDS, and high-temperature scanning transmission electron microscopy and XRD. Results of the study revealed that OsB 2 ceramics interact readily with oxygen present in reducing atmosphere, especially at high temperature and produces boric acid, which decomposes on the surface of the powder resulting in the formation of boron vacancies in the hexagonal OsB 2 lattice as well as changes in the stoichiometry of the compound. It was also found that under low oxygen partial pressure,more » sintering of OsB 2 powders occurred at a relatively low temperature (900°C). Finally, hexagonal OsB 2 ceramic is prone to oxidation and it is very sensitive to oxygen partial pressures, especially at high temperatures.« less

Formation mechanism of graphite hexagonal pyramids by argon plasma etching of graphite substrates

NASA Astrophysics Data System (ADS)

Glad, X.; de Poucques, L.; Bougdira, J.

2015-12-01

A new graphite crystal morphology has been recently reported, namely the graphite hexagonal pyramids (GHPs). They are hexagonally-shaped crystals with diameters ranging from 50 to 800 nm and a constant apex angle of 40°. These nanostructures are formed from graphite substrates (flexible graphite and highly ordered pyrolytic graphite) in low pressure helicon coupling radiofrequency argon plasma at 25 eV ion energy and, purportedly, due to a physical etching process. In this paper, the occurrence of peculiar crystals is shown, presenting two hexagonal orientations obtained on both types of samples, which confirms such a formation mechanism. Moreover, by applying a pretreatment step with different time durations of inductive coupling radiofrequency argon plasma, for which the incident ion energy decreases at 12 eV, uniform coverage of the surface can be achieved with an influence on the density and size of the GHPs.

Oxygen interaction with hexagonal OsB 2 at high temperature

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

Xie, Zhilin; Blair, Richard G.; Orlovskaya, Nina

The stability of ReB 2-type hexagonal OsB 2 powder at high temperature with oxygen presence has been studied by thermogravimetric analysis, differential scanning calorimetry, SEM, EDS, and high-temperature scanning transmission electron microscopy and XRD. Results of the study revealed that OsB 2 ceramics interact readily with oxygen present in reducing atmosphere, especially at high temperature and produces boric acid, which decomposes on the surface of the powder resulting in the formation of boron vacancies in the hexagonal OsB 2 lattice as well as changes in the stoichiometry of the compound. It was also found that under low oxygen partial pressure,more » sintering of OsB 2 powders occurred at a relatively low temperature (900°C). Finally, hexagonal OsB 2 ceramic is prone to oxidation and it is very sensitive to oxygen partial pressures, especially at high temperatures.« less

Water freezing and ice melting

DOE PAGES

Malolepsza, Edyta; Keyes, Tom

2015-10-12

The generalized replica exchange method (gREM) is designed to sample states with coexisting phases and thereby to describe strong first order phase transitions. The isobaric MD version of the gREM is presented and applied to freezing of liquid water, and melting of hexagonal and cubic ice. It is confirmed that coexisting states are well sampled. The statistical temperature as a function of enthalpy, T S(H), is obtained. Hysteresis between freezing and melting is observed and discussed. The entropic analysis of phase transitions is applied and equilibrium transition temperatures, latent heats, and surface tensions are obtained for hexagonal ice↔liquid and cubicmore » ice↔liquid, with excellent agreement with published values. A new method is given to assign water molecules among various symmetry types. As a result, pathways for water freezing, ultimately leading to hexagonal ice, are found to contain intermediate layered structures built from hexagonal and cubic ice.« less

Study of cavity type antenna structure of large-area 915 MHz ultra-high frequency wave plasma device based on three-dimensional finite difference time-domain analysis

NASA Astrophysics Data System (ADS)

Chang, Xijiang; Kunii, Kazuki; Liang, Rongqing; Nagatsu, Masaaki

2013-11-01

A large-area planar plasma source with a resonant cavity type launcher driven by a 915 MHz ultra-high frequency wave was developed. Theoretical analysis with the three-dimensional finite difference time-domain simulation was carried out to determine the optimized launcher structure by analyzing the resonant transverse magnetic mode in the resonant cavity. Numerical result expects that the resonant electric field distribution inside the cavity dominantly consists of the TM410 mode. The resonant cavity type launcher having 8 holes in an octagonal geometry was designed to fit the resonant transverse magnetic mode. Adjusting 8 hole positions of the launcher to the field pattern of the resonant TM410 mode, we found that the plasma density increased about 40%˜50% from 1.0˜1.1 × 1011 cm-3 to ˜1.5 × 1011 cm-3 at the same incident power of 2.5 kW, compared with the previous results with the launcher having 6 holes in the hexagonal geometry. It is also noted that the electron density changes almost linearly with the incident wave power without any mode jumps.

Corrosion of Type 316L stainless steel in Pb-17Li

NASA Astrophysics Data System (ADS)

Barker, M. G.; Lees, J. A.; Sample, T.; Hubberstey, P.

1991-03-01

Corrosion tests carried out in Pb-17Li in both capsules and a convection loop (hot leg temperature 768 K, cold leg temperature 748 K, flow rate 10 mm/s) have shown that Type 316 stainless steel undergoes almost complete loss of Ni and Mn, and extensive loss of Cr to form a porous ferritic zone. Ferritic zone depths measured on the loop samples exposed between 1000 and 4000 h were in good agreement with previous data. Some evidence was found for the interaction of chromium with oxygen dissolved in Pb-17Li. Examination of the cold leg samples revealed deposition products of iron and chromium but no deposits containing nickels were observed. These observations were rationalised in terms of recent measurements of the solubilities of metals in Pb-17Li.

Tunable biasing magnetic field design of ferrite tuner for ICRF heating system in EAST

NASA Astrophysics Data System (ADS)

Manman, XU; Yuntao, SONG; Gen, CHEN; Yanping, ZHAO; Yuzhou, MAO; Guang, LIU; Zhen, PENG

2017-11-01

Ion cyclotron range of frequency (ICRF) heating has been used in tokamaks as one of the most successful auxiliary heating tools and has been adopted in the EAST. However, the antenna load will fluctuate with the change of plasma parameters in the ICRF heating process. To ensure the steady operation of the ICRF heating system in the EAST, fast ferrite tuner (FFT) has been carried out to achieve real-time impedance matching. For the requirements of the FFT impedance matching system, the magnet system of the ferrite tuner (FT) was designed by numerical simulations and experimental analysis, where the biasing magnetic circuit and alternating magnetic circuit were the key researched parts of the ferrite magnet. The integral design goal of the FT magnetic circuit is that DC bias magnetic field is 2000 Gs and alternating magnetic field is ±400 Gs. In the FTT, E-type magnetic circuit was adopted. Ferrite material is NdFeB with a thickness of 30 mm by setting the working point of NdFeB, and the ampere turn of excitation coil is 25 through the theoretical calculation and simulation analysis. The coil inductance to generate alternating magnetic field is about 7 mH. Eddy-current effect has been analyzed, while the magnetic field distribution has been measured by a Hall probe in the medium plane of the biasing magnet. Finally, the test results show the good performance of the biasing magnet satisfying the design and operating requirements of the FFT.

Solid solution cermet: (Ti,Nb)(CN)-Ni cermet.

PubMed

Kwon, Hanjung; Jung, Sun-A

2014-11-01

Solid solution powders without W, (Ti,Nb)(CN) powders with a B1 structure (NaCl like), were synthesized by high energy milling and carbothermal reduction in nitrogen. The range of molar ratios of Ti/Nb for forming complete (Ti,Nb)(CN) phase was broader than that of Ti/W for the (Ti,W)(CN) phase because carbide or carbonitride of Nb had a B1 crystal structure identical to Ti(CN) while WC had a hexagonal crystal structure. The results revealed that the hardness of (Ti,Nb)(CN)-Ni cermets was higher than that of (Ti,W)(CN)-Ni cermets. The lower density of the (Ti,Nb)(CN) powder contributed to the higher hardness compared to (Ti,W)(CN) because the volumetric ratio of (Ti,Nb)(CN) in the (Ti,Nb)(CN)-Ni cermets was higher than that of (Ti,Nb)(CN) in the (Ti,W)(CN)-Ni cermets at the same weight ratio of Ni. Additionally, it was assumed that intrinsic the properties of (Ti,Nb)(CN) could also be the cause for the high hardness of the (Ti,Nb)(CN)-Ni cermets.

Magnetic field role on the structure and optical response of photonic crystals based on ferrofluids containing Co{sub 0.25}Zn{sub 0.75}Fe{sub 2}O{sub 4} nanoparticles

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

López, J., E-mail: javier.lopez@correounivalle.edu.co; González, Luz E.; Quiñonez, M. F.

2014-05-21

Ferrofluids based on magnetic Co{sub 0.25}Zn{sub 0.75}Fe{sub 2}O{sub 4} ferrite nanoparticles were prepared by co-precipitation method from aqueous salt solutions of Co (II), ZnSO{sub 4}, and Fe (III) in an alkaline medium. Ferrofluids placed in an external magnetic field show properties that make them interesting as magneto-controllable soft photonic crystals. Morphological and structural characterizations of the samples were obtained from Scanning Electron Microscopy and Transmission Electron Microscopy studies. Magnetic properties were investigated with the aid of a vibrating sample magnetometer at room temperature. Herein, the Co{sub 0.25}Zn{sub 0.75}Fe{sub 2}O{sub 4} samples showed superparamagnetic behavior, according to hysteresis loop results. Takingmore » in mind that the Co-Zn ferrite hysteresis loop is very small, our magnetic nanoparticles can be considered soft magnetic material with interesting technological applications. In addition, by using the plane-wave expansion method, we studied the photonic band structure of 2D photonic crystals made of ferrofluids with the same nanoparticles. Previous experimental results show that a magnetic field applied perpendicular to the ferrofluid plane agglomerates the magnetic nanoparticles in parallel rods to form a hexagonal 2D photonic crystal. We calculated the photonic band structure of photonic crystals by means of the effective refractive index of the magnetic fluid, basing the study on the Maxwell-Garnett theory, finding that the photonic band structure does not present any band gaps under the action of applied magnetic field strengths used in our experimental conditions.« less

A 2 TiO 5 (A = Dy, Gd, Er, Yb) at High Pressure

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

Park, Sulgiye; Rittman, Dylan R.; Tracy, Cameron L.

The structural evolution of lanthanide A2TiO5 (A = Dy, Gd, Yb, and Er) at high pressure is investigated using synchrotron X-ray diffraction. The effects of A-site cation size and of the initial structure are systematically examined by varying the composition of the isostructural lanthanide titanates, and the structure of dysprosium titanate polymorphs (orthorhombic, hexagonal and cubic), respectively. All samples undergo irreversible high pressure phase transformations, but with different onset pressures depending on the initial structure. While individual phase exhibits different phase transformation histories, all samples commonly experience a sluggish transformation to a defect cotunnite-like (Pnma) phase for a certain pressuremore » range. Orthorhombic Dy2TiO5 and Gd2TiO5 form P21am at pressures below 9 GPa and Pnma above 13 GPa. Pyrochlore-type Dy2TiO5 and Er2TiO5 as well as defect-fluorite-type Yb2TiO5 form Pnma at ~ 21 GPa, followed by Im-3m. Hexagonal Dy2TiO5 forms Pnma directly, although a small amount of remnants of hexagonal Dy2TiO5 is observed even at the highest pressure (~ 55 GPa) reached, indicating a kinetic limitations in the hexagonal Dy2TiO5 phase transformations at high pressure. Decompression of these materials leads to different metastable phases. Most interestingly, a high pressure cubic X-type phase (Im-3m) is confirmed using highresolution transmission electron microscopy on recovered pyrochlore-type Er2TiO5. The kinetic constraints on this metastable phase yield a mixture of both the X-type phase and amorphous domains upon pressure release. This is the first observation of an X-type phase for an A2BO5 composition at high pressure.« less

Ferrite grain refinement in low carbon Cu–P–Cr–Ni–Mo weathering steel at various temperatures in the (α + γ) region

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

Zhang, Chunling, E-mail: zhangchl@ysu.edu.cn; School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300401; Zhang, Mengmeng

2016-03-15

Self-designed Cu–P–Cr–Ni–Mo weathering steel was subjected to compression test to determine the mechanism of ferrite grain refinement from 750 °C to 925 °C. Optical microscopic images showed that ferrite grain size declined, whereas the ferrite volume fraction increased with increasing compression temperature. Electron backscatter diffraction patterns revealed that several low-angle boundaries shifted to high-angle boundaries, thereby generating fine ferrite grains surrounded by high-angle boundaries. Numerous low-angle boundaries were observed within ferrite grains at 750 °C, which indicated the existence of pre-eutectoid ferrite. Results showed that ferrite grain refinement could be due to continuous dynamic recrystallization at 750 °C and 775more » °C, and deformation-induced ferrite transformation could be the main mechanism at 800 °C and 850 °C. Fine equiaxed ferrite grains with size ranging from 1.77 μm to 2.69 μm were produced in the (α + γ) dual-phase region. - Graphical abstract: There is a close relationship between the microstructure evolution and flow curves during deformation. Fine equiaxed ferrite grains with size ranging from 1.77 μm to 2.69 μm were achieved in the (α + γ) dual-phase region. Ferrite grain refinement could be due to continuous dynamic recrystallization at 750 °C and 775 °C, and deformation-induced ferrite transformation at 800 °C and 850 °C. The occurrence of deformation-induced ferrite transformation and continuous dynamic recrystallization can be monitored by analysis of flow curves and microstructures. Deformation-induced ferrite transformation leads to the dynamic softening in flow curve when temperature just below A{sub r3}, while the dynamic softening in flow curve is ferrite continuous dynamic recrystallization (Special Fig. 5b). - Highlights: • Compression deformation was operated at temperatures from 750 °C to 925 °C at a strain rate of 0.1 s–1, and a strain of 1.2. • Fine equiaxed ferrite grains of ~1.77–2.19 μm were obtained at 750 °C and 775 °C via continuous dynamic recrystallization. • Ferrite grain size of ~2.31–2.69 μm at 800 °C and 850 °C can be obtained by deformation-induced ferrite transformation. • With decreasing deformation temperature the average grain size of ferrite decreased while volume fraction increased. • Ferrite refinement was from deformation-induced ferrite to continuous dynamic recrystallization as temperature reduced.« less

Supercapacitors incorporating hollow cobalt sulfide hexagonal nanosheets

NASA Astrophysics Data System (ADS)

Yang, Zusing; Chen, Chia-Ying; Chang, Huan-Tsung

We have prepared hollow cobalt sulfide (CoS) hexagonal nanosheets (HNSs) from Co(NO 3) 2 and thioacetamide in the presence of poly(vinylpyrrolidone) (PVP) at 100 °C under alkaline condition. The as-prepared hollow CoS HNSs have an average edge length ca. 110 ± 27 nm and an outer shell of 16 ± 4 nm in thickness from 500 counts. The CoS HNSs are deposited onto transparent fluorine-doped tin oxide (FTO) substrates through a drop-dry process to prepare two types of supercapacitors (SCs); high rate and large per-area capacitance. The electrolyte used in this study is KOH (aq). The CoS HNSs (8 μg cm -2) electrodes exhibit excellent capacity properties, including high energy density (13.2 h kg -1), power density (17.5 kW kg -1), energy deliverable efficiency (81.3-85.3%), and stable cycle life (over 10,000 cycles) at a high discharge current density of 64.6 A g -1. With their fast charging and discharging rates (<3 s), the CoS HNSs show characteristics of high-rate SCs. The CoS HNS SCs having high mass loading (9.7 mg cm -2) provide high per-area capacitance of 1.35 F cm -2 and per-mass capacitance of 138 F g -1, respectively, showing characteristics of SCs with large per-area capacitance. Our results have demonstrated the potential of the CoS HNS electrodes hold great practical potential in many fields such as automobile and computer industries.

Modeling of Microstructure Evolution During the Thermomechanical Processing of Titanium Alloys (Preprint)

DTIC Science & Technology

2008-07-01

Tailoring the Properties of Aluminum and Titanium Alloys", Deformation, Processing, and Structure , G. Krauss, ed., ASM International, Materials Park, OH...1984, pp. 279-354. 51. G.W. Kuhlman, "A Critical Appraisal of Thermomechanical Processing of Structural Titanium Alloys", Microstructure/ Property ... titanium alloys is heavily dependent on the allotropic transformation from a hexagonal-close-packed crystal structure (denoted as alpha phase) found at

Highly Stable, Dual-Gated MoS2 Transistors Encapsulated by Hexagonal Boron Nitride with Gate-Controllable Contact, Resistance, and Threshold Voltage.

PubMed

Lee, Gwan-Hyoung; Cui, Xu; Kim, Young Duck; Arefe, Ghidewon; Zhang, Xian; Lee, Chul-Ho; Ye, Fan; Watanabe, Kenji; Taniguchi, Takashi; Kim, Philip; Hone, James

2015-07-28

Emerging two-dimensional (2D) semiconductors such as molybdenum disulfide (MoS2) have been intensively studied because of their novel properties for advanced electronics and optoelectronics. However, 2D materials are by nature sensitive to environmental influences, such as temperature, humidity, adsorbates, and trapped charges in neighboring dielectrics. Therefore, it is crucial to develop device architectures that provide both high performance and long-term stability. Here we report high performance of dual-gated van der Waals (vdW) heterostructure devices in which MoS2 layers are fully encapsulated by hexagonal boron nitride (hBN) and contacts are formed using graphene. The hBN-encapsulation provides excellent protection from environmental factors, resulting in highly stable device performance, even at elevated temperatures. Our measurements also reveal high-quality electrical contacts and reduced hysteresis, leading to high two-terminal carrier mobility (33-151 cm(2) V(-1) s(-1)) and low subthreshold swing (80 mV/dec) at room temperature. Furthermore, adjustment of graphene Fermi level and use of dual gates enable us to separately control contact resistance and threshold voltage. This novel vdW heterostructure device opens up a new way toward fabrication of stable, high-performance devices based on 2D materials.

High brightness nonpolar a-plane (11-20) GaN light-emitting diodes

NASA Astrophysics Data System (ADS)

Jung, Sukkoo; Chang, Younghak; Bang, Kyu-Hyun; Kim, Hyung-Gu; Choi, Yoon-Ho; Hwang, Sung-Min; Baik, Kwang Hyeon

2012-02-01

We report on high brightness nonpolar a-plane InGaN/GaN LEDs using patterned lateral overgrowth (PLOG) epitaxy. High crystal-quality and smooth surfaces for a-plane GaN (a-GaN) films were achieved using PLOG with an array of hexagonal SiO2 patterns. The XRC FWHMs of as-grown PLOG a-GaN films were found to be 414 and 317 arcsec (450 and 455 arcsec for planar a-GaN films) along the c-axis and m-axis directions, respectively. Plan-view CL clearly reveals the periodic hexagonal patterns with higher band edge emission intensity, implying that the luminescence properties of a-GaN films lying above the SiO2 mask are improved. The light output powers of a-InGaN/GaN PLOG LEDs were measured to be 7.5 mW and 20 mW at drive currents of 20 mA and 100 mA, respectively. A negligible blue-shift was observed in the peak emission wavelength with increasing drive current up to 100 mA, indicating that there are no strong internal fields in nonpolar a-InGaN/GaN LEDs. We believe that nonpolar a-plane InGaN/GaN LEDs hold promise for efficient nitride emitters if the growth conditions are further optimized.

Current status and recent research achievements in ferritic/martensitic steels

NASA Astrophysics Data System (ADS)

Tavassoli, A.-A. F.; Diegele, E.; Lindau, R.; Luzginova, N.; Tanigawa, H.

2014-12-01

When the austenitic stainless steel 316L(N) was selected for ITER, it was well known that it would not be suitable for DEMO and fusion reactors due to its irradiation swelling at high doses. A parallel programme to ITER collaboration already had been put in place, under an IEA fusion materials implementing agreement for the development of a low activation ferritic/martensitic steel, known for their excellent high dose irradiation swelling resistance. After extensive screening tests on different compositions of Fe-Cr alloys, the chromium range was narrowed to 7-9% and the first RAFM was industrially produced in Japan (F82H: Fe-8%Cr-2%W-TaV). All IEA partners tested this steel and contributed to its maturity. In parallel several other RAFM steels were produced in other countries. From those experiences and also for improving neutron efficiency and corrosion resistance, European Union opted for a higher chromium lower tungsten grade, Fe-9%Cr-1%W-TaV steel (Eurofer), and in 1997 ordered the first industrial heats. Other industrial heats have been produced since and characterised in different states, including irradiated up to 80 dpa. China, India, Russia, Korea and US have also produced their grades of RAFM steels, contributing to overall maturity of these steels. This paper reviews the work done on RAFM steels by the fusion materials community over the past 30 years, in particular on the Eurofer steel and its design code qualification for RCC-MRx.

Batch fabrication process development for ferrite logic conductors

NASA Technical Reports Server (NTRS)

Heckler, C. H., Jr.; Bhiwandker, N. C.

1972-01-01

A process for fabricating ultrareliable magnetic ferrite logic circuits is described in which the conductors are formed by a combination of two batch type processes - photolithography and electroplating - and a mechanized writing process for completing conductors in the third dimension. Up to 4 turns, through an aperture 1 mm in diameter, are formed by the described process. The number of joints in the conductors is reduced by use of this process to only those which are required for input, output and power connections of a logic block. To demonstrate feasibility, 8-stage magnetic ring counter circuits have been fabricated.

Lonsdaleite has been used as an indicator of shock from cratering events, but does it exist?

NASA Astrophysics Data System (ADS)

Nemeth, P.; Garvie, L. A.; Buseck, P. R.

2013-12-01

In 1967 a new diamond polymorph was described from the Canyon Diablo iron meteorite [1] and called lonsdaleite (also referred to as hexagonal diamond. It was identified from reflections (e.g., at 0.218, 0.193, and 0.150 nm), additional to those in diamond, that were indexed in terms of a hexagonal cell [1]. Lonsdaleite was attributed to shock-induced transformation of graphite within the iron meteorite upon impact [1, 2] and has subsequently been used as an indicator of shock and meteorite impact [3, 4, 5]. Given the importance of lonsdaleite, we reinvestigated the structure of the shock-formed diamond and lonsdaleite from the Canyon Diablo meteorite with an aberration-corrected ultra-high-resolution scanning transmission electron microscope (STEM), with the view of providing further insights into the shock-forming mechanism. The STEM images allowed direct structural interpretation at 0.1-nm resolution and showed that the samples consist of single-crystal and twinned diamond, as well as graphite intimately associated at the nanoscale. A characteristic feature of the STEM images is stacking faults and twins (111, 200, 113) that interrupt the regularity of the crystal structure. Uncommon, subnanometer-sized regions occur with two- and four-layer hexagonal symmetry, though these regions merge into diamond with stacking faults. Although we did not find lonsdaleite, the defects can give rise to extra reflections like those attributed to lonsdaleite. For example, the (113) diamond twin results in a 0.216-nm spacing that matches that of the broad 0.218-nm lonsdaleite peak. Our observations from Canyon Diablo provide a new understanding of shocked diamond structures and question the existence of lonsdaleite and its inferred geologic implication, although the abundance of diamond twinning and stacking faults may be indicative of shock metamorphism. [1] Frondel, C. & Marvin, U.B. (1967) Lonsdaleite, a hexagonal polymorph of diamond. Nature 217, 587-589. [2] Lipschutz, M. & Anders, E. (1961) The record in the meteorites-IV: Origin of diamonds in iron meteorites. Geochimica et Cosmochimica Acta 24, 83-105. [3] Kennet, D. J., Kennet, J. P., West, A., Mercer, C., Que Hee, S. S., Bement, L., Bunch, T. E., Sellers, M., & Wolbach, W. S. (2009) Nanodiamonds in the Younger Dryas boundary sediment layers. Science 323, 94. [4] Le Guillou, C., Rouzaud, J.N., Remusat, L., Jambon, A., & Bourot-Denise, M. (2010) Structures, origin and evolution of various carbon phases in the ureilite Northwest Africa 4742 compared with laboratory-shocked graphite. Geochimica Et Cosmochimica Acta 74(14), 4167-4185. [5] Hough, R.M., Gilmour, I., Pillinger, C.T., Arden, J.W., Gilkes, K.W.R., Yuan, J. & Milledge, H.J. (1995) Diamond and silicon carbide in an impact melt rock from the Ries impact crater. Nature 378, 41-44.

Annealing Time Effect on Nanostructured n-ZnO/p-Si Heterojunction Photodetector Performance

NASA Astrophysics Data System (ADS)

Habubi, Nadir. F.; Ismail, Raid. A.; Hamoudi, Walid K.; Abid, Hassam. R.

2015-02-01

In this work, n-ZnO/p-Si heterojunction photodetectors were prepared by drop casting of ZnO nanoparticles (NPs) on single crystal p-type silicon substrates, followed by (15-60) min; step-annealing at 600∘C. Structural, electrical, and optical properties of the ZnO NPs films deposited on quartz substrates were studied as a function of annealing time. X-ray diffraction studies showed a polycrystalline, hexagonal wurtizte nanostructured ZnO with preferential orientation along the (100) plane. Atomic force microscopy measurements showed an average ZnO grain size within the range of 75.9 nm-99.9 nm with a corresponding root mean square (RMS) surface roughness between 0.51 nm-2.16 nm. Dark and under illumination current-voltage (I-V) characteristics of the n-ZnO/p-Si heterojunction photodetectors showed an improving rectification ratio and a decreasing saturation current at longer annealing time with an ideality factor of 3 obtained at 60 min annealing time. Capacitance-voltage (C-V) characteristics of heterojunctions were investigated in order to estimate the built-in-voltage and junction type. The photodetectors, fabricated at optimum annealing time, exhibited good linearity characteristics. Maximum sensitivity was obtained when ZnO/Si heterojunctions were annealed at 60 min. Two peaks of response, located at 650 nm and 850 nm, were observed with sensitivities of 0.12-0.19 A/W and 0.18-0.39 A/W, respectively. Detectivity of the photodetectors as function of annealing time was estimated.

Characterizing crustal and uppermost mantle anisotropy with a depth-dependent tilted hexagonally symmetric elastic tensor: theory and examples

NASA Astrophysics Data System (ADS)

Feng, L.; Xie, J.; Ritzwoller, M. H.

2017-12-01

Two major types of surface wave anisotropy are commonly observed by seismologists but are only rarely interpreted jointly: apparent radial anisotropy, which is the difference in propagation speed between horizontally and vertically polarized waves inferred from Love and Rayleigh waves, and apparent azimuthal anisotropy, which is the directional dependence of surface wave speeds (usually Rayleigh waves). We describe a method of inversion that interprets simultaneous observations of radial and azimuthal anisotropy under the assumption of a hexagonally symmetric elastic tensor with a tilted symmetry axis defined by dip and strike angles. With a full-waveform numerical solver based on the spectral element method (SEM), we verify the validity of the forward theory used for the inversion. We also present two examples, in the US and Tibet, in which we have successfully applied the tomographic method to demonstrate that the two types of apparent anisotropy can be interpreted jointly as a tilted hexagonally symmetric medium.

ZnO nanodisk based UV detectors with printed electrodes.

PubMed

Alenezi, Mohammad R; Alshammari, Abdullah S; Alzanki, Talal H; Jarowski, Peter; Henley, Simon John; Silva, S Ravi P

2014-04-08

The fabrication of highly functional materials for practical devices requires a deep understanding of the association between morphological and structural properties and applications. A controlled hydrothermal method to produce single crystal ZnO hexagonal nanodisks, nanorings, and nanoroses using a mixed solution of zinc sulfate (ZnSO4) and hexamethylenetetramine (HMTA) without the need of catalysts, substrates, or templates at low temperature (75 °C) is introduced. Metal-semiconductor-metal (MSM) ultraviolet (UV) detectors were fabricated based on individual and multiple single-crystal zinc oxide (ZnO) hexagonal nanodisks. High quality single crystal individual nanodisk devices were fabricated with inkjet-printed silver electrodes. The detectors fabricated show record photoresponsivity (3300 A/W) and external quantum efficiency (1.2 × 10(4)), which we attribute to the absence of grain boundaries in the single crystal ZnO nanodisk and the polarity of its exposed surface.

Enhanced magnetic domain relaxation frequency and low power losses in Zn2+ substituted manganese ferrites potential for high frequency applications

NASA Astrophysics Data System (ADS)

Praveena, K.; Chen, Hsiao-Wen; Liu, Hsiang-Lin; Sadhana, K.; Murthy, S. R.

2016-12-01

Nowadays electronic industries prerequisites magnetic materials, i.e., iron rich materials and their magnetic alloys. However, with the advent of high frequency applications, the standard techniques of reducing eddy current losses, using iron cores, were no longer efficient or cost effective. Current market trends of the switched mode power supplies industries required even low energy losses in power conversion with maintenance of adequate initial permeability. From the above point of view, in the present study we aimed at the production of Manganese-Zinc ferrites prepared via solution combustion method using mixture of fuels and achieved low loss, high saturation magnetization, high permeability, and high magnetic domain relaxation frequency. The as-synthesized Zn2+ substituted MnFe2O4 were characterized by X-ray diffractometer (XRD) and transmission electron microscopy (TEM). The fractions of Mn2+, Zn2+ and Fe2+ cations occupying tetrahedral sites along with Fe occupying octahedral sites within the unit cell of all ferrite samples were estimated by Raman scattering spectroscopy. The magnetic domain relaxation was investigated by inductance spectroscopy (IS) and the observed magnetic domain relaxation frequency (fr) was increased with the increase in grain size. The real and imaginary part of permeability (μ‧ and μ″) increased with frequency and showed a maximum above 100 MHz. This can be explained on the basis of spin rotation and domain wall motion. The saturation magnetization (Ms), remnant magnetization (Mr) and magneton number (μB) decreased gradually with increasing Zn2+ concentration. The decrease in the saturation magnetization was discussed with Yafet-Kittel (Y-K) model. The Zn2+ concentration increases the relative number of ferric ions on the A sites, reduces the A-B interactions. The frequency dependent total power losses decreased as the zinc concentration increased. At 1 MHz, the total power loss (Pt) changed from 358 mW/cm3 for x=0-165 mW/cm3 for x=0.9. Pt for all the Zn doped samples exhibited the temperature stability up to 100 °C.

Magnetic induction spectroscopy (MIS)-probe design for cervical tissue measurements.

PubMed

Wang, Jau-Yi; Healey, Timothy; Barker, Anthony; Brown, Brian; Monk, Chris; Anumba, Dilly

2017-05-01

Gradiometers have the advantage of increasing measuring sensitivity, which is particularly useful in magnetic induction spectroscopy (MIS) for bio-impedance measurements. Traditional gradiometers use a pair of field sensing coils equally distant and on opposite sides of a drive coil, which provides high immunity to interference. In this paper, a ferrite-cored coaxial gradiometer probe of 29 mm diameter has been developed for measuring the impedance spectra of cervical tissues in vivo. It consists of a ferrite rod with outer ferrite confinement screening in order to eliminate the signals from surrounding tissue. The magnetic screening efficiency was compared with an air-cored gradiometer probe. For both gradiometer probes, a drive coil and two sensing coils were wound on a borosilicate glass former aligned coaxially with two sensing coils equidistant from the drive coil. The signal sensitivity of those two MIS gradiometers has been measured using saline samples with a conductivity range between 0.1 and 1.1 S m -1 . Finite element methods using COMSOL Multiphysics have been used to simulate the distribution of sensitivity to conductivity over the face of each probe and with depth. The ferrite-cored probe has a sensitivity confined to the volume defined by the gap between the ferrite core and outer tube of ferrite while the air-cored probe without any magnetic shielding had a wide sensitivity over the face and the side of the probe. Four saline samples and one of distilled water with conductivities from 0.1 to 1.1 S m -1 have been used to make conductivity measurements at frequencies of 50 kHz, 100 kHz, and 300 kHz. The measurement accuracy of the air-cored MIS probe was 0.09 S m -1 at 50 kHz, improving to 0.05 S m -1 at 300 kHz. For the ferrite-cored MIS probe, the measurement accuracy was 0.28 S m -1 at 50 kHz, improving to 0.04 S m -1 at 300 kHz. In vivo measurements on human hand have been performed using both types of gradiometers and the conductivity is consistent with reported data.

Recent advances in nanosized Mn-Zn ferrite magnetic fluid hyperthermia for cancer treatment.

PubMed

Lin, Mei; Huang, Junxing; Sha, Min

2014-01-01

This paper reviews the recent research and development of nanosized manganese zinc (Mn-Zn) ferrite magnetic fluid hyperthermia (MFH) for cancer treatment. Mn-Zn ferrite MFH, which has a targeted positioning function that only the temperature of tumor tissue with magnetic nanoparticles can rise, while normal tissue without magnetic nanoparticles is not subject to thermal damage, is a promising therapy for cancer. We introduce briefly the composition and properties of magnetic fluid, the concept of MFH, and features of Mn-Zn ferrite magnetic nanoparticles for MFH such as thermal bystander effect, universality, high specific absorption rate, the targeting effect of small size, uniformity of hyperthermia temperature, and automatic temperature control and constant temperature effect. Next, preparation methods of Mn-Zn ferrite magnetic fluid are discussed, and biocompatibility and biosecurity of Mn-Zn ferrite magnetic fluid are analyzed. Then the applications of nanosized Mn-Zn ferrite MFH in cancer are highlighted, including nanosized Mn-Zn ferrite MFH alone, nanosized Mn-Zn ferrite MFH combined with As2O3 chemotherapy, and nanosized Mn-Zn ferrite MFH combined with radiotherapy. Finally, the combination application of nanosized Mn-Zn ferrite MFH and gene-therapy is conceived, and the challenges and perspectives for the future of nanosized Mn-Zn ferrite MFH for oncotherapy are discussed.

Could binary mixture of Nd-Ni ions control the electrical behavior of strontium-barium M-type hexaferrite nanoparticles?

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

Iqbal, Muhammad Javed, E-mail: mjiqauchem@yahoo.com; Farooq, Saima

2011-05-15

Research highlights: {yields} Strontium-barium hexaferrites (Sr{sub 0.5}Ba{sub 0.5}Fe{sub 12}O{sub 19}) in single magnetoplumbite phase solid structure are synthesized by the co-precipitation method. {yields} Structural and electrical properties of Nd-Ni substituted ferrites are investigated. {yields} These ferrite materials possess high electrical resistivity (108 {Omega} cm) that is essential to curb the eddy current loss, which is pre-requisite for surface mount devices. -- Abstract: Cationic substitution in M-type hexaferrites is considered to be an important tool for modification of their electrical properties. This work is part of our comprehensive study on the synthesis and characterization of Nd-Ni doped strontium-barium hexaferrite nanomaterials ofmore » nominal composition Sr{sub 0.5}Ba{sub 0.5-x}Nd{sub x}Fe{sub 12-y}Ni{sub y}O{sub 19} (x = 0.00-0.10; y = 0.00-1.00). Doping with this binary mixture modulates the physical and electrical properties of strontium-barium hexaferrite nanoparticles. Structural and electrical properties of the co-precipitated ferrites are investigated using state-of-the-art techniques. The results of X-ray diffraction analysis reveal that the lattice parameters and cell volume are inversely related to the dopant content. Temperature dependent DC-electrical resistivity measurements infer that resistivity of strontium-barium hexaferrites decreases from 1.8 x 10{sup 10} to 2.0 x 10{sup 8} {Omega} cm whereas the drift mobility, dielectric constant and dielectric loss tangent are directly related to the Nd-Ni content. The results of the study demonstrate a relationship between the modulation of electrical properties of substituted ferrites and nature of cations and their lattice site occupancy.« less

High-velocity DC-VPS for diffusion and protecting barrier layers in solid oxide fuel cells (SOFCs)

NASA Astrophysics Data System (ADS)

Henne, R. H.; Franco, T.; Ruckdäschel, R.

2006-12-01

High-temperature fuel cells of the solid oxide fuel cell (SOFC) type as direct converter of chemical into electrical energy show a high potential for reducing considerably the specific energy consumption in different application fields. Of particular interest are advanced lightweight planar cells for electricity supply units in cars and other mobile systems. Such cells, in one new design, consist mainly of metallic parts, for example, of ferrite steels. These cells shall operate in the temperature range of 700 to 800 °C where oxidation and diffusion processes can be of detrimental effect on cell performance for long-term operation. Problems arise in particular by diffusion of chromium species from the interconnect or the cell containment into the electrolyte/cathode interface forming insulating phases and by the mutual diffusion of substrate and anode material, for example, iron and chromium from the ferrite into the anode and nickel from the anode into the ferrite, which in both cases reduces performance and system lifetime. Additional intermediate layers of perovskite-type material, (e.g., doped LaCrO3) applied with high-velocity direct-current vacuum plasma spraying (DC-VPS) can reduce such effects considerably if they are stable and of high electronic conductivity.

Hierarchically self-assembled hexagonal honeycomb and kagome superlattices of binary 1D colloids.

PubMed

Lim, Sung-Hwan; Lee, Taehoon; Oh, Younghoon; Narayanan, Theyencheri; Sung, Bong June; Choi, Sung-Min

2017-08-25

Synthesis of binary nanoparticle superlattices has attracted attention for a broad spectrum of potential applications. However, this has remained challenging for one-dimensional nanoparticle systems. In this study, we investigate the packing behavior of one-dimensional nanoparticles of different diameters into a hexagonally packed cylindrical micellar system and demonstrate that binary one-dimensional nanoparticle superlattices of two different symmetries can be obtained by tuning particle diameter and mixing ratios. The hexagonal arrays of one-dimensional nanoparticles are embedded in the honeycomb lattices (for AB 2 type) or kagome lattices (for AB 3 type) of micellar cylinders. The maximization of free volume entropy is considered as the main driving force for the formation of superlattices, which is well supported by our theoretical free energy calculations. Our approach provides a route for fabricating binary one-dimensional nanoparticle superlattices and may be applicable for inorganic one-dimensional nanoparticle systems.Binary mixtures of 1D particles are rarely observed to cooperatively self-assemble into binary superlattices, as the particle types separate into phases. Here, the authors design a system that avoids phase separation, obtaining binary superlattices with different symmetries by simply tuning the particle diameter and mixture composition.

Comparison effects and electron spin resonance studies of α-Fe2O4 spinel type ferrite nanoparticles.

PubMed

Bayrakdar, H; Yalçın, O; Cengiz, U; Özüm, S; Anigi, E; Topel, O

2014-11-11

α-Fe2O4 spinel type ferrite nanoparticles have been synthesized by cetyltrimethylammonium bromide (CTAB) and ethylenediaminetetraacetic acid (EDTA) assisted hydrothermal route by using NaOH solution. Electron spin resonance (ESR/EPR) measurements of α-Fe2O4 nanoparticles have been performed by a conventional x-band spectrometer at room temperature. The comparison effect of nanoparticles prepared by using CTAB and EDTA in different α-doping on the structural and morphological properties have been investigated in detail. The effect of EDTA-assisted synthesis for α-Fe2O4 nanoparticles are refined, and thus the spectroscopic g-factor are detected by using ESR signals. These samples can be considered as great benefits for magnetic recording media, electromagnetic and drug delivery applications. Copyright © 2014 Elsevier B.V. All rights reserved.

Thermodynamic modeling and experimental validation of the Fe-Al-Ni-Cr-Mo alloy system

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

Teng, Zhenke; Zhang, F; Miller, Michael K

2012-01-01

NiAl-type precipitate-strengthened ferritic steels have been known as potential materials for the steam turbine applications. In this study, thermodynamic descriptions of the B2-NiAl type nano-scaled precipitates and body-centered-cubic (BCC) Fe matrix phase for four alloys based on the Fe-Al-Ni-Cr-Mo system were developed as a function of the alloy composition at the aging temperature. The calculated phase structure, composition, and volume fraction were validated by the experimental investigations using synchrotron X-ray diffraction and atom probe tomography. With the ability to accurately predict the key microstructural features related to the mechanical properties in a given alloy system, the established thermodynamic model inmore » the current study may significantly accelerate the alloy design process of the NiAl-strengthened ferritic steels.« less

Dielectric and conductivity studies of Co-Cu mixed ferrite

NASA Astrophysics Data System (ADS)

Parveez, Asiya; Shekhawat, M. S.; Nayeem, Firdous; Mohd. Shariff, S.; Sinha, R. R.; Khader, S. Abdul

2018-05-01

Nanoparticles of Co-Cu mixed ferrite having the basic composition Co1-xCuxFe2O4(x=0, 0.2, 0.4, 0.6, 0.8 and 1.0) were synthesized using nitrate-citrate combustion method. Structural, dielectric and a.c conductivity of nanopowders, which are sintered at 900°C were studied. Powder X-ray diffraction studies confirmed phase and their nanocrystalline nature. The peaks observed in the XRD spectrum indicated single phase spinel cubic structure for the synthesized samples. Surface morphology of the samples has been investigated using High ResolutionScanning Electron Microscope. The dielectric constant (ɛ') and dielectric loss factor (ɛ″) of nanocrystalline Co-Cu mixed ferrites were investigated as a function of frequency and Cu+2 concentration at room temperature over the frequency range 100 Hz to 1 MHz using Hioki make LCR Hi-Tester 3250. Synthesized mixed ferrites exhibited usual dielectric dispersion, dependence of ɛ' and ɛ″ with the frequency of the alternating applied electric field is in accordance with the Maxwell-Wagner type interfacial polarization. The electrical conductivity (σac) deduced from the measured dielectric data has been thoroughly analyzed and found that the conduction mechanism in Co1-xCuxFe2O4 mixed nanoferrites are in conformity with the electron hopping model.

Structural, Magnetic and Microwave Absorption Properties of Hydrothermally Synthesized (Gd, Mn, Co) Substituted Ba-Hexaferrite Nanoparticles

NASA Astrophysics Data System (ADS)

Torabi, Z.; Arab, A.; Ghanbari, F.

2018-02-01

Gd, Mn and Co substituted barium hexagonal ferrite nanoparticles, according to the formula Ba1- x Gd x Fe12-2 y (MnCo) y O19 and the proportion of y = x/2 (and x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1), have been prepared by hydrothermal method. Structural, magnetic and absorption microwave properties of the compositions were evaluated by x-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), vibrating sample magnetometry, and vector network analysis. Studying the XRDs data showed the single-phase structure of all samples without any impurities at 900°C calcination temperature. FE-SEM micrographs demonstrated that the morphology of the nanoparticles has planar and nearly hexagonal morphology. The nanoparticles size calculated within the range of 62-85 nm. Study of the room temperature hysteresis loops of calcined samples indicated that maximum magnetizations and coercivities decreased compared to undoped composite with respect to x. The alterations of magnetizations and coercivities are related to the site occupation of substituted ions, change in grain growth inhibition and the effect of spin canting. Moreover, the results of microwave absorption measurements demonstrated that the maximum reflection loss of substituted Ba-hexaferrite equivalent to - 47 dB in sample x = 0.5 with thickness 5.6 mm at a frequency about 17.2 GHz and a bandwidth of 2 GHz greater than - 10 dB. The results showed that Gd has good potential for use as a rare-earth substitution in permanent magnet hexaferrites and these composites can be employed as absorbers in the gigahertz frequency range.

Austenite decomposition to carbide-rich products in Fe-0.30C-6.3W

NASA Astrophysics Data System (ADS)

Hackenberg, R. E.; Granada, D. G.; Shiflet, G. J.

2002-12-01

The kinetics, morphology, and elemental distributions associated with the decomposition of austenite in Fe-0.30C-6.3W were surveyed, especially in the bay region of the time-temperature-transformation (TTT) diagram. Carbide precipitation characteristics were of particular interest. Similar to Fe-C-Mo and Fe-C-Cr alloys, grain- and twin-boundary bainite containing sheets of alloy carbides dominated the microstructure at and above the bay, while popcorn-like bainite was observed immediately below the bay. Nonequilibrium carbide-phase combinations were obtained both above and below the bay, although W partitioning to the alloy carbides was always observed. The carbon level in the remaining austenite increased with reaction time at a given temperature, which, at the later stages of reaction, helped trigger the growth of a constituent containing a high density of nonlamellar carbides. These nonequilibrium reaction-path characteristics are considered to originate from crystallographic and interfacial structure constraints affecting the nucleation of carbides at ferrite-austenite interfaces.

Deciphering the Possible Role of Strain Path on the Evolution of Microstructure, Texture, and Magnetic Properties in a Fe-Cr-Ni Alloy

NASA Astrophysics Data System (ADS)

Kumar, Amit; Khatirkar, Rajesh Kisni; Gupta, Aman; Shekhawat, Satish K.; Suwas, Satyam

2018-06-01

In the present work, the influence of strain path on the evolution of microstructure, crystallographic texture, and magnetic properties of a two-phase Fe-Cr-Ni alloy was investigated. The Fe-Cr-Ni alloy had nearly equal proportion of austenite and ferrite and was cold rolled up to a true strain of 1.6 (thickness reduction) using two different strain paths—unidirectional rolling and multi-step cross rolling. The microstructures were characterized by scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD), while crystallographic textures were determined using X-ray diffraction. For magnetic characterization, B-H loops and M-H curves were measured and magnetic force microscopy was performed. After unidirectional rolling, ferrite showed the presence of strong α-fiber (rolling direction, RD//<110>) and austenite showed strong brass type texture (consisting of Brass (Bs) ({110}<112>), Goss ({110}<001>), and S ({123}<634>)). After multi-step cross rolling, strong rotated cube ({100}<110>) was developed in ferrite, while austenite showed ND (normal direction) rotated brass ( 10 deg) texture. The strain-induced martensite (SIM) was found to be higher in unidirectionally rolled samples than multi-step cross-rolled samples. The coherently diffracting domain size, micro-strain, coercivity, and core loss also showed a strong correlation with strain and strain path. More strain was partitioned into austenite than ferrite during deformation (unidirectional as well as cross rolling). Further, the strain partitioning (in both austenite and ferrite) was found to be higher in unidirectionally rolled samples.

Load partitioning between the bcc-iron matrix and NiAl-type precipitates in a ferritic alloy on multiple length scales

PubMed Central

Sun, Zhiqian; Song, Gian; Sisneros, Thomas A.; Clausen, Bjørn; Pu, Chao; Li, Lin; Gao, Yanfei; Liaw, Peter K.

2016-01-01

An understanding of load sharing among constituent phases aids in designing mechanical properties of multiphase materials. Here we investigate load partitioning between the body-centered-cubic iron matrix and NiAl-type precipitates in a ferritic alloy during uniaxial tensile tests at 364 and 506 °C on multiple length scales by in situ neutron diffraction and crystal plasticity finite element modeling. Our findings show that the macroscopic load-transfer efficiency is not as high as that predicted by the Eshelby model; moreover, it depends on the matrix strain-hardening behavior. We explain the grain-level anisotropic load-partitioning behavior by considering the plastic anisotropy of the matrix and elastic anisotropy of precipitates. We further demonstrate that the partitioned load on NiAl-type precipitates relaxes at 506 °C, most likely through thermally-activated dislocation rearrangement on the microscopic scale. The study contributes to further understanding of load-partitioning characteristics in multiphase materials. PMID:26979660

Load partitioning between the bcc-iron matrix and NiAl-type precipitates in a ferritic alloy on multiple length scales

DOE PAGES

Sun, Zhiqian; Song, Gian; Sisneros, Thomas A.; ...

2016-03-16

An understanding of load sharing among constituent phases aids in designing mechanical properties of multiphase materials. Here we investigate load partitioning between the body-centered-cubic iron matrix and NiAl-type precipitates in a ferritic alloy during uniaxial tensile tests at 364 and 506 C on multiple length scales by in situ neutron diffraction and crystal plasticity finite element modeling. Our findings show that the macroscopic load-transfer efficiency is not as high as that predicted by the Eshelby model; moreover, it depends on the matrix strain-hardening behavior. We explain the grain-level anisotropic load-partitioning behavior by considering the plastic anisotropy of the matrix andmore » elastic anisotropy of precipitates. We further demonstrate that the partitioned load on NiAl-type precipitates relaxes at 506 C, most likely through thermally-activated dislocation rearrangement on the microscopic scale. Furthermore, the study contributes to further understanding of load-partitioning characteristics in multiphase materials.« less

Nano-sized precipitate stability and its controlling factors in a NiAl-strengthened ferritic alloy

DOE PAGES

Sun, Zhiqian; Song, Gian; Ilavsky, Jan; ...

2015-11-05

Coherent B2-ordered NiAl-type precipitates have been used to reinforce solid-solution bodycentered- cubic iron for high-temperature application in fossil-energy power plants. In this study, the stability of nano-sized precipitates in a NiAl-strengthened ferritic alloy was investigated at 700 - 950°C using ultra-small angle X-ray scattering and electron microscopies. Here we show that the coarsening kinetics of NiAl-type precipitates is in excellent agreement with the ripening model in multicomponent alloys. We further demonstrate that the interfacial energy between the matrix and NiAl-type precipitates is strongly dependent to differences in the matrix/precipitate compositions. The results profile the ripening process in multicomponent alloys bymore » illustrating controlling factors (i.e., interfacial energy, diffusivities, and element partitioning). As a result, the study provides guidelines to design and develop high-temperature alloys with stable microstructures for long-term service.« less

Probing Formability Improvement of Ultra-thin Ferritic Stainless Steel Bipolar Plate of PEMFC in Non-conventional Forming Process

NASA Astrophysics Data System (ADS)

Bong, Hyuk Jong; Barlat, Frédéric; Lee, Myoung-Gyu

2016-08-01

Formability increase in non-conventional forming profiles programmed in the servo-press was investigated using finite element analysis. As an application, forming experiment on a 0.15-mm-thick ferritic stainless steel sheet for a bipolar plate, a primary component of a proton exchange membrane fuel cell, was conducted. Four different forming profiles were considered to investigate the effects of forming profiles on formability and shape accuracy. The four motions included conventional V motion, holding motion, W motion, and oscillating motion. Among the four motions, the holding motion, in which the slide was held for a certain period at the bottom dead point, led to the best formability. Finite element simulations were conducted to validate the experimental results and to probe the formability improvement in the non-conventional forming profiles. A creep model to address stress relaxation effect along with tool elastic recovery was implemented using a user-material subroutine, CREEP in ABAQUS finite element software. The stress relaxation and variable contact conditions during the holding and oscillating profiles were found to be the main mechanism of formability improvement.

Effect of thermo-mechanical treatments on the microstructure and mechanical properties of an ODS ferritic steel

NASA Astrophysics Data System (ADS)

Oksiuta, Z.; Mueller, P.; Spätig, P.; Baluc, N.

2011-05-01

The Fe-14Cr-2W-0.3Ti-0.3Y 2O 3 oxide dispersion strengthened (ODS) reduced activation ferritic (RAF) steel was fabricated by mechanical alloying of a pre-alloyed, gas atomised powder with yttria nano-particles, followed by hot isostatic pressing and thermo-mechanical treatments (TMTs). Two kinds of TMT were applied: (i) hot pressing, or (ii) hot rolling, both followed by annealing in vacuum at 850 °C. The use of a thermo-mechanical treatment was found to yield strong improvement in the microstructure and mechanical properties of the ODS RAF steel. In particular, hot pressing leads to microstructure refinement, equiaxed grains without texture, and an improvement in Charpy impact properties, especially in terms of the upper shelf energy (about 4.5 J). Hot rolling leads to elongated grains in the rolling direction, with a grain size ratio of 6:1, higher tensile strength and reasonable ductility up to 750 °C, and better Charpy impact properties, especially in terms of the ductile-to-brittle transition temperature (about 55 °C).

Tritium retention in reduced-activation ferritic/martensitic steels

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

Hatano, Y.; Abe, S.; Matsuyama, M.

Reduced-activation ferritic/martensitic (RAFM) steels are structural material candidates for breeding blankets of future fusion reactors. Therefore, tritium (T) retention in RAFM steels is an important problem in assessing the T inventory of blankets. In this study, specimens of RAFM steels were subjected to irradiation of 20 MeV W ions to 0.54 displacements per atom (dpa), exposure to high flux D plasmas at 400 and 600 K and that to pulsed heat loads. The specimens thus prepared were exposed to DT gas at 473 K. Despite severe modification in the surface morphology, heat loads had negligible effects on T retention. Significantmore » increase in T retention at the surface and/or subsurface was observed after D plasma exposure. However, T trapped at the surface/subsurface layer was easily removed by maintaining the specimens in the air at about 300 K. Displacement damage led to increase in T retention in the bulk due to the trapping effects of defects, and T trapped was stable at 300 K. It was therefore concluded that displacement damages had the largest influence on T retention under the present conditions.« less

Surface chemistry, friction, and wear of Ni-Zn and Mn-Zn ferrites in contact with metals

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1983-01-01

X-ray photoelectron and Auger electron spectroscopy analysis were used in sliding friction experiments. These experiments were conducted with hot-pressed polycrystalline Ni-Zn and Mn-Zn ferrites, and single-crystal Mn-Zn ferrite in contact with various transition metals at room temperature in both vacuum and argon. The results indicate that Ni2O3 and Fe3O4 were present on the Ni-Zn ferrite surface in addition to the nominal bulk constituents, while MnO2 and Fe3O4 were present on the Mn-Zn ferrite surface in addition to the nominal bulk constituents. The coefficients of friction for the ferrites in contact with metals were related to the relative chemical activity of these metals. The more active the metal, the higher is the coefficient of friction. The coefficients of friction for the ferrites were correlated with the free energy of formation of the lowest metal oxide. The interfacial bond can be regarded as a chemical bond between the metal atoms and the oxygen anions in the ferrite surfaces. The adsorption of oxygen on clean metal and ferrite does strengthen the metal-ferrite contact and increase the friction. The ferrites exhibit local cracking and fracture with sliding under adhesive conditions. All the metals transferred to the surfaces of the ferrites in sliding. Previously announced in STAR as N83-19901

Surface chemistry, friction and wear of Ni-Zn and Mn-Zn ferrites in contact with metals

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1982-01-01

X-ray photoelectron and Auger electron spectroscopy analysis were used in sliding friction experiments. These experiments were conducted with hot-pressed polycrystalline Ni-Zn and Mn-Zn ferrites, and single-crystal Mn-Zn ferrite in contact with various transition metals at room temperature in both vacuum and argon. The results indicate that Ni2O3 and Fe3O4 were present on the Ni-Zn ferrite surface in addition to the nominal bulk constituents, while MnO2 and Fe3O4 were present on the Mn-Zn ferrite surface in addition to the nominal bulk constituents. The coefficients of friction for the ferrites in contact with metals were related to the relative chemical activity of these metals. The more active the metal, the higher is the coefficient of friction. The coefficients of friction for the ferrites were correlated with the free energy of formation of the lowest metal oxide. The interfacial bond can be regarded as a chemical bond between the metal atoms and the oxygen anions in the ferrite surfaces. The adsorption of oxygen on clean metal and ferrite does strengthen the metal-ferrite contact and increase the friction. The ferrites exhibit local cracking and fracture with sliding under adhesive conditions. All the metals transferred to he surfaces of the ferrites in sliding.

Microstructural Evolution and the Precipitation Behavior in X90 Linepipe Steel During Isothermal Processing

NASA Astrophysics Data System (ADS)

Tian, Y.; Wang, H. T.; Wang, Z. D.; Misra, R. D. K.; Wang, G. D.

2018-03-01

Thermomechanical controlled processing of 560-MPa (X90) linepipe steel was simulated in the laboratory using a thermomechanical simulator to study the microstructural evolution and precipitation behavior during isothermal holding. The results indicated that martensite was obtained when the steels were isothermally held for 5 s at 700 °C. Subsequently, granular bainite and acicular ferrite transformation occurred with increased holding time. Different amount of polygonal ferrite formed after isothermally holding for 600-3600 s. Pearlite nucleated after isothermally holding for 3600 s. Precipitation occurred after isothermal holding for 5 s and continuous precipitation occurred at grain boundaries after isothermally holding for 600 s. After isothermally holding for 3600 s, large Nb/Ti carbide precipitated. The presence of MX-type precipitates was confirmed by diffraction pattern. The interphase precipitation (IP) occurred between 5 and 30 s. Maximum hardness was obtained after isothermally holding for 600 s when IP occurred and rapidly decreased to a low value, mainly because polygonal ferrite dominated the microstructure after isothermally holding for 3600 s.

The Effects of One and Double Heat Treatment Cycles on the Microstructure and Mechanical Properties of a Ferritic-Bainitic Dual Phase Steel

NASA Astrophysics Data System (ADS)

Piri, Reza; Ghasemi, Behrooz; Yousefpour, Mardali

2018-03-01

In this study, samples with ferritic-bainitic dual phase structures consisting of 62 pct bainite were obtained from the AISI 4140 steel by applying one and double heat treatment cycles. Microstructural investigations by electron and optical microscopy indicated that the sample heat treated through double cycle benefited from finer ferrite and bainite grains. Additionally, results obtained from mechanical tests implied that the double-cycle heat-treated sample not only has a higher tensile strength as well as ultimate strength but also benefits from a higher ductility along with a higher impact energy than the one-cycle heat-treated sample. Moreover, fractography results showed that the type of fracture in both samples is a combination of the brittle and the ductile fracture. Besides, the ratio of the ductile fracture is higher for the double-cycle heat-treated sample than for the one-cycle sample, due to the lower aggregation of sulfur at grain boundaries.

Precipitation in AISI 316L(N) during creep tests at 550 and 600 °C up to 10 years

NASA Astrophysics Data System (ADS)

Padilha, A. F.; Escriba, D. M.; Materna-Morris, E.; Rieth, M.; Klimenkov, M.

2007-05-01

The precipitation behaviour in the gauge lengths and in the heads of initially solution annealed type 316L(N) austenitic stainless steel specimens tested in creep at 550 and 600 °C for periods of up to 85 000 h has been studied using several metallographic techniques. Three phases were detected: M 23C 6, Laves, and sigma phase. The volume fraction of the precipitated sigma phase was significantly higher than that of carbides and the Laves phase. M 23C 6 carbide precipitation occurred very rapidly and was followed by the sigma and Laves phases formation in the delta ferrite islands. Sigma and Laves phases precipitated at grain boundaries after longer times. Two different mechanisms of sigma phase precipitation have been proposed, one for delta ferrite decomposition and another for grain boundary precipitation. Small quantities of the Laves phase were detected in delta ferrite, at grain boundaries and inside the grains.

Theoretical study on third-order nonlinear optical properties in hexagonal graphene nanoflakes: Edge shape effect

NASA Astrophysics Data System (ADS)

Nagai, Hiroshi; Nakano, Masayoshi; Yoneda, Kyohei; Fukui, Hitoshi; Minami, Takuya; Bonness, Sean; Kishi, Ryohei; Takahashi, Hideaki; Kubo, Takashi; Kamada, Kenji; Ohta, Koji; Champagne, Benoît; Botek, Edith

2009-08-01

Using hybrid density functional theory methods, we investigate the second hyperpolarizabilities ( γ) of hexagonal shaped finite graphene fragments, which are referred to as hexagonal graphene nanoflakes (HGNFs), with two types of edge shapes: zigzag (Z) and armchair (A) edges. It is found that Z-HGNF, which gives intermediate diradical characters ( y), exhibits about 3.3 times larger orthogonal components of γ ( γ xxxx = γ yyyy in this case) than A-HGNF, which gives zero y value (closed-shell system). The γ density analysis reveals that this enhancement originates in the significant contribution of γ densities on edge regions in Z-HGNF. These observations strongly indicate that Z-HGNF is a promising candidate of open-shell singlet NLO systems.

Morphology controlled synthesis of nanoporous Co3O4 nanostructures and their charge storage characteristics in supercapacitors.

PubMed

Deori, Kalyanjyoti; Ujjain, Sanjeev Kumar; Sharma, Raj Kishore; Deka, Sasanka

2013-11-13

Cubic spinel Co3O4 nanoparticles with spherical (0D) and hexagonal platelet (2D) morphologies were synthesized using a simple solvothermal method by tuning the reaction time. XRD and HRTEM analyses revealed pure phase with growth of Co3O4 particles along [111] and [110] directions. UV-vis studies showed two clear optical absorption peaks corresponding to two optical band gaps in the range of 400-500 nm and 700-800 nm, respectively, related to the ligand to metal charge transfer events (O(2-) → Co(2+,3+)). Under the electrochemical study in two electrode assembly system (Co3O4/KOH/Co3O4) without adding any large area support or a conductive filler, the hexagonal platelet Co3O4 particles exhibited comparatively better characteristics with high specific capacitance (476 F g(-1)), energy density 42.3 Wh kg(-1) and power density 1.56 kW kg(-1) at current density of 0.5 Ag(-1), that suited for potential applications in supercapacitors. The observed better electrochemical properties of the nanoporous Co3O4 particles is attributed to the layered platelet structural arrangement of the hexagonal platelet and the presence of exceptionally high numbers of regularly ordered pores.

Tellurite microstructure fibers with small hexagonal core for supercontinuum generation.

PubMed

Liao, Meisong; Chaudhari, Chitrarekha; Qin, Guanshi; Yan, Xin; Suzuki, Takenobu; Ohishi, Yasutake

2009-07-06

Tellurite glass microstructure fibers with a 1 microm hexagonal core were fabricated successfully by accurately controlling the temperature field in the fiber-drawing process. The diameter ratio of holey region to core (DRHC) for the fiber can be adjusted freely in the range of 1-20 by pumping a positive pressure into the holes when drawing fiber, which provides much freedom in engineering the chromatic dispersion. With the increase of DRHC from 3.5 to 20, the zero dispersion wavelengths were shifted several hundred nanometers, the cutoff wavelength due to confinement loss was increased from 1600 nm to 3800 nm, and the nonlinear coefficient gamma was increased from 3.9 to 5.7 W(-1)/m. Efficient visible emissions due to third harmonic generation were found for fibers with a DRHC of 10 and 20 under the 1557 nm pump of a femtosecond fiber laser. One octave flattened supercontinuum spectrum was generated from fibers with a DRHC of 3.5, 10 and 20 by the 1064 nm pump of a picosecond fiber laser. To the best of our knowledge, we have for the first time fabricated a hexagonal core fiber by soft glass with such a small core size, and have demonstrated a large influence of the holey region on the dispersion, nonlinear coefficient and supercontinuum generation for such fiber.

Hexagonal OsB 2: Sintering, microstructure and mechanical properties

DOE PAGES

Xie, Zhilin; Lugovy, Mykola; Orlovskaya, Nina; ...

2015-02-07

In this study, the metastable high pressure ReB 2-type hexagonal OsB 2 bulk ceramics was produced by spark plasma sintering. The phase composition, microstructure, and mechanical behavior of the sintered OsB 2 were studied by X-ray diffraction, optical microscopy, TEM, SEM, EDS, and nanoindentation. The produced ceramics was rather porous and contained a mixture of hexagonal (~80 wt.%) and orthorhombic (~20 wt.%) phases as identified by X-ray diffraction and EBSD analysis. Two boron-rich phases, which do not contain Os, were also identified by TEM and SEM/EDS analysis. Nanoindentation measurements yielded a hardness of 31 ± 9 GPa and Young’s modulusmore » of 574 ± 112 GPa, indicating that the material is rather hard and very stiff; but, it is very prone to crack formation and propagation, which is indicative of a very brittle nature of this material. Improvements in the sintering regime are required in order to produce dense, homogeneous and single phase hexagonal OsB 2 bulk ceramics.« less

Strong and weak second-order topological insulators with hexagonal symmetry and ℤ3 index

NASA Astrophysics Data System (ADS)

Ezawa, Motohiko

2018-06-01

We propose second-order topological insulators (SOTIs) whose lattice structure has a hexagonal symmetry C6. We start with a three-dimensional weak topological insulator constructed on a stacked triangular lattice, which has only side topological surface states. We then introduce an additional mass term which gaps out the side surface states but preserves the hinge states. The resultant system is a three-dimensional SOTI. The bulk topological quantum number is shown to be the Z3 index protected by inversion time-reversal symmetry I T and rotoinversion symmetry I C6 . We obtain three phases: trivial, strong, and weak SOTI phases. We argue the origin of these two types of SOTIs. A hexagonal prism is a typical structure respecting these symmetries, where six topological hinge states emerge at the side. The building block is a hexagon in two dimensions, where topological corner states emerge at the six corners in the SOTI phase. Strong and weak SOTIs are obtained when the interlayer hopping interaction is strong and weak, respectively.

Conversion between hexagonal GaN and beta-Ga(2)O(3) nanowires and their electrical transport properties.

PubMed

Li, Jianye; An, Lei; Lu, Chenguang; Liu, Jie

2006-02-01

We have observed that the hexagonal GaN nanowires grown from a simple chemical vapor deposition method using gallium metal and ammonia gas are usually gallium-doped. By annealing in air, the gallium-doped hexagonal GaN nanowires could be completely converted to beta-Ga(2)O(3) nanowires. Annealing the beta-Ga(2)O(3) nanowires in ammonia could convert them back to undoped hexagonal GaN nanowires. Field effect transistors based on these three kinds of nanowires were fabricated, and their performances were studied. Because of gallium doping, the as-grown GaN nanowires show a weak gating effect. Through the conversion process of GaN nanowires (gallium-doped) --> Ga(2)O(3) nanowires --> GaN nanowires (undoped) via annealing, the final undoped GaN nanowires display different electrical properties than the initial gallium-doped GaN nanowires, show a pronounced n-type gating effect, and can be completely turned off.

Researches on tungsten carbide

NASA Astrophysics Data System (ADS)

1994-11-01

This paper summarizes results of the researches on tungsten carbide (WC), carried out in the 5-year period starting 1989 by the Science and Technology Agency's National Institute for Researches in Inorganic Materials. The high-frequency heating, floating zone technique, generally suited for growth of large-size, single crystals of high melting materials, is inapplicable to the hexagonal WC system, which is decomposed. This problem has been solved by adding boron to the system, to allow it to exist with the W-C-B melt at an equilibrium. The computer-aided control techniques have enabled automatic growth of the single crystals of carbides and borides. The de Haas-Van Alphen effect of the single WC crystals has been observed, to establish the Fermi surface model. The single crystals of transition metal carbides, such as WC, have been coated with the monolayer of graphite at high repeatability, to create the surface layer materials. An attempt has been done to produce the halite type structure by substituting Ti as the atom in the outermost layer of TiC by W. The new method, based on the low-speed deuterium ion scattering, has been developed to analyze the surface bonding conditions, clarifying the conditions of alkalis adsorbed on and bonded to metallic surfaces, and their surface reactivities.

ACCELERATORS: RF system design and measurement of HIRF-CSRe

NASA Astrophysics Data System (ADS)

Xu, Zhe; Zhao, Hong-Wei; Wang, Chun-Xiao; Xia, Jia-Wen; Zhan, Wen-Long; Bian, Zhi-Bin

2009-05-01

An RF system for the CSRe (cooling storage experimental ring) is designed and manufactured domestically. The present paper mainly describes the RF system design in five main sections: ferrite ring, RF cavity, RF generator, low level system and cavity cooling. The cavity is based on a type of coaxial resonator which is shorted at the end with one gap and loaded with domestic ferrite rings. The RF generator is designed in the push-pull mode and the low level control system is based on a DSP+FGPA+DDS+USB interface and has three feedback loops. Finally we give the results of the measurement on our system.

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

Tan, Lizhen; Yang, Ying; Chen, Tianyi

Advanced nuclear reactors as well as the life extension of light water reactors require advanced alloys capable of satisfactory operation up to neutron damage levels approaching 200 displacements per atom (dpa). Extensive studies, including fundamental theories, have demonstrated the superior resistance to radiation-induced swelling in ferritic steels, primarily inherited from their body-centered cubic (bcc) structure. This study aims at developing nanoprecipitates strengthened advanced ferritic alloys for advanced nuclear reactor applications. To be more specific, this study aims at enhancing the amorphization ability of some precipitates, such as Laves phase and other types of intermetallic phases, through smart alloying strategy, andmore » thereby promote the crystalline®amorphous transformation of these precipitates under irradiation.« less

Electromagnon in the Y-type hexaferrite BaSrCoZnFe11AlO22

NASA Astrophysics Data System (ADS)

Vít, Jakub; Kadlec, Filip; Kadlec, Christelle; Borodavka, Fedir; Chai, Yi Sheng; Zhai, Kun; Sun, Young; Kamba, Stanislav

2018-04-01

We investigated static and dynamic magnetoelectric properties of single crystalline BaSrCoZnFe11AlO22 , which is a room-temperature multiferroic with Y-type hexaferrite crystal structure. Below 300 K, a purely electric-dipole-active electromagnon at ≈1.2 THz with the electric polarization oscillating along the hexagonal axis was observed by THz and Raman spectroscopies. We investigated the behavior of the electromagnon with applied dc magnetic field and linked its properties to static measurements of the magnetic structure. Our analytical calculations determined selection rules for electromagnons activated by the magnetostriction mechanism in various magnetic structures of Y-type hexaferrite. Comparison with our experiment supports that the electromagnon is indeed activated by the magnetostriction mechanism involving spin vibrations along the hexagonal axis.

Effect of Al on the microstructure, magnetic and millimeter-wave properties of high oriented barium hexaferrite thin films

NASA Astrophysics Data System (ADS)

Chen, Daming; Chen, Zhuo; Wang, Guijuan; Chen, Yong; Li, Yuanxun; Liu, Yingli

2017-12-01

The microstructure, magnetic and millimeter-wave properties of high oriented barium hexaferrite (BaAlxFe12-xO19) thin films with Al doping level x from 0 to 2 are reported. The films were grown on Pt/TiO2/SiO2/Si substrate by Sol-gel method. It is found that with increasing x from 0 to 2 the hexagonal grain disappear, together with Curie temperature dropped from 449 °C to 332 °C and saturated magnetization (4πMs) decreased from 3.8 kG to 1.9 kG, it is attributed to the fact that the Fe ions were substituted by non-magnetic Al ions, leading to the Fe3+-O-Fe3+ super-exchange interaction became weak. The ferromagnetic resonance (FMR) measurement showed that the FMR linewidths is as low as 113 Oe @ 58 GHz, and the FMR frequency shifted to higher frequency range when increasing Al doping level. These result offer the potential application of barium ferrite thin films in tunable millimeter wave devices such as filter, circulator and isolator.

THE INFLUENCE OF SCREW TYPE, ALLOY AND CYLINDER POSITION ON THE MARGINAL FIT OF IMPLANT FRAMEWORKS BEFORE AND AFTER LASER WELDING

PubMed Central

Castilio, Daniela; Pedreira, Ana Paula Ribeiro do Vale; Rossetti, Paulo Henrique Orlato; Rossetti, Leylha Maria Nunes; Bonachela, Wellington Cardoso

2006-01-01

Misfit at the abutment-prosthetic cylinder interface can cause loss of preload, leading to loosening or fracture of gold and titanium screws. Objectives: To evaluate the influence of screw type, alloy, and cylinder position on marginal fit of implant frameworks before and after laser welding. Methods: After Estheticone-like abutments were screwed to the implants, thirty plastic prosthetic cylinders were mounted and waxed-up to fifteen cylindrical bars. Each specimen had three interconnected prosthetic components. Five specimens were one-piece cast in titanium and five in cobalt-chromium alloy. On each specimen, tests were conducted with hexagonal titanium and slotted gold screws separately, performing a total of thirty tested screws. Measurements at the interfaces were performed using an optical microscope with 5 μm accuracy. After sectioning, specimens were laser welded and new measurements were obtained. Data were submitted to a four-way ANOVA and Tukey's multiple comparisons test (α =0.05). Results: Slotted and hexagonal screws did not present significant differences regarding to the fit of cylinders cast in titanium, either in one-piece casting framework or after laser welding. When slotted and hexagonal screws were tested on the cobalt-chromium specimens, statistically significant differences were found for the one-piece casting condition, with the slotted screws presenting better fit (24.13μm) than the hexagonal screws (27.93 μm). Besides, no statistically significant differences were found after laser welding. Conclusions: 1) The use of different metal alloys do exert influence on the marginal fit, 2) The slotted and hexagonal screws play the exclusive role of fixing the prosthesis, and did not improve the fit of cylinders, and 3) cylinder position did not affect marginal fit values. PMID:19089035

Solvation Dynamics in Different Phases of the Lyotropic Liquid Crystalline System.

PubMed

Roy, Bibhisan; Satpathi, Sagar; Gavvala, Krishna; Koninti, Raj Kumar; Hazra, Partha

2015-09-03

Reverse hexagonal (HII) liquid crystalline material based on glycerol monooleate (GMO) is considered as a potential carrier for drugs and other important biomolecules due to its thermotropic phase change and excellent morphology. In this work, the dynamics of encapsulated water, which plays important role in stabilization and formation of reverse hexagonal mesophase, has been investigated by time dependent Stokes shift method using Coumarin-343 as a solvation probe. The formation of the reverse hexagonal mesophase (HII) and transformation to the L2 phase have been monitored using small-angle X-ray scattering and polarized light microscopy experiments. REES studies suggest the existence of different polar regions in both HII and L2 systems. The solvation dynamics study inside the reverse hexagonal (HII) phase reveals the existence of two different types of water molecules exhibiting dynamics on a 120-900 ps time scale. The estimated diffusion coefficients of both types of water molecules obtained from the observed dynamics are in good agreement with the measured diffusion coefficient collected from the NMR study. The calculated activation energy is found to be 2.05 kcal/mol, which is associated with coupled rotational-translational water relaxation dynamics upon the transition from "bound" to "quasi-free" state. The observed ∼2 ns faster dynamics of the L2 phase compared to the HII phase may be associated with both the phase transformation as well as thermotropic effect on the relaxation process. Microviscosities calculated from time-resolved anisotropy studies infer that the interface is almost ∼22 times higher viscous than the central part of the cylinder. Overall, our results reveal the unique dynamical features of water inside the cylinder of reverse hexagonal and inverse micellar phases.

The influence of screw type, alloy and cylinder position on the marginal fit of implant frameworks before and after laser welding.

PubMed

Castilio, Daniela; Pedreira, Ana Paula Ribeiro do Vale; Rossetti, Paulo Henrique Orlato; Rossetti, Leylha Maria Nunes; Bonachela, Wellington Cardoso

2006-04-01

Misfit at the abutment-prosthetic cylinder interface can cause loss of preload, leading to loosening or fracture of gold and titanium screws. To evaluate the influence of screw type, alloy, and cylinder position on marginal fit of implant frameworks before and after laser welding. After Estheticone-like abutments were screwed to the implants, thirty plastic prosthetic cylinders were mounted and waxed-up to fifteen cylindrical bars. Each specimen had three interconnected prosthetic components. Five specimens were one-piece cast in titanium and five in cobalt-chromium alloy. On each specimen, tests were conducted with hexagonal titanium and slotted gold screws separately, performing a total of thirty tested screws. Measurements at the interfaces were performed using an optical microscope with 5mm accuracy. After sectioning, specimens were laser welded and new measurements were obtained. Data were submitted to a four-way ANOVA and Tukey's multiple comparisons test (alpha=0.05). Slotted and hexagonal screws did not present significant differences regarding to the fit of cylinders cast in titanium, either in one-piece casting framework or after laser welding. When slotted and hexagonal screws were tested on the cobalt-chromium specimens, statistically significant differences were found for the one-piece casting condition, with the slotted screws presenting better fit (24.13 microm) than the hexagonal screws (27.93 microm). Besides, no statistically significant differences were found after laser welding. 1) The use of different metal alloys do exert influence on the marginal fit, 2) The slotted and hexagonal screws play the exclusive role of fixing the prosthesis, and did not improve the fit of cylinders, and 3) cylinder position did not affect marginal fit values.

Self-assembled quantum dot structures in a hexagonal nanowire for quantum photonics.

PubMed

Yu, Ying; Dou, Xiu-Ming; Wei, Bin; Zha, Guo-Wei; Shang, Xiang-Jun; Wang, Li; Su, Dan; Xu, Jian-Xing; Wang, Hai-Yan; Ni, Hai-Qiao; Sun, Bao-Quan; Ji, Yuan; Han, Xiao-Dong; Niu, Zhi-Chuan

2014-05-01

Two types of quantum nanostructures based on self-assembled GaAs quantumdots embedded into GaAs/AlGaAs hexagonal nanowire systems are reported, opening a new avenue to the fabrication of highly efficient single-photon sources, as well as the design of novel quantum optics experiments and robust quantum optoelectronic devices operating at higher temperature, which are required for practical quantum photonics applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Unraveling the Effect of Thermomechanical Treatment on the Dissolution of Delta Ferrite in Austenitic Stainless Steels

NASA Astrophysics Data System (ADS)

Rezayat, Mohammad; Mirzadeh, Hamed; Namdar, Masih; Parsa, Mohammad Habibi

2016-02-01

Considering the detrimental effects of delta ferrite stringers in austenitic stainless steels and the industrial considerations regarding energy consumption, investigating, and optimizing the kinetics of delta ferrite removal is of vital importance. In the current study, a model alloy prone to the formation of austenite/delta ferrite dual phase microstructure was subjected to thermomechanical treatment using the wedge rolling test aiming to dissolve delta ferrite. The effect of introducing lattice defects and occurrence of dynamic recrystallization (DRX) were investigated. It was revealed that pipe diffusion is responsible for delta ferrite removal during thermomechanical process, whereas when the DRX is dominant, the kinetics of delta ferrite dissolution tends toward that of the static homogenization treatment for delta ferrite removal that is based on the lattice diffusion of Cr and Ni in austenite. It was concluded that the optimum condition for dissolution of delta ferrite can be defined by the highest rolling temperature and strain in which DRX is not pronounced.

Atomic engineering of mixed ferrite and core-shell nanoparticles.

PubMed

Morrison, Shannon A; Cahill, Christopher L; Carpenter, Everett E; Calvin, Scott; Harris, Vincent G

2005-09-01

Nanoparticulate ferrites such as manganese zinc ferrite and nickel zinc ferrite hold great promise for advanced applications in power electronics. The use of these materials in current applications requires fine control over the nanoparticle size as well as size distribution to maximize their packing density. While there are several techniques for the synthesis of ferrite nanoparticles, reverse micelle techniques provide the greatest flexibility and control over size, crystallinity, and magnetic properties. Recipes for the synthesis of manganese zinc ferrite, nickel zinc ferrite, and an enhanced ferrite are presented along with analysis of the crystalline and magnetic properties. Comparisons are made on the quality of nanoparticles produced using different surfactant systems. The importance of various reaction conditions is explored with a discussion on the corresponding effects on the magnetic properties, particle morphology, stoichiometry, crystallinity, and phase purity.

AAuAl (A = Ca, Sc, and Ti): Peierls Distortion, Atomic Coloring, and Structural Competition

DOE PAGES

Pham, Joyce; Miller, Gordon J.

2018-04-02

Using density functional theory, the crystal structure variation of AAuAl (A = Ca, Sc, and Ti) from orthorhombic Co 2Si-type to distorted hexagonal Fe 2P-type and then Ni 2In-type structures is shown to correlate with their electronic structures and valence electron counts, sizes of the active metals A, and site preferences for Au and Al atoms, which are arranged to maximize Au–Al nearest neighbor contacts. An evaluation of chemical pressure imposed by the varying A metals using total energy vs volume calculations indicates that larger unit cell volumes favor the orthorhombic structure, whereas smaller volumes favor the hexagonal structures. Themore » electronic origin of the Mg 2Ga-type crystal structure of ScAuAl, refined as a distorted Fe 2P-type supercell doubled along the c-axis, indicates a Peierls-type distortion mechanism of the Au chains along the c-axis.« less

AAuAl (A = Ca, Sc, and Ti): Peierls Distortion, Atomic Coloring, and Structural Competition

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

Pham, Joyce; Miller, Gordon J.

Using density functional theory, the crystal structure variation of AAuAl (A = Ca, Sc, and Ti) from orthorhombic Co 2Si-type to distorted hexagonal Fe 2P-type and then Ni 2In-type structures is shown to correlate with their electronic structures and valence electron counts, sizes of the active metals A, and site preferences for Au and Al atoms, which are arranged to maximize Au–Al nearest neighbor contacts. An evaluation of chemical pressure imposed by the varying A metals using total energy vs volume calculations indicates that larger unit cell volumes favor the orthorhombic structure, whereas smaller volumes favor the hexagonal structures. Themore » electronic origin of the Mg 2Ga-type crystal structure of ScAuAl, refined as a distorted Fe 2P-type supercell doubled along the c-axis, indicates a Peierls-type distortion mechanism of the Au chains along the c-axis.« less

A correlative approach to segmenting phases and ferrite morphologies in transformation-induced plasticity steel using electron back-scattering diffraction and energy dispersive X-ray spectroscopy.

PubMed

Gazder, Azdiar A; Al-Harbi, Fayez; Spanke, Hendrik Th; Mitchell, David R G; Pereloma, Elena V

2014-12-01

Using a combination of electron back-scattering diffraction and energy dispersive X-ray spectroscopy data, a segmentation procedure was developed to comprehensively distinguish austenite, martensite, polygonal ferrite, ferrite in granular bainite and bainitic ferrite laths in a thermo-mechanically processed low-Si, high-Al transformation-induced plasticity steel. The efficacy of the ferrite morphologies segmentation procedure was verified by transmission electron microscopy. The variation in carbon content between the ferrite in granular bainite and bainitic ferrite laths was explained on the basis of carbon partitioning during their growth. Copyright © 2014 Elsevier B.V. All rights reserved.

Wear-resistant and electromagnetic absorbing behaviors of oleic acid post-modified ferrite-filled epoxy resin composite coating

NASA Astrophysics Data System (ADS)

Wang, Wenjie; Zang, Chongguang; Jiao, Qingjie

2015-03-01

The post-modified Mn-Zn ferrite was prepared by grafting oleic acid on the surface of Mn-Zn ferrite to inhibit magnetic nanoparticle aggregation. Fourier Transform Infrared (FT-IR) spectroscopy was used to characterize the particle surfaces. The friction and electromagnetic absorbing properties of a thin coating fabricated by dispersing ferrite into epoxy resin (EP) were investigated. The roughness of the coating and water contact angle were measured using the VEECO and water contact angle meter. Friction tests were conducted using a stainless-steel bearing ball and a Rockwell diamond tip, respectively. The complex permittivity and complex permeability of the composite coating were studied in the low frequency (10 MHz-1.5 GHz). Surface modified ferrites are found to improve magnetic particles dispersion in EP resulting in significant compatibility between inorganic and organic materials. Results also indicate that modified ferrite/EP coatings have a lower roughness average value and higher water contact angle than original ferrite/EP coatings. The enhanced tribological properties of the modified ferrite/EP coatings can be seen from the increased coefficient value. The composite coatings with modified ferrite are observed to exhibit better reflection loss compared with the coatings with original ferrite.

Electromagnetic absorption behaviour of ferrite loaded three phase carbon fabric composites

NASA Astrophysics Data System (ADS)

Jagatheesan, Krishnasamy; Ramasamy, Alagirusamy; Das, Apurba; Basu, Ananjan

2018-02-01

This article investigates the electromagnetic absorption behaviours of carbon helical yarn fabric reinforced composites and manganese-zinc (Mn-Zn) ferrite particles loaded 3 phase fabric composites. A carbon helical yarn having stainless steel core was prepared and made into single jersey knitted fabric. The composite was prepared by sandwiching a fabric with polypropylene films and thermal pressed. The absorption values of helical yarn fabric composite was observed to be less in the C band region (4-8 GHz). For improving the absorption coefficients of composite, Mn-Zn ferrite particles were dispersed in the polypropylene (PP) composite. The ferrite loaded PP composites exhibited better permittivity and permeability values, hence the absorption loss of the composite was improved. The helical yarn fabric reinforced with Mn-Zn ferrite/PP composite showed larger absorption coefficients than virgin PP/fabric composite. The change in thermal stability and particle size distribution in the Mn-Zn ferrite/PP composite was also analyzed. At higher ferrite concentration, bimodal particle distribution was observed which increased the conductivity and shielding effectiveness (SE) of the composite. In addition, complex permittivity value was also increased for higher incident frequency (4-8 GHz). As the ferrite content increases, the dielectric loss and magnetic permeability of PP/ferrite increases due to increased magnetic loss. Hence, ferrite loaded PP composite showed the total SE of -14.2 dB with the absorption coefficients of 0.717. The S1C7 fabric composite having ferrite dispersion showed the better absorption loss and lower reflection coefficient of 14.2 dB and 0.345 respectively compared to virgin PP/helical yarn fabric composite. The increasing ferrite content (45 wt%) improved the absorption loss and total SE. Though, ferrite based fabric composite exhibits moderate absorptive shielding, it can be used as shielding panels in the electronic industries.

Development of accident tolerant FeCrAl-ODS steels utilizing Ce-oxide particles dispersion

NASA Astrophysics Data System (ADS)

Shibata, Hiroki; Ukai, Shigeharu; Oono, Naoko H.; Sakamoto, Kan; Hirai, Mutsumi

2018-04-01

FeCrAl-ODS ferritic steels with Ce-oxide dispersion instead of Y-oxide were produced for the accident tolerant fuel cladding of the light water reactor. Excess oxygen (Ex.O) was added to improve the mechanical property. The tensile strength at Ex.O = 0 is around 200 MPa at 700 °C, mainly owing to dispersed Ce2O3 particles in less than 10 nm size. The formation of the fine Ce2O3 particles is dominated by a coherent interface with ferritic matrix. With increasing Ex.O, an increased of number density of coarser Ce-Al type oxide particles over 10 nm size is responsible for the improvement of the tensile strength. Change of the type of oxide particle, CeO2, Ce2O3, CeAlO3, Al2O3, in FeCrAl-ODS steel was thermodynamically analyzed as a parameter of Ex.O.

Cobalt ferrite based magnetostrictive materials for magnetic stress sensor and actuator applications

NASA Technical Reports Server (NTRS)

Jiles, David C. (Inventor); Paulsen, Jason A. (Inventor); Snyder, John E. (Inventor); Lo, Chester C. H. (Inventor); Ring, Andrew P. (Inventor); Bormann, Keith A. (Inventor)

2008-01-01

Magnetostrictive material based on cobalt ferrite is described. The cobalt ferrite is substituted with transition metals (such manganese (Mn), chromium (Cr), zinc (Zn) and copper (Cu) or mixtures thereof) by substituting the transition metals for iron or cobalt to form substituted cobalt ferrite that provides mechanical properties that make the substituted cobalt ferrite material effective for use as sensors and actuators. The substitution of transition metals lowers the Curie temperature of the material (as compared to cobalt ferrite) while maintaining a suitable magnetostriction for stress sensing applications.

The barium iron ruthenium oxide system

NASA Technical Reports Server (NTRS)

Kemmler-Sack, S.; Ehmann, A.

1986-01-01

In the system BaFe(1-x)Ru(x)O(3-y), three phases, separated by immiscibility gaps, are present: an Fe-rich phase (x = 0 to 0.75) with hexagonal BaTiO3 structure (6H; sequence (hcc)2), a Ru-rich phase (x = 0.9) of hexagonal 4H-type (sequence (hc)2), and the pure Ru compounds BaRuO3 with rhombohedral 9R structure (sequence (hhc)3). By vibrational spectroscopic investigations in the 6H phase a transition from n-type semiconduction (Fe-rich compounds with complete O lattice) can be detected. The 4H and 9R stacking polytypes are good, metal-like conductors. The lattice parameters are given.

Investigation on the structures and magnetic properties of carbon or nitrogen doped cobalt ferrite nanoparticles.

PubMed

Cao, Derang; Pan, Lining; Li, Jianan; Cheng, Xiaohong; Zhao, Zhong; Xu, Jie; Li, Qiang; Wang, Xia; Li, Shandong; Wang, Jianbo; Liu, Qingfang

2018-05-21

Carbon or nitrogen doped cobalt ferrite nanoparticles were synthesized in the air by a facile calcination process. X-ray diffraction, mapping, X-ray photoelectron spectroscopy, and mössbauer spectra results indicate that the nonmetal elements as the interstitial one are doped into cobalt ferrite nanoparticles. The morphologies of doped cobalt ferrite nanoparticles change from near-spherical to irregular cubelike shapes gradually with the increased carbon or nitrogen concentration, and their particles sizes also increase more than 200 nm. Furthermore, the saturation magnetization of carbon doped cobalt ferrite is improved. Although the saturation magnetization of N-doped cobalt ferrite is not enhanced obviously due to the involved hematite, they also do not drop drastically. The results reveal an approach to synthesize large scale ferrite nanoparticles, and improve the magnetic properties of ferrite nanoparticles, and also provide the potential candidates to synthesis co-doped functional magnetic materials.

Rhombic organization of microvilli domains found in a cell model of the human intestine

PubMed Central

Grünebaum, Jonas; Schäfer, Marcus; Mulac, Dennis; Rehfeldt, Florian; Langer, Klaus; Kramer, Armin; Riethmüller, Christoph

2018-01-01

Symmetry is rarely found on cellular surfaces. An exception is the brush border of microvilli, which are essential for the proper function of transport epithelia. In a healthy intestine, they appear densely packed as a 2D-hexagonal lattice. For in vitro testing of intestinal transport the cell line Caco-2 has been established. As reported by electron microscopy, their microvilli arrange primarily in clusters developing secondly into a 2D-hexagonal lattice. Here, atomic force microscopy (AFM) was employed under aqueous buffer conditions on Caco-2 cells, which were cultivated on permeable filter membranes for optimum differentiation. For analysis, the exact position of each microvillus was detected by computer vision; subsequent Fourier transformation yielded the type of 2D-lattice. It was confirmed, that Caco-2 cells can build a hexagonal lattice of microvilli and form clusters. Moreover, a second type of arrangement was discovered, namely a rhombic lattice, which appeared at sub-maximal densities of microvilli with (29 ± 4) microvilli / μm2. Altogether, the findings indicate the existence of a yet undescribed pattern in cellular organization. PMID:29320535

Study of cavity type antenna structure of large-area 915 MHz ultra-high frequency wave plasma device based on three-dimensional finite difference time-domain analysis

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

Chang, Xijiang; Graduate School of Science and Engineering, Shizuoka University, 3-5-1 Johoku, Hamamatsu 432-8561; Kunii, Kazuki

2013-11-14

A large-area planar plasma source with a resonant cavity type launcher driven by a 915 MHz ultra-high frequency wave was developed. Theoretical analysis with the three-dimensional finite difference time-domain simulation was carried out to determine the optimized launcher structure by analyzing the resonant transverse magnetic mode in the resonant cavity. Numerical result expects that the resonant electric field distribution inside the cavity dominantly consists of the TM{sub 410} mode. The resonant cavity type launcher having 8 holes in an octagonal geometry was designed to fit the resonant transverse magnetic mode. Adjusting 8 hole positions of the launcher to the fieldmore » pattern of the resonant TM{sub 410} mode, we found that the plasma density increased about 40%∼50% from 1.0∼1.1 × 10{sup 11} cm{sup −3} to ∼1.5 × 10{sup 11} cm{sup −3} at the same incident power of 2.5 kW, compared with the previous results with the launcher having 6 holes in the hexagonal geometry. It is also noted that the electron density changes almost linearly with the incident wave power without any mode jumps.« less

The role of yttrium and titanium during the development of ODS ferritic steels obtained through the STARS route: TEM and XAS study

NASA Astrophysics Data System (ADS)

Ordás, Nerea; Gil, Emma; Cintins, Arturs; de Castro, Vanessa; Leguey, Teresa; Iturriza, Iñigo; Purans, Juris; Anspoks, Andris; Kuzmin, Alexei; Kalinko, Alexandr

2018-06-01

Oxide Dispersion Strengthened Ferritic Steels (ODS FS) are candidate materials for structural components in future fusion reactors. Their high strength and creep resistance at elevated temperatures and their good resistance to neutron radiation damage is obtained through extremely fine microstructures containing a high density of nanometric precipitates, generally yttrium and titanium oxides. This work shows transmission electron microscopy (TEM) and extended X-ray absorption fine structure (EXAFS) characterization of Fe-14Cr-2W-0.3Ti-0.24Y ODS FS obtained by the STARS route (Surface Treatment of gas Atomized powder followed by Reactive Synthesis), an alternative method to obtain ODS alloys that avoids the mechanical alloying to introduce Y2O3 powder particles. In this route, FS powders already containing Ti and Y, precursors of the nanometric oxides, are obtained by gas atomization. Then, a metastable Cr- and Fe-rich oxide layer is formed on the surface of the powder particles. During consolidation by HIP at elevated temperatures, and post-HIP heat treatments above the HIP temperature, this oxide layer at Prior Particle Boundaries (PPBs) dissociates, the oxygen diffuses, and Y-Ti-O nano-oxides precipitate in the ferritic matrix. TEM characterization combined with XAFS and XANES analyses have proven to be suitable tools to follow the evolution of the nature of the different oxides present in the material during the whole processing route and select appropriate HIP and post-HIP parameters to promote profuse and fine Y-Ti-O nanometric precipitates.

Ferrite film growth on semiconductor substrates towards microwave and millimeter wave integrated circuits

NASA Astrophysics Data System (ADS)

Chen, Z.; Harris, V. G.

2012-10-01

It is widely recognized that as electronic systems' operating frequency shifts to microwave and millimeter wave bands, the integration of ferrite passive devices with semiconductor solid state active devices holds significant advantages in improved miniaturization, bandwidth, speed, power and production costs, among others. Traditionally, ferrites have been employed in discrete bulk form, despite attempts to integrate ferrite as films within microwave integrated circuits. Technical barriers remain centric to the incompatibility between ferrite and semiconductor materials and their processing protocols. In this review, we present past and present efforts at ferrite integration with semiconductor platforms with the aim to identify the most promising paths to realizing the complete integration of on-chip ferrite and semiconductor devices, assemblies and systems.

Optimal Design of Litz Wire Coils With Sandwich Structure Wirelessly Powering an Artificial Anal Sphincter System.

PubMed

Ke, Lei; Yan, Guozheng; Yan, Sheng; Wang, Zhiwu; Li, Xiaoyang

2015-07-01

Transcutaneous energy transfer system (TETS) is widely used to energize implantable biomedical devices. As a key part of the TETS, a pair of applicable coils with low losses, high unloaded Q factor, and strong coupling is required to realize an efficient TETS. This article presents an optimal design methodology of planar litz wire coils sandwiched between two ferrite substrates wirelessly powering a novel mechanical artificial anal sphincter system for treating severe fecal incontinence, with focus on the main parameters of the coils such as the wire diameter, number of turns, geometry, and the properties of the ferrite substrate. The theoretical basis of optimal power transfer efficiency in an inductive link was analyzed. A set of analytical expressions are outlined to calculate the winding resistance of a litz wire coil on ferrite substrate, taking into account eddy-current losses, including conduction losses and induction losses. Expressions that describe the geometrical dimension dependence of self- and mutual inductance are derived. The influence of ferrite substrate relative permeability and dimensions is also considered. We have used this foundation to devise an applicable coil design method that starts with a set of realistic constraints and ends with the optimal coil pair geometries. All theoretical predictions are verified with measurements using different types of fabricated coils. The results indicate that the analysis is useful for optimizing the geometry design of windings and the ferrite substrate in a sandwich structure as part of which, in addition to providing design insight, allows speeding up the system efficiency-optimizing design process. Copyright © 2015 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Zonal wavefront estimation using an array of hexagonal grating patterns

NASA Astrophysics Data System (ADS)

Pathak, Biswajit; Boruah, Bosanta R.

2014-10-01

Accuracy of Shack-Hartmann type wavefront sensors depends on the shape and layout of the lenslet array that samples the incoming wavefront. It has been shown that an array of gratings followed by a focusing lens provide a substitution for the lensslet array. Taking advantage of the computer generated holography technique, any arbitrary diffraction grating aperture shape, size or pattern can be designed with little penalty for complexity. In the present work, such a holographic technique is implemented to design regular hexagonal grating array to have zero dead space between grating patterns, eliminating the possibility of leakage of wavefront during the estimation of the wavefront. Tessellation of regular hexagonal shape, unlike other commonly used shapes, also reduces the estimation error by incorporating more number of neighboring slope values at an equal separation.

Hardness analysis of welded joints of austenitic and duplex stainless steels

NASA Astrophysics Data System (ADS)

Topolska, S.

2016-08-01

Stainless steels are widely used in the modern world. The continuous increase in the use of stainless steels is caused by getting greater requirements relating the corrosion resistance of all types of devices. The main property of these steels is the ability to overlap a passive layer of an oxide on their surface. This layer causes that they become resistant to oxidation. One of types of corrosion-resistant steels is ferritic-austenitic steel of the duplex type, which has good strength properties. It is easily formable and weldable as well as resistant to erosion and abrasive wear. It has a low susceptibility to stress-corrosion cracking, to stress corrosion, to intercrystalline one, to pitting one and to crevice one. For these reasons they are used, among others, in the construction of devices and facilities designed for chemicals transportation and for petroleum and natural gas extraction. The paper presents the results which shows that the particular specimens of the ][joint representing both heat affected zones (from the side of the 2205 steel and the 316L one) and the weld are characterized by higher hardness values than in the case of the same specimens for the 2Y joint. Probably this is caused by machining of edges of the sections of metal sheets before the welding process, which came to better mixing of native materials and the filler metal. After submerged arc welding the 2205 steel still retains the diphase, austenitic-ferritic structure and the 316L steel retains the austenitic structure with sparse bands of ferrite σ.

Reason for high strength and good ductility in dual phase steels composed of soft ferrite and hard martensite

NASA Astrophysics Data System (ADS)

Terada, Daisuke; Ikeda, Gosuke; Park, Myeong-heom; Shibata, Akinobu; Tsuji, Nobuhiro

2017-07-01

Dual phase (DP) steels in which the microstructures are composed of a soft ferrite phase and a hard martensite phase are known to show good strain-hardening, high strength and large elongation, but reasons for their superior mechanical properties are still unclear. In the present study, two types of DP structures, having either networked martensite or isolated martensite were fabricated in a low-carbon steel by different heat treatment routes, and their tensile deformation behavior was analyzed using the digital image correlation (DIC) technique. It was revealed that the DP specimens having networked martensite microstructures showed a better strength-ductility balance than the DP specimens with isolated martensite structures. The microscopic DIC analysis of identical areas showed that the strain distribution within the DP microstructures was not uniform and the plastic strain was localized in soft ferrite grains. The strain localized regions tended to detour around hard martensite but eventually propagated across the martensite. It was found also from the DIC analysis that the degree of strain partitioning between ferrite and martensite in the networked DP structure was lower than that in the isolated DP structure. The deformation became more homogeneous when the hard phase (martensite) was connected to form a network structure, which could be one of the reasons for the better strength-ductility balance in the networked DP structure compared to that in the isolated DP structure.

Giant magneto-optical Kerr rotation, quality factor and figure of merit in cobalt-ferrite magnetic nanoparticles doped in silica matrix as the only defect layer embedded in magnetophotonic crystals

NASA Astrophysics Data System (ADS)

Zamani, Mehdi; Hocini, Abdesselam

2018-03-01

In this work, we report on the theoretical study of one-dimensional magnetophotonic crystals (MPC) comprising of periodic dielectric structure Si/SiO and of silica matrix doped with cobalt-ferrite (CoFe2O4) magnetic nanoparticles as the only magnetic defect layer. Such structure can be prepared by sol-gel dip coating method that controls the thickness of each layer with nanometer level, hence, can overcome the problem of integration of the magneto-optical (MO) devices. We have studied the influence of the volume fraction (concentration of magnetic nanoparticles VF%) on the optical (reflectance, transmittance and absorption) and MO (Kerr rotation) responses in reflection-type one-dimensional MPCs. During investigation of the influence of magnetic nanoparticle's concentration, we found that giant Kerr rotations (even ≈135° for VF = 39%) can be obtained accompanied by large reflectance and low amounts for transmittance and absorption. We report on the demonstration of large MO quality factor and figure of merit in cobalt-ferrite magnetic nanoparticles in the infrared regime. Given the large Kerr rotation, high reflectance accompanied by low absorption and nearly zero transmittance of the 1D MPC containing cobalt-ferrite magnetic nanoparticles, large MO Q factor and figure of merit are obtained.

Precipitation Behavior of Nanometer-Sized Carbides in a Nb-Ti-Bearing Low-Carbon Steel

NASA Astrophysics Data System (ADS)

Xiaolin, Li; Zhaodong, Wang; Xiangtao, Deng; Yong, Yang; Dan, Song; Guodong, Wang

The microstructure, mechanical property and precipitation behavior in a low carbon Nb-Ti micro-alloyed steel were investigated using dilatometer, optical microscopy and transmission electron microscope. The results show that the microstructure of the experimental steel treated by isothermal quenching process mainly consists of ferrite and martensite. The volume fraction of ferrite increases with a decrease in the isothermal temperature. It is found that both of interphase precipitation and supersaturated precipitation would appear in the samples treated by isothermal quenching process. Along with the isothermal temperature decreasing, the precipitation state changes from interphase precipitation to supersaturated precipitation. The interphase precipitation of these carbides with different row spacing and different orientation in ferrite grains, is related to the mobility of interfaces during γ/α transformation based on ledge mechanism. In addition to {110}α plane suggested by the ledge mechanism, the planar sheets of interphase precipitation are also found to be parallel with{035}a planes. Moreover, the interphase precipitation carbides were identified to have a NaCl-type crystal structure with a lattice parameter of 0.432 nm and obey the Baker-Nutting (B-N) orientation relationship with respect to ferrite matrix. The contribution of the precipitation hardening to the yield strength of the experiment steel has been estimated to be 337 MPa at 620 °C, based on Orowan mechanism.

The Preparation of Soft Magnetic Composites Based on FeSi and Ferrite Fibers

NASA Astrophysics Data System (ADS)

Strečková, Magdaléna; Fáberová, Mária; Bureš, Radovan; Kurek, Pavel

2016-12-01

The fields of soft magnetic composites and powder metallurgy technologies have a powerful potential to redesign the way of electric motor preparation, and will continue to grow for years to come. A design of the novel soft microcomposite material composed of spherical FeSi particles and Ni0.3Zn0.7Fe2O4 ferrite nanofibers is reported together with a characterization of basic mechanical and electrical properties. The needle-less electrospinning method was used for a preparation of Ni0.3Zn0.7Fe2O4 ferrite nanofibers, which has a spinel-type crystal structure as verified by XRD and TEM analysis. The dielectric coating was prepared by mixing of nanofibers with glycerol and ethanol because of safe manipulation with fumed fibers and homogeneous distribution of the coating around the FeSi particle surface. The final microcomposite samples were prepared by a combination of the traditional PM compaction technique supplemented with a conventional sintering process of the prepared green compacts. The composition and distribution of the secondary phase formed by the spinel ferrite fibers were examined by SEM. It is demonstrated that the prepared composite material has a tight arrangement without any significant porosity, which manifest itself through superior mechanical properties (high mechanical hardness, Young modulus, and transverse rupture strength) and specific electric resistivity compared to the related composite materials including resin as the organic binder.

Laser weldability of 21Cr-6Ni-9Mn stainless steel: Part II - Weldability diagrams

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

Tate, Stephen B.; Javernick, Daniel Anthony; Lienert, Thomas J.

In this second part of the study, weldability diagrams developed to relate solidification crack susceptibility and chemical composition for laser welded type 21Cr-6Ni-9Mn (21-6-9) stainless steel are presented. Sigmajig testing on 14 commercial 21-6-9 alloys, 20 experimental 21-6-9 alloys, and 7 other high-N, high-Mn austenitic stainless steels was used to develop weldability diagrams for solidification crack susceptibility for laser welding of type 21-6-9. Three travel speeds were used to show the changes in minimum Cr eq/Ni eq for primary ferrite solidification as solidification rate increase d with travel speed . Primary austenite solidification was observed below 1.55 Cr eq/Ni eqmore » (Espy equivalents) at 21 mm/s travel speed. At 42 mm/s travel speed , a mix of solidification modes were displayed for alloys from 1.55-1.75 Cr eq/Ni eq. Primary ferrite solidification was observed above 1.75 Cr eq/Ni eq at both 42 and 85 mm/s travel speeds. No solidification cracking was observed for alloys with primary ferrite solidification. Lastly, variable cracking behavior was found in alloys with primary austenite solidification, but in general cracking was observed in alloys with greater than 0.02 wt-% combined impurity content according to (P+0.2S).« less

Low loss factor Co{sub 2}Z ferrite composites with equivalent permittivity and permeability for ultra-high frequency applications

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

Su, Zhijuan; Chang, Hong; Sokolov, Alexander S.

2014-08-11

Ferrite composites of nominal composition Ba{sub 3}Co{sub 2+x}Ir{sub x}Fe{sub 24−2x}O{sub 41} were studied in order to achieve low magnetic and dielectric losses and equivalent permittivity and permeability over a frequency range of 0.3–1 GHz. Crystallographic structure was characterized by X-ray diffraction, which revealed a Z-type phase accompanied by increasing amounts of Y-type phase as the iridium amount was increased. The measured microwave dielectric and magnetic properties showed that the loss tan δ{sub ε} and loss tan δ{sub μ} decreased by 80% and 90% at 0.8 GHz with the addition of iridium of x = 0.12 and 0.15, respectively. An effective medium approximation was adopted to analyzemore » the composite ferrites having mixed phase structures. Moreover, adding Bi{sub 2}O{sub 3} enabled equivalent values of real permittivity and real permeability over the studied frequency range. The resultant data give rise to low loss factors, i.e., tan δ{sub ε}/ε′ = 0.008 and tan δ{sub μ}/μ′ = 0.037 at 0.8 GHz, while characteristic impedance was the same as that of free space.« less

Laser weldability of 21Cr-6Ni-9Mn stainless steel: Part II - Weldability diagrams

DOE PAGES

Tate, Stephen B.; Javernick, Daniel Anthony; Lienert, Thomas J.; ...

2016-11-02

In this second part of the study, weldability diagrams developed to relate solidification crack susceptibility and chemical composition for laser welded type 21Cr-6Ni-9Mn (21-6-9) stainless steel are presented. Sigmajig testing on 14 commercial 21-6-9 alloys, 20 experimental 21-6-9 alloys, and 7 other high-N, high-Mn austenitic stainless steels was used to develop weldability diagrams for solidification crack susceptibility for laser welding of type 21-6-9. Three travel speeds were used to show the changes in minimum Cr eq/Ni eq for primary ferrite solidification as solidification rate increase d with travel speed . Primary austenite solidification was observed below 1.55 Cr eq/Ni eqmore » (Espy equivalents) at 21 mm/s travel speed. At 42 mm/s travel speed , a mix of solidification modes were displayed for alloys from 1.55-1.75 Cr eq/Ni eq. Primary ferrite solidification was observed above 1.75 Cr eq/Ni eq at both 42 and 85 mm/s travel speeds. No solidification cracking was observed for alloys with primary ferrite solidification. Lastly, variable cracking behavior was found in alloys with primary austenite solidification, but in general cracking was observed in alloys with greater than 0.02 wt-% combined impurity content according to (P+0.2S).« less

Magnetic properties of Ni substituted Y-type barium ferrite

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

Won, Mi Hee; Kim, Chul Sung, E-mail: cskim@kookmin.ac.kr

2014-05-07

Y-type barium hexaferrite is attractive material for various applications, such as high frequency antennas and RF devices, because of its interesting magnetic properties. Especially, Ni substituted Y- type hexaferrites have higher magnetic ordering temperature than other Y-type. We have investigated macroscopic and microscopic properties of Y-type barium hexaferrite. Ba{sub 2}Co{sub 2−x}Ni{sub x}Fe{sub 12}O{sub 22} (x = 0, 0.5, 1.0, 1.5, and 2.0) samples are prepared by solid-state reaction method and studied by X-ray diffraction (XRD), vibrating sample magnetometer, and Mössbauer spectroscopy, as well as a network analyzer for high frequency characteristics. The XRD pattern is analyzed by Rietveld refinement method and confirmsmore » the hexagonal structure with R-3m. The hysteresis curve shows ferrimagnetic behavior. Saturation magnetization (M{sub s}) decreases with Ni contents. Ni{sup 2+}, which preferentially occupies the octahedral site with up-spin sub-lattice, has smaller spin value S of 1 than Co{sup 2+} having S = 3/2. The zero-field-cooled (ZFC) measurement of Ba{sub 2}Co{sub 1.5}Ni{sub 0.5}Fe{sub 12}O{sub 22} shows that Curie and spin transition temperatures are found to be 718 K and 209 K, respectively. The Curie temperature T{sub C} is increased with Ni contents, while T{sub S} is decreased with Ni. The Mössbauer spectra were measured at various temperatures and fitted by using a least-squares method with six sextet of six Lorentzian lines for Fe sites, corresponding to the 3b{sub VI}, 6c{sub IV}*, 6c{sub VI}, 18h{sub VI}, 6c{sub IV}, and 3a{sub IV} sites at below T{sub C}. From Mössbauer measurements, we confirmed the spin state of Fe ion to be Fe{sup 3+} and obtained the isomer shift (δ), magnetic hyperfine field (H{sub hf}), and the occupancy ratio of Fe ions at six sub-lattices. The complex permeability and permittivity are measured between 100 MHz and 4 GHz, suggesting that Y-type barium hexaferrite is promising for antenna applications in UHF band.« less

Highly non-linear solid core photonic crystal fiber with one nano hole

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

Gangwar, Rahul Kumar, E-mail: rahul0889@gmail.com; Bhardwaj, Vanita, E-mail: bhardwajphy12@gmail.com; Singh, Vinod Kumar, E-mail: singh.vk.ap@ismdhanbad.co.in

2015-08-28

The numerical study of newly designed solid core photonic crystal fiber (SCPCF) having three hexagonal air hole rings in cladding region and one small nano hole at the center are presented. By using full vectorial finite element method (FV-FEM), we analyses the optical properties like effective area, nonlinearity and confinement loss of the proposed PCF. Results show that the change in core diameter controls the effective area, nonlinearity and confinement loss. A low effective area (3.34 µm{sup 2}), high nonlinearity (36.34 W{sup −1}km{sup −1}) and low confinement loss (0.00106 dB/km) are achieved at the communication wavelength 1.55 µm for themore » SCPCF having core air hole diameter 0.10 µm, cladding air holes diameter 1.00 µm and pitch 2.50 µm. This type of PCF is very useful in non-linear applications such as supercontinuum generation, four wave mixing, second harmonic generation etc.« less

Corrosion behavior of magnetic ferrite coating prepared by plasma spraying

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

Liu, Yi; Wei, Shicheng, E-mail: wsc33333@163.com; Tong, Hui

Graphical abstract: The saturation magnetization (M{sub s}) of the ferrite coating is 34.417 emu/g while the M{sub s} value of the ferrite powder is 71.916 emu/g. It can be seen that plasma spray process causes deterioration of the room temperature soft magnetic properties. - Highlights: • Spinel ferrite coatings have been prepared by plasma spraying. • The coating consists of nanocrystalline grains. • The saturation magnetization of the ferrite coating is 34.417 emu/g. • Corrosion behavior of the ferrite coating was examined in NaCl solution. - Abstract: In this study, spray dried spinel ferrite powders were deposited on the surfacemore » of mild steel substrate through plasma spraying. The structure and morphological studies on the ferrite coatings were carried out using X-ray diffraction, scanning electron microscope and Raman spectroscopy. It was showed that spray dried process was an effective method to prepare thermal spraying powders. The coating showed spinel structure with a second phase of LaFeO{sub 3}. The magnetic property of the ferrite samples were measured by vibrating sample magnetometer. The saturation magnetization (M{sub s}) of the ferrite coating was 34.417 emu/g. The corrosion behavior of coating samples was examined by electrochemical impedance spectroscopy. EIS diagrams showed three corrosion processes as the coating immersed in 3.5 wt.% NaCl solution. The results suggested that plasma spraying was a promising technology for the production of magnetic ferrite coatings.« less

Analysis of ferrite nanoparticles in the flow of ferromagnetic nanofluid.

PubMed

Muhammad, Noor; Nadeem, Sohail; Mustafa, M T

2018-01-01

Theoretical analysis has been carried out to establish the heat transport phenomenon of six different ferromagnetic MnZnFe2O4-C2H6O2 (manganese zinc ferrite-ethylene glycol), NiZnFe2O4-C2H6O2 (Nickel zinc ferrite-ethylene glycol), Fe2O4-C2H6O2 (magnetite ferrite-ethylene glycol), NiZnFe2O4-H2O (Nickel zinc ferrite-water), MnZnFe2O4-H2O (manganese zinc ferrite-water), and Fe2O4-H2O (magnetite ferrite-water) nanofluids containing manganese zinc ferrite, Nickel zinc ferrite, and magnetite ferrite nanoparticles dispersed in a base fluid of ethylene glycol and water mixture. The performance of convective heat transfer is elevated in boundary layer flow region via nanoparticles. Magnetic dipole in presence of ferrites nanoparticles plays a vital role in controlling the thermal and momentum boundary layers. In perspective of this, the impacts of magnetic dipole on the nano boundary layer, steady, and laminar flow of incompressible ferromagnetic nanofluids are analyzed in the present study. Flow is caused by linear stretching of the surface. Fourier's law of heat conduction is used in the evaluation of heat flux. Impacts of emerging parameters on the magneto-thermomechanical coupling are analyzed numerically. Further, it is evident that Newtonian heating has increasing behavior on the rate of heat transfer in the boundary layer. Comparison with available results for specific cases show an excellent agreement.

Development of a monolithic ferrite memory array

NASA Technical Reports Server (NTRS)

Heckler, C. H., Jr.; Bhiwandker, N. C.

1972-01-01

The results of the development and testing of ferrite monolithic memory arrays are presented. This development required the synthesis of ferrite materials having special magnetic and physical characteristics and the development of special processes; (1) for making flexible sheets (laminae) of the ferrite composition, (2) for embedding conductors in ferrite, and (3) bonding ferrite laminae together to form a monolithic structure. Major problems encountered in each of these areas and their solutions are discussed. Twenty-two full-size arrays were fabricated and fired during the development of these processes. The majority of these arrays were tested for their memory characteristics as well as for their physical characteristics and the results are presented. The arrays produced during this program meet the essential goals and demonstrate the feasibility of fabricating monolithic ferrite memory arrays by the processes developed.

Effects of alloying and processing modifications on precipitation and strength in 9%Cr ferritic/martensitic steels for fast reactor cladding

NASA Astrophysics Data System (ADS)

Tippey, Kristin E.

P92 was modified with respect to alloying and processing in the attempt to enhance high-temperature microstructural stability and mechanical properties. Alloying effects were modeled in ThermoCalcRTM and analyzed with reference to literature. ThermoCalcRTM modeling was conducted to design two low-carbon P92-like low-carbon alloys with austenite stabilized by alternative alloying; full conversion to austenite allows for a fully martensitic structure. Goals included avoidance of Z-phase, decrease of M23C6 phase fraction and maintained or increased MX phase fraction. Fine carbonitride precipitation was optimized by selecting alloying compositions such that all V and Nb could be solutionized at temperatures outside the delta-ferrite phase field. A low-carbon alloy (LC) and a low-carbon-zero-niobium alloy (0Nb) were identified and fabricated. This low-carbon approach stems from the increased creep resistance reported in several low-carbon alloys, presumably from reduced M23C6 precipitation and maintained MX precipitation [1], although these low-carbon alloys also contained additional tungsten (W) and cobalt (Co) compared to the base P92 alloy. The synergistic effect of Co and W on the microstructure and mechanical properties are difficult to deconvolute. Higher solutionizing temperatures allow more V and Nb into solution and increase prior austenite grain size; however, at sufficiently high temperatures delta-ferrite forms. Optimal solutionizing temperatures to maximize V and Nb in solution, while avoiding the onset of the delta ferrite phase field, were analyzed in ThermoCalcRTM. Optical microscopy showed ThermoCalc RTM predicted higher delta-ferrite onset temperatures of 20 °C in P92 alloys to nearly 50 °C in the designed alloys of the critical temperature. Identifying the balance where maximum fine precipitation is achieved and delta-ferrite avoided is a key factor in the design of an acceptable P92-like alloy for Generation IV reactor cladding. Processing was further modified utilizing thermomechanical processing (TMP) simulations with the GleebleRTM 3500. Hardness increased substantially in thermomechanically processed alloys, with increased hardness strongly correlating to decreased TMP temperature. The most significant difference between low- and high-temperature thermomechanically processed specimens was an increase in crystallite size at the higher temperature. The fundamental reason for higher strength in the TMP conditions is higher dislocation density, as precipitate volume fraction was not specifically improved in TMP conditions. Thermal stability of the base P92 and of the experimental alloys was analyzed by aging the alloys for times ranging from 500 to 10,000 h at 550, 600, 650, and 700 °C. Results suggest the hardness and thermal stability of LC is greater than that of 0Nb at lower aging temperatures and shorter times, with 0Nb surpassing LC microhardness at 10,000 h at 650 °C and for most conditions aged at 700 °C. Small- and wide-angle x-ray scattering (SAXS/WAXS) was conducted at Argonne National Laboratory (ANL). Atom probe tomography (APT) and scanning transmission electron microscopy high-angle annular dark field (STEM-HAADF) in conjunction with EDS were used to elucidate x-ray findings. These microstructural characteristics were then correlated with mechanical properties, including Vickers microhardness testing, elevated-temperature tensile testing, and creep rupture testing. The designed alloys exhibited less stable microstructures leading to less favorable mechanical potencies, as compared to the base P92 alloy. It is posited that factors other than inclination towards MX over M23C6 precipitation are important in generating thermal stability and high-temperature strength, i.e. perhaps the solid solution or diffusion controlling effects of Co in the low-carbon variation of Taneike's alloys [1] delay martensite recovery. The refined thermal profiles, however, put both P92 and LC creep strengths beyond those found in literature.

Ternary germanides RERhGe2 (RE = Y, Gd-Ho) - New representatives of the YIrGe2 type

NASA Astrophysics Data System (ADS)

Voßwinkel, Daniel; Heletta, Lukas; Hoffmann, Rolf-Dieter; Pöttgen, Rainer

2016-11-01

The YIrGe2 type ternary germanides RERhGe2 (RE = Y, Gd-Ho) were synthesized from the elements by arc-melting and characterized by powder X-ray diffraction. The structure of DyRhGe2 was refined from single crystal X-ray diffractometer data: Immm, a = 426.49(9), b = 885.0(2), c = 1577.4(3) pm, wR2 = 0.0533, 637 F2 values, 30 variables (300 K data). The structure contains two crystallographically independent dysprosium atoms in pentagonal prismatic and hexagonal prismatic coordination. The three-dimensional [RhGe2] polyanion is stabilized through covalent Rh-Ge (243-261 pm) and Ge-Ge (245-251 pm) bonding. The close structural relationship with the slightly rhodium-poorer germanides RE5Rh4Ge10 (≡ RERh0.8Ge2) is discussed. Temperature-dependent magnetic susceptibility measurements reveal Pauli paramagnetism for YRhGe2 and Curie-Weiss paramagnetism for RERhGe2 with RE = Gd, Tb, Dy and Ho. These germanides order antiferromagnetically at TN = 7.2(5), 10.6(5), 8.1(5), and 6.4(5) K, respectively.

Advanced Microwave Ferrite Research (AMFeR): Phase Three

DTIC Science & Technology

2008-07-31

lApril 1, 2006 thru June 30, 2008 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Advanced Microwave Ferrite Research (AMFeR): Phase Three 5b. GRANT NUMBER...Advance Microwave Ferrite Research (AMFeR), Phase III project. The purpose of this research endeavor is to devise ferrite materials for microwave, self...biased circulator applications. The central task of the project is to fabricate ferrites that have a high magnetic saturation, high coercivity and low

A battery-run pulsed motor with inherent dynamic electronic switch control

NASA Astrophysics Data System (ADS)

Tripathi, K. C.; Lal, P.; Sarma, P. R.; Sharma, A. K.; Prakash, V.

1980-02-01

A new type of battery-run brushless ferrite-magnet dc motor system is described. Its rotor part consists of a few permanent ceramic (ferrite) magnets uniformly spread on the rim of a disk (wheel) and the stator part consists of electromagnets placed in such a way that when energized, they always form a repulsive couple to rotate the disk. A sensor coil is placed to give an induced pulse signal, which acts as an inherent dynamic switching time control for the automatic electronic control system. Control of speed, brake system, and safety measures are also discussed. Experimental values for the present system are given. Some possible applications are suggested.

Delta ferrite is ubiquitous in type 304 stainless steel: Consequences for magnetic characterization

NASA Astrophysics Data System (ADS)

Graham, C. D.; Lorenz, B. E.

2018-07-01

Using a vibrating-sample magnetometer with a maximum field of 20.5 kOe, we have measured over 50 samples of annealed 304 stainless steel, which is usually considered to be non-magnetic. In almost every case, we observe the presence of a small, usually less than 0.01, fraction of a ferromagnetic phase, which we believe to be equilibrium bcc delta ferrite. The consequences of this observation for the measurement and specification of the magnetic properties of annealed 304 stainless are discussed. Our measurements also establish the most likely value for the magnetic permeability of the fcc austenitic phase in 304 stainless steel austenite as 1.0033 ± 0.0003.

Electrochemical and passive behaviour of tin alloyed ferritic stainless steel in concrete environment

NASA Astrophysics Data System (ADS)

Luo, Hong; Su, Huaizhi; Li, Baosong; Ying, Guobing

2018-05-01

In the present work, the electrochemical behavior and semiconducting properties of a tin alloyed ferritic stainless steel in simulated concrete solution in presence of NaCl were estimated by conventional electrochemical methods such as potentiodynamic polarization, electrochemical impedance spectroscopy, and capacitance measurement (Mott-Schottky approach). The surface passive film was analyzed by X-ray photoelectron spectroscopy. The results revealed a good agreement between pitting corrosion, electrochemical behaviour, and electronic properties. The p and n-type bilayer structure passive film were observed. The increase of Sn4+ oxide species in the passive film shows no beneficial effects on the pitting corrosion. In addition, the dehydration of the passive film was further discussed.

Estimation of the effective growth rate of a plate of bainitic ferrite in dynamic theory

NASA Astrophysics Data System (ADS)

Kashchenko, M. P.; Chashchina, V. G.

2013-03-01

The growth of a bainite plate is considered to be a relay-type process, in which fast (with τg ˜ 10-10 s) acts of the formation of sublaths (with a width 3 d ˜ 1 μm, where d is the thickness of the sublath) occur in an ultrasonic regime and the successive acts are separated by pauses of length τp ˜ 10-2 s. The value τp corresponds to the time of diffusion on a scale d with allowance for the pipe diffusion. The effective growth rate of the plate of bainite ferrite v eff is estimated by the relationship 3 d/τp.

RHIC ABORT KICKER WITH REDUCED COUPLING IMPEDANCE.

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

HAHN,H.; DAVINO,D.

2002-06-02

Kicker magnets typically represent the most important contributors to the transverse impedance budget of accelerators and storage rings. Methods of reducing the impedance value of the SNS extraction kicker presently under construction and, in view of a future performance upgrade, that of the RHIC abort kicker have been thoroughly studied at this laboratory. In this paper, the investigation of a potential improvement from using ferrite different from the BNL standard CMD5005 is reported. Permeability measurements of several ferrite types have been performed. Measurements on two kicker magnets using CMD5005 and C2050 suggest that the impedance of a magnet without externalmore » resistive damping, such as the RHIC abort kicker, would benefit.« less

Hexaferrite multiferroics: from bulk to thick films

NASA Astrophysics Data System (ADS)

Koutzarova, T.; Ghelev, Ch; Peneva, P.; Georgieva, B.; Kolev, S.; Vertruyen, B.; Closset, R.

2018-03-01

We report studies of the structural and microstructural properties of Sr3Co2Fe24O41 in bulk form and as thick films. The precursor powders for the bulk form were prepared following the sol-gel auto-combustion method. The prepared pellets were synthesized at 1200 °C to produce Sr3Co2Fe24O41. The XRD spectra of the bulks showed the characteristic peaks corresponding to the Z-type hexaferrite structure as a main phase and second phases of CoFe2O4 and Sr3Fe2O7-x. The microstructure analysis of the cross-section of the bulk pellets revealed a hexagonal sheet structure. Large areas were observed of packages of hexagonal sheets where the separate hexagonal particles were ordered along the c axis. Sr3Co2Fe24O41 thick films were deposited from a suspension containing the Sr3Co2Fe24O41 powder. The microstructural analysis of the thick films showed that the particles had the perfect hexagonal shape typical for hexaferrites.

Tunable magnetic and transport properties of Mn3Ga thin films on Ta/Ru seed layer

NASA Astrophysics Data System (ADS)

Hu, Fang; Xu, Guizhou; You, Yurong; Zhang, Zhi; Xu, Zhan; Gong, Yuanyuan; Liu, Er; Zhang, Hongguo; Liu, Enke; Wang, Wenhong; Xu, Feng

2018-03-01

Hexagonal D019-type Mn3Z alloys that possess large anomalous and topological-like Hall effects have attracted much attention due to their great potential in antiferromagnetic spintronic devices. Herein, we report the preparation of Mn3Ga films in both tetragonal and hexagonal phases with a tuned Ta/Ru seed layer on a thermally oxidized Si substrate. Large coercivity together with large anomalous Hall resistivity is found in the Ta-only sample with a mixed tetragonal phase. By increasing the thickness of the Ru layer, the tetragonal phase gradually disappears and a relatively pure hexagonal phase is obtained in the Ta(5)/Ru(30) buffered sample. Further magnetic and transport measurements revealed that the anomalous Hall conductivity nearly vanishes in the pure hexagonal sample, while an abnormal asymmetric hump structure emerges in the low field region. The extracted additional Hall term is robust in a large temperature range and presents a sign reversal above 200 K. The abnormal Hall properties are proposed to be closely related to the frustrated spin structure of D019 Mn3Ga.

Magnetic and absorbing properties of M-type substituted hexaferrites BaFe{sub 12–x}Ga{sub x}O{sub 19} (0.1 < x < 1.2)

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

Trukhanov, S. V., E-mail: trukhanov@ifttp.bas-net.by; Trukhanov, A. V.; Kostishin, V. G.

2016-09-15

X-ray powder diffraction is used to determine the unit cell parameters and to refine the crystal structure of the solid solutions of M-type hexagonal barium ferrite BaFe{sub 12–x}Ga{sub x}O{sub 19} (x = 0.1–1.2) with isostructural diamagnetic cation Ga{sup 3+} substitution at T = 300 K. As the level of substitution increases, the unit cell parameters are shown to decrease monotonically. The temperature (300 K ≤ T ≤ 750 K, H = 8.6 kOe) and field (T = 300 K,–20 kOe ≤ H ≤ 20 kOe) dependences of the saturation magnetization of these solid solutions are studied with a vibrating-sample magnetometer.more » The concentration dependences of the Curie temperature T{sub C}, the specific spontaneous magnetization, and the coercive force are plotted. The magnetic parameters are found to decrease with increasing substitution. The microwave properties of the solid solutions are analyzed in an external magnetic field (0 ≤ H ≤ 4 kOe). As the cation Ga{sup 3+} concentration increases from x = 0.1 to 0.6, the natural ferromagnetic resonance (NFMR) frequency decreases; as the concentration increases further to x = 1.2, this frequency again increases. As the cation Ga{sup 3+} concentration increases, the NFMR line width increases, which indicates a widening of the frequency range where electromagnetic radiation is intensely absorbed. Here, the resonance curve peak amplitude changes insignificantly. The shift of the NFMR frequency in an applied magnetic field is more pronounced for samples with low cation Ga{sup 3+} concentrations. The role of diamagnetic substitution is revealed, and the prospects and advantages of Ga-substituted beryllium hexaferrite as the material absorbing high-frequency electromagnetic radiation are demonstrated.« less

Sol gel method for synthesis of semiconducting ferrite and the study of FTIR, DTA, SEM and CV

NASA Astrophysics Data System (ADS)

Alva, Sagir; Hua, Tang Ing; Kalmar Nizar, Umar; Wahyudi, Haris; Sundari, Rita

2018-03-01

In this study, a sol gel method using citric acid as anionic surfactant is used for synthesis of magnesium ferrite. Calcinations of magnesium ferrite at temperature (300°C, 600°C and 800°C) have been conducted after sol gel process. Characterization study of the prepared magnesium ferrite related to calcinations using Fourier transform infrared spectrometry (FTIR), Differential thermogravic analysis (DTA), and Scanning electron microscope (SEM) has been discussed. The study of Cyclic voltammetry (CV) of the prepared magnesium ferrite has been examined to assay the semiconducting behavior of magnesium ferrite in relation to its electrochemical behavior.

TRANSMISSION ELECTRON MICROSCOPY STUDY OF HELIUM BEARING FUSION WELDS

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

Tosten, M; Michael Morgan, M

2008-12-12

A transmission electron microscopy (TEM) study was conducted to characterize the helium bubble distributions in tritium-charged-and-aged 304L and 21Cr-6Ni-9Mn stainless steel fusion welds containing approximately 150 appm helium-3. TEM foils were prepared from C-shaped fracture toughness test specimens containing {delta} ferrite levels ranging from 4 to 33 volume percent. The weld microstructures in the low ferrite welds consisted mostly of austenite and discontinuous, skeletal {delta} ferrite. In welds with higher levels of {delta} ferrite, the ferrite was more continuous and, in some areas of the 33 volume percent sample, was the matrix/majority phase. The helium bubble microstructures observed were similarmore » in all samples. Bubbles were found in the austenite but not in the {delta} ferrite. In the austenite, bubbles had nucleated homogeneously in the grain interiors and heterogeneously on dislocations. Bubbles were not found on any austenite/austenite grain boundaries or at the austenite/{delta} ferrite interphase interfaces. Bubbles were not observed in the {delta} ferrite because of the combined effects of the low solubility and rapid diffusion of tritium through the {delta} ferrite which limited the amount of helium present to form visible bubbles.« less

Humidity effects on adhesion of nickel-zinc ferrite in elastic contact with magnetic tape and itself

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.; Kusaka, T.; Maeda, C.

1985-01-01

The effects of humidity on the adhesion of Ni-Zn ferrite and magnetic tape in elastic contact with a Ni-Zn ferrite hemispherical pin in moist nitrogen were studied. Adhesion was independent of normal load in dry, humid, and saturated nitrogen. Ferrites adhere to ferrites in a saturated atmosphere primarily from the surface tension effects of a thin film of water adsorbed on the ferrite surfaces. The surface tension of the water film calculated from the adhesion results was 48 times 0.00001 to 56 times 0.00001 N/cm; the accepted value for water is 72.7 x 0.00001 N/cm. The adhesion of ferrite-ferrite contacts increased gradually with increases in relative humidity to 80 percent, but rose rapidly above 80 percent. The adhesion at saturation was 30 times or more greater than that below 80 percent relative humidity. Although the adhesion of magnetic tape - ferrite contacts remained low below 40 percent relative humidity and the effect of humidity was small, the adhesion increased considerably with increasing relative humidity above 40 percent. The changes in adhesion of elastic contacts were reversible on humidifying and dehumidifying.

High Frequency Magneto Dielectric Effects In Self Assembled Ferrite Ferroelectric Core Shell Nanoparticles

DTIC Science & Technology

2014-09-10

2008). 2 Y. Yang, S. Priya, J. Li , and D. Viehland, J. Am. Ceram. Soc. 92, 1552 (2009). 3 J. Ma, J. Hu, Z. Li , and C. W. Nan, Adv. Mater. 23, 1062...2013) 9 Yongke Yan, Yuan Zhou, and Shashank Priya, Appl. Phys. Lett. 104, 032911 (2014) 10 Gaojian Wu, Tianxiang Nan, Ru Zhang, Ning Zhang, Shandong Li ...Kim, L. T. Schelhas, S. Keller, J. L. Hockel, S. H. Tolbert, and G. P. Carman, Nano Lett. 13, 884 (2013). 13 S. Zhang, Y. G. Zhao, P. S. Li , J. J

Containerless Processing: Fabrication of Advanced Functional Materials from Undercooled Oxide Melt

NASA Astrophysics Data System (ADS)

Kumar, M. S. Vijaya; Ishikawa, Takehiko; Yoda, Shinichi; Kuribayashi, Kazuhiko

2012-07-01

Materials science in Microgravity condition is one of newly established cutting edge science field. After the effort of space development and space utilization, microgravity of space environment has been considered as one of novel tools for materials science because it assures containerless levitation. Containerless processing is a promising technique to explore the technologically important materials using rapid solidification of an undercooled melt. Recently, rare-earth ferrites and manganites have attracted great interest towards their wide applications in the field of electronic industry. Among these new hexagonal phases with a space group of P6 _{3}cm are technologically important materials because of multiferroic characteristics, i.e., the coexistence of ferroelectricity and magnetism in one compound. In the present study, containerless solidification of the R-Fe-O, and R-Mn-O melts were carried out to fabricate multiferroics under the controlled Po _{2}. Containerless processing is a promising technique to explore the new materials using rapid solidification of an undercooled melt because it provides large undercooling prior to nucleation. In order to undercool the melt deeply below the melting temperature under a precisely controlled oxygen partial pressure, an aerodynamic levitator (ADL) combined with ZrO _{2} oxygen sensor was designed. A spherical RFeO _{3} and RMnO _{3} sample was levitated by an ADL and completely melted by a CO _{2} laser in an atmosphere with predetermined Po _{2}.The surface temperature of the levitated droplet was monitored by a two-color pyrometer. Then, the droplet was cooled by turning off the CO _{2} laser. The XRD results of the rapidly solidified LuFeO _{3} and LuMnO _{3} samples at Po _{2} of 1x10 ^{5} Pa confirms the existence of the hexagonal metastable LuFeO _{3} phase. On the other hand, orthorhombic RFeO _{3} (R=Yb, Er, Y and Dy)and hexagonal RMnO _{3} (R=Ho-Lu)phases were identified. The cross-sectioned scanning electron microscopy (SEM) images and TG/DTA results revealed the existence of the stable and metastable phases with decreasing Po _{2}. The magnetic properties of the as-solidified samples were studied using vibrating sample magnetometer (VSM). These results indicate that a metastable and stable phase solidifies directly from the undercooled melt even when the melt is undercooled much below the peritectic temperature.

Structural Characterization of Atomically Thin Hexagonal Boron Nitride via Raman Spectroscopy

DTIC Science & Technology

2014-03-27

thickness and the use of depth profiling to maximize spectral returns. Chapter 3 also outlines the experimental set-up and procedures related to...section. 46 Figure 4.8: Unaltered spectral return of both Site 1 (A) and Site 2 ( B ). As to be expected the relative intensity of the Raman...Dent, Modern Raman Spectroscopy : A Practical Approach. Wiley, 2006, p. 224. 59 25. A. B . Kaul, E. W . Wong, L. Epp, and B . D. Hunt, “Two

Soft ferrite cores characterization for integrated micro-inductors

NASA Astrophysics Data System (ADS)

Nguyen, Yen Mai; Lopez, Thomas; Laur, Jean-Pierre; Bourrier, David; Charlot, Samuel; Valdez-Nava, Zarel; Bley, Vincent; Combettes, Céline; Brunet, Magali

2013-12-01

Ferrite-based micro-inductors are proposed for hybrid integration on silicon for low-power medium frequency DC-DC converters. Due to their small coercive field and their high resistivity, soft ferrites are good candidates for a magnetic core working at moderate frequencies in the range of 5-10 MHz. We have studied several soft ferrites including commercial ferrite film and U70 and U200 homemade ferrites. The inductors are fabricated at wafer level using micromachining and assembling techniques. The proposed process is based on a sintered ferrite core placed in between thick electroplated copper windings. The low profile ferrite cores of 1.2 × 2.6 × 0.2 mm3 are produced by two methods from green tape-casted films and ferrite powder. This paper presents the magnetic characterization of the sintered ferrite films cut and printed in rectangular shape and sintered at different temperatures. The comparison is made in order to find out the best material for the core that can reach the required inductance (470 nH at 6 MHz) under 0.6A current DC bias and that generate the smallest losses. An inductance density of 285 nH/ mm2 up to 6 MHz was obtained for ESL 40011 cores that is much higher than the previously reported devices. The small size of our devices is also a prominent point.

Preparation of high-permeability NiCuZn ferrite.

PubMed

Hu, Jun; Yan, Mi

2005-06-01

Appropriate addition of CuO/V2O5 and the reduction of the granularity of the raw materials particle decrease the sintering temperature of NiZn ferrite from 1200 degrees C to 930 degrees C. Furthermore, the magnetic properties of the NiZn ferrite prepared at low temperature of 930 degrees C is superior to that of the NiZn ferrite prepared by sintering at high temperature of 1200 degrees C because the microstructure of the NiZn ferrite sintered at 930 degrees C is more uniform and compact than that of the NiZn ferrite sintered at 1200 degrees C. The high permeability of 1700 and relative loss coefficient tandelta/mu(i) of 9.0x10(-6) at 100 kHz was achieved in the (Ni0.17Zn0.63Cu0.20)Fe1.915O4 ferrite.

Templated synthesis of nanoporous titania/nanocarbon composites

NASA Astrophysics Data System (ADS)

Mistry, Jayur

Hexagonally patterned (honeycomb structured) nano-porous titania finds distinct applications in the field of material science, electronics, and catalysis. The preparation of titania/nanocarbon composites was carried out using titanium iso-propoxide precursor and a viscous surfactant templated system arranged into nanoscopic channels of water and iso-octane. Nanocarbon was introduced into the titania pores, as it was dispersed into the water (used to increase the W0), while making templets. Prepared titania/nanocarbon composites were analyzed under scanning electron microscopy (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD) after a specific heat treatment. SEM and TEM allows us to see the morphology of the hexagonally patterned templates and XRD shows the change in the crystallinity of the titania after the heat treatment. Further tests are run with the Solartron™ CellTest potentiostat syste, which, allows us to study the electrical properties of the nanocomposites. The composites synthesized have wide applications in number of fields, including energy, sensors and electronics.

Effect of additional elements on compositional modulated atomic layered structure of hexagonal Co{sub 80}Pt{sub 20} alloy films with superlattice diffraction

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

Hinata, Shintaro; Research Fellowship Division Japan Society for the Promotion of Science; Yamane, Akira

2016-05-15

The effect of additional element on compositionally modulated atomic layered structure of hexagonal Co{sub 80}Pt{sub 20} alloy films with superlattice diffraction was investigated. In this study it is found that the addition of Cr or W element to Co{sub 80}Pt{sub 20} alloy film shows less deterioration of hcp stacking structure and compositionally modulated atomic layer stacking structure as compared to Si or Zr or Ti with K{sub u} of around 1.4 or 1.0 × 10{sup 7} erg/cm{sup 3} at 5 at.% addition. Furthermore, for O{sub 2} addition of O{sub 2} ≥ 5.0 × 10{sup −3} Pa to CoPt alloy, compositionallymore » modulated atomic layer stacking structure will be deteriorated with enhancement of formation of hcp stacking structure which leads higher K{sub u} of 1.0 × 10{sup 7} erg/cm{sup 3}.« less

The ARIANNA Hexagonal Radio Array - performance and prospects

NASA Astrophysics Data System (ADS)

Hallgren, Allan

2016-04-01

The origin of the highest energy cosmic rays at ˜1020 eV is still unknown. Ultra-high energy neutrinos from the GZK process should provide information on the sources and their properties. A promising and cost effective method for observing GZK-neutrinos is based on detection of Askaryan radio pulses with antennas installed in ice. The ARIANNA project aims at instrumenting a 36*36 km2 large area on the Ross Ice Shelf with an array of radio detection stations. The deployment of a test system for ARIANNA, the Hexagonal Radio Array (HRA), was completed in December 2014. The three first stations were installed in 2012. Solar panels are used to drive the < 10 W stations. The system hibernated at sunset in April and all stations returned to operation in September. The site is essentially free of anthropogenic noise. Simple cuts eliminate background and provides for efficient selection of neutrino events. Prospects for the sensitivity of the full ARIANNA array to the flux of GZK neutrinos are shown.

Phase Transformations of an Fe-0.85 C-17.9 Mn-7.1 Al Austenitic Steel After Quenching and Annealing

NASA Astrophysics Data System (ADS)

Cheng, Wei-Chun

2014-09-01

Low-density Mn-Al steels could potentially be substitutes for commercial Ni-Cr stainless steels. However, the development of the Mn-Al stainless steels requires knowledge of the phase transformations that occur during the steel making processes. Phase transformations of an Fe-0.85 C-17.9 Mn-7.1 Al (wt.%) austenitic steel, which include spinodal decomposition, precipitation transformations, and cellular transformations, have been studied after quenching and annealing. The results show that spinodal decomposition occurs prior to the precipitation transformation in the steel after quenching and annealing at temperatures below 1023 K and that coherent fine particles of L12-type carbide precipitate homogeneously in the austenite. The cellular transformation occurs during the transformation of high-temperature austenite into lamellae of austenite, ferrite, and kappa carbide at temperatures below 1048 K. During annealing at temperatures below 923 K, the austenite decomposes into lamellar austenite, ferrite, κ-carbide, and M23C6 carbide grains for another cellular transformation. Last, when annealing at temperatures below 873 K, lamellae of ferrite and κ-carbide appear in the austenite.

Synthesis and Characterization of Cobalt Substituted Zinc Ferrite Nanoparticles by Microwave Combustion Method.

PubMed

Sundararajan, M; Kennedy, L John; Vijaya, J Judith

2015-09-01

Pure and cobalt doped zinc ferrites were prepared by microwave combustion method using L-arginine as a fuel. The prepared samples were characterized by various instrumental techniques such as X-ray powder diffractometry, high resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray analysis, Fourier transformed infrared (FT-IR) spectroscopy, photoluminescence spectroscopy and UV-Visible diffuse reflectance spectroscopy. Vibrating sample magnetometry at room temperature was recorded to study the magnetic behavior of the samples. X-ray analysis confirmed the formation of zinc ferrites normal spinel-type structure with an average crystallite sizes in the range, 25.69 nm to 35.68 nm. The lattice parameters decreased as cobalt fraction was increased. The HR-SEM images showed nanoparticles are agglomerated. The estimated band gap energy value was found to decrease with an increase in cobalt content (1.87 to 1.62 eV). Broad visible emissions are observed in the photoluminescence spectra. A gradual increase in the coercivity and saturation magnetization (M(s)) were noted at relatively higher cobalt doping fractions.

Analysis of ferrite nanoparticles in the flow of ferromagnetic nanofluid

PubMed Central

Nadeem, Sohail; Mustafa, M. T.

2018-01-01

Theoretical analysis has been carried out to establish the heat transport phenomenon of six different ferromagnetic MnZnFe2O4—C2H6O2 (manganese zinc ferrite-ethylene glycol), NiZnFe2O4—C2H6O2 (Nickel zinc ferrite-ethylene glycol), Fe2O4—C2H6O2 (magnetite ferrite-ethylene glycol), NiZnFe2O4—H2O (Nickel zinc ferrite-water), MnZnFe2O4—H2O (manganese zinc ferrite-water), and Fe2O4—H2O (magnetite ferrite-water) nanofluids containing manganese zinc ferrite, Nickel zinc ferrite, and magnetite ferrite nanoparticles dispersed in a base fluid of ethylene glycol and water mixture. The performance of convective heat transfer is elevated in boundary layer flow region via nanoparticles. Magnetic dipole in presence of ferrites nanoparticles plays a vital role in controlling the thermal and momentum boundary layers. In perspective of this, the impacts of magnetic dipole on the nano boundary layer, steady, and laminar flow of incompressible ferromagnetic nanofluids are analyzed in the present study. Flow is caused by linear stretching of the surface. Fourier’s law of heat conduction is used in the evaluation of heat flux. Impacts of emerging parameters on the magneto—thermomechanical coupling are analyzed numerically. Further, it is evident that Newtonian heating has increasing behavior on the rate of heat transfer in the boundary layer. Comparison with available results for specific cases show an excellent agreement. PMID:29320488

Effect of Different Structural Materials on Neutronic Performance of a Hybrid Reactor

NASA Astrophysics Data System (ADS)

Übeyli, Mustafa; Tel, Eyyüp

2003-06-01

Selection of structural material for a fusion-fission (hybrid) reactor is very important by taking into account of neutronic performance of the blanket. Refractory metals and alloys have much higher operating temperatures and neutron wall load (NWL) capabilities than low activation materials (ferritic/martensitic steels, vanadium alloys and SiC/SiC composites) and austenitic stainless steels. In this study, effect of primary candidate refractory alloys, namely, W-5Re, T111, TZM and Nb-1Zr on neutronic performance of the hybrid reactor was investigated. Neutron transport calculations were conducted with the help of SCALE 4.3 System by solving the Boltzmann transport equation with code XSDRNPM. Among the investigated structural materials, tantalum had the worst performance due to the fact that it has higher neutron absorption cross section than others. And W-5Re and TZM having similar results showed the best performance.

Comparative study of torque resistance and microgaps between a combined Octatorx-cone connection and an internal hexagon implant-abutment connection.

PubMed

Khongkhunthian, Pathawee; Khongkhunthian, Sakornratana; Weerawatprachya, Winai; Pongpat, Kanuengnit; Aunmeungtong, Weerapan

2015-05-01

Although the implant-abutment connection may prevent crestal bone loss around dental implants, its failure often leads to treatment failure. Microgap and micromovement of the implant-abutment connection could be causes of bone resorption around dental implant neck. The purpose of this study was to compare torque resistance and microgaps between a new cone and index connection (Octatorx) and an internal hexagon implant-abutment connection (Internal hex). Twenty Octatorx and 20 internal hexagon connections were attached with retaining screws at 30 Ncm. In a torsion resistance test, 10 of each type of connection were attached to a universal testing machine. Torque resistance with 90 degrees per minute rotation speed was recorded. For microgap measurement, each of 10 connections was embedded in clear acrylic resin. The blocks were cut longitudinally. Twenty specimens of each connection were evaluated. Twelve measurements of microgaps (6 on each side of specimen) were recorded under scanning electron microscopy. The average torsion resistance of Octatorx (203.6 ±17.4 Ncm) was significantly greater than that of the internal hexagon (146.4 ±16.1 Ncm, P<.05). For the microgap, there was a significant difference (P=.001) between the median values of Octatorx (1.19 μm) and the internal hexagon (3.80 μm). In this study, the new connection, Octatorx, had a smaller microgap and greater torque resistance than the internal hexagon connection. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Zonal wavefront estimation using an array of hexagonal grating patterns

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

Pathak, Biswajit, E-mail: b.pathak@iitg.ernet.in, E-mail: brboruah@iitg.ernet.in; Boruah, Bosanta R., E-mail: b.pathak@iitg.ernet.in, E-mail: brboruah@iitg.ernet.in

2014-10-15

Accuracy of Shack-Hartmann type wavefront sensors depends on the shape and layout of the lenslet array that samples the incoming wavefront. It has been shown that an array of gratings followed by a focusing lens provide a substitution for the lensslet array. Taking advantage of the computer generated holography technique, any arbitrary diffraction grating aperture shape, size or pattern can be designed with little penalty for complexity. In the present work, such a holographic technique is implemented to design regular hexagonal grating array to have zero dead space between grating patterns, eliminating the possibility of leakage of wavefront during themore » estimation of the wavefront. Tessellation of regular hexagonal shape, unlike other commonly used shapes, also reduces the estimation error by incorporating more number of neighboring slope values at an equal separation.« less

Oriented graphene nanoribbons embedded in hexagonal boron nitride trenches

PubMed Central

Chen, Lingxiu; He, Li; Wang, Hui Shan; Wang, Haomin; Tang, Shujie; Cong, Chunxiao; Xie, Hong; Li, Lei; Xia, Hui; Li, Tianxin; Wu, Tianru; Zhang, Daoli; Deng, Lianwen; Yu, Ting; Xie, Xiaoming; Jiang, Mianheng

2017-01-01

Graphene nanoribbons (GNRs) are ultra-narrow strips of graphene that have the potential to be used in high-performance graphene-based semiconductor electronics. However, controlled growth of GNRs on dielectric substrates remains a challenge. Here, we report the successful growth of GNRs directly on hexagonal boron nitride substrates with smooth edges and controllable widths using chemical vapour deposition. The approach is based on a type of template growth that allows for the in-plane epitaxy of mono-layered GNRs in nano-trenches on hexagonal boron nitride with edges following a zigzag direction. The embedded GNR channels show excellent electronic properties, even at room temperature. Such in-plane hetero-integration of GNRs, which is compatible with integrated circuit processing, creates a gapped channel with a width of a few benzene rings, enabling the development of digital integrated circuitry based on GNRs. PMID:28276532

Role of polytypism and degree of hexagonality on the photoinduced optical second harmonic generation in SiC nanocrystalline films

NASA Astrophysics Data System (ADS)

Semenov, A.; Puziko, V.; Skorik, S.; Wojciechowski, A.; Fedorchuk, A. O.; Maciąg, A.

2015-05-01

Photoinduced optiсal second harmonic generation was studied in nanocrystalline SiC films prepared by the method of direct ion deposition. For the studies were chosen three types of polytypes (with different degree of hexagonality) - 24R with degree hexagonality G=25, 27R-G=44, 33R with - G=36. The bicolor photoinduced treatment was performed by the wavelengths 1064nm/532 nm by 15 ns YAG:Nd laser. The efficiency of the output SHG was evaluated by ratio of the corresponding signal intensities with respect to the references and by the time delay between the SHG and the fundamental maxima. Explanation of the observed effect is given within a framework of the occurrence of the nano-trapping levels in the film crystalline interfaces.

Fiber laser welding of dual-phase galvanized sheet steel (DP590): traditional analysis and new quality assessment techniques

NASA Astrophysics Data System (ADS)

Miller, Stephanie; Pfeif, Erik; Kazakov, Andrei; Baumann, Esther; Dowell, Marla

2016-03-01

Laser welding has many advantages over traditional joining methods, yet remains underutilized. NIST has undertaken an ambitious initiative to improve predictions of weldability, reliability, and performance of laser welds. This study investigates butt welding of galvanized and ungalvanized dual-phase automotive sheet steels (DP 590) using a 10 kW commercial fiber laser system. Parameter development work, hardness profiles, microstructural characterization, and optical profilometry results are presented. Sound welding was accomplished in a laser power range of 2.0 kW to 4.5 kW and travel speed of 2000 mm/min to 5000 mm/min. Vickers hardness ranged from approximately 2 GPa to 4 GPa across the welds, with limited evidence of heat affected zone softening. Decreased hardness across the heat affected zone directly correlated to the appearance of ferrite. A technique was developed to non-destructively evaluate weld quality based on geometrical criteria. Weld face profilometry data were compared between light optical, metallographic sample, and frequency-modulated continuous-wave laser detection and ranging (FMCW LADAR) methods.

Effect of Low-Temperature Sensitization on the Corrosion Behavior of AISI Type 304L SS Weld Metal in Simulated Groundwater

NASA Astrophysics Data System (ADS)

Suresh, Girija; Nandakumar, T.; Viswanath, A.

2018-04-01

The manuscript presents the investigations carried out on the effect of low-temperature sensitization (LTS) of 304L SS weld metal on its corrosion behavior in simulated groundwater, for its application as a canister material for long-term storage of nuclear vitrified high-level waste in geological repositories. AISI type 304L SS weld pad was fabricated by multipass gas tungsten arc welding process using 308L SS filler wire. The as-welded specimens were subsequently subjected to carbide nucleation and further to LTS at 500 °C for 11 days to simulate a temperature of 300 °C for 100-year life of the canister in geological repositories. Delta ferrite (δ-ferrite) content of the 304L SS weld metal substantially decreased on carbide nucleation treatment and further only a marginal decrease occurred on LTS treatment. The microstructure of the as-welded consisted of δ-ferrite as a minor phase distributed in austenite matrix. The δ-ferrite appeared fragmented in the carbide-nucleated and LTS-treated weld metal. The degree of sensitization measured by double-loop electrochemical potentokinetic reactivation method indicated an increase in carbide nucleation treatment when compared to the as-welded specimens, and further increase occurred on LTS treatment. Potentiodynamic anodic polarization investigations in simulated groundwater indicated a substantial decrease in the localized corrosion resistance of the carbide-nucleated and LTS 304L SS weld metals, when compared to the as-welded specimens. Post-experimental micrographs indicated pitting as the primary mode of attack in the as-welded, while pitting and intergranular corrosion (IGC) occurred in the carbide-nucleated weld metal. LTS-treated weld metal predominantly underwent IGC attack. The decrease in the localized corrosion resistance of the weld metal after LTS treatment was found to have a direct correlation with the degree of sensitization and the weld microstructure. The results are detailed in the manuscript.

Correlation of Microstructure and Texture in a Two-Phase High-Mn Twinning-Induced Plasticity Steel During Cold Rolling

NASA Astrophysics Data System (ADS)

Ashiq, Mohammad; Dhekne, Pushkar; Hamada, Atef Saad; Sahu, Puspendu; Mahato, B.; Minz, R. K.; Ghosh Chowdhury, Sandip; Pentti Karjalainen, L.

2017-10-01

The evolution of microstructure and texture of a two-phase austenite-ferrite twinning-induced plasticity steel during cold rolling was investigated and different deformation mechanisms were found to become active with increasing thickness reductions. Optical microscopy showed the formation of brass-type shear bands across several austenite grains at reductions greater than 50 pct. TEM observations reveal the presence of deformation twinning in austenite. The austenite phase initially shows the Cu-type texture, i.e., Cu {1 1 2}〈1 1 1〉, Goss {0 1 1}〈1 0 0〉 with a spread toward Brass {1 1 0}〈1 1 2〉. With continued cold rolling, the Cu {1 1 2}〈1 1 1〉 component moves toward CuT component {552}〈115〉 and the other two components increase in intensity. There is also emergence of {111} fiber after 90 pct cold rolling. The ferrite phase exhibits the evolution of ND-rotated Cube component {001}〈110〉 along with 〈110〉 fiber at lower as well as at higher rolling reductions. An exception is at 75 pct reduction, when the ferrite texture contains {111} fiber in place of 〈110〉 fiber with a weak rotated-Cube component. Phase fraction analysis by X-ray diffraction indicates a decrease in the austenite fraction up to 75 pct reduction followed by an increase at 90 pct reduction. After 90 pct cold rolling, the phase fraction is similar to that of the "as-received" state. Elongated grains of ferrite phase in finer dimensions after 90 pct cold rolling indicate softening within that phase; at similar stage, there are finer scale austenite grains mostly at the grain boundaries. The above has been suggested to be related with the adiabatic heating during cold rolling due to the high strain hardening of the austenite phase.

Effect of Low-Temperature Sensitization on the Corrosion Behavior of AISI Type 304L SS Weld Metal in Simulated Groundwater

NASA Astrophysics Data System (ADS)

Suresh, Girija; Nandakumar, T.; Viswanath, A.

2018-05-01

The manuscript presents the investigations carried out on the effect of low-temperature sensitization (LTS) of 304L SS weld metal on its corrosion behavior in simulated groundwater, for its application as a canister material for long-term storage of nuclear vitrified high-level waste in geological repositories. AISI type 304L SS weld pad was fabricated by multipass gas tungsten arc welding process using 308L SS filler wire. The as-welded specimens were subsequently subjected to carbide nucleation and further to LTS at 500 °C for 11 days to simulate a temperature of 300 °C for 100-year life of the canister in geological repositories. Delta ferrite ( δ-ferrite) content of the 304L SS weld metal substantially decreased on carbide nucleation treatment and further only a marginal decrease occurred on LTS treatment. The microstructure of the as-welded consisted of δ-ferrite as a minor phase distributed in austenite matrix. The δ-ferrite appeared fragmented in the carbide-nucleated and LTS-treated weld metal. The degree of sensitization measured by double-loop electrochemical potentokinetic reactivation method indicated an increase in carbide nucleation treatment when compared to the as-welded specimens, and further increase occurred on LTS treatment. Potentiodynamic anodic polarization investigations in simulated groundwater indicated a substantial decrease in the localized corrosion resistance of the carbide-nucleated and LTS 304L SS weld metals, when compared to the as-welded specimens. Post-experimental micrographs indicated pitting as the primary mode of attack in the as-welded, while pitting and intergranular corrosion (IGC) occurred in the carbide-nucleated weld metal. LTS-treated weld metal predominantly underwent IGC attack. The decrease in the localized corrosion resistance of the weld metal after LTS treatment was found to have a direct correlation with the degree of sensitization and the weld microstructure. The results are detailed in the manuscript.

Hot-rolling of reduced activation 8CrODS ferritic steel

NASA Astrophysics Data System (ADS)

Wu, Xiaochao; Ukai, Shigeharu; Leng, Bin; Oono, Naoko; Hayashi, Shigenari; Sakasegawa, Hideo; Tanigawa, Hiroyasu

2013-11-01

The 8CrODS ferritic steel is based on J1-lot developed for the advanced fusion blanket material to increase the coolant outlet temperature. A hot-rolling was conducted at the temperature above Ar3 of 716 °C, and its effect on the microstructure and tensile strength in 8CrODS ferritic steel was evaluated, comparing together with normalized and tempered specimen. It was confirmed that hot-rolling leads to slightly increased fraction of the ferrite and highly improved tensile strength. This ferrite was formed by transformation from the hot-rolled austenite during cooling due to fine austenite grains induced by hot-rolling. The coarsening of the transformed ferrite in hot-rolled specimen can be attributed to the crystalline rotation and coalescence of the similar oriented grains. The improved strength of hot-rolled specimen was ascribed to the high dislocation density and replacement of easily deformed martensite with the transformed coarse ferrite.

Preparation of high-permeability NiCuZn ferrite*

PubMed Central

Hu, Jun; Yan, Mi

2005-01-01

Appropriate addition of CuO/V2O5 and the reduction of the granularity of the raw materials particle decrease the sintering temperature of NiZn ferrite from 1200 °C to 930 °C. Furthermore, the magnetic properties of the NiZn ferrite prepared at low temperature of 930 °C is superior to that of the NiZn ferrite prepared by sintering at high temperature of 1200 °C because the microstructure of the NiZn ferrite sintered at 930 °C is more uniform and compact than that of the NiZn ferrite sintered at 1200 °C. The high permeability of 1700 and relative loss coefficient tanδ/μi of 9.0×10−6 at 100 kHz was achieved in the (Ni0.17Zn0.63Cu0.20)Fe1.915O4 ferrite. PMID:15909348

Effect of microstructural evolution by isothermal aging on the mechanical properties of 9Cr-1WVTa reduced activation ferritic/martensitic steels

NASA Astrophysics Data System (ADS)

Park, Min-Gu; Lee, Chang-Hoon; Moon, Joonoh; Park, Jun Young; Lee, Tae-Ho; Kang, Namhyun; Chan Kim, Hyoung

2017-03-01

The influence of microstructural changes caused by aging condition on tensile and Charpy impact properties was investigated for reduced activation ferritic-martensitic (RAFM) 9Cr-1WVTa steels having single martensite and a mixed microstructure of martensite and ferrite. For the mixed microstructure of martensite and ferrite, the Charpy impact properties deteriorated in both as-normalized and tempered conditions due to the ferrite and the accompanying M23C6 carbides at the ferrite grain boundaries which act as path and initiation sites for cleavage cracks, respectively. However, aging at 550 °C for 20-100 h recovered gradually the Charpy impact toughness without any distinct drop in strength, as a result of the spheroidization of the coarse M23C6 carbides at the ferrite grain boundaries, which makes crack initiation more difficult.

X-ray photoelectron spectroscopy and friction studies of nickel-zinc and manganese-zinc ferrites in contact with metals

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1983-01-01

X-ray photoelectron spectroscopy analysis and sliding friction experiments were conducted with hot-pressed, polycrystalline Ni-Zn and Mn-Zn ferrites in sliding contact with various transition metals at room temperature in a vacuum of 30 nPa. The results indicate that the coefficients of friction for Ni-Zn and Mn-Zn ferrites in contact with metals are related to the relative chemical activity in these metals: the more active the metal, the higher is the coefficient of friction. The coefficients of friction for the ferrites correlate with the free energy of formation of the lowest metal oxide. The interfacial bond can be regarded as a chemical bond between the metal atoms and the oxygen anions in the ferrite surfaces. The adsorption of oxygen on clean metal and ferrite surfaces increases the coefficients of friction for the Ni-Zn and Mn-Zn ferrite-metal interfaces.

40 CFR 721.10223 - Styrenyl surface treated manganese ferrite with acrylic ester polymer (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... ferrite with acrylic ester polymer (generic). 721.10223 Section 721.10223 Protection of Environment... manganese ferrite with acrylic ester polymer (generic). (a) Chemical substance and significant new uses... manganese ferrite with acrylic ester polymer (PMN P-09-582) is subject to reporting under this section for...

40 CFR 721.10223 - Styrenyl surface treated manganese ferrite with acrylic ester polymer (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... ferrite with acrylic ester polymer (generic). 721.10223 Section 721.10223 Protection of Environment... manganese ferrite with acrylic ester polymer (generic). (a) Chemical substance and significant new uses... manganese ferrite with acrylic ester polymer (PMN P-09-582) is subject to reporting under this section for...

40 CFR 721.10223 - Styrenyl surface treated manganese ferrite with acrylic ester polymer (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... ferrite with acrylic ester polymer (generic). 721.10223 Section 721.10223 Protection of Environment... manganese ferrite with acrylic ester polymer (generic). (a) Chemical substance and significant new uses... manganese ferrite with acrylic ester polymer (PMN P-09-582) is subject to reporting under this section for...

40 CFR 721.10223 - Styrenyl surface treated manganese ferrite with acrylic ester polymer (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... ferrite with acrylic ester polymer (generic). 721.10223 Section 721.10223 Protection of Environment... manganese ferrite with acrylic ester polymer (generic). (a) Chemical substance and significant new uses... manganese ferrite with acrylic ester polymer (PMN P-09-582) is subject to reporting under this section for...

Effect of abrasive grit size on wear of manganese-zinc ferrite under three-body abrasion

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa

1987-01-01

Wear experiments were conducted using replication electron microscopy and reflection electron diffraction to study abrasion and deformed layers produced in single-crystal Mn-Zn ferrites under three-body abrasion. The abrasion mechanism of Mn-Zn ferrite changes drastically with the size of abrasive grits. With 15-micron (1000-mesh) SiC grits, abrasion of Mn-Zn ferrite is due principally to brittle fracture; while with 4- and 2-micron (4000- and 6000-mesh) SiC grits, abrasion is due to plastic deformation and fracture. Both microcracking and plastic flow produce polycrystalline states on the wear surfaces of single-crystal Mn-Zn ferrites. Coefficient of wear, total thickness of the deformed layers, and surface roughness of the wear surfaces increase markedly with an increase in abrasive grit size. The total thicknesses of the deformed layers are 3 microns for the ferrite abraded by 15-micron SiC, 0.9 microns for the ferrite abraded by 4-micron SiC, and 0.8 microns for the ferrite abraded by 1-micron SiC.

Microstructural Evolution During Cold Rolling and Subsequent Annealing in Low-Carbon Steel with Different Initial Microstructures

NASA Astrophysics Data System (ADS)

Ogawa, Toshio; Dannoshita, Hiroyuki; Maruoka, Kuniaki; Ushioda, Kohsaku

2017-08-01

Microstructural evolution during cold rolling and subsequent annealing of low-carbon steel with different initial microstructures was investigated from the perspective of the competitive phenomenon between recrystallization of ferrite and reverse phase transformation from ferrite to austenite. Three kinds of hot-rolled sheet specimens were prepared. Specimen P consisted of ferrite and pearlite, specimen B consisted of bainite, and specimen M consisted of martensite. The progress of recovery and recrystallization of ferrite during annealing was more rapid in specimen M than that in specimens P and B. In particular, the recrystallized ferrite grains in specimen M were fine and equiaxed. The progress of ferrite-to-austenite phase transformation during intercritical annealing was more rapid in specimen M than in specimens P and B. In all specimens, the austenite nucleation sites were mainly at high-angle grain boundaries, such as those between recrystallized ferrite grains. The austenite distribution was the most uniform in specimen M. Thus, we concluded that fine equiaxed recrystallized ferrite grains were formed in specimen M, leading to a uniform distribution of austenite.

Tensile deformation and fracture properties of a 14YWT nanostructured ferritic alloy

DOE PAGES

Alam, M. Ershadul; Pal, Soupitak; Fields, Kirk; ...

2016-08-13

Here, a new larger heat of a 14YWT nanostructured ferritic alloy (NFA), FCRD NFA-1, was synthesized by ball milling FeO and argon atomized Fe-14Cr-3W-0.4Ti-0.2Y (wt%) powders, followed by hot extrusion, annealing and cross rolling to produce an ≈10 mm-thick plate. NFA-1 contains a bimodal size distribution of pancake-shaped, mostly very fine scale, grains. The as-processed plate also contains a large population of microcracks running parallel to its broad surfaces. The small grains and large concentration of Y–Ti–O nano-oxides (NOs) result in high strength up to 800 °C. The uniform and total elongations range from ≈1–8%, and ≈10–24%, respectively. The strengthmore » decreases more rapidly above ≈400 °C and deformation transitions to largely viscoplastic creep by ≈600 °C. While the local fracture mechanism is generally ductile-dimple microvoid nucleation, growth and coalescence, perhaps the most notable feature of tensile deformation behavior of NFA-1 is the occurrence of periodic delamination, manifested as fissures on the fracture surfaces.« less

Development of Creep-Resistant, Alumina-Forming Ferrous Alloys for High-Temperature Structural Use

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

Yamamoto, Yukinori; Brady, Michael P.; Muralidharan, Govindarajan

This paper overviews recent advances in developing novel alloy design concepts of creep-resistant, alumina-forming Fe-base alloys, including both ferritic and austenitic steels, for high-temperature structural applications in fossil-fired power generation systems. Protective, external alumina-scales offer improved oxidation resistance compared to chromia-scales in steam-containing environments at elevated temperatures. Alloy design utilizes computational thermodynamic tools with compositional guidelines based on experimental results accumulated in the last decade, along with design and control of the second-phase precipitates to maximize high-temperature strengths. The alloys developed to date, including ferritic (Fe-Cr-Al-Nb-W base) and austenitic (Fe-Cr-Ni-Al-Nb base) alloys, successfully incorporated the balanced properties of steam/water vapor-oxidationmore » and/or ash-corrosion resistance and improved creep strength. Development of cast alumina-forming austenitic (AFA) stainless steel alloys is also in progress with successful improvement of higher temperature capability targeting up to ~1100°C. Current alloy design approach and developmental efforts with guidance of computational tools were found to be beneficial for further development of the new heat resistant steel alloys for various extreme environments.« less

Effect of neutron irradiation at low temperature on the embrittlement of the reduced-activation ferritic steels

NASA Astrophysics Data System (ADS)

Rybin, V. V.; Kursevich, I. P.; Lapin, A. N.

1998-10-01

Effects of neutron irradiation to fluence of 2.0 × 10 24 n/m 2 ( E > 0.5 MeV) in temperature range 70-300°C on mechanical properties and structure of the experimental reduced-activation ferritic 0.1%C-(2.5-12)%Cr-(1-2)%W-(0.2-0.7)%V alloys were investigated. The steels were studied in different initial structural conditions obtained by changing the modes of heat treatments. Effect of neutron irradiation estimated by a shift in ductile-brittle transition temperature (ΔDBTT) and reduction of upper shelf energy (ΔUSE) highly depends on both irradiation condition and steel chemical composition and structure. For the steel with optimum chemical composition (9Cr-1.5WV) after irradiation to 2 × 10 24 n/m 2 ( E ⩾ 0.5 MeV) at 280°C the ΔDBTT does not exceed 25°C. The shift in DBTT increased from 35°C to 110°C for the 8Cr-1.5WV steel at a decrease in irradiation temperature from 300°C to 70°C. The CCT diagrams are presented for several reduced-activated steels.

Transmutation and activation of reduced activation ferritic martensitic steel in molten salt cooled fusion power plants

NASA Astrophysics Data System (ADS)

Cheng, E. T.

2004-08-01

Neutron activation analysis was conducted for the reduced activation ferritic/martensitic (RAFM) steel used in flibe molten-salt cooled fusion blankets. After 22.4 MW yr/m 2 of neutron exposure, the RAFM steel first wall in a molten salt blanket with 40% lithium-6 enrichment in lithium was found to be within 1 mSv/h in contact dose rate after 100 yr of cooling. The contact dose rate drops to 30 and 20 μSv/h or less, respectively, when the cooling times are 300 and 500 yr after discharge. The RAFM steel discharged from the high-temperature shield component would be allowed for hands-on recycling after 100 yr of cooling, when the contact dose rate is 10 μSv/h or less. The most significant changes found in the RAFM steel first wall due to nuclear transmutation, are 10% decrease in W and 10% increase in Ti. Additionally, there are minor elements produced: Mn - <1.2%, V - <0.26%, Re - <0.2%, Ta - <0.08%, and Os - <0.1%, all in weight percent. The gaseous elements generated are H and He, and the, respectively, accumulated quantities are about 260 and 190 wppm.

Nonstoichiometric Zn Ferrite and ZnFe2O4/Fe2O3 Composite Spheres: Preparation, Magnetic Properties, and Chromium Removal

NASA Astrophysics Data System (ADS)

Hang, Chun-Liang; Yang, Li-Xia; Sun, Chang-Mei; Liang, Ying

2018-03-01

Monodisperse and porous nonstoichiometric Zn ferrite can be prepared by a solvothermal method. Such non-Zn ferrite was used to be the precursor for synthesis of ZnFe2O4/Fe2O3 composite via calcination at 600°C for 3 h in air. X-ray powder diffractometer (XRD) and Energy Dispersive Spectrometer (EDS) proved the nonstoichiometry of Zn ferrite synthesized by solvothermal method and the formation of ZnFe2O4/Fe2O3 composite via calcination. TEM image showed that non-Zn ferrite spheres with wormlike nanopore structure were made of primary nanocrystals. BET surface area of non-Zn ferrite was much higher than that of ZnFe2O4/Fe2O3 composite. Saturation magnetization of non-Zn ferrites was significantly higher than that of ZnFe2O4/Fe2O3 composites. Calcination of non-Zn ferrite resulted in the formation of large amount of non-magnetic Fe2O3,which caused a low magnetization of composite. Because of higher BET surface area and higher saturation magnetization, non-Zn ferrite presented better Cr6+ adsorption property than ZnFe2O4/Fe2O3 composites.

Corrosion behavior in high heat input welded heat-affected zone of Ni-free high-nitrogen Fe–18Cr–10Mn–N austenitic stainless steel

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

Moon, Joonoh, E-mail: mjo99@kims.re.kr; Ha, Heon-Young; Lee, Tae-Ho

2013-08-15

The pitting corrosion and interphase corrosion behaviors in high heat input welded heat-affected zone (HAZ) of a metastable high-nitrogen Fe–18Cr–10Mn–N austenitic stainless steel were explored through electrochemical tests. The HAZs were simulated using Gleeble simulator with high heat input welding condition of 300 kJ/cm and the peak temperature of the HAZs was changed from 1200 °C to 1350 °C, aiming to examine the effect of δ-ferrite formation on corrosion behavior. The electrochemical test results show that both pitting corrosion resistance and interphase corrosion resistance were seriously deteriorated by δ-ferrite formation in the HAZ and their aspects were different with increasingmore » δ-ferrite fraction. The pitting corrosion resistance was decreased by the formation of Cr-depleted zone along δ-ferrite/austenite (γ) interphase resulting from δ-ferrite formation; however it didn't depend on δ-ferrite fraction. The interphase corrosion resistance depends on the total amount of Cr-depleted zone as well as ferrite area and thus continuously decreased with increasing δ-ferrite fraction. The different effects of δ-ferrite fraction on pitting corrosion and interphase corrosion were carefully discussed in terms of alloying elements partitioning in the HAZ based on thermodynamic consideration. - Highlights: • Corrosion behavior in the weld HAZ of high-nitrogen austenitic alloy was studied. • Cr{sub 2}N particle was not precipitated in high heat input welded HAZ of tested alloy. • Pitting corrosion and interphase corrosion show a different behavior. • Pitting corrosion resistance was affected by whether or not δ-ferrite forms. • Interphase corrosion resistance was affected by the total amount of δ-ferrite.« less

Oxidative stress mediated apoptosis induced by nickel ferrite nanoparticles in cultured A549 cells.

PubMed

Ahamed, Maqusood; Akhtar, Mohd Javed; Siddiqui, Maqsood A; Ahmad, Javed; Musarrat, Javed; Al-Khedhairy, Abdulaziz A; AlSalhi, Mohamad S; Alrokayan, Salman A

2011-05-10

Due to the interesting magnetic and electrical properties with good chemical and thermal stabilities, nickel ferrite nanoparticles are being utilized in many applications including magnetic resonance imaging, drug delivery and hyperthermia. Recent studies have shown that nickel ferrite nanoparticles produce cytotoxicity in mammalian cells. However, there is very limited information concerning the toxicity of nickel ferrite nanoparticles at the cellular and molecular level. The aim of this study was to investigate the cytotoxicity, oxidative stress and apoptosis induction by well-characterized nickel ferrite nanoparticles (size 26 nm) in human lung epithelial (A549) cells. Nickel ferrite nanoparticles induced dose-dependent cytotoxicity in A549 cells demonstrated by MTT, NRU and LDH assays. Nickel ferrite nanoparticles were also found to induce oxidative stress evidenced by generation of reactive oxygen species (ROS) and depletion of antioxidant glutathione (GSH). Further, co-treatment with the antioxidant L-ascorbic acid mitigated the ROS generation and GSH depletion due to nickel ferrite nanoparticles suggesting the potential mechanism of oxidative stress. Quantitative real-time PCR analysis demonstrated that following the exposure of A549 cells to nickel ferrite nanoparticles, the level of mRNA expressions of cell cycle checkpoint protein p53 and apoptotic proteins (bax, caspase-3 and caspase-9) were significantly up-regulated, whereas the expression of anti-apoptotic proteins (survivin and bcl-2) were down-regulated. Moreover, activities of caspase-3 and caspase-9 enzymes were also significantly higher in nickel ferrite nanoparticles exposed cells. To the best of our knowledge this is the first report showing that nickel ferrite nanoparticles induced apoptosis in A549 cells through ROS generation and oxidative stress via p53, survivin, bax/bcl-2 and caspase pathways. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Static High Pressure Structural studies on Dy to 119 GPa

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

Patterson, J R; Saw, C K; Akella, J

2003-11-12

Structural phase transitions in the rare-earth metal Dysprosium have been studied in a Diamond Anvil Cell (DAC) to 119 GPa by x-ray diffraction. Four transformations following the sequence hcp {yields} Sm-type {yields} dhcp {yields} hR24 (hexagonal) {yields} bcm (monoclinic) are observed at 6, 15, 43, and 73 GPa respectively. The hexagonal to monoclinic transformation is accompanied by a 6% reduction in volume, which is attributed to delocalization of the 4f electrons, similar to that seen in Ce, Pr, and Gd.

Gain and Bandwidth Enhancement of Ferrite-Loaded CBS Antenna Using Material Shaping and Positioning

NASA Astrophysics Data System (ADS)

Askarian Amiri, Mikal

Loading a cavity-backed slot (CBS) antenna with ferrite material and applying a biasing static magnetic field can be used to control its resonant frequency. Such a mechanism results in a frequency reconfigurable antenna. However, placing a lossy ferrite material inside the cavity can reduce the gain or negatively impact the impedance bandwidth. This thesis develops guidelines, based on a non-uniform applied magnetic field and non-uniform magnetic field internal to the ferrite specimen, for the design of ferrite-loaded CBS antennas which enhance their gain and tunable bandwidth by shaping the ferrite specimen and judiciously locating it within the cavity. To achieve these objectives, it is necessary to examine the influence of the shape and relative location of the ferrite material, and also the proximity of the ferrite specimen from the probe on the DC magnetic field and RF electric field distributions inside the cavity. The geometry of the probe and its impacts on figures-of-merit of the antenna is of interest as well. Two common cavity backed-slot antennas (rectangular and circular cross-section) were designed, and corresponding simulations and measurements were performed and compared. The cavities were mounted on 30 cm × 30 cm perfect electric conductor (PEC) ground planes and partially loaded with ferrite material. The ferrites were biased with an external magnetic field produced by either an electromagnet or permanent magnets. Simulations were performed using FEM-based commercial software, Ansys' Maxwell 3D and HFSS. Maxwell 3D is utilized to model the non-uniform DC applied magnetic field and non-uniform magnetic field internal to the ferrite specimen; HFSS however, is used to simulate and obtain the RF characteristics of the antenna. To validate the simulations they were compared with measurements performed in ASU's EM Anechoic Chamber. After many examinations using simulations and measurements, some optimal designs guidelines with respect to the gain, return loss and tunable impedance bandwidth, were obtained and recommended for ferrite-loaded CBS antennas.

Effect of composition on SILAR deposited CdxZn1-xS thin films

NASA Astrophysics Data System (ADS)

Ashith V., K.; Gowrish Rao, K.

2018-04-01

In the group of II-VI compound semiconductor, cadmium zinc sulphide (CdxZn1-xS) thin films have broad application in photovoltaic, optoelectronic devices etc. For heterojunction aspects, CdxZn1-xS thin film can be used as heterojunction partner for CdTe as the absorber layer. In this work, CdZnS thin films prepared on glass substrates by Successive Ion Layer Adsorption and Reaction (SILAR) method by varying the composition. The XRD patterns of deposited films showed polycrystalline with the hexagonal phase. The crystallite size of the films was estimated from W-H plot. The bond length of the film varied w.r.to the composition of the CdxZn1-xS films. The urbach energy of the films was calcualted from absorbance data.

Superconductivity of lanthanum revisited: enhanced critical temperature in the clean limit.

PubMed

Löptien, P; Zhou, L; Khajetoorians, A A; Wiebe, J; Wiesendanger, R

2014-10-22

The thickness dependence of the superconducting energy gap ΔLa of double hexagonally close packed (dhcp) lanthanum islands grown on W(110) is studied by scanning tunneling spectroscopy, from the bulk to the thin-film limit. Superconductivity is suppressed by the boundary conditions for the superconducting wavefunction on the surface and W/La interface, leading to a linear decrease of the critical temperature Tc as a function of the inverse film thickness. For the thick, bulk-like films, ΔLa and Tc are 40% larger compared to the literature values of dhcp La as measured by other techniques. This finding is reconciled by examining the effects of surface contamination as probed by modifications of the surface state, suggesting that the large Tc originates in the superior purity of the samples investigated here.

Superconductivity of lanthanum revisited: enhanced critical temperature in the clean limit

NASA Astrophysics Data System (ADS)

Löptien, P.; Zhou, L.; Khajetoorians, A. A.; Wiebe, J.; Wiesendanger, R.

2014-10-01

The thickness dependence of the superconducting energy gap ΔLa of double hexagonally close packed (dhcp) lanthanum islands grown on W(110) is studied by scanning tunneling spectroscopy, from the bulk to the thin-film limit. Superconductivity is suppressed by the boundary conditions for the superconducting wavefunction on the surface and W/La interface, leading to a linear decrease of the critical temperature Tc as a function of the inverse film thickness. For the thick, bulk-like films, ΔLa and Tc are 40% larger compared to the literature values of dhcp La as measured by other techniques. This finding is reconciled by examining the effects of surface contamination as probed by modifications of the surface state, suggesting that the large Tc originates in the superior purity of the samples investigated here.

Structural characterization of sputter-deposited SS304+x aluminum (x = 0, 4, 7 and 10 wt.%) coatings and mechanically milled titanium, zirconium and hafnium powders

NASA Astrophysics Data System (ADS)

Seelam, Uma Maheswara Rao

Study of the metastable phases obtained by non-equilibrium processing techniques has come a long way during the past five decades. New metastable phases have often given new perspectives to the research on synthesis of novel materials systems. Metastable materials produced by two non-equilibrium processing methods were studied for this dissertation---304-type austenitic stainless steel (SS304 or Fe-18Cr-8Ni)+aluminum coatings produced by plasma enhanced magnetron sputter-deposition (PEMS) and nanocrystalline Ti, Zr and Hf powders processed by mechanical milling (MM). The objective of the study was to understand the crystallographic and microstructural aspects of these materials. Four SS304+Al coatings with a nominal Al percentages of 0, 4, 7 and 10 wt.% in the coatings were deposited on an SS304 substrate by PEMS using SS304 and Al targets. The as-deposited coatings were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and three-dimensional atom probe microscopy (3DAP). Surface morphology and chemical analysis were studied by SEM. Phase identification was carried out by XRD and TEM. The microstructural features of all the coatings, as observed in the TEM, consisted of columnar grains with the columnar grain width (a measure of grain size) increasing with an increase in the Al content. The coatings had grains with average grain sizes of about 100, 290, 320 and 980 nm, respectively for 0, 4, 7 and 10 wt.% Al. The observed grain structures and increase in grain size were related to substrate temperature during deposition. XRD results indicated that the Al-free coating consisted of the non-equilibrium ferrite and sigma phases. In the 4Al, 7Al and 10Al coatings, equilibrium ferrite and B2 phases were observed but no sigma phase was found. In 10Al coating, we were able to demonstrate experimentally using 3DAP studies that NiAl phase formation is preferred over the FeAl phase at nano scale. During mechanical milling of the hexagonal close packed (HCP) metals Hf, Ti and Zr powders, unknown nanocrystalline phases with face centered cubic (FCC) structure were found. The FCC phases could be either allotropes of the respective metals or impurity stabilized phases. However, upon MM under high purity conditions, it was revealed that the FCC phases were impurity stabilized. The decrease in crystallite size down to nanometer levels, an increase in atomic volume, lattice strain, and possible contamination were the factors responsible for the transformation.

Interlayer excitons in MoSe2/WSe2 heterostructures from first principles

NASA Astrophysics Data System (ADS)

Gillen, Roland; Maultzsch, Janina

2018-04-01

Based on ab initio theoretical calculations of the optical spectra of vertical heterostructures of MoSe2 (or MoS2) and WSe2 sheets, we reveal two spin-orbit-split Rydberg series of excitonic states below the A excitons of MoSe2 and WSe2 with a significant binding energy on the order of 250 meV for the first excitons in the series. At the same time, we predict from accurate many-body G0W0 calculations that crystallographically aligned MoSe2/WSe2 heterostructures exhibit an indirect fundamental band gap. Due to the type-II nature of the MoSe2/WSe2 heterostructure, the indirect transition and the exciton Rydberg series corresponding to a direct transition exhibit a distinct interlayer nature with spatial charge separation of the coupled electrons and holes. Our calculations confirm the recent experimental observation of a doublet nature of the long-lived states in photoluminescence spectra of Mo X2/W Y2 heterostructures, and we attribute these two contributions to momentum-direct interlayer excitons at the K point of the hexagonal Brillouin zone and to momentum-indirect excitons at the indirect fundamental band gap. Our calculations further suggest a noticeable effect of stacking order on the electronic band gaps and on the peak energies of the interlayer excitons and their oscillation strengths.

Novel 18650 lithium-ion battery surrogate cell design with anisotropic thermophysical properties for studying failure events

NASA Astrophysics Data System (ADS)

Spinner, Neil S.; Hinnant, Katherine M.; Mazurick, Ryan; Brandon, Andrew; Rose-Pehrsson, Susan L.; Tuttle, Steven G.

2016-04-01

Cylindrical 18650-type surrogate cells were designed and fabricated to mimic the thermophysical properties and behavior of active lithium-ion batteries. An internal jelly roll geometry consisting of alternating stainless steel and mica layers was created, and numerous techniques were used to estimate thermophysical properties. Surrogate cell density was measured to be 1593 ± 30 kg/m3, and heat capacity was found to be 727 ± 18 J/kg-K. Axial thermal conductivity was determined to be 5.1 ± 0.6 W/m-K, which was over an order of magnitude higher than radial thermal conductivity due to jelly roll anisotropy. Radial heating experiments were combined with numerical and analytical solutions to the time-dependent, radial heat conduction equation, and from the numerical method an additional estimate for heat capacity of 805 ± 23 J/kg-K was found. Using both heat capacities and analysis techniques, values for radial thermal conductivity were between 0.120 and 0.197 W/m-K. Under normal operating conditions, relatively low radial temperature distributions were observed; however, during extreme battery failure with a hexagonal cell package, instantaneous radial temperature distributions as high as 43-71 °C were seen. For a vertical cell package, even during adjacent cell failure, similar homogeneity in internal temperatures were observed, demonstrating thermal anisotropy.

Dielectric and magnetic studies of Cr+3 doped nickel ferrite by combustion method

NASA Astrophysics Data System (ADS)

Parveez, Asiya; Shekhawat, M. S.; Sindhu, S.; Srikanth, C.; Nayeem, Firdous; Mohd. Shariff, S.; Sinha, R. R.; Chaudhuri, Arka; Khader, S. Abdul

2018-05-01

Cr+3 doped nickel ferrite nanoparticles having the basic composition NiCrxFe2-xO4 (x=0, 0.1, 0.15, 0.2, 1) were prepared using auto combustion method. Structural, dielectric, a.c conductivity and magnetic properties of these samples, which are sintered at 800°C were studied. The structures of the synthesized samples were probed by X-ray diffraction (XRD) studies. The peaks observed in the XRD spectrum indicated single phase spinel cubic structure for the synthesized samples. Surface morphology of the samples has been investigated using Field Emission Scanning Electron Microscope (FESEM). The dielectric constant (ɛ') and dielectric loss factor (ɛ″) of nanocrystalline nickel ferrites were investigated as a function of frequency and Cr+3 concentration at room temperature over the frequency range 100 Hz to 1 MHz using Hioki make LCR Hi-Tester 3250. The dependence of ɛ' and ɛ″ with the frequency of the alternating applied electric field is in accordance with the Maxwell-Wagner type interfacial polarization, which is in agreement with the Koop's theory. The electrical conductivity (σac) deduced from the measured dielectric data has been thoroughly analyzed and found that the conduction mechanism in NiCrxFe2-xO4 nanoferrites are in conformity with the electron hopping model. The magnetic properties of Cr+3 doped nano-nickel ferrite were analyzed using a Vibrating Sample Magnetometer (VSM). It is observed that the values of saturation magnetization decreases along with the increase in chromium content.

Study of gamma ray energy absorption and exposure buildup factors for ferrites by geometric progression fitting method

NASA Astrophysics Data System (ADS)

Raut, S. D.; Awasarmol, V. V.; Shaikh, S. F.; Ghule, B. G.; Ekar, S. U.; Mane, R. S.; Pawar, P. P.

2018-04-01

The gamma ray energy absorption and exposure buildup factors (EABF and EBF) were calculated for ferrites such as cobalt ferrite (CoFe2O4), zinc ferrite (ZnFe2O4), nickel ferrite (NiFe2O4) and magnesium ferrite (MgFe2O4) using five parametric geometric progression (G-P fitting) formula in the energy range 0.015-15.00 MeV up to the penetration depth 40 mean free path (mfp). The obtained data of absorption and exposure buildup factors have been studied as a function of incident photon energy and penetration depth. The obtained EABF and EBF data are useful for radiation dosimetry and radiation therapy.

Defect sensitive etching of hexagonal boron nitride single crystals

NASA Astrophysics Data System (ADS)

Edgar, J. H.; Liu, S.; Hoffman, T.; Zhang, Yichao; Twigg, M. E.; Bassim, Nabil D.; Liang, Shenglong; Khan, Neelam

2017-12-01

Defect sensitive etching (DSE) was developed to estimate the density of non-basal plane dislocations in hexagonal boron nitride (hBN) single crystals. The crystals employed in this study were precipitated by slowly cooling (2-4 °C/h) a nickel-chromium flux saturated with hBN from 1500 °C under 1 bar of flowing nitrogen. On the (0001) planes, hexagonal-shaped etch pits were formed by etching the crystals in a eutectic mixture of NaOH and KOH between 450 °C and 525 °C for 1-2 min. There were three types of pits: pointed bottom, flat bottom, and mixed shape pits. Cross-sectional transmission electron microscopy revealed that the pointed bottom etch pits examined were associated with threading dislocations. All of these dislocations had an a-type burgers vector (i.e., they were edge dislocations, since the line direction is perpendicular to the [ 2 11 ¯ 0 ]-type direction). The pit widths were much wider than the pit depths as measured by atomic force microscopy, indicating the lateral etch rate was much faster than the vertical etch rate. From an Arrhenius plot of the log of the etch rate versus the inverse temperature, the activation energy was approximately 60 kJ/mol. This work demonstrates that DSE is an effective method for locating threading dislocations in hBN and estimating their densities.

Effect of strain rate and notch geometry on tensile properties and fracture mechanism of creep strength enhanced ferritic P91 steel

NASA Astrophysics Data System (ADS)

Pandey, Chandan; Mahapatra, M. M.; Kumar, Pradeep; Saini, N.

2018-01-01

Creep strength enhanced ferritic (CSEF) P91 steel were subjected to room temperature tensile test for quasi-static (less than 10-1/s) strain rate by using the Instron Vertical Tensile Testing Machine. Effect of different type of notch geometry, notch depth and angle on mechanical properties were also considered for different strain rate. In quasi-static rates, the P91 steel showed a positive strain rate sensitivity. On the basis of tensile data, fracture toughness of P91 steel was also calculated numerically. For 1 mm notch depth (constant strain rate), notch strength and fracture toughness were found to be increased with increase in notch angle from 45° to 60° while the maximum value attained in U-type notch. Notch angle and notch depth has found a minute effect on P91 steel strength and fracture toughness. The fracture surface morphology was studied by field emission scanning electron microscopy (FESEM).

Carbon concentration measurements by atom probe tomography in the ferritic phase of high-silicon steels

DOE PAGES

Rementeria, Rosalia; Poplawsky, Jonathan D.; Aranda, Maria M.; ...

2016-12-19

Current studies using atom probe tomography (APT) show that bainitic ferrite formed at low temperature contains more carbon than what is consistent with the paraequilibrium phase diagram. However, nanocrystalline bainitic ferrite exhibits a non-homogeneous distribution of carbon atoms in arrangements with specific compositions, i.e. Cottrell atmospheres, carbon clusters, and carbides, in most cases with a size of a few nanometers. The ferrite volume within a single platelet that is free of these carbon-enriched regions is extremely small. Proximity histograms can be compromised on the ferrite side, and a great deal of care should be taken to estimate the carbon contentmore » in regions of bainitic ferrite free from carbon agglomeration. For this purpose, APT measurements were first validated for the ferritic phase in a pearlitic sample and further performed for the bainitic ferrite matrix in high-silicon steels isothermally transformed between 200 °C and 350 °C. Additionally, results were compared with the carbon concentration values derived from X-ray diffraction (XRD) analyses considering a tetragonal lattice and previous APT studies. In conclusion, the present results reveal a strong disagreement between the carbon content values in the bainitic ferrite matrix as obtained by APT and those derived from XRD measurements. Those differences have been attributed to the development of carbon-clustered regions with an increased tetragonality in a carbon-depleted matrix.« less

Continuous cooling transformations and microstructures in a low-carbon, high-strength low-alloy plate steel

NASA Astrophysics Data System (ADS)

Thompson, S. W.; Vin, D. J., Col; Krauss, G.

1990-06-01

A continuous-cooling-transformation (CCT) diagram was determined for a high-strength low-alloy plate steel containing (in weight percent) 0.06 C, 1.45 Mn, 1.25 Cu, 0.97 Ni, 0.72 Cr, and 0.42 Mo. Dilatometric measurements were supplemented by microhardness testing, light microscopy, and transmission electron microscopy. The CCT diagram showed significant suppression of polygonal ferrite formation and a prominent transformation region, normally attributed to bainite formation, at temperatures intermediate to those of polygonal ferrite and martensite formation. In the intermediate region, ferrite formation in groups of similarly oriented crystals about 1 μm in size and containing a high density of dislocations dominated the transformation of austenite during continuous cooling. The ferrite grains assumed two morphologies, elongated or acicular and equiaxed or granular, leading to the terms “acicular ferrite” and “granular ferrite,” respectively, to describe these structures. Austenite regions, some transformed to martensite, were enriched in carbon and retained at interfaces between ferrite grains. Coarse interfacial ledges and the nonacicular morphology of the granular ferrite grains provided evidence for a phase transformation mechanism involving reconstructive diffusion of substitutional atoms. At slow cooling rates, polygonal ferrite and Widmanstätten ferrite formed. These latter structures contained low dislocation densities and e-copper precipitates formed by an interphase transformation mechanism.

Synthesis of Highly Uniform and Compact Lithium Zinc Ferrite Ceramics via an Efficient Low Temperature Approach.

PubMed

Xu, Fang; Liao, Yulong; Zhang, Dainan; Zhou, Tingchuan; Li, Jie; Gan, Gongwen; Zhang, Huaiwu

2017-04-17

LiZn ferrite ceramics with high saturation magnetization (4πM s ) and low ferromagnetic resonance line widths (ΔH) represent a very critical class of material for microwave ferrite devices. Many existing approaches emphasize promotion of the grain growth (average size is 10-50 μm) of ferrite ceramics to improve the gyromagnetic properties at relatively low sintering temperatures. This paper describes a new strategy for obtaining uniform and compact LiZn ferrite ceramics (average grains size is ∼2 μm) with enhanced magnetic performance by suppressing grain growth in great detail. The LiZn ferrites with a formula of Li 0.415 Zn 0.27 Mn 0.06 Ti 0.1 Fe 2.155 O 4 were prepared by solid reaction routes with two new sintering strategies. Interestingly, results show that uniform, compact, and pure spinel ferrite ceramics were synthesized at a low temperature (∼850 °C) without obvious grain growth. We also find that a fast second sintering treatment (FSST) can further improve their gyromagnetic properties, such as higher 4πM s and lower ΔH. The two new strategies are facile and efficient for densification of LiZn ferrite ceramics via suppressing grain growth at low temperatures. The sintering strategy reported in this study also provides a referential experience for other ceramics, such as soft magnetism ferrite ceramics or dielectric ceramics.

First-principles study on influence of molybdenum on acicular ferrite formation on TiC particles in microallyed steels

NASA Astrophysics Data System (ADS)

Hua, Guomin; Li, Changsheng; Cheng, Xiaonong; Zhao, Xinluo; Feng, Quan; Li, Zhijie; Li, Dongyang; Szpunar, Jerzy A.

2018-01-01

In this study, influences of molybdenum on acicular ferrite formation on precipitated TiC particles are investigated from thermodynamic and kinetic respects. In thermodynamics, Segregation of Mo towards austenite/TiC interface releases the interfacial energy and induces phase transformation from austenite to acicular ferrite on the precipitated TiC particles. The Phase transformation can be achieved by displacive deformation along uniaxial Bain path. In addition, the segregation of Mo atom will also lead to the enhanced stability of ferrite in comparison with austenite no matter at low temperature or at high temperature. In kinetics, the Mo solute in acicular ferrite can effectively suppress the diffusion of carbon atoms, which ensures that orientation relationship between acicular ferrite and austenitized matrix can be satisfied during the diffusionless phase transformation. In contrast to ineffectiveness of TiC particles, the alloying Mo element can facilitate the formation of acicular ferrite on precipitated TiC particles, which is attributed to the above thermodynamic and kinetic reasons. Furthermore, Interfacial toughness and ductility of as-formed acicular ferrite/TiC interface can be improved simultaneously by segregation of Mo atom.

Performance of a Wideband Cadmium Ferrite Microstrip Patch Antenna in the X-Band Region

NASA Astrophysics Data System (ADS)

Bhongale, S. R.; Ingavale, H. R.; Shinde, T. J.; Vasambekar, P. N.

2018-01-01

Magnesium-substituted cadmium ferrites with the chemical composition Mg x Cd1- x Fe2O4 ( x = 0, 0.4 and 0.8) were prepared by an oxalate co-precipitation method under microwave sintering technique. The structural properties of ferrites were studied by x-ray diffraction, Fourier transform infrared spectroscopy and field emission scanning electron microscope techniques. The scattering parameters such as reflection coefficient ( S 11) and transmission coefficient ( S 21) at microwave frequencies of palletized ferrites were measured by using a vector network analyzer. The software module 85071E followed by scattering parameters was used to determine the electromagnetic properties of the ferrites. The values determined for electromagnetic parameters such as the real part of permittivity ( ɛ'), permeability ( μ'), dielectric loss tangent (tan δ e) and magnetic loss tangent (tan δ m) of synthesized ferrites were used to design rectangular microstrip patch antennas. The performance of magnesium-substituted Cd ferrites as substrate for microstrip patch antennas was investigated. The antenna parameters such as return loss, bandwidth, voltage standing wave ratio, Smith chart and radiation pattern were studied. It is found that the Cd ferrite has applicability as a substrate for wideband antennas in the X-band region.

Efficiency of Launching Highly Confined Polaritons by Infrared Light Incident on a Hyperbolic Material.

PubMed

Dai, Siyuan; Ma, Qiong; Yang, Yafang; Rosenfeld, Jeremy; Goldflam, Michael D; McLeod, Alex; Sun, Zhiyuan; Andersen, Trond I; Fei, Zhe; Liu, Mengkun; Shao, Yinming; Watanabe, Kenji; Taniguchi, Takashi; Thiemens, Mark; Keilmann, Fritz; Jarillo-Herrero, Pablo; Fogler, Michael M; Basov, D N

2017-09-13

We investigated phonon-polaritons in hexagonal boron nitride-a naturally hyperbolic van der Waals material-by means of the scattering-type scanning near-field optical microscopy. Real-space nanoimages we have obtained detail how the polaritons are launched when the light incident on a thin hexagonal boron nitride slab is scattered by various intrinsic and extrinsic inhomogeneities, including sample edges, metallic nanodisks deposited on its top surface, random defects, and surface impurities. The scanned tip of the near-field microscope is itself a polariton launcher whose efficiency proves to be superior to all the other types of polariton launchers we studied. Our work may inform future development of polaritonic nanodevices as well as fundamental studies of collective modes in van der Waals materials.

Analysis of mechanical behavior of implant-supported prostheses in the anterior maxilla: analysis by speckle pattern interferometry

NASA Astrophysics Data System (ADS)

Corrêa, Cássia B.; Ramos, Nuno V.; Monteiro, Jaime; Vaz, Luis G.; Vaz, Mario A. P.

2012-10-01

The use of implants to rehabilitation of total edentulous, partial edentulous or single tooth is increasing, it is due to the high rate of success that this type of treatment present. The objective of this study was to analyze the mechanical behavior of different positions of two dental implants in a rehabilitation of 4 teeth in the region of maxilla anterior. The groups studied were divided according the positioning of the implants. The Group 1: Internal Hexagonal implant in position of lateral incisors and pontic in region of central incisors; Group 2: Internal Hexagonal implant in position of central incisors and cantilever of the lateral incisors and Group3 - : Internal Hexagonal implants alternate with suspended elements. The Electronic Speckle Pattern Interferometry (ESPI) technique was selected for the mechanical evaluation of the 3 groups performance. The results are shown in interferometric phase maps representing the displacement field of the prosthetic structure.

Optimal solution of full fuzzy transportation problems using total integral ranking

NASA Astrophysics Data System (ADS)

Sam’an, M.; Farikhin; Hariyanto, S.; Surarso, B.

2018-03-01

Full fuzzy transportation problem (FFTP) is a transportation problem where transport costs, demand, supply and decision variables are expressed in form of fuzzy numbers. To solve fuzzy transportation problem, fuzzy number parameter must be converted to a crisp number called defuzzyfication method. In this new total integral ranking method with fuzzy numbers from conversion of trapezoidal fuzzy numbers to hexagonal fuzzy numbers obtained result of consistency defuzzyfication on symmetrical fuzzy hexagonal and non symmetrical type 2 numbers with fuzzy triangular numbers. To calculate of optimum solution FTP used fuzzy transportation algorithm with least cost method. From this optimum solution, it is found that use of fuzzy number form total integral ranking with index of optimism gives different optimum value. In addition, total integral ranking value using hexagonal fuzzy numbers has an optimal value better than the total integral ranking value using trapezoidal fuzzy numbers.

Temperature dependent viscosity of cobalt ferrite / ethylene glycol ferrofluids

NASA Astrophysics Data System (ADS)

Kharat, Prashant B.; Somvanshi, Sandeep B.; Kounsalye, Jitendra S.; Deshmukh, Suraj S.; Khirade, Pankaj P.; Jadhav, K. M.

2018-04-01

In the present work, cobalt ferrite / ethylene glycol ferrofluid is prepared in 0 to 1 (in the step of 0.2) volume fraction of cobalt ferrite nanoparticles synthesized by co-precipitation method. The XRD results confirmed the formation of single phase spinel structure. The Raman spectra have been deconvoluted into individual Lorentzian peaks. Cobalt ferrite has cubic spinel structure with Fd3m space group. FT-IR spectra consist of two major absorption bands, first at about 586 cm-1 (υ1) and second at about 392 cm-1 (υ2). These absorption bands confirm the formation of spinel-structured cobalt ferrite. Brookfield DV-III viscometer and programmable temperature-controlled bath was used to study the relationship between viscosity and temperature. Viscosity behavior with respect to temperature has been studied and it is revealed that the viscosity of cobalt ferrite / ethylene glycol ferrofluids increases with an increase in volume fraction of cobalt ferrite. The viscosity of the present ferrofluid was found to decrease with increase in temperature.

Effects of thermomechanical processing on the microstructure and mechanical properties of a Ti-V-N steel

NASA Astrophysics Data System (ADS)

Dogan, B.; Collins, L. E.; Boyd, J. D.

1988-05-01

Based on studies of austenite deformation behavior and continuous-cooling-transformation behavior of a Ti-V microalloyed steel by cam plastometer and quench-deformation dilatometer, respectively, plate rolling schedules were designed to produce (i) recrystallized austenite, (ii) unrecrystallized austenite, (iii) deformed ferrite + unrecrystallized austenite. The effects of austenite condition and cooling rate on the final microstructure and mechanical properties were investigated. To rationalize the variation in final ferrite grain size with different thermomechanical processing schedules, it is necessary to consider the kinetics of ferrite grain growth in addition to the density of ferrite nucleation sites. The benefit of dilatometer studies in determining the optimum deformation schedule and cooling rate for a given steel is domonstrated. A wide range of tensile and impact properties results from the different microstructures studied. Yield strength is increased by increasing the amount of deformed ferrite, bainite, or martensite, and by decreasing the ferrite grain size. Impact toughness is most strongly influenced by ferrite grain size and occurrence of rolling plane delaminations.

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

Kantor, M. M., E-mail: Kantor@imet.ac.ru; Vorkachev, K. G., E-mail: KGV@imet.ac.ru

The efficiency of different techniques application for the investigation of orientation inhomogeneities in polycrystalline materials was studied using FEG SEM-FIB dual beam station equipped with EBSD. It is shown that for the visualization of pearlitic ferrite fragments it is more appropriate to acquire the images in secondary electrons induced by Ga ions. At the same time for the visualization of nano-sized particles it is more prospective to use images in forward scatter electrons in combination with IQ maps. It is established that pearlitic ferrite fragments are not flat. Complicated spatial configuration of orientation inhomogeneities in pearlitic ferrite is shown bymore » means of 3-d reconstruction. The features of ferrites aggregation are revealed depending on pearlitic ferrite fragmentation criterion. The existence of long-range misorientations in the aggregation area of proeutectoid and pearlitic ferrites is shown.« less

Spatial partitioning of environmental correlates of avian biodiversity in the conterminous United States

USGS Publications Warehouse

O'Connor, R.J.; Jones, M.T.; White, D.; Hunsaker, C.; Loveland, Tom; Jones, Bruce; Preston, E.

1996-01-01

Classification and regression tree (CART) analysis was used to create hierarchically organized models of the distribution of bird species richness across the conterminous United States. Species richness data were taken from the Breeding Bird Survey and were related to climatic and land use data. We used a systematic spatial grid of approximately 12,500 hexagons, each approximately 640 square kilometres in area. Within each hexagon land use was characterized by the Loveland et al. land cover classification based on Advanced Very High Resolution Radiometer (AVHRR) data from NOAA polar orbiting meteorological satellites. These data were aggregated to yield fourteen land classes equivalent to an Anderson level II coverage; urban areas were added from the Digital Chart of the World. Each hexagon was characterized by climate data and landscape pattern metrics calculated from the land cover. A CART model then related the variation in species richness across the 1162 hexagons for which bird species richness data were available to the independent variables, yielding an R2-type goodness of fit metric of 47.5% deviance explained. The resulting model recognized eleven groups of hexagons, with species richness within each group determined by unique sequences of hierarchically constrained independent variables. Within the hierarchy, climate data accounted for more variability in the bird data, followed by land cover proportion, and then pattern metrics. The model was then used to predict species richness in all 12,500 hexagons of the conterminous United States yielding a map of the distribution of these eleven classes of bird species richness as determined by the environmental correlates. The potential for using this technique to interface biogeographic theory with the hierarchy theory of ecology is discussed. ?? 1996 Blackwell Science Ltd.

Synergistic cosolubilization of omega-3 fatty acid esters and CoQ10 in dilutable microemulsions.

PubMed

Deutch-Kolevzon, Rivka; Aserin, Abraham; Garti, Nissim

2011-10-01

Water-dilutable microemulsions were prepared and loaded with two types of omega-3 fatty acid esters (omega-3 ethyl esters, OEE; and omega-3 triacylglycerides, OTG), each separately and together with ubiquinone (CoQ(10)). The microemulsions showed high and synergistic loading capabilities. The linear fatty acid ester (OEE) solubilization capacity was greater than that of the bulky and robust OTG. The location of the guest molecules within the microemulsions at any dilution point were determined by electrical conductivity, viscosity, DSC, SAXS, cryo-TEM, SD-NMR, and DLS. We found that OEE molecules pack well within the surfactant tails to form reverse micelles that gradually, upon water dilution, invert into bicontinuous phase and finally into O/W droplets. The CoQ(10) increases the stabilization and solubilization of the omega-3 fatty acid esters because it functions as a kosmotropic agent in the micellar system. The hydrophobic and bulky OTG molecule strongly interferes with the tail packing and spaces them significantly - mainly in the low and medium range water dilutions. When added to the micellar system, CoQ(10) forms some reverse hexagonal mesophases. The inversion into direct micelles is more difficult in comparison to the OEE system and requires additional water dilution. The OTG with or without CoQ(10) destabilizes the structures and decreases the solubilization capacity since it acts as a chaotropic agent to the micellar system and as a kosmotropic agent to hexagonal packing. These results explain the differences in the behavior of these molecules with vehicles that solubilize them in aqueous phases. Temperature disorders the bicontinuous structures and reduces the supersaturation of the system containing OEE with CoQ(10); as a result CoQ(10) crystallization is retarded. Copyright © 2011. Published by Elsevier Ireland Ltd.

Triangular laser-induced submicron textures for functionalising stainless steel surfaces

NASA Astrophysics Data System (ADS)

Romano, Jean-Michel; Garcia-Giron, Antonio; Penchev, Pavel; Dimov, Stefan

2018-05-01

Processing technologies that engineer surfaces with sub-micron topographies are of a growing interest to a range of optical, hydrophobic and microbiological applications. One of the promising technologies for creating such topographies employs ultra-short laser pulses to produce laser-induced periodic surface structures (LIPSS) that often result in non-regular, quasi-periodic nanoripples and nanopillars. In this research near infrared ultra-short pulses of 310 fs with a circular polarisation was used to texture ferritic stainless steel workpieces. A single-step process was designed to generate low spatial frequency LIPSS (LSFL) over relatively large areas. Apart from highly regular and homogeneous parallel lines with approximately 900 nm periodicity, extraordinarily uniform triangular-LSFL in hexagonal arrangements was created. The generation of such LSFL was found to be highly repeatable but very sensitive to the used laser processing settings. Therefore, the sensitivity of triangular-LSFL formation to the used laser processing settings, i.e. pulse to pulse distance, pulse fluence and focal plane offsets, were investigated in regard to the resulting morphologies and functional properties, i.e. structural colors and super-hydrophobicity. Finally, the capability of this technology for producing uniform triangular-shaped LSFL on relatively large surface areas of stainless steel plates was studied.

A new nanoscale metastable iron phase in carbon steels

PubMed Central

Liu, Tianwei; Zhang, Danxia; Liu, Qing; Zheng, Yanjun; Su, Yanjing; Zhao, Xinqing; Yin, Jiang; Song, Minghui; Ping, Dehai

2015-01-01

Metastable ω phase is common in body-centred cubic (bcc) metals and alloys, including high-alloying steels. Recent theoretical calculations also suggest that the ω structure may act as an intermediate phase for face-centred cubic (fcc)-to-bcc transformation. Thus far, the role of the ω phase played in fcc-bcc martensitic transformation in carbon steels has not been reported. In previous investigations on martensitic carbon steels, extra electron diffraction spots were frequently observed by transmission electron microscopy (TEM), and these spots were historically ascribed to the diffraction arising from either internal twins or carbides. In this paper, an intensive TEM investigation revealed that the extra spots are in fact attributed to the metastable ω phase in particle-like morphology with an overall size of several or dozens of nanometres. The strict orientation relationships between the ω phase and the ferrite matrix are in good agreement with those of the hexagonal (P6/mmm) ω phase in other bcc metals and alloys. The identification of the ω phase as well as the extra diffraction spots might provide a clue to help understand the physical mechanism of martensitic transformation in steels. PMID:26503890

Hardening of ODS ferritic steels under irradiation with high-energy heavy ions

NASA Astrophysics Data System (ADS)

Ding, Z. N.; Zhang, C. H.; Yang, Y. T.; Song, Y.; Kimura, A.; Jang, J.

2017-09-01

Influence of the nanoscale oxide particles on mechanical properties and irradiation resistance of oxide-dispersion-strengthened (ODS) ferritic steels is of critical importance for the use of the material in fuel cladding or blanket components in advanced nuclear reactors. In the present work, impact of structures of oxide dispersoids on the irradiation hardening of ODS ferritic steels was studied. Specimens of three high-Cr ODS ferritic steels containing oxide dispersoids with different number density and average size were irradiated with high-energy Ni ions at about -50 °C. The energy of the incident Ni ions was varied from 12.73 MeV to 357.86 MeV by using an energy degrader at the terminal so that a plateau of atomic displacement damage (∼0.8 dpa) was produced from the near surface to a depth of 24 μm in the specimens. A nanoindentor (in constant stiffness mode with a diamond Berkovich indenter) and a Vickers micro-hardness tester were used to measure the hardeness of the specimens. The Nix-Gao model taking account of the indentation size effect (ISE) was used to fit the hardness data. It is observed that the soft substrate effect (SSE) can be diminished substantially in the irradiated specimens due to the thick damaged regions produced by the Ni ions. A linear correlation between the nano-hardeness and the micro-hardness was found. It is observed that a higher number density of oxide dispersoids with a smaller average diameter corresponds to an increased resistance to irradiation hardening, which can be ascribed to the increased sink strength of oxides/matrix interfaces to point defects. The rate equation approach and the conventional hardening model were used to analyze the influence of defect clusters on irradiation hardening in ODS ferritic steels. The numerical estimates show that the hardening caused by the interstitial type dislocation loops follows a similar trend with the experiment data.

Crystallographic and magnetic properties of the spinel-type ferrites ZnxCo1-xFe2O4 (0.0 ≤ x ≤ 0.75)

NASA Astrophysics Data System (ADS)

Azad, A. K.; Zakaria, A. K. M.; Jewel, Md. Yusuf; Khan, Abu Saeed; Yunus, S. M.; Kamal, I.; Datta, T. K.; Eriksson, S.-G.

2015-05-01

Ultrahigh frequencies (UHF) have applications in signal and power electronics to minimize product sizes, increase production quantity and lower manufacturing cost. In the UHF range of 300 MHz to 3 GHz, ferrimagnetic iron oxides (ferrites) are especially useful because they combine the properties of a magnetic material with that of an electrical insulator. Ferrites have much higher electrical resistivity than metallic ferromagnetic materials, resulting in minimization of the eddy current losses, and total penetration of the electromagnetic (EM) field. Hence ferrites are frequently applied as circuit elements, magnetic storage media like read/write heads, phase shifters and Faraday rotators. The electromagnetic properties of ferrites are affected by operating conditions such as field strength, temperature and frequency. The spinel system ZnxCo1-xFe2O4 (x=0.0, 0.25, 0.50 and 0.75) has been prepared by the standard solid state sintering method. X-ray and neutron powder diffraction measurements were performed at room temperature. Neutron diffraction data analysis confirms the cubic symmetry corresponding to the space group Fd3m. The distribution of three cations Zn2+, Co2+ and Fe3+ over the spinel lattice and other crystallographic parameters like lattice constant, oxygen position parameter, overall temperature factor and occupancies of different ions in different lattice sites for the samples have been determined from the analysis of neutron diffraction data. The lattice constant increases with increasing Zn content in the system. The magnetic structure was found to be ferrimagnetic for the samples with x≤0.50. Magnetization measurements show that with the increase of Zn content in the system the value of saturation magnetization first increases and then decreases. The variation of the magnetic moment with Zn substitution has been discussed in terms of the distribution of magnetic and non-magnetic ions over the A and B sub-lattices and their exchange coupling.

Nucleation of intragranular ferrite in Fe-Ni-P alloys

NASA Astrophysics Data System (ADS)

Narayan, C.; Goldstein, J. I.

1984-05-01

The nucleation of intragranular ferrite from austenite in Fe-Ni-P alloys was investigated in order to understand the development of the Widmanstätten pattern in iron meteorites. Alloys containing 5 to 10 wt pct Ni and 0 to 1 wt pct P were used to simulate iron meteorite compositions. In the isothermal and controlled cooling experiments the reaction path γ → α + γ serves only to nucleate ferrite along austenite grain boundaries. It is necessary for (FeNi)3P to be present within y grains in order to nucleate intragranular ferrite. The reaction path γ → γ + phosphide → α + γ + phosphide yields rod shaped ferrite nuclei that bear a near Kurdjumov-Sachs orientation relationship with the surrounding matrix. The precipitation of ferrite, both along grain boundaries and within the austenite grains, is suppressed in the absence of P.

A New Grain Refiner for Ferritic Steels

NASA Astrophysics Data System (ADS)

Li, Ming; Li, Jian-Min; Zheng, Qing; Qiu, Dong; Wang, Geoff; Zhang, Ming-Xing

2017-12-01

A new grain refiner, LaB6, was identified for ferritic steels based on the crystallographic calculation using the edge-to-edge matching model. Addition of 0.5 wt pct LaB6 led to a reduction of the average grain size from 765 to 92 μm and the proportion of the columnar structure from 35 to 8 pct in an as-cast Fe-4Si ferritic alloy. Although LaB6 was supposed to act as an active inoculant for δ-ferrite, thermodynamic calculation indicated that LaB6 is not thermodynamically stable in the melt of the Fe-4Si alloy. It was subject to decompose into La and B solutes. Consequently, both La and B reacted with Fe, O and S, forming different compounds. Microstructural examination at room temperature observed La2SO2 and La2O3 particles within the ferrite grains and Fe2B along the grain boundaries in the samples. Through EBSD analysis, a reproducible orientation relationship between ferrite and La2SO2 was identified. In addition, the edge-to-edge matching calculation also predicted the high potency for La2SO2 to be an effective nucleant for δ-ferrite. It was considered that the grain refinement of LaB6 was attributed to the enhanced heterogeneous nucleation of δ-ferrite by La2SO2, and the solute effect of B due to the high Q-value in ferrite.

ARO 1.2: Solid Mechanics: Augmented Finite Element Method for High-Fidelity Analysis of Structural Composites

DTIC Science & Technology

2017-10-03

Physics of Solids, 78 (314-332). 2014. 6. C . X. Zhang, J . Z. Song, Q. D. Yang, “Periodic buckling patterns of graphene/hexagonal boron nitride...Mechanics, 139 (78-97), 2015. 9. Y. C . Gu, J . Jung, Q. D. Yang, and W. Q. Chen, “A New Stabilizing Method for Numerical Analyses with Severe...Local and Global Instability”, ASME Journal of Applied Mechanics, 82 (101010-1, -12), 2015 10. J . Jung, B. C . Do, and Q. D. Yang, “A-FEM for Arbitrary

Deformation mechanisms in a precipitation-strengthened ferritic superalloy revealed by in situ neutron diffraction studies at elevated temperatures

DOE PAGES

Huang, Shenyan; Gao, Yanfei; An, Ke; ...

2014-10-22

In this study, the ferritic superalloy Fe–10Ni–6.5Al–10Cr–3.4Mo strengthened by ordered (Ni,Fe)Al B2-type precipitates is a candidate material for ultra-supercritical steam turbine applications above 923 K. Despite earlier success in improving its room-temperature ductility, the creep resistance of this material at high temperatures needs to be further improved, which requires a fundamental understanding of the high-temperature deformation mechanisms at the scales of individual phases and grains. In situ neutron diffraction has been utilized to investigate the lattice strain evolution and the microscopic load-sharing mechanisms during tensile deformation of this ferritic superalloy at elevated temperatures. Finite-element simulations based on the crystal plasticitymore » theory are employed and compared with the experimental results, both qualitatively and quantitatively. Based on these interphase and intergranular load-partitioning studies, it is found that the deformation mechanisms change from dislocation slip to those related to dislocation climb, diffusional flow and possibly grain boundary sliding, below and above 873 K, respectively. Insights into microstructural design for enhancing creep resistance are also discussed.« less

Effects of C and Si on strain aging of strain-based API X60 pipeline steels

NASA Astrophysics Data System (ADS)

Sung, Hyo Kyung; Lee, Dong Ho; Lee, Sunghak; Lee, Byeong-Joo; Hong, Seung-Pyo; Kim, Young-Woon; Yoo, Jang Yong; Hwang, Byoungchul; Shin, Sang Yong

2017-05-01

Four types of strain-based API X60 pipeline steels were fabricated by varying the C and Si contents, and the effects of C and Si on strain aging were investigated. The 0.05 wt% C steels consisted mainly of polygonal ferrite (PF), whereas the 0.08 wt% C steels consisted of acicular ferrite (AF). The volume fraction of AF increased with increasing C content because C is an austenite stabilizer element. The volume fractions of bainitic ferrite (BF) of the 0.15 wt% Si steels were higher than those of the 0.25 wt% Si steels, whereas the volume fractions of the secondary phases were lower. From the tensile properties before and after the aging process of the strainbased API X60 pipeline steels, the yield strength increased and the uniform and total elongation decreased, which is the strain aging effect. The strain aging effect in the strain-based API X60 pipeline steels was minimized when the volume fraction of AF was increased and secondary phases were distributed uniformly. On the other hand, an excessively high C content formed fine precipitates, and the strain aging effect occurred because of the interactions among dislocations and fine precipitates.

Preparation and performances of Co-Mn spinel coating on a ferritic stainless steel interconnect material for solid oxide fuel cell application

NASA Astrophysics Data System (ADS)

Zhang, H. H.; Zeng, C. L.

2014-04-01

Ferritic stainless steels have become the candidate materials for interconnects of intermediate temperature solid oxide fuel cell (SOFC). The present issues to be solved urgently for the application of ferritic stainless steel interconnects are their rapid increase in contact resistance and Cr poisoning. In the present study, a chloride electrolyte suspension has been developed to electro-deposit a Co-Mn alloy on a type 430 stainless steel, followed by heat treatment at 750 °C in argon and at 800 °C in air to obtain Co-Mn spinel coatings. The experimental results indicate that an adhesive and compact Co-Mn alloy layer can be deposited in the chloride solution. After heat treatment, a complex coating composed of an external MnCo2O4 layer and an inner Cr-rich oxide layer has been formed on 430SS. The coating improves the oxidation resistance of the steel at 800 °C in air, especially in wet air, and inhibits the outward diffusion of Cr from the Cr-rich scale. Moreover, a low contact resistance has been achieved with the application of the spinel coatings.

Effect of Cooling Rate on Microstructure and Centerline Segregation of a High-Strength Steel for Shipbuilding

NASA Astrophysics Data System (ADS)

Ye, Qibin; Liu, Zhenyu; Wang, Guodong

Ultra-fast cooling (UFC) has been increasingly applied in industry, but accompanying with great changes of rolling strategy. It is therefore of importance to evaluate the characteristics of steels produced by UFC as compared to those processed by conventional accelerated cooling (ACQ. The present study examines the microstructure through thickness and centerline segregation of solute elements between UFC and ACC steels, both of which were rolled at a final rolling temperature at around non-recrystallized temperature. UFC steel showed the pronounced microstructural transition from lath-type bainite with Widmanstätten ferrite at subsurface to acicular ferrite in an average size of 5 µm dispersed with degenerate pearlite in the interior. In contrast, ACC steel had the homogeneous microstructure through the thickness, which was distinguished with coarser polygonal ferrite grains and pearlite nodules. Moreover, the centerline segregation was significantly suppressed by applying UFC at a higher cooling rate of 40 K/s compared to 17K/s for ACC steel. The significant differences in the microstructure and centerline segregation caused by various cooling rate is discussed from the view of γ→α transformation.

Influence of carboxylic acid type on microstructure and magnetic properties of polymeric complex sol-gel driven NiFe2O4

NASA Astrophysics Data System (ADS)

Hessien, M. M.; Mostafa, Nasser Y.; Abd-Elkader, Omar H.

2016-01-01

Citric, oxalic and tartaric acids were used for synthesis of NiFe2O4 using polymeric complex precursor route. The dry precursor gels were calcined at various temperatures (400-1100 °C) for 2 h. All carboxylic acids produce iron-deficient NiFe2O4 with considerable amount of α-Fe2O3 at 400 °C. Increase in the annealing temperature caused reaction of α-Fe2O3 with iron-deficient ferrite phase. The amount of initially formed α-Fe2O3 is directly correlated with stability constant and inversely correlated with the decomposition temperature of Fe(III) carboxylate precursors. In case of tartaric acid precursor, single phase of the ferrite was obtained at 450 °C. However, in case of oxalic acid and citric acid precursors, single phase ferrite was obtained at 550 °C and 700 °C, respectively. The lattice parameters were increased with increasing annealing temperature and with decreasing the amount of α-Fe2O3. Maximum saturation magnetization (55 emu/g) was achieved using tartaric acid precursor annealed at 1100 °C.

Factors Affecting the Strength and Toughness of Ultra-Low Carbon Steel Weld Metal

DTIC Science & Technology

1999-12-01

ferrite or martensite due to its strength and toughness, respectively. Ferrite with non-aligned second phase is associated with ferrite completely...with interphase carbides and pearlite. It forms at high temperatures and slow cooling rates than ferrite with secondary phase or martensite . It is...therefore termed a diffusionless transformation . In low carbon steels, the transformation occurs from fccy (austenite) to beta’ ( martensite ),

Induction of apoptosis in cancer cells by NiZn ferrite nanoparticles through mitochondrial cytochrome C release.

PubMed

Al-Qubaisi, Mothanna Sadiq; Rasedee, Abdullah; Flaifel, Moayad Husein; Ahmad, Sahrim Hj; Hussein-Al-Ali, Samer; Hussein, Mohd Zobir; Zainal, Zulkarnain; Alhassan, Fatah H; Taufiq-Yap, Yun H; Eid, Eltayeb E M; Arbab, Ismail Adam; Al-Asbahi, Bandar A; Webster, Thomas J; El Zowalaty, Mohamed Ezzat

2013-01-01

The long-term objective of the present study was to determine the ability of NiZn ferrite nanoparticles to kill cancer cells. NiZn ferrite nanoparticle suspensions were found to have an average hydrodynamic diameter, polydispersity index, and zeta potential of 254.2 ± 29.8 nm, 0.524 ± 0.013, and -60 ± 14 mV, respectively. We showed that NiZn ferrite nanoparticles had selective toxicity towards MCF-7, HepG2, and HT29 cells, with a lesser effect on normal MCF 10A cells. The quantity of Bcl-2, Bax, p53, and cytochrome C in the cell lines mentioned above was determined by colorimetric methods in order to clarify the mechanism of action of NiZn ferrite nanoparticles in the killing of cancer cells. Our results indicate that NiZn ferrite nanoparticles promote apoptosis in cancer cells via caspase-3 and caspase-9, downregulation of Bcl-2, and upregulation of Bax and p53, with cytochrome C translocation. There was a concomitant collapse of the mitochondrial membrane potential in these cancer cells when treated with NiZn ferrite nanoparticles. This study shows that NiZn ferrite nanoparticles induce glutathione depletion in cancer cells, which results in increased production of reactive oxygen species and eventually, death of cancer cells.

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

Rementeria, Rosalia; Poplawsky, Jonathan D.; Aranda, Maria M.

Current studies using atom probe tomography (APT) show that bainitic ferrite formed at low temperature contains more carbon than what is consistent with the paraequilibrium phase diagram. However, nanocrystalline bainitic ferrite exhibits a non-homogeneous distribution of carbon atoms in arrangements with specific compositions, i.e. Cottrell atmospheres, carbon clusters, and carbides, in most cases with a size of a few nanometers. The ferrite volume within a single platelet that is free of these carbon-enriched regions is extremely small. Proximity histograms can be compromised on the ferrite side, and a great deal of care should be taken to estimate the carbon contentmore » in regions of bainitic ferrite free from carbon agglomeration. For this purpose, APT measurements were first validated for the ferritic phase in a pearlitic sample and further performed for the bainitic ferrite matrix in high-silicon steels isothermally transformed between 200 °C and 350 °C. Additionally, results were compared with the carbon concentration values derived from X-ray diffraction (XRD) analyses considering a tetragonal lattice and previous APT studies. In conclusion, the present results reveal a strong disagreement between the carbon content values in the bainitic ferrite matrix as obtained by APT and those derived from XRD measurements. Those differences have been attributed to the development of carbon-clustered regions with an increased tetragonality in a carbon-depleted matrix.« less

Effect of Phase Contiguity and Morphology on the Evolution of Deformation Texture in Two-Phase Alloys

NASA Astrophysics Data System (ADS)

Gurao, N. P.; Suwas, Satyam

2017-02-01

Deformation texture evolution in two-phase xFe- yNi-(100- x- y)Cr model alloys and Ti-13Nb-13Zr alloy was studied during rolling to develop an understanding of micro-mechanisms of deformation in industrially relevant two-phase FCC-BCC steels and HCP-BCC titanium alloys, respectively. It was found that volume fraction and contiguity of phases lead to systematic changes in texture, while morphology affects the strength of texture. There was a characteristic change in texture from typical Brass-type to a weaker Copper-type texture in the austenite phase accompanied with a change from alpha fiber to gamma fiber in ferrite phase for Fe-Ni-Cr alloys with increase in fraction of harder ferrite phase. However, similar characteristic texture evolution was noted in both α and β phase irrespective of the different initial morphologies in Ti-13Nb-13Zr alloy. Viscoplastic self-consistent simulations with two-phase scheme were able to qualitatively predict texture evolution in individual phases. It is proposed that the transition from iso-strain-type behavior for equiaxed microstructure at low strain to iso-stress-type behavior at higher strain is aided by the presence of higher volume fraction of the second phase and increasing aspect ratio of individual phases in two-phase alloys.

Field dependence of the electron drift velocity along the hexagonal axis of 4H-SiC

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

Ivanov, P. A., E-mail: Pavel.Ivanov@mail.ioffe.ru; Potapov, A. S.; Samsonova, T. P.

The forward current–voltage characteristics of mesa-epitaxial 4H-SiC Schottky diodes are measured in high electric fields (up to 4 × 10{sup 5} V/cm) in the n-type base region. A semi-empirical formula for the field dependence of the electron drift velocity in 4H-SiC along the hexagonal axis of the crystal is derived. It is shown that the saturated drift velocity is (1.55 ± 0.05) × 10{sup 7} cm/s in electric fields higher than 2 × 10{sup 5} V/cm.

Topological dynamics of vortex-line networks in hexagonal manganites

NASA Astrophysics Data System (ADS)

Xue, Fei; Wang, Nan; Wang, Xueyun; Ji, Yanzhou; Cheong, Sang-Wook; Chen, Long-Qing

2018-01-01

The two-dimensional X Y model is the first well-studied system with topological point defects. On the other hand, although topological line defects are common in three-dimensional systems, the evolution mechanism of line defects is not fully understood. The six domains in hexagonal manganites converge to vortex lines in three dimensions. Using phase-field simulations, we predicted that during the domain coarsening process, the vortex-line network undergoes three types of basic topological changes, i.e., vortex-line loop shrinking, coalescence, and splitting. It is shown that the vortex-antivortex annihilation controls the scaling dynamics.

Process for stabilizing dimensions of duplex stainless steels for service at elevated temperatures

DOEpatents

Hull, Frederick C.; Tobin, John C.

1981-01-01

Duplex stainless steel materials containing austenite plus delta ferrite, are dimensionally stabilized by heating the material to a reaction temperature between about 1050.degree.-1450.degree. F. (566.degree.-788.degree. C.), holding it at this temperature during transformation of delta ferrite to austenite plus sigma phase, and subsequently heating to a reversion temperature between about 1625.degree.-1750.degree. F. (885.degree.-954.degree. C.), whereby the sigma phase transforms back to ferrite, but the austenite remains dispersed in the ferrite phase. Final controlled cooling permits transformation of ferrite to austenite plus sigma and, later, precipitation of carbides.

Method for making conductors for ferrite memory arrays. [from pre-formed metal conductors

NASA Technical Reports Server (NTRS)

Heckler, C. H.; Baba, P. D.; Bhiwandker, N. C. (Inventor)

1974-01-01

The ferrite memory arrays are made from pre-formed metal conductors for the ferrite arrays. The conductors are made by forming a thin sheet of a metallizing paste of metal alloy powder, drying the paste layer, bisque firing the dried sheet at a first temperature, and then punching the conductors from the fired sheet. During the bisque firing, the conductor sheet shrinks to 58 percent of its pre-fired volume and the alloy particles sinter together. The conductors are embedded in ferrite sheet material and finally fired at a second higher temperature during which firing the conductors shrink approximately the same degree as the ferrite material.

Magnetic and microwave properties of U-type hexaferrite films with high remanence and low ferromagnetic resonance linewidth

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

Su, Zhijuan; Bennett, Steven; Hu, Bolin

2014-05-07

U-type barium hexaferrite films (Ba{sub 4}Ni{sub 1.4}Co{sub 0.6}Fe{sub 36}O{sub 60}) were deposited on (0001) sapphire substrates by pulsed laser deposition. Microstructure and magnetic properties of the films were characterized by X-ray diffraction, scanning electron microscopy and vibrating sample magnetometry. Ferromagnetic resonance (FMR) measurements were performed at X-band. The results indicate an anisotropy field of ∼8 kOe, and the saturation magnetization (4πM{sub s}) of ∼3.6 kG. An optimal post-deposition annealing of films results in a strong (0 0 n) crystallographic texture and a high hysteresis loop squareness (M{sub r}/M{sub s} = 92%) leading to self biased properties. Furthermore, the highly self-biased ferrite films exhibitedmore » an FMR linewidth of ∼200 Oe. The U-type hexaferrite films having low microwave loss, low magnetic anisotropy field, and high squareness are a suitable alternative to Sc or In doped BaM ferrites that have been the choice material for self-biased microwave devices at X-band frequencies.« less

Mechanism and experimental research on ultra-precision grinding of ferrite

NASA Astrophysics Data System (ADS)

Ban, Xinxing; Zhao, Huiying; Dong, Longchao; Zhu, Xueliang; Zhang, Chupeng; Gu, Yawen

2017-02-01

Ultra-precision grinding of ferrite is conducted to investigate the removal mechanism. Effect of the accuracy of machine tool key components on grinding surface quality is analyzed. The surface generation model of ferrite ultra-precision grinding machining is established. In order to reveal the surface formation mechanism of ferrite in the process of ultraprecision grinding, furthermore, the scientific and accurate of the calculation model are taken into account to verify the grinding surface roughness, which is proposed. Orthogonal experiment is designed using the high precision aerostatic turntable and aerostatic spindle for ferrite which is a typical hard brittle materials. Based on the experimental results, the influence factors and laws of ultra-precision grinding surface of ferrite are discussed through the analysis of the surface roughness. The results show that the quality of ferrite grinding surface is the optimal parameters, when the wheel speed of 20000r/mm, feed rate of 10mm/min, grinding depth of 0.005mm, and turntable rotary speed of 5r/min, the surface roughness Ra can up to 75nm.

Synthesis, structure and electromagnetic properties of Mn-Zn ferrite by sol-gel combustion technique

NASA Astrophysics Data System (ADS)

Wang, Wenjie; Zang, Chongguang; Jiao, Qingjie

2014-01-01

The electromagnetic absorbing behaviors of a thin coating fabricated by mixing Mn-Zn ferrite with epoxy resin (EP) were studied. The spinel ferrites Mn1-xZnxFe2O4 (x=0.2, 0.5 and 0.8) were synthesized with citrate acid as complex agent by sol-gel combustion method. The microstructure and surface morphology of Mn-Zn ferrite powders were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The complex permittivity and complex permeability of the fabricated ferrite/EP composites were investigated in terms of their contributions to the absorbing properties in the low frequency (10 MHz to 1 GHz). The microwave absorption of the prepared ferrite/EP composites could be tailored by matching the dielectric loss and magnetic loss and by controlling the doped metal ratio. The composites with the ferrite composition x=0.2 are found to show higher reflection loss compared with the composites with other compositions. It is proposed that the prepared composites can potentially be applied in electromagnetic microwave absorbing field.

Synthesis and properties of precipitated cobalt ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Ristic, Mira; Krehula, Stjepko; Reissner, Michael; Jean, Malick; Hannoyer, Beatrice; Musić, Svetozar

2017-07-01

The formation and properties of cobalt ferrite were investigated with XRD, FT-IR, FE-SEM, Mössbauer and magnetometry. Cobalt ferrite samples were prepared (a) by combining coprecipitation Co(OH)2/2Fe(OH)3, using NaOH between pH 5.2 and 11.4 and autoclaving, and (b) by autoclaving the Co(OH)2/2Fe(OH)3 coprecipitate in a very strong alkaline medium. XRD and FE SEM showed that both CoFe2O4 crystallites and particles were in the nanosize range. The FT-IR spectra were typical of spinel ferrites. Cobalt ferrite precipitated at pH 7.2 and at 11.4 contained a small fraction of α-Fe2O3, whereas in the sample precipitated at pH 11.4 a very small amount (traces) of α-FeOOH were detected by FT-IR, additionally. Parameters obtained by Mössbauer spectroscopy suggested a structural migration of cobalt and iron ions in prepared cobalt ferrite spinels with the prolonged time of autoclaving. Magnetic measurements showed the magnetic behaviour typical of spinel ferrite nanoparticles.

Novel high-pressure phase of ZrO{sub 2}: An ab initio prediction

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

Durandurdu, Murat, E-mail: murat.durandurdu@agu.edu.tr

2015-10-15

The high-pressure behavior of the orthorhombic cotunnite type ZrO{sub 2} is explored using an ab initio constant pressure technique. For the first time, a novel hexagonal phase (Ni{sub 2}In type) within P6{sub 3}/mmc symmetry is predicted through the simulation. The Ni{sub 2}In type crystal is the densest high-pressure phase of ZrO{sub 2} proposed so far and has not been observed in other metal dioxides at high pressure before. The phase transformation is accompanied by a small volume drop and likely to occur around 380 GPa in experiment. - Graphical abstract: Post-cotunnite Ni{sub 2}In type hexagonal phase forms in zirconia atmore » high pressure. - Highlights: • A post-cotunnite phase is predicted for ZrO{sub 2} through an ab initio simulation. • Cotunnite ZrO{sub 2} adopts the Ni{sub 2}In type structure at high pressure. • The Ni{sub 2}In type structure is the densest high-pressure phase of ZrO{sub 2} proposed so far. • The preferred mechanism in ZrO{sub 2} differs from the other metal dioxides.« less

Smart magnetic markers use in hydraulic fracturing.

PubMed

Zawadzki, Jarosław; Bogacki, Jan

2016-11-01

One of the main challenges and unknowns during shale gas exploration is to assess the range and efficiency of hydraulic fracturing. It is also essential to assess the distribution of proppant, which keeps the fracture pathways open. Solving these problems may considerably increase the efficiency of the shale gas extraction. Because of that, the idea of smart magnetic marker, which can be detected when added to fracturing fluid, has been considered for a long time. This study provides overview of the possibilities of magnetic marker application for shale gas extraction. The imaging methods using electromagnetic markers, are considered or developed in two directions. The first possibility is the markers' electromagnetic activity throughout the whole volume of the fracturing fluid. Thus, it can be assumed that the whole fracturing fluid is the marker. Among these type of hydraulic fracturing solutions, ferrofluid could be considered. The second possibility is marker, which is just one of many components of the fracturing fluid. In this case feedstock magnetic materials, ferrites and nanomaterials could be considered. Magnetic properties of magnetite could be too low and ferrofluids' or nanomaterials' price is unacceptably high. Because of that, ferrites, especially ZnMn ferrites seems to be the best material for magnetic marker. Because of the numerous applications in electronics, it is cheap and easily available, although the price is higher, then that of magnetite. The disadvantage of using ferrite, could be too small mechanical strength. It creates an essential need for combining magnetic marker with proppant into magnetic-ceramic composite. Copyright © 2016 Elsevier Ltd. All rights reserved.

Electrodynamic properties of a hypercrystal with ferrite and semiconductor layers in an external magnetic field

NASA Astrophysics Data System (ADS)

Fedorin, Illia V.

2018-01-01

Electrodynamic properties of a photonic hypercrystal formed by periodically alternating two types of anisotropic metamaterials are studied. The first metamaterial consists of ferrite and dielectric layers, while the second metamaterial consists of semiconductor and dielectric layers. The system is assumed to be placed in an external magnetic field, which applied parallel to the boundaries of the layers. An effective medium theory which is suitable for calculation of properties of long-wavelength electromagnetic modes is applied in order to derive averaged expressions for effective constitutive parameters. It has been shown that providing a conscious choice of the constitutive parameters and material fractions of magnetic, semiconductor, and dielectric layers, the system under study shows hypercrystal properties for both TE and TM waves in the different frequency ranges.

Delta ferrite-containing austenitic stainless steel resistant to the formation of undesirable phases upon aging

DOEpatents

Leitnaker, James M.

1981-01-01

Austenitic stainless steel alloys containing delta ferrite, such as are used as weld deposits, are protected against the transformation of delta ferrite to sigma phase during aging by the presence of carbon plus nitrogen in a weight percent 0.015-0.030 times the volume percent ferrite present in the alloy. The formation of chi phase upon aging is controlled by controlling the Mo content.

Synthesis of Trimagnetic Multishell MnFe2 O4 @CoFe2 O4 @NiFe2 O4 Nanoparticles.

PubMed

Gavrilov-Isaac, Véronica; Neveu, Sophie; Dupuis, Vincent; Taverna, Dario; Gloter, Alexandre; Cabuil, Valérie

2015-06-10

The synthesis and characterization of original ferrite multishell magnetic nanoparticles made of a soft core (manganese ferrite) covered with two successive shells, a hard one (cobalt ferrite) and then a soft one (nickel ferrite), are described. The results demonstrate the modulation of the coercivity when new magnetic shells are added. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Delta ferrite-containing austenitic stainless steel resistant to the formation of undesirable phases upon aging

DOEpatents

Leitnaker, J.M.

Austenitic stainless steel alloys containing delta ferrite, such as are used as weld deposits, are protected against the transformation of delta ferrite to sigma phase during aging by the presence of carbon plus nitrogen in a weight percent 0.015 to 0.030 times the volume percent ferrite present in the alloy. The formation of chi phase upon aging is controlled by controlling the Mo content.

Synthesis and characterization of CoFe2O4/polyaniline nanocomposites for electromagnetic interference applications.

PubMed

Praveena, K; Srinath, S

2014-06-01

The Cobalt ferrite (CoFe2O4) powders were synthesized by Co-precipitation method. The as prepared ferrite powders were incorporated into a polyaniline matrix at various volumetric ratios. The as prepared composites of ferrite and polyaniline powders were characterized using X-ray diffraction (XRD), transmission electron microscope (TEM). The particle size of CoFe2O4 is found to be 20 nm. The saturation magnetization (M(s)) of all the composites was found to be decreasing with decrease of ferrite content, while coercivity (H(c)) remained at the value corresponding to pure cobalt ferrite nanopowders. The complex permittivity (epsilon' and epsilon") and permeability (mu' and mu") of composite samples were measured in the range of 1 MHz to 1.1 GHz. The value of epsilon' and mu' found to be increased with ferrite volume concentration.

Synthesis And Characterization Of Reduced Size Ferrite Reinforced Polymer Composites

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

Borah, Subasit; Bhattacharyya, Nidhi S.

2008-04-24

Small sized Co{sub 1-x}Ni{sub x}Fe{sub 2}O{sub 4} ferrite particles are synthesized by chemical route. The precursor materials are annealed at 400, 600 and 800 C. The crystallographic structure and phases of the samples are characterized by X-ray diffraction (XRD). The annealed ferrite samples crystallized into cubic spinel structure. Transmission Electron Microscopy (TEM) micrographs show that the average particle size of the samples are <20 nm. Particulate magneto-polymer composite materials are fabricated by reinforcing low density polyethylene (LDPE) matrix with the ferrite samples. The B-H loop study conducted at 10 kHz on the toroid shaped composite samples shows reduction in magneticmore » losses with decrease in size of the filler sample. Magnetic losses are detrimental for applications of ferrite at high powers. The reduction in magnetic loss shows a possible application of Co-Ni ferrites at high microwave power levels.« less

Nanocrystalline nickel ferrite particles synthesized by non-hydrolytic sol-gel method and their composite with biodegradable polymer.

PubMed

Yin, H; Casey, P S; Chow, G M

2012-11-01

Targeted drug delivery has been one of the most important biomedical applications for magnetic particles. Such applications require magnetic particles to have functionalized surfaces/surface coatings that facilitate their incorporation into a polymer matrix to produce a polymer composite. In this paper, nanocrystalline nickel ferrite particles with an oleic acid surface coating were synthesized using a non-hydrolytic sol-gel method and incorporated into a biodegradable polymer matrix, poly(D,L-lactide) PLA prepared using a double emulsion method. As-synthesized nickel ferrite particles had a multi-crystalline structure with chemically adsorbed oleic acid on their surface. After forming the PLA composite, nickel ferrite particles were encapsulated in PLA microspheres. At low nickel ferrite concentrations, composites showed very similar surface charges to that of PLA. The composites were magnetically responsive and increasing the nickel ferrite concentration was found to increase magnetization of the composite.

Feasibility of low-cost magnetic rail designs by integrating ferrite magnets and NdFeB magnets for HTS Maglev systems

NASA Astrophysics Data System (ADS)

Sun, R. X.; Deng, Z. G.; Gou, Y. F.; Li, Y. J.; Zheng, J.; Wang, S. Y.; Wang, J. S.

2015-09-01

Permanent magnet guideway (PMG) is an indispensable part of high temperature superconducting (HTS) Maglev systems. Present PMGs are made of NdFeB magnets with excellent performance and cost much. As another permanent magnet material, the ferrite magnet is weak at magnetic energy product and coercive force, but inexpensive. So, it is a possible way to integrate the ferrite and NdFeB magnets for cutting down the cost of present PMGs. In the paper, the equivalent on magnetic field intensity between ferrite magnets and NdFeB magnets was evaluated by finite element simulation. According to the calculation results, the magnetic field of the PMG integrating ferrite magnets and NdFeB magnets can be increased remarkably comparing with the pure ferrite PMG. It indicates that low-cost PMG designs by integrating the two permanent magnet materials are feasible for the practical HTS Maglev system.

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

Voßwinkel, Daniel; Heletta, Lukas; Hoffmann, Rolf-Dieter

The YIrGe{sub 2} type ternary germanides RERhGe{sub 2} (RE = Y, Gd-Ho) were synthesized from the elements by arc-melting and characterized by powder X-ray diffraction. The structure of DyRhGe{sub 2} was refined from single crystal X-ray diffractometer data: Immm, a = 426.49(9), b = 885.0(2), c = 1577.4(3) pm, wR2 = 0.0533, 637 F{sup 2} values, 30 variables (300 K data). The structure contains two crystallographically independent dysprosium atoms in pentagonal prismatic and hexagonal prismatic coordination. The three-dimensional [RhGe{sub 2}] polyanion is stabilized through covalent Rh–Ge (243–261 pm) and Ge–Ge (245–251 pm) bonding. The close structural relationship with the slightlymore » rhodium-poorer germanides RE{sub 5}Rh{sub 4}Ge{sub 10} (≡ RERh{sub 0.8}Ge{sub 2}) is discussed. Temperature-dependent magnetic susceptibility measurements reveal Pauli paramagnetism for YRhGe{sub 2} and Curie-Weiss paramagnetism for RERhGe{sub 2} with RE = Gd, Tb, Dy and Ho. These germanides order antiferromagnetically at T{sub N} = 7.2(5), 10.6(5), 8.1(5), and 6.4(5) K, respectively. - Graphical abstract: The germanides RERhGe{sub 2} (RE = Y, Gd-Ho) are new representatives of the YIrGe{sub 2} type.« less