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Sample records for lutetium borides

  1. Heat capacity and thermal expansion of icosahedral lutetium boride LuB66

    SciTech Connect

    Novikov, V V; Avdashchenko, D V; Matovnikov, A V; Mitroshenkov, N V; Bud’ko, S L

    2014-01-07

    The experimental values of heat capacity and thermal expansion for lutetium boride LuB66 in the temperature range of 2-300 K were analysed in the Debye-Einstein approximation. It was found that the vibration of the boron sub-lattice can be considered within the Debye model with high characteristic temperatures; low-frequency vibration of weakly connected metal atoms is described by the Einstein model.

  2. Gradient boride layers formed by diffusion carburizing and laser boriding

    NASA Astrophysics Data System (ADS)

    Kulka, M.; Makuch, N.; Dziarski, P.; Mikołajczak, D.; Przestacki, D.

    2015-04-01

    Laser boriding, instead of diffusion boriding, was proposed to formation of gradient borocarburized layers. The microstructure and properties of these layers were compared to those-obtained after typical diffusion borocarburizing. First method of treatment consists in diffusion carburizing and laser boriding only. In microstructure three zones are present: laser borided zone, hardened carburized zone and carburized layer without heat treatment. However, the violent decrease in the microhardness was observed below the laser borided zone. Additionally, these layers were characterized by a changeable value of mass wear intensity factor thus by a changeable abrasive wear resistance. Although at the beginning of friction the very low values of mass wear intensity factor Imw were obtained, these values increased during the next stages of friction. It can be caused by the fluctuations in the microhardness of the hardened carburized zone (HAZ). The use of through hardening after carburizing and laser boriding eliminated these fluctuations. Two zones characterized the microstructure of this layer: laser borided zone and hardened carburized zone. Mass wear intensity factor obtained a constant value for this layer and was comparable to that-obtained in case of diffusion borocarburizing and through hardening. Therefore, the diffusion boriding could be replaced by the laser boriding, when the high abrasive wear resistance is required. However, the possibilities of application of laser boriding instead of diffusion process were limited. In case of elements, which needed high fatigue strength, the substitution of diffusion boriding by laser boriding was not advisable. The surface cracks formed during laser re-melting were the reason for relatively quickly first fatigue crack. The preheating of the laser treated surface before laser beam action would prevent the surface cracks and cause the improved fatigue strength. Although the cohesion of laser borided carburized layer was

  3. Lutetium Oxide Coatings by PVD

    PubMed Central

    Topping, Stephen G; Park, CH; Rangan, SK; Sarin, VK

    2009-01-01

    Due to its high density and cubic structure, Lutetium oxide (Lu2O3) has been extensively researched for scintillating applications. Present manufacturing methods, such as hot pressing and sintering, do not provide adequate resolution due to light scattering of polycrystalline materials. Vapor deposition has been investigated as an alternative manufacturing method. Lutetium oxide transparent optical coatings by magnetron sputtering offer a means of tailoring the coating for optimum scintillation and resolution. Sputter deposited coatings typically have inherent stress and defects that adversely affect transparency and emission. The effect of process parameters on the coating properties is being investigated via x-ray diffraction (XRD), scanning electron microscopy (SEM) and emission spectroscopy, and will be presented and discussed. PMID:20390046

  4. Borides in Thin Film Technology

    NASA Astrophysics Data System (ADS)

    Mitterer, Christian

    1997-10-01

    The borides of transition and rare-earth metals are considered for application as wear- and corrosion-resistant, decorative or thermionic coatings. After a review of physical vapor deposition (PVD) techniques used for the deposition of these coatings, a survey of investigations to apply these coatings is given. As a result of the strong directionality of covalent boron-boron bonds, boride coatings show an increasing tendency to amorphous film growth with increasing B/Meatomic ratio and, for rare-earth hexaborides, with decreasing metallic radius of the rare-earth metal. Mechanical and optical properties are strongly influenced by the crystallographic structure of the boride phase. Because of their high hardness combined with good adhesion, crystalline films based on the diborides of transition metals seem to be promising candidates for wear resistant coatings on cutting tools. Alloying of these films with nitrogen by reactive PVD processes results in the formation of extremely fine-grained multiphase hard coatings with excellent tribological and corrosion behavior, thus offering new applications in the coating of engineering components. Because of their distinct colorations, some of the hexaborides of rare-earth elements may be used as decorative coatings on consumer products like wristwatch casings or eyeglass frames. Another promising field is the development of thermionic coatings based on rare-earth hexaborides, which may offer the possibility of the production of inexpensive and simple high emission filaments.

  5. Field free, directly heated lanthanum boride cathode

    DOEpatents

    Leung, Ka-Ngo; Moussa, D.; Wilde, S.B.

    1987-02-02

    A directly heated cylindrical lanthanum boride cathode assembly is disclosed which minimizes generation of magnetic field which would interfere with electron emission from the cathode. The cathode assembly comprises a lanthanum boride cylinder in electrical contact at one end with a central support shaft which functions as one electrode to carry current to the lanthanum boride cylinder and in electrical contact, at its opposite end with a second electrode which is coaxially position around the central support shaft so that magnetic fields generated by heater current flowing in one direction through the central support shaft are cancelled by an opposite magnetic field generated by current flowing through the lanthanum boride cylinder and the coaxial electrode in a direction opposite to the current flow in the central shaft.

  6. Field free, directly heated lanthanum boride cathode

    DOEpatents

    Leung, Ka-Ngo; Moussa, David; Wilde, Stephen B.

    1991-01-01

    A directly heated cylindrical lanthanum boride cathode assembly is disclosed which minimizes generation of magnetic fields which would interfere with electron emission from the cathode. The cathode assembly comprises a lanthanum boride cylinder in electrical contact at one end with a central support shaft which functions as one electrode to carry current to the lanthanum boride cylinder and in electrical contact, at its opposite end with a second electrode which is coaxially position around the central support shaft so that magnetic fields generated by heater current flowing in one direction through the central support shaft are cancelled by an opposite magnetic field generated by current flowing through the lanthanum boride cylinder and the coaxial electrode in a direction opposite to the current flow in the central shaft.

  7. Selective photoionisation of lutetium isotopes

    SciTech Connect

    D'yachkov, Aleksei B; Kovalevich, S K; Labozin, Valerii P; Mironov, Sergei M; Panchenko, Vladislav Ya; Firsov, Valerii A; Tsvetkov, G O; Shatalova, G G

    2012-10-31

    A three-stage laser photoionisation scheme intended for enriching the {sup 176}Lu isotope from natural lutetium was considered. An investigation was made of the hyperfine structure of the second excited state 5d6s7s {yields} {sup 4}D{sub 3/2} with an energy of 37194 cm{sup -1} and the autoionisation state with an energy of 53375 cm{sup -1} of the {sup 176}Lu and {sup 175}Lu isotopes. The total electron momentum of the autoionisation level and the constant A of hyperfine magnetic interaction were determined. Due to a small value of the isotopic shift between {sup 176}Lu and {sup 175}Lu, appreciable selectivity of their separation may be achieved with individual hyperfine structure components. The first tentative enrichment of the 176Lu isotope was performed to a concentration of 60 % - 70 %. (laser applications and other topics in quantum electronics)

  8. Lutetium +: A better clock candidate

    NASA Astrophysics Data System (ADS)

    Arnold, Kyle; Paez, Eduardo; Haciyev, Elnur; Arifin, Arifin; Cazan, Radu; Barrett, Murray

    2015-05-01

    With the extreme precision now reached by optical clocks it is reasonable to consider redefinition of the frequency standard. In doing so it is important to look beyond the current best-case efforts and have an eye on future possibilities. We will argue that singly ionized Lutetium is a strong candidate for the next generation of optical frequency standards. Lu + has a particularly narrow optical transition in combination with several advantageous properties for managing systematic uncertainties compared to the other atomic species. We summarize these properties and our specific strategies for managing the uncertainties due to external perturbations. Finally, we present the status of our ongoing experiments with trapped Lu +, including the results of precision measurements of its atomic structure.

  9. Kinetics of electrochemical boriding of low carbon steel

    NASA Astrophysics Data System (ADS)

    Kartal, G.; Eryilmaz, O. L.; Krumdick, G.; Erdemir, A.; Timur, S.

    2011-05-01

    In this study, the growth kinetics of the boride layers forming on low carbon steel substrates was investigated during electrochemical boriding which was performed at a constant current density of 200 mA/cm 2 in a borax based electrolyte at temperatures ranging from 1123 K to 1273 K for periods of 5-120 min. After boriding, the presence of both FeB and Fe 2B phases were confirmed by the X-ray diffraction method. Cross-sectional microscopy revealed a very dense and thick morphology for both boride phases. Micro hardness testing of the borided steel samples showed a significant increase in the hardness of the borided surfaces (i.e., up to (1700 ± 200) HV), while the hardness of un-borided steel samples was approximately (200 ± 20) HV. Systematic studies over a wide range of boriding time and temperature confirmed that the rate of the boride layer formation is strongly dependent on boriding duration and has a parabolic character. The activation energy of boride layer growth for electrochemical boriding was determined as (172.75 ± 8.6) kJ/mol.

  10. The fracture toughness of borides formed on boronized cold work tool steels

    SciTech Connect

    Sen, Ugur; Sen, Saduman

    2003-06-15

    In this study, the fracture toughness of boride layers of two borided cold work tool steels have been investigated. Boriding was carried out in a salt bath consisting of borax, boric acid, ferro-silicon and aluminum. Boriding was performed at 850 and 950 deg. C for 2 to 7 h. The presence of boride phases were determined by X-ray diffraction (XRD) analysis. Hardness and fracture toughness of borides were measured via Vickers indenter. Increasing of boriding time and temperature leads to reduction of fracture toughness of borides. Metallographic examination showed that boride layer formed on cold work tool steels was compact and smooth.

  11. Investigation of the fracture mechanics of boride composites

    NASA Technical Reports Server (NTRS)

    Kaufman, L.; Clougherty, E. V.; Nesor, H.

    1971-01-01

    Fracture energies of WC-6Co, Boride 5 (ZrB2+SiC), Boride 8(ZrB2+SiC+C) and Boride 8-M2(ZrB2+SiC+C) were measured by slow bend and impact tests of notched charpy bars. Cobalt bonded tungsten carbide exhibited impact energies of 0.76 ft-lb or 73.9 in-lb/square inch. Boride 5 and the Boride 8 exhibit impact energies one third and one quarter of that observed for WC-6Co comparing favorably with measurements for SiC and Si3N4. Slow bend-notched bar-fracture energies for WC-6Co were near 2.6 in-lb/square inch or 1/20 the impact energies. Slow bend energies for Boride 8-M2, Boride 8 and Boride 5 were 58%, 42% and 25% of the value observed for WC-6Co. Fractograph showed differences for WC-6Co where slow bend testing resulted in smooth transgranular cleavage while samples broken by impact exhibited intergranular failures. By contrast the boride fractures showed no distinction based on testing method. Fabrication studies were conducted to effect alteration of the boride composites by alloying and introduction of graphite cloth.

  12. Fracture Microindentation on boride layers on AISI 1020 steel

    NASA Astrophysics Data System (ADS)

    Prince, M.; Thanu, A. Justin; Arjun, S. L.; Velmurugan, U.; Gopalakrishnan, P.

    2016-02-01

    In this paper, an attempt has been made to enhance the fracture toughness (Kc) of boride layer using multi-component (Ni, Cr and B) laser bonding. The fracture toughness of continuously pack borided, interrupted pack borided and multi-component (Ni, Cr and B) laser borided steel specimens was measured using Vickers microindentation fracture toughness test as per ASTM E384 standard. The fracture toughness of continuously pack borided layer was - 3.3 MPa.m1/2. The fracture toughness of interrupted boride layer was in the range of - 4.9 MPa.m1/2. The fracture toughness of multi-component (Ni, Cr and B) laser borided layer was in the range of 13.8 - 18.3 MPa.m1/2. A significant improvement in fracture toughness of laser treated specimens was observed from the experimental results. This may be due to better distribution of boron, nickel, chromium and other alloying elements due to laser treatment and relatively more uniform boride layer as compared with continuously pack borided layer and interrupted pack borided layer.

  13. Electrochemical Evaluation of Corrosion on Borided and Non-borided Steels Immersed in 1 M HCl Solution

    NASA Astrophysics Data System (ADS)

    Mejía-Caballero, I.; Martínez-Trinidad, J.; Palomar-Pardavé, M.; Romero-Romo, M.; Herrera-Hernández, H.; Herrera-Soria, O.; Campos Silva, I.

    2014-08-01

    In this study the corrosion resistances of AISI 1018 and AISI 304 borided and non-borided steels were estimated using polarization resistance and electrochemical impedance spectroscopy (EIS) techniques. Boriding of the steel samples was conducted using the powder-pack method at 1223 K with 6 h of exposure. Structural examinations of the surfaces of the borided steels showed the presence of a Fe2B layer with isolated FeB teeth on the AISI 1018 steel, whereas a compact layer of FeB/Fe2B was formed on the AISI 304 steel. Polarization resistance and EIS of the borided and non-borided steels surfaces were performed in a corrosive solution of 1 M HCl. The EIS data were analyzed during 43 days of exposure to the acid solution. Impedance curves obtained during this period for the borided and non-borided steels were modeled using equivalent electrical circuits. The results of both electrochemical techniques indicated that boride layers formed at the steel surfaces effectively protect the samples from the corrosive effects of HCl. The main corrosion processes observed on the boride layers were pitting and crevice corrosion.

  14. Colloidal nickel boride catalyst for hydrogenation of olefins

    SciTech Connect

    Nakao, Y.; Fujishige, S.

    1981-04-01

    Colloidal nickel boride was prepared from nickel(II) chloride by reduction with sodium borohydride in the presence of polyvinylpyrrolidone in ethanol. Hydrogenation of various olefins was examined over the colloidal catalyst at 30/sup 0/C and atmospheric pressure. The colloidal nickel boride was much more effective than the precipitated nickel boride prepared in the absence of polyvinylpyrrolidone as a hydrogenation catalyst, especially for isopropenyl compounds. Additional amines and sodium acetate were slightly inhibitive to the colloidal catalyst, while, being strongly promotive to the precipitated catalyst. The colloidal nickel boride was superior to the charcoal-supported metals of the platinum group in catalytic activity for ..cap alpha..-methylstyrene.

  15. Investigation of the diffusion kinetics of borided stainless steels

    NASA Astrophysics Data System (ADS)

    Kayali, Yusuf

    2013-12-01

    In this study, the kinetics of borides formed on AISI 420, AISI 304 and AISI 304L stainless steels was investigated. Boronizing treatment was carried out using Ekabor-II powders at the processing temperatures of 1123, 1173 and 1223 K for 2, 4 and 6 h. The phases of the boride layers of borided AISI 420, AISI 304 and AISI 304L stainless steels were FeB, Fe2B, CrB and NiB, respectively. The thickness of the boride layer formed on the borided steels ranged from 4.6 to 64 μm depending on the boriding temperature, boriding time and alloying elements of the stainless steels. Depending on the chemical composition, temperature and layer thickness, the activation energies of boron in AISI 420, AISI 304 and AISI 304L stainless steels were found to be 206.161, 234.641 and 222.818 kJ/mol, respectively. The kinetics of growth of the boride layers formed on the AISI 420, AISI 304 and AISI 304L stainless steels and the thickness of the boride layers were investigated.

  16. Mechanism of boriding from pastes in a glow discharge

    SciTech Connect

    Isakov, S.A.; Al'tshuler, S.A.

    1987-09-01

    The authors investigate the boridation of steel 45 from the standpoint of the glow-discharge dissociation of a borax paste and the plasma arc spraying of the resulting boron into the steel. The effects of process parameters on the impregnation of boron into the steel and its phase behavior in the boridation process are discussed.

  17. The influence of carbon content in the borided Fe-alloys on the microstructure of iron borides

    SciTech Connect

    Kulka, M. . E-mail: coolka@sol.put.poznan.pl; Pertek, A. . E-mail: pertek@sol.put.poznan.pl; Klimek, L. . E-mail: kemilk@p.lodz.pl

    2006-04-15

    This paper presents the results of Electron Back-Scatter Diffraction (EBSD) analyses of the borided layers produced on substrate of varying carbon content. Two types of materials were investigated: borided Armco iron of very low carbon content and borocarburized chromium- and nickel-based steels of high carbon content beneath iron borides. The tetragonal phase Fe{sub 2}B was identified in all materials studied. It was difficult to obtain an EBSD pattern from iron boride (FeB) because of its presence at low depths below the surface, and because of the rounded corners of the specimens. EBSD provided information on the orientation of Fe{sub 2}B crystals. In case of the low-carbon Armco iron the crystallographic orientation was constant along the full length of the Fe{sub 2}B needle. The EBSPs obtained from borocarburized steel indicate that the crystallographic orientation of the Fe{sub 2}B phase changes along the length of the needle. This is the result of hindered boron diffusion due to boriding of the carburized substrate. The increased resistance to friction wear of borocarburized layers arises from two reasons. One is the decreased microhardness gradient between the iron borides and the substrate, which causes a decrease in the brittleness of the iron borides and an improved distribution of internal stresses in the diffusion layer. The second is the changeable crystallographic orientation of iron borides, which leads to the lower texture and porosity of borided layers. These advantageous properties of the borocarburized layer can be obtained if the carbon content beneath the iron borides is no more than about 1.0-1.2 wt.% C.

  18. Boriding of high carbon high chromium cold work tool steel

    NASA Astrophysics Data System (ADS)

    Muhammad, W.

    2014-06-01

    High-carbon high-chromium cold work tool steels are widely used for blanking and cold forming of punches and dies. It is always advantageous to obtain an increased wear resistant surface to improve life and performance of these steels. In this connection boriding of a high-carbon high-chromium cold work die steel, D3, was conducted in a mixture of 30% B4C, 70% borax at 950 °C for two, four and six hours. Case depth of the borided layer obtained was between 40 to 80 μm. After boriding, the surface hardness achieved was between 1430 to 1544 HV depending upon the process time. X-ray diffraction studies confirmed the formation of a duplex compound layer consisting of FeB and Fe2B. It is generally considered that FeB is undesirable because of its inherent brittleness. Post boriding treatment (homogenization) transformed the compound layer into single-phase layer of Fe2B, while surface hardness decreased to 1345-1430 HV. Pin-on-disc wer test showed that wear resistance of the borided samples was superior as compared to non-borided material and increased with boriding time.

  19. Method of making an icosahedral boride structure

    DOEpatents

    Hersee, Stephen D.; Wang, Ronghua; Zubia, David; Aselage, Terrance L.; Emin, David

    2005-01-11

    A method for fabricating thin films of an icosahedral boride on a silicon carbide (SiC) substrate is provided. Preferably the icosahedral boride layer is comprised of either boron phosphide (B.sub.12 P.sub.2) or boron arsenide (B.sub.12 As.sub.2). The provided method achieves improved film crystallinity and lowered impurity concentrations. In one aspect, an epitaxially grown layer of B.sub.12 P.sub.2 with a base layer or substrate of SiC is provided. In another aspect, an epitaxially grown layer of B.sub.12 As.sub.2 with a base layer or substrate of SiC is provided. In yet another aspect, thin films of B.sub.12 P.sub.2 or B.sub.12 As.sub.2 are formed on SiC using CVD or other vapor deposition means. If CVD techniques are employed, preferably the deposition temperature is above 1050.degree. C., more preferably in the range of 1100.degree. C. to 1400.degree. C., and still more preferably approximately 1150.degree. C.

  20. Synthesis and properties of nanoscale titanium boride

    NASA Astrophysics Data System (ADS)

    Efimova, K. A.; Galevskiy, G. V.; Rudneva, V. V.

    2015-09-01

    This work reports the scientific and technological grounds for plasma synthesis of titanium diboride, including thermodynamic and kinetic conditions of boride formation when titanium and titanium dioxide are interacting with products resulting from boron gasification in the nitrogen - hydrogen plasma flow, and two variations of its behavior using the powder mixtures: titanium - boron and titanium dioxide - boron. To study these technology variations, the mathematical models were derived, describing the relation between element contents in the synthesized products of titanium and free boron and basic parameters. The probable mechanism proposed for forming titanium diboride according to a "vapour - melt - crystal" pattern was examined, covering condensation of titanium vapour in the form of aerosol, boriding of nanoscale melt droplets by boron hydrides and crystallization of titanium - boron melt. The comprehensive physical - chemical certification of titanium diboride was carried out, including the study of its crystal structure, phase and chemical composition, dispersion, morphology and particle oxidation. Technological application prospects for use of titanium diboride nanoscale powder as constituent element in the wettable coating for carbon cathodes having excellent physical and mechanical performance and protective properties.

  1. Lutetium oxide-based transparent ceramic scintillators

    DOEpatents

    Seeley, Zachary; Cherepy, Nerine; Kuntz, Joshua; Payne, Stephen A.

    2016-01-19

    In one embodiment, a transparent ceramic of sintered nanoparticles includes gadolinium lutetium oxide doped with europium having a chemical composition (Lu.sub.1-xGd.sub.x).sub.2-YEu.sub.YO.sub.3, where X is any value within a range from about 0.05 to about 0.45 and Y is any value within a range from about 0.01 to about 0.2, and where the transparent ceramic exhibits a transparency characterized by a scatter coefficient of less than about 10%/cm. In another embodiment, a transparent ceramic scintillator of sintered nanoparticles, includes a body of sintered nanoparticles including gadolinium lutetium oxide doped with a rare earth activator (RE) having a chemical composition (Lu.sub.1-xGd.sub.x).sub.2-YRE.sub.YO.sub.3, where RE is selected from the group consisting of: Sm, Eu, Tb, and Dy, where the transparent ceramic exhibits a transparency characterized by a scatter coefficient of less than about 10%/cm.

  2. Pack-boriding of Fe-Mn binary alloys: Characterization and kinetics of the boride layers

    SciTech Connect

    Bektes, M.; Calik, A.; Ucar, N.; Keddam, M.

    2010-02-15

    In this work, the boronizing of Fe-Mn binary alloys at 0.42, 0.76 and 0.94 wt.% Mn was carried out in a solid medium using the powder pack method. In this method, commercial Ekabor-II boron source and activator (ferro-silicon) were thoroughly mixed to form the boriding medium. The samples were boronized in an electrical resistance furnace for exposure times of 2, 4, 6 and 8 h at 1173 K under atmospheric pressure and a series of boronized samples in the temperature range 1073-1373 K for 3 h. After the furnace process, boronized samples were removed from the furnace and cooled in air. Afterwards, the boride layers generated by the pack-boronizing process were characterized by optical microscopy, scanning electron microscopy, XRD analysis, Vickers microhardness and tensile testing. The generated boride layers, showing a saw-tooth morphology, had a surface microhardness in the range 1400-1270 HV0.1. It was shown that the values of yield stresses and ultimate tensile stresses were increased as the Mn content increases in the boronized Fe-Mn binary alloys. In contrast, the values of elongations determined from the stress-strain curves were decreased. Furthermore, it was found that the calculated mean value of the activation energy of boron diffusion was close to 119 J/mol.

  3. Certain physical properties of cobalt and nickel borides

    NASA Technical Reports Server (NTRS)

    Kostetskiy, I. I.; Lvov, S. N.

    1981-01-01

    The temperature dependence of the electrical resistivity, the thermal conductivity, and the thermal emf of cobalt and nickel borides were studied. In the case of the nickel borides the magnetic susceptibility and the Hall coefficient were determined at room temperature. The results are discussed with allowance for the current carrier concentration, the effect of various mechanisms of current-carrier scattering and the location of the Fermi level in relation to the 3d band.

  4. Ultralow friction behavior of borided steel surfaces after flash annealing

    SciTech Connect

    Bindal, C.; Erdemir, A.

    1996-02-01

    In this letter, we describe the ultralow friction mechanism of borided steel surfaces subjected to a short-duration, or {open_quote}{open_quote}flash,{close_quote}{close_quote} annealing procedure. In this procedure, a borided steel surface is exposed to high temperature (600 to 800{degree}C) for a short time (3 to 5 min) and then cooled to room temperature in open air. During the high-temperature exposure, boron atoms within the borided layer diffuse to the surface and react spontaneously with oxygen in air. The reaction product is a thin boron oxide film. During cooling, the boron oxide reacts spontaneously with moisture in the surrounding air to form a thin boric acid film. The sliding friction coefficient of a Si{sub 3}N{sub 4} ball against this flash-annealed surface is about 0.06, but is 0.5 and higher against the unborided or borided-only surfaces. Mechanistically, we propose that the ultralow friction behavior of the borided and flash-annealed surface is due mainly to the layered-crystal structure of the boric acid film that forms on the sliding surface. {copyright} {ital 1996 American Institute of Physics.}

  5. The characterization of boride layer on the St37 iron

    NASA Astrophysics Data System (ADS)

    Sutrisno, Soegijono, Bambang

    2012-06-01

    The property such as microhardness of boride layer formed on St37 iron was investigated. Boronizing was carried out in a solid medium consisting of nano size powders of 50% B4C as a donor, 45% SiC as a diluent, and 5% KBF4 as an activator treated at the temperature of 1000°C for 8 hours. The phases that were formed on the substrate was found as Fe2B and FeB layer that had smooth and flate shape morphology. The hardness of boride layer on St37 was over 2000 HV, while the hardness of untreated St37 iron was about 123,82 HV. Depending on process time and temperature, the depth of boride layer ranges from 20 to 60 μm, leading to a diffusion controlled process.

  6. Static and Dynamical Properties of heavy actinide Monopnictides of Lutetium

    PubMed Central

    Mir, Showkat H.; Jha, Prakash C.; Islam, M. S.; Banarjee, Amitava; Luo, Wei; Dabhi, Shweta D.; Jha, Prafulla K.; Ahuja, R.

    2016-01-01

    In this work, density functional theory within the framework of generalized gradient approximation has been used to investigate the structural, elastic, mechanical, and phonon properties of lutetium monopnictides in rock-salt crystal structure. The spin orbit coupling and Hubbard-U corrections are included to correctly predict the essential properties of these compounds. The elastic constants, Young’s modulus E, Poisson’s ratio v, shear modulus G, anisotropy factor A and Pugh’s ratio are computed. We found that all lutetium monopnictides are anisotropic and show brittle character. From the wave velocities along [100], [110] and [111] directions, melting temperature of lutetium monopnictides are predicted. Dynamical stability of these monopnictides has been studied by density functional perturbation theory. PMID:27384709

  7. Static and Dynamical Properties of heavy actinide Monopnictides of Lutetium.

    PubMed

    Mir, Showkat H; Jha, Prakash C; Islam, M S; Banarjee, Amitava; Luo, Wei; Dabhi, Shweta D; Jha, Prafulla K; Ahuja, R

    2016-01-01

    In this work, density functional theory within the framework of generalized gradient approximation has been used to investigate the structural, elastic, mechanical, and phonon properties of lutetium monopnictides in rock-salt crystal structure. The spin orbit coupling and Hubbard-U corrections are included to correctly predict the essential properties of these compounds. The elastic constants, Young's modulus E, Poisson's ratio v, shear modulus G, anisotropy factor A and Pugh's ratio are computed. We found that all lutetium monopnictides are anisotropic and show brittle character. From the wave velocities along [100], [110] and [111] directions, melting temperature of lutetium monopnictides are predicted. Dynamical stability of these monopnictides has been studied by density functional perturbation theory. PMID:27384709

  8. Superconductivity and magnetism of complex rhodium borides

    NASA Astrophysics Data System (ADS)

    Burkhanov, G. S.; Lachenkov, S. A.; Khlybov, E. P.; Dankin, D. G.; Kulikova, L. F.

    2013-05-01

    A number of complex rhodium borides with an LuRu4B4-type structure is synthesized; these are DyRh4B4 (samples HP) with T c ≈ 4.5 K, DyRh3.8Ru0.2B4 (samples AM) with T c ≈ 4.5 K, Dy0.8Er0.2Rh3.8Ru0.2B4 (samples AM) with T c ≈ 6.3 K, and HoRh3.8Ru0.2B4 (samples AM) with T c ≈ 6.0 K. The temperature dependence of upper critical field B c2( T) for all the samples under study exhibits an anomalous behavior. In all cases, the curve B c2( T) demonstrates a point of inflection, after which the curve deviates from the classical parabolic law abruptly upward for DyRh4B4 and DyRh3.8Ru0.2B4 (the 1st group of compounds) and downward for the Dy0.8Er0.2Rh3.8Ru0.2B4 and HoRh3.8Ru0.2B4 compounds (the 2nd group). These compounds are found to be characterized by of the following phase transitions: paramagnet → ferrimagnet → superconductor (retained ferrimagnetism) → antiferromagnet (retained superconductivity). The latter transition to the antiferromagnetic state occurs only in the compounds of the 1st group. It is found that, for the DyRh3.8Ru0.2B4 compound, no traditional Meissner effect is observed but the so-called Volleben effect (paramagnetic Meissner effect) takes place.

  9. Hydrothermal synthesis of lutetium disilicate nanoparticles

    SciTech Connect

    Tang Xiaoping; Gao Yanfeng; Chen Hongfei; Luo Hongjie

    2012-04-15

    A simple, low-cost hydrothermal method was developed to synthesize irregular-and rod-shaped lutetium disilicate (Lu{sub 2}Si{sub 2}O{sub 7}) powders with sizes ranging from 71 to 340 nm. The synthesis temperature was 260 Degree-Sign C, which is nearly 1300 Degree-Sign C lower than that required for the solid-state reaction. The results indicated that both the hydrothermal temperature and pH values had great influences on the composition, crystalline phase and morphology of the powders. The formation mechanism, basic thermophysical properties, stability and anticorrosion properties of the Lu{sub 2}Si{sub 2}O{sub 7} powders were also investigated. The obtained powders possessed low thermal conductivity, a suitable thermal expansion coefficient (3.92-5.17 Multiplication-Sign 10{sup -6} K{sup -1}) with the silicon-based substrate and excellent thermal and structural stability. During hot corrosion testing, the surfaces of the samples appeared to react with the water and molten salt vapors, but no serious failure occurred. - Graphical abstract: An image for the as-prepared Lu{sub 2}Si{sub 2}O{sub 7} powders (left) and XRD pattern (right) (inset shows the SEM graph of powders). Highlights: Black-Right-Pointing-Pointer We synthesized Lu{sub 2}Si{sub 2}O{sub 7} powders via a hydrothermal process at 260 Degree-Sign C. Black-Right-Pointing-Pointer Crystalline phase and morphology of the powders changed with experimental parameter. Black-Right-Pointing-Pointer Hot corrosion was determined in an airflow environment containing alkaline vapor.

  10. Subminiature eddy current transducers for studying boride coatings

    NASA Astrophysics Data System (ADS)

    Dmitriev, S. F.; Ishkov, A. V.; Malikov, V. N.; Sagalakov, A. M.

    2016-07-01

    Strengthening of parts and units of machines, increased reliability and longer service life is an important task of modern mechanical engineering. The main objects of study in the work were selected steel 65G and 50HGA, wear-resistant boride coatings ternary system Fe-B-Fe n B which were investigated by scanning electron microscopy and eddy-current nondestructive methods.

  11. Development and application of high strength ternary boride base cermets

    SciTech Connect

    Takagi, Ken-ichi . E-mail: u4381@toyokohan.co.jp

    2006-09-15

    Reaction boronizing sintering is a novel strategy to form a ternary boride coexisting with a metal matrix in a cermet during liquid phase sintering. This new sintering technique has successfully developed world first ternary boride base cermets with excellent mechanical properties such as Mo{sub 2}FeB{sub 2}, Mo{sub 2}NiB{sub 2} and WCoB base ones. In these cermets Mo{sub 2}FeB{sub 2} and Mo{sub 2}NiB{sub 2} base ones consist of a tetragonal M {sub 3}B{sub 2} (M: metal)-type complex boride as a hard phase and a transition metal base matrix. The cermets have already been applied to wear resistant applications such as injection molding machine parts, can making tools, and hot copper extruding dies, etc. This paper focuses on the characteristics, effects of the additional elements on the mechanical properties and structure, and practical applications of the ternary boride base cermets. - Graphical abstract: TRS and hardness of Ni-5B-51Mo-17.5Cr and Ni-5B-51Mo-12.5Cr-5V-xMn mass% cermets as functions of Mn content (Fig. 17)

  12. Discovery of gallium, germanium, lutetium, and hafnium isotopes

    SciTech Connect

    Gross, J.L.; Thoennessen, M.

    2012-09-15

    Currently, twenty-eight gallium, thirty-one germanium, thirty-five lutetium, and thirty-six hafnium isotopes have been observed and the discovery of these isotopes is described here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  13. Nanosize cobalt boride particles: Control of the size and properties

    NASA Astrophysics Data System (ADS)

    Petit, C.; Pileni, M. P.

    1997-02-01

    Cobalt boride is obtained by the reduction of cobalt (2-ethyl hexyl) sulfosuccinate, Co(AOT) 2, by sodium borohydride either in reverse micelles or in a diphasic system. In Co(AOT) 2/Na(AOT)/H 2O reverse micellar solution, the size and polydispersity of the Co 2B particles is controlled by the size of the water droplets, which increases from 4 to 7.5 nm by increasing the water content. In a diphasic system of Co(AOT) 2/isooctane and sodium borohydride in aqueous solution, large and polydisperse particles of cobalt boride are formed (˜ 10 nm), and their magnetization properties are presented. The smallest particles are in a superparamagnetic regime at room temperature, whereas the largest particles show ferromagnetic behavior.

  14. Optical Response of Shocked Cerium-Doped Lutetium Oxyorthosilicate

    SciTech Connect

    G. D. Stevens

    2003-03-01

    Shock experiments were performed in order to characterize the triboluminescent signature of cerium-doped lutetium oxyorthosilicate (LSO:Ce). This material shows prompt, nano-second timescale light emission when driven by explosive detonation. When properly applied to a surface, it may be used as a shock arrival sensor, and also for imaging the propagation of a shock front. Triboluminescent rise times, spectral content, and spatial resolution measurements are presented.

  15. Microstructural characterization and some mechanical properties of gas-borided Inconel 600-alloy

    NASA Astrophysics Data System (ADS)

    Makuch, N.; Kulka, M.

    2014-09-01

    The excellent resistance of Ni-based alloys to corrosion and oxidation is well-known. Boriding can be applied to these alloys in order to obtain suitable wear protection. In this paper, two-stage gas boronizing in N2-H2-BCl3 atmosphere is proposed for the producing the boride layer on Inconel®600-alloy. This process consists in two stages alternately repeated: saturation by boron and diffusion annealing. Such a gas boriding is applied in order to accelerate the saturation by boron and its diffusion. It turns out to be more effective because of eliminating the excess of boron, diffusing into the substrate, during the second stage. Microstructure and some mechanical properties of the produced layer are presented. Microstructural characterization is studied with using an optical microscope, scanning electron microscope, energy-dispersive x-ray microanalysis and x-ray diffraction. The diffusion zone consists of the mixture of nickel and chromium borides, occurring in the compact boride zone and in the area located beneath, at grain boundaries. The improved hardness and wear resistance characterize the layer. The formed boride layer is significantly thicker than those-obtained by the pack-boronizing or paste process at comparable temperature and time. Simultaneously, the measured depth of layer is slightly smaller than that-reported for electrolytic boriding.

  16. Characterisation of titanium-titanium boride composites processed by powder metallurgy techniques

    SciTech Connect

    Selva Kumar, M.; Chandrasekar, P.; Chandramohan, P.; Mohanraj, M.

    2012-11-15

    In this work, a detailed characterisation of titanium-titanium boride composites processed by three powder metallurgy techniques, namely, hot isostatic pressing, spark plasma sintering and vacuum sintering, was conducted. Two composites with different volume percents of titanium boride reinforcement were used for the investigation. One was titanium with 20% titanium boride, and the other was titanium with 40% titanium boride (by volume). Characterisation was performed using X-ray diffraction, electron probe micro analysis - energy dispersive spectroscopy and wavelength dispersive spectroscopy, image analysis and scanning electron microscopy. The characterisation results confirm the completion of the titanium boride reaction. The results reveal the presence of titanium boride reinforcement in different morphologies such as needle-shaped whiskers, short agglomerated whiskers and fine plates. The paper also discusses how mechanical properties such as microhardness, elastic modulus and Poisson's ratio are influenced by the processing techniques as well as the volume fraction of the titanium boride reinforcement. - Highlights: Black-Right-Pointing-Pointer Ti-TiB composites were processed by HIP, SPS and vacuum sintering. Black-Right-Pointing-Pointer The completion of Ti-TiB{sub 2} reaction was confirmed by XRD, SEM and EPMA studies. Black-Right-Pointing-Pointer Hardness and elastic properties of Ti-TiB composites were discussed. Black-Right-Pointing-Pointer Processing techniques were compared with respect to their microstructure.

  17. Processing and properties of some alumina-boride composites

    SciTech Connect

    Edirisinghe, M.J.

    1995-10-01

    Alumina (Al{sub 2}O{sub 3}) test bars containing a small (5--10%) volume of titanium diboride (TiB{sub 2}) or zirconium diboride (ZrB{sub 2}) particles have been pressed and sintered (pressureless) in an argon atmosphere. The microstructure of the sintered bodies was characterized by X-ray diffraction and a range of microscopical techniques and shows that 3 ppm (by volume) of oxygen present in the argon caused the boride particles in the surface regions of the test bars to oxidize during sintering, to a greater extent in the Al{sub 2}O{sub 3}-TiB{sub 2} composites. Mechanisms of oxidation are discussed. The boride particles retarded the densification of the composites, to a greater extent in the Al{sub 2}O{sub 3}-ZrB{sub 2} bodies. However, densification in the Al{sub 2}O{sub 3}-ZrB{sub 2} system was enhanced by sintering in an Ar-4% H{sub 2} atmosphere. The decrease in flexural strength due to the retardation of sintering has been overcome in both types of composites.

  18. Reactive Boride Brazing on Low-Alloy Automotive Grade Steel

    NASA Astrophysics Data System (ADS)

    Palanisamy, B.; Upadhyaya, A.

    2011-11-01

    Brazing is a widely used process to improve the performance of steels used in automotive applications. The substrate material is often exposed to harsh conditions in these applications and may affect the service life of the component. Reactive boride brazing aims to improve the mechanical properties of the substrate material by forming a ceramic-metal composite coating in a single-step process in situ. In this study, sintered Ancor 4300 low-alloy steel is used as the substrate with chromium-rich braze and chromium-lean braze materials. The mechanical properties of the brazed samples were studied in detail using microindentation hardness measurements and the transverse rupture test. The results indicate that the brazed superlayer has a 10 times higher hardness. There was a significant improvement in the transverse rupture strength of the steel brazed with the chromium-rich boride as compared to the pure substrate material. In an effort to reduce processing time, green compacts of the substrate were also directly brazed and yielded favorable results.

  19. Discovery of elusive structures of multifunctional transition-metal borides.

    PubMed

    Liang, Yongcheng; Wu, Zhaobing; Yuan, Xun; Zhang, Wenqing; Zhang, Peihong

    2016-01-14

    A definitive determination of crystal structures is an important prerequisite for designing and exploiting new functional materials. Even though tungsten and molybdenum borides (TMBx) are the prototype for transition-metal light-element compounds with multiple functionalities, their elusive crystal structures have puzzled scientists for decades. Here, we discover that the long-assumed TMB2 phases with the simple hP3 structure (hP3-TMB2) are in fact a family of complex TMB3 polytypes with a nanoscale ordering along the axial direction. Compared with the energetically unfavorable and dynamically unstable hP3-TMB2 phase, the energetically more favorable and dynamically stable TMB3 polytypes explain the experimental structural parameters, mechanical properties, and X-ray diffraction (XRD) patterns better. We demonstrate that such a structural and compositional modification from the hP3-TMB2 phases to the TMB3 polytypes originates from the relief of the strong antibonding interaction between d electrons by removing one third of metal atoms systematically. These results resolve the longstanding structural mystery of this class of metal borides and uncover a hidden family of polytypic structures. Moreover, these polytypic structures provide an additional hardening mechanism by forming nanoscale interlocks that may strongly hinder the interlayer sliding movements, which promises to open a new avenue towards designing novel superhard nanocomposite materials by exploiting the coexistence of various polytypes. PMID:26660270

  20. Enhancement of lutetium texaphyrin phototherapy with Mitomycin C

    NASA Astrophysics Data System (ADS)

    Thiemann, Patricia A.; Woodburn, Kathryn W.

    1998-05-01

    Lutetium texaphyrin (Lu-Tex) photodynamic therapy (PDT) relies on the presence of the water-soluble Lu-Tex, oxygen, and light (activation around 730 nm). Cytotoxic oxygen species are produced that cause irreversible damage to biological substrates. Damage may be inflicted via direct cell kill mechanisms or through vasculature effects that cause hypoxia. The addition of hypoxia enhanced drugs, such as Mitomycin C (MMC), can potentially increase the anti-tumor response. RIF-1 bearing C3H mice received 10 micrometers ol Lu-Tex/kg and were illuminated with 100 J/cm2 3 hours postinjection. Mice received MMC (2.5 or 5 mg/kg, before and after light) in conjunction with PDT and were compared to subsets of drug alone controls. A significant improvement in PDT response was observed when MMC was added to the dosing regimen; the effect was more pronounced at the highest MMC dose of 5 mg/kg: MMC prior to PDT gave a median tumor regrowth time (10X original volume) of 28 days compared to MMC and PDT alone, 16.3 and 14.9 days, respectively. The anti-tumor activity of lutetium texaphyrin induced PDT was improved by the addition of the bioreductive alkylating agent mitomycin C.

  1. The Electronic Properties of Metal Borides and Borocarbides: Differences and Similarities

    NASA Astrophysics Data System (ADS)

    Lassoued, Souheila; Gautier, Régis; Halet, Jean-François

    The bonding and structural arrangement in a few representative ring- or chain-containing solid-state metal borides and boride carbides are analyzed with respect to the electron count of the non-metal entities. Similarities and differences between them are emphasized. More specifically, the bonding in some layered ternary borides of RETB4 formula (RE = rare-earth metal and T = transition metal) is first analyzed and compared to that of the metal boride carbide ScB2C2, which contains a similar non-metal arrangement. Oxidation states are proposed for the boron or boron-carbon networks encountered in these compounds. It seems that they are electron-richer than graphite-like boron networks. In a second part, the bonding in linear boron and boron-carbon chains encapsulated in channels of LiB or RE xByCz is discussed and compared. Cumulenic bond character is favored in these chains.

  2. An alternative method of gas boriding applied to the formation of borocarburized layer

    SciTech Connect

    Kulka, M. Makuch, N.; Pertek, A.; Piasecki, A.

    2012-10-15

    The borocarburized layers were produced by tandem diffusion processes: carburizing followed by boriding. An alternative method of gas boriding was proposed. Two-stage gas boronizing in N{sub 2}-H{sub 2}-BCl{sub 3} atmosphere was applied to the formation of iron borides on a carburized substrate. This process consisted in two stages, which were alternately repeated: saturation by boron and diffusion annealing. The microstructure and microhardness of produced layer were compared to those-obtained in case of continuous gas boriding in H{sub 2}-BCl{sub 3} atmosphere, earlier used. The first objective of two-stage boronizing, consisting in acceleration of boron diffusion, has been efficiently implemented. Despite the lower temperature and shorter duration of boronizing, about 1.5 times larger iron borides' zone has been formed on carburized steel. Second objective, the absolute elimination of brittle FeB phase, has failed. However, the amount of FeB phase has been considerably limited. Longer diffusion annealing should provide the boride layer with single-phase microstructure, without FeB phase. - Highlights: Black-Right-Pointing-Pointer Alternative method of gas boriding in H{sub 2}-N{sub 2}-BCl{sub 3} atmosphere was proposed. Black-Right-Pointing-Pointer The process consisted in two stages: saturation by boron and diffusion annealing. Black-Right-Pointing-Pointer These stages of short duration were alternately repeated. Black-Right-Pointing-Pointer The acceleration of boron diffusion was efficiently implemented. Black-Right-Pointing-Pointer The amount of FeB phase in the boride zone was limited.

  3. Nanosized Borides and Carbides for Electroplating. Metal-Matrix Coatings: Specifications, Performance Evaluation

    NASA Astrophysics Data System (ADS)

    Galevskiy, G. V.; Rudneva, V. V.; Galevskiy, S. G.; Il’yashchenko, D. P.; Kartsev, D. S.

    2016-04-01

    This paper summarizes experience of application of nano-sized carbides and borides of titanium and chromium, silicon carbide as components of electro-depositable coating compositions based on nickel, zinc, and chromium. Basic physical and mechanical properties of the coatings are determined. Technological and economic evaluation is completed; practicability of high-cost nano-diamonds substitution for nano-sized borides and carbides is justified.

  4. Plasma boriding of a cobalt-chromium alloy as an interlayer for nanostructured diamond growth

    NASA Astrophysics Data System (ADS)

    Johnston, Jamin M.; Jubinsky, Matthew; Catledge, Shane A.

    2015-02-01

    Chemical vapor deposited (CVD) diamond coatings can potentially improve the wear resistance of cobalt-chromium medical implant surfaces, but the high cobalt content in these alloys acts as a catalyst to form graphitic carbon. Boriding by high temperature liquid baths and powder packing has been shown to improve CVD diamond compatibility with cobalt alloys. We use the microwave plasma-enhanced (PE) CVD process to deposit interlayers composed primarily of the borides of cobalt and chromium. The use of diborane (B2H6) in the plasma feedgas allows for the formation of a robust boride interlayer for suppressing graphitic carbon during subsequent CVD of nano-structured diamond (NSD). This metal-boride interlayer is shown to be an effective diffusion barrier against elemental cobalt for improving nucleation and adhesion of NSD coatings on a CoCrMo alloy. Migration of elemental cobalt to the surface of the interlayer is significantly reduced and undetectable on the surface of the subsequently-grown NSD coating. The effects of PECVD boriding are compared for a range of substrate temperatures and deposition times and are evaluated using glancing-angle X-ray diffraction (XRD), cross-sectional scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and micro-Raman spectroscopy. Boriding of CoCrMo results in adhered nanostructured diamond coatings with low surface roughness.

  5. The Growth Behavior of Titanium Boride Layers in α and β Phase Fields of Titanium

    NASA Astrophysics Data System (ADS)

    Lv, Xiaojun; Hu, Lingyun; Shuang, Yajing; Liu, Jianhua; Lai, Yanqing; Jiang, Liangxing; Li, Jie

    2016-07-01

    In this study, the commercially pure titanium was successfully electrochemical borided in a borax-based electrolyte. The process was carried out at a constant cathodic current density of 300 mA cm-2 and at temperatures of 1123 K and 1223 K (850 °C and 950 °C) for 0.5, 1, 2, 3, and 5 hours. The growth behavior of titanium boride layers in the α phase field of titanium was compared with that in the β phase field. After boriding, the presence of both the TiB2 top layer and TiB whisker sub-layer was confirmed by the X-ray diffraction (XRD) and scanning electron microscope. The relationship between the thickness of boride layers and boriding time was found to have a parabolic character in both α and β phase fields of titanium. The TiB whiskers showed ultra-fast growth rate in the β phase field. Its growth rate constant was found to be as high as 3.2002 × 10-13 m2 s-1. Besides, the chemical resistance of the TiB2 layer on the surface of titanium substrate was characterized by immersion tests in molten aluminum.

  6. Metal boride catalysts for indirect liquefaction. Quarterly technical progress report, December 1, 1983-February 29, 1984

    SciTech Connect

    Bartholomew, C.H.

    1984-04-12

    During the sixth quarter four boron-promoted cobalt catalysts were prepared by a new boriding process using diborane gas as the boriding agent. These catalysts were characterized by chemical analysis, BET, H/sub 2/ chemisorption, and x-ray diffraction. Temperature-programmed desorption spectra of H/sub 2/ were obtained for a sodium-promoted cobalt boride and a sodium-promoted Co/SiO/sub 2/. Four cobalt catalysts (unsupported, boron-promoted, sodium-promoted, and doubly-promoted) were tested for CO hydrogenation activity and selectivity at 1 atm and 3 to 4 temperatures in the range of 190 to 240/sup 0/C. About 10% of the surface of cobalt boride consists of reduced metallic cobalt. The addition of sodium to cobalt increases its binding energy with H/sub 2/ and its activation energy for H/sub 2/ adsorption. Boron does not affect the activity of cobalt; sodium decreases it by a factor of 10. Cobalt boride produces lighter hydrocarbon products relative to cobalt; sodium-promoted cobalt produces heavier products, more alcohols, and more CO/sub 2/. 29 references, 10 figures, 4 tables.

  7. The Growth Behavior of Titanium Boride Layers in α and β Phase Fields of Titanium

    NASA Astrophysics Data System (ADS)

    Lv, Xiaojun; Hu, Lingyun; Shuang, Yajing; Liu, Jianhua; Lai, Yanqing; Jiang, Liangxing; Li, Jie

    2016-04-01

    In this study, the commercially pure titanium was successfully electrochemical borided in a borax-based electrolyte. The process was carried out at a constant cathodic current density of 300 mA cm-2 and at temperatures of 1123 K and 1223 K (850 °C and 950 °C) for 0.5, 1, 2, 3, and 5 hours. The growth behavior of titanium boride layers in the α phase field of titanium was compared with that in the β phase field. After boriding, the presence of both the TiB2 top layer and TiB whisker sub-layer was confirmed by the X-ray diffraction (XRD) and scanning electron microscope. The relationship between the thickness of boride layers and boriding time was found to have a parabolic character in both α and β phase fields of titanium. The TiB whiskers showed ultra-fast growth rate in the β phase field. Its growth rate constant was found to be as high as 3.2002 × 10-13 m2 s-1. Besides, the chemical resistance of the TiB2 layer on the surface of titanium substrate was characterized by immersion tests in molten aluminum.

  8. Kinetics of borided 31CrMoV9 and 34CrAlNi7 steels

    SciTech Connect

    Efe, Goezde Celebi; Ipek, Mediha; Ozbek, Ibrahim; Bindal, Cuma

    2008-01-15

    In this study, kinetics of borides formed on the surface of 31CrMoV9 and 34CrAlNi7 steels borided in solid medium consisting of Ekabor II at 850-900-950 deg. C for 2, 4, 6 and 8 h were investigated. Scanning electron microscopy and optical microscopy examinations showed that borides formed on the surface of borided steels have columnar morphology. The borides formed in the coating layer confirmed by X-ray diffraction analysis are FeB, Fe{sub 2}B, CrB, and Cr{sub 2}B. The hardnesses of boride layers are much higher than that of matrix. It was found that depending on process temperature and time the fracture toughness of boride layers ranged from 3.93 to 4.48 MPa m{sup 1/2} for 31CrMoV9 and from 3.87 to 4.40 MPa m{sup 1/2} for 34CrAlNi7 steel. Activation energy, growth rate and growth acceleration of boride layer calculated according to these kinetic studies revealed that lower activation energy results in the fast growth rate and high growth acceleration.

  9. Synthesis and densification of lutetium pyrosilicate from lutetia and silica

    SciTech Connect

    Tripathi, Himansu S.; Sarin, Vinod K. . E-mail: sarin@bu.edu

    2007-02-15

    Cerium-doped lutetium pyrosilicate (Lu{sub 2}Si{sub 2}O{sub 7}:Ce) powder was synthesized by solid state reaction of Lu{sub 2}O{sub 3} and SiO{sub 2}. Stoichiometric mixtures of the starting materials were heat treated at various different temperatures and their phase contents were measured by XRD technique. It was found that the first step in the formation of Lu{sub 2}Si{sub 2}O{sub 7} (LPS) is the appearance of Lu{sub 2}SiO{sub 5} (LSO). This takes place at 1100 deg. C, fully 300 deg. C below the first appearance of LPS. Between 1400 and 1500 deg. C both LSO and LPS coexist in the calcined batch, but by 1550 deg. C all LSO is completely converted to LPS. LPS formation temperature does not have appreciable effect on the density of the hot pressed samples. Hot pressed samples obtained from powder synthesized at 1650 deg. C are nearly transparent, although the particle size of the starting powder is higher than that of the powder formed at lower temperatures.

  10. Theranostic Applications of Lutetium-177 in Radionuclide Therapy.

    PubMed

    Das, Tapas; Banerjee, Sharmila

    2016-01-01

    Lutetium-177 has been widely discussed as a radioisotope of choice for targeted radionuclide therapy. The simultaneous emission of imageable gamma photons [208 keV (11%) and 113 keV (6.4%)] along with particulate β(-) emission [β(max) = 497 keV] makes it a theranostically desirable radioisotope. In the present article, the possibility of using two 177Lu-based agents viz. 177Lu-EDTMP and 177Lu-DOTATATE for theranostic applications in metastatic bone pain palliation (MBPP) and peptide receptor radionuclide therapy (PRRT), have been explored. In the case of 177Lu-EDTMP, the whole-body images obtained are compared with those recorded using 99mTc-MDP in the same patient. On the other hand, pre-therapy images acquired with 177Lu-DOTA-TATE are compared with similar images obtained with standard agents, such as 99mTc-HYNIC-TOC (SPECT) and 68Ga-DOTA-TOC (PET) in the same patient. The advantage of the long physical half-life (T1/2) of 177Lu has been utilized in mapping the pharmacokinetics of two additional agents, 177Lu-labeled hydroxyapatite (HA) in radiation synovectomy of knee joints and 177Lu-HA for therapy of hepatocellular carcinoma. Results of these multiple studies conclusively document the potential of 177Lu as a theranostic radioisotope. PMID:25771364

  11. Nano-Disperse Borides and Carbides: Plasma Technology Production, Specific Properties, Economic Evaluation

    NASA Astrophysics Data System (ADS)

    Galevskii, G. V.; Rudneva, V. V.; Galevskii, S. G.; Tomas, K. I.; Zubkov, M. S.

    2016-04-01

    The experience of production and study on properties of nano-disperse chromium and titanium borides and carbides, and silicon carbide has been generalized. The structure and special service aspects of utilized plasma-metallurgical complex equipped with a three-jet direct-flow reactor with a capacity of 150 kW have been outlined. Processing, heat engineering and service life characteristics of the reactor are specified. The synthesis parameters of borides and carbides, as well as their basic characteristics in nano-disperse condition and their production flow diagram are outlined. Engineering and economic performance of synthesizing borides in laboratory and industrial conditions is assessed, and the respective segment of the international market as well. The work is performed at State Siberian Industrial University as a project part of the State Order of Ministry of Science and Education of the Russian Federation No. 11.1531/2014/K.

  12. Boride-based nano-laminates with MAX-phase-like behaviour

    SciTech Connect

    Telle, Rainer . E-mail: telle@ghi.rwth-aachen.de; Momozawa, Ai; Music, Denis; Schneider, Jochen M.

    2006-09-15

    MAX-phases being usually composed of transition metals, group A elements and carbon/nitrogen are considered interesting materials for many applications because of their tremendous bulk modulus, 'reversible' plasticity, and machinability. This is mainly due to their unique kind of bonding comprising covalent, ionic as well as metallic bonds providing 'easy' planes of rupture and deformability due to the layered crystal structures. In transition metal boride systems, similar types of bonding are available. In particular the W{sub 2}B{sub 5}-structure type and its stacking variations allow the synthesis of strongly layered crystal structures exhibiting unique delamination phenomena. The paper presents ab initio calculations showing the similarities of bonding between the ternary carbides and the corresponding ternary or quaternary borides. Formation of boride-based nano-laminates from auxiliary liquid phases, from the melt as well as during sintering and precipitation from supersaturated solid solutions will be discussed by means of SEM and TEM studies. The role of impurities weakening the interlayer bonding will be addressed in particular. The pronounced cleavage parallel to the basal plane gives rise for crack deflection and pull-out mechanisms if the laminates are dispersed in brittle matrices such as boron carbide, silicon carbide or other transition metal borides. - Graphical abstract: Some transition metal borides crystallise in a layered structure of alternating stacks of metal and boron atoms giving rise for strongly anisotropic properties. Their preferred cleavage parallel and the deformability perpendicular to the basal plan are similar to the peculiar mechanical behaviour recently described for MAX-phases. Ab initio calculations of the crystal structure prove the weak bonds between the layers for a variety of borides which can be used to reinforce ceramic materials on a nano-scale level.

  13. Surface hardening of steel by boriding in a cold rf plasma

    NASA Technical Reports Server (NTRS)

    Finberg, I.; Avni, R.; Grill, A.; Spalvins, T.; Buckley, D. H.

    1985-01-01

    Scanning electron spectroscopy, X-ray diffractometry, Auger electron spectroscopy, and microhardness measurements, are used to study the surfaces of 4340-steel samples that have been borided in a cold RF plasma which had been initiated in a gas mixture of 2.7 percent diborane in Ar. As a result of the dislocation of the diborane in the plasma, boron is deposited on the surface of the steel substrate and two crystalline phases, tetragonal Fe2B and orthorhombic FeB, are formed. The formation of boride phases then increases the surface microhardness from 2650 MPa to a maximum value of 7740 MPa.

  14. Lutetium-doped EuO films grown by molecular-beam epitaxy

    SciTech Connect

    Melville, A.; Heeg, T.; Mairoser, T.; Schmehl, A.; Shai, D. E.; Monkman, E. J.; Harter, J. W.; Hollaender, B.; Schubert, J.; Shen, K. M.; Mannhart, J.; Schlom, D. G.

    2012-05-28

    The effect of lutetium doping on the structural, electronic, and magnetic properties of epitaxial EuO thin films grown by reactive molecular-beam epitaxy is experimentally investigated. The behavior of Lu-doped EuO is contrasted with doping by lanthanum and gadolinium. All three dopants are found to behave similarly despite differences in electronic configuration and ionic size. Andreev reflection measurements on Lu-doped EuO reveal a spin-polarization of 96% in the conduction band, despite non-magnetic carriers introduced by 5% lutetium doping.

  15. Synthesis and characterisation of chromium lutetium gallium garnet solid solution

    SciTech Connect

    Galindo, R.; Badenes, J.A. . E-mail: jbadenes@qio.uji.es; Llusar, M.; Tena, M.A.; Monros, G.

    2007-03-22

    The chromium lutetium gallium garnet system has been studied. Samples with 2xCaOxCr{sub 2}O{sub 3}(3 - 2x)Lu{sub 2}O{sub 3}5Ga{sub 2}O{sub 3} (x = 0.025, 0.05, 0.075, 0.1, 0.2 and 0.3,) and xCr{sub 2}O{sub 3}(3 - x)Lu{sub 2}O{sub 3}5Ga{sub 2}O{sub 3} (x = 0, 0.05, 0.075 and 0.3) compositions have been prepared in Ca,Cr:LGG and Cr:LGG systems, respectively. Samples were prepared by ceramic method, fired at 1250 deg. C/6 h and characterised by XRD, lattice parameters, UV-vis-NIR spectroscopy, CIE L * a * b * measurements and SEM/EDX. Results indicate that Ca,Cr:LGG and Cr:LGG solid solutions are obtained. In Cr:LGG system only Cr(III) is stabilised in octahedral positions substituting for Lu(III) and Ga(III). Both Cr(III) and Cr(IV) are present in Ca,Cr:LGG. The calcium is a charge compensator to stabilise Cr(IV) and this is the predominant oxidation state up to x = 0.075 composition. From this composition, Cr(III) becomes more stabilised in garnet lattice. Cr(IV) occupies generally tetrahedral and dodecahedral sites substituting for Ga(III) and Lu(III), while Cr(III) is in octahedral site substituting for Ga(III)

  16. Metal-boride phase formation on tungsten carbide (WC-Co) during microwave plasma chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Johnston, Jamin M.; Catledge, Shane A.

    2016-02-01

    Strengthening of cemented tungsten carbide by boriding is used to improve the wear resistance and lifetime of carbide tools; however, many conventional boriding techniques render the bulk carbide too brittle for extreme conditions, such as hard rock drilling. This research explored the variation in metal-boride phase formation during the microwave plasma enhanced chemical vapor deposition process at surface temperatures from 700 to 1100 °C. We showed several well-adhered metal-boride surface layers consisting of WCoB, CoB and/or W2CoB2 with average hardness from 23 to 27 GPa and average elastic modulus of 600-730 GPa. The metal-boride interlayer was shown to be an effective diffusion barrier against elemental cobalt; migration of elemental cobalt to the surface of the interlayer was significantly reduced. A combination of glancing angle X-ray diffraction, electron dispersive spectroscopy, nanoindentation and scratch testing was used to evaluate the surface composition and material properties. An evaluation of the material properties shows that plasma enhanced chemical vapor deposited borides formed at substrate temperatures of 800 °C, 850 °C, 900 °C and 1000 °C strengthen the material by increasing the hardness and elastic modulus of cemented tungsten carbide. Additionally, these boride surface layers may offer potential for adhesion of ultra-hard carbon coatings.

  17. Surface hardening of St41 low carbon steel by using the hot-pressing powder-pack boriding method

    NASA Astrophysics Data System (ADS)

    Sutrisno, Soegijono, Bambang

    2014-03-01

    This research describes a powder-pack boriding process by using hot-pressing technic for St41 low carbon steel which will improve the hardness on the substrate by forming boride layer solid solution. Those method can reduce the operational cost of the research if it is compared by the conventional method with the asmospheric condition both vacuum system and gas inert condition. The concept of boriding by hot-pressing technic was verified in a laboratory scale. Welldefined and reusedable technic was achieved by using the stainless steel 304 as the container and sealed with a 5 ton pressure. This container was filled boronizing powder consisting of 5%B4C, 90%SiC, and 5%KBF4 to close the St41 low carbon steel specimen inside the container. The St41 boriding specimen was treated at the temperature of 900°C for 8 hours. The boride layer on the substrate was found as FeB and Fe2B phase with the hardness about 1800 HV. This value was more than ten times if compared with the untreated specimen that only had the hardness of 123 HV. Depend on heat treatment temperature, heat treatment time, and powder-pack boriding pressure, the depth of boride layer range from 127 to 165 μm, leading to a diffusion controlled process.

  18. Superabrasive boride and a method of preparing the same by mechanical alloying and hot pressing

    DOEpatents

    Cook, Bruce A.; Harringa, Joel L.; Russell, Alan M.

    2002-08-13

    A ceramic material which is an orthorhombic boride of the general formula: AlMgB.sub.14 :X, with X being a doping agent. The ceramic is a superabrasive, and in most instances provides a hardness of 40 GPa or greater.

  19. Ultra-Fast Boriding in High-Temperature Materials Processing Industries

    SciTech Connect

    2008-12-01

    This factsheet describes a research project whose main objective is to further develop, optimize, scale-up, and commercialize an ultra-fast boriding (also referred to as “boronizing”) process that can provide much higher energy efficiency, productivity, and near-zero emissions in many of the high-temperature materials processing industries.

  20. Structures and stability of novel transition-metal (M =Co ,Rh ,Co and Ir ) borides

    NASA Astrophysics Data System (ADS)

    Wang, Yachun; Wu, Lailei; Lin, Yangzheng; Hu, Qingyang; Li, Zhiping; Liu, Hanyu; Zhang, Yunkun; Gou, Huiyang; Yao, Yansun; Zhang, Jingwu; Gao, Faming; Mao, Ho-kwang

    2015-11-01

    Recent progress of high-pressure technology enables the synthesis of novel metal borides with diverse compositions and interesting properties. A precise characterization of these borides, however, is sometimes hindered by multiphase intergrowth and grain-size limitation in the synthesis process. Here, we theoretically explored new transition-metal borides (M =Co , Rh, and Ir) using a global structure searching method and discovered a series of stable compounds in this family. The predicted phases display a rich variety of stoichiometries and distinct boron networks resulting from the electron-deficient environments. Significantly, we identified a new Ir B1.25 structure as the long-sought structure of the first synthesized Ir-B compound. The simulated x-ray diffraction pattern of the proposed Ir B1.25 structure matches well with the experiment, and the convex hull calculation establishes its thermodynamic stability. Results of the present paper should advance the understanding of transition-metal borides and stimulate experimental explorations of these new and promising materials.

  1. Niobium boride layers deposition on the surface AISI D2 steel by a duplex treatment

    NASA Astrophysics Data System (ADS)

    Kon, O.; Pazarlioglu, S.; Sen, S.; Sen, U.

    2015-03-01

    In this paper, we investigated the possibility of deposition of niobium boride layers on the surface of AISI D2 steel by a duplex treatment. At the first step of duplex treatment, boronizing was performed on AISI D2 steel samples at 1000oC for 2h and then pre-boronized samples niobized at 850°C, 900°C and 950°C using thermo-reactive deposition method for 1-4 h. The presence of the niobium boride layers such as NbB, NbB2 and Nb3B4 and also iron boride phases such as FeB, Fe2B were examined by X-ray diffraction analysis. Scanning electron microscope (SEM) and micro-hardness measurements were realized. Experimental studies showed that the depth of the coating layers increased with increasing temperature and times and also ranged from 0.42 µm to 2.43 µm, depending on treatment time and temperature. The hardness of the niobium boride layer was 2620±180 HV0.005.

  2. Niobium boride layers deposition on the surface AISI D2 steel by a duplex treatment

    SciTech Connect

    Kon, O.; Pazarlioglu, S.

    2015-03-30

    In this paper, we investigated the possibility of deposition of niobium boride layers on the surface of AISI D2 steel by a duplex treatment. At the first step of duplex treatment, boronizing was performed on AISI D2 steel samples at 1000{sup o}C for 2h and then pre-boronized samples niobized at 850°C, 900°C and 950°C using thermo-reactive deposition method for 1–4 h. The presence of the niobium boride layers such as NbB, NbB{sub 2} and Nb{sub 3}B{sub 4} and also iron boride phases such as FeB, Fe{sub 2}B were examined by X-ray diffraction analysis. Scanning electron microscope (SEM) and micro-hardness measurements were realized. Experimental studies showed that the depth of the coating layers increased with increasing temperature and times and also ranged from 0.42 µm to 2.43 µm, depending on treatment time and temperature. The hardness of the niobium boride layer was 2620±180 HV{sub 0.005}.

  3. Photon-avalanche upconversion in thulium-doped lutetium aluminum garnet.

    PubMed

    Patel, D N; Reddy, B R; Nash-Stevenson, S K

    1999-05-20

    Strong blue fluorescence at 487 nm corresponding to the (1)G(4) --> (3)H(6) transition was generated from Tm(3+)-doped lutetium aluminum garnet on excitation with a 618-nm dye laser as a result of a photon-avalanche upconversion mechanism. PMID:18319920

  4. Lutetium-177 DOTATATE Production with an Automated Radiopharmaceutical Synthesis System

    PubMed Central

    Aslani, Alireza; Snowdon, Graeme M; Bailey, Dale L; Schembri, Geoffrey P; Bailey, Elizabeth A; Pavlakis, Nick; Roach, Paul J

    2015-01-01

    Objective(s): Peptide Receptor Radionuclide Therapy (PRRT) with yttrium-90 (90Y) and lutetium-177 (177Lu)-labelled SST analogues are now therapy option for patients who have failed to respond to conventional medical therapy. In-house production with automated PRRT synthesis systems have clear advantages over manual methods resulting in increasing use in hospital-based radiopharmacies. We report on our one year experience with an automated radiopharmaceutical synthesis system. Methods: All syntheses were carried out using the Eckert & Ziegler Eurotope’s Modular-Lab Pharm Tracer® automated synthesis system. All materials and methods used were followed as instructed by the manufacturer of the system (Eckert & Ziegler Eurotope, Berlin, Germany). Sterile, GMP-certified, no-carrier added (NCA) 177Lu was used with GMP-certified peptide. An audit trail was also produced and saved by the system. The quality of the final product was assessed after each synthesis by ITLC-SG and HPLC methods. Results: A total of 17 [177Lu]-DOTATATE syntheses were performed between August 2013 and December 2014. The amount of radioactive [177Lu]-DOTATATE produced by each synthesis varied between 10-40 GBq and was dependant on the number of patients being treated on a given day. Thirteen individuals received a total of 37 individual treatment administrations in this period. There were no issues and failures with the system or the synthesis cassettes. The average radiochemical purity as determined by ITLC was above 99% (99.8 ± 0.05%) and the average radiochemical purity as determined by HPLC technique was above 97% (97.3 ± 1.5%) for this period. Conclusions: The automated synthesis of [177Lu]-DOTATATE using Eckert & Ziegler Eurotope’s Modular-Lab Pharm Tracer® system is a robust, convenient and high yield approach to the radiolabelling of DOTATATE peptide benefiting from the use of NCA 177Lu and almost negligible radiation exposure of the operators. PMID:27408890

  5. Potential and limitations of microanalysis SEM techniques to characterize borides in brazed Ni-based superalloys

    SciTech Connect

    Ruiz-Vargas, J.; Siredey-Schwaller, N.; Noyrez, P.; Mathieu, S.; Bocher, P.; and others

    2014-08-15

    Brazed Ni-based superalloys containing complex phases of different Boron contents remain difficult to characterize at the micrometer scale. Indeed Boron is a light element difficult to measure precisely. The state-of-the-art microanalysis systems have been tested on a single crystal MC2 based metal brazed with BNi-2 alloy to identify boride precipitates. Effort has been made to evaluate the accuracy in Boron quantitation. Energy-dispersive and wavelength-dispersive X-ray spectroscopy attached to a Scanning Electron Microscope have first been used to determine the elemental composition of Boron-free phases, and then applied to various types of borides. Results have been compared to the ones obtained using a dedicated electron probe microanalysis, considered here as the reference technique. The most accurate method to quantify Boron using EDS is definitely by composition difference. A precision of 5 at.% could be achieved with optimized data acquisition and post-processing schemes. Attempts that aimed at directly quantifying Boron with various standards using EDS or coupled EDS/WDS gave less accurate results. Ultimately, Electron Backscatter Diffraction combined with localized EDS analysis has proved invaluable in conclusively identifying micrometer sized boride precipitates; thus further improving the characterization of brazed Ni-based superalloys. - Highlights: • We attempt to accurately identify Boron-rich phases in Ni-based superalloys. • EDS, WDS, EBSD systems are tested for accurate identification of these borides. • Results are compared with those obtained by electron probe microanalysis. • Boron was measured with EDS by composition difference with a precision of 5 at. %. • Additional EBSD in phase identification mode conclusively identifies the borides.

  6. Additive-assisted synthesis of boride, carbide, and nitride micro/nanocrystals

    SciTech Connect

    Chen, Bo; Yang, Lishan; Heng, Hua; Chen, Jingzhong; Zhang, Linfei; Xu, Liqiang; Qian, Yitai; Yang, Jian

    2012-10-15

    General and simple methods for the syntheses of borides, carbides and nitrides are highly desirable, since those materials have unique physical properties and promising applications. Here, a series of boride (TiB{sub 2}, ZrB{sub 2}, NbB{sub 2}, CeB{sub 6}, PrB{sub 6}, SmB{sub 6}, EuB{sub 6}, LaB{sub 6}), carbide (SiC, TiC, NbC, WC) and nitride (TiN, BN, AlN, MgSiN{sub 2}, VN) micro/nanocrystals were prepared from related oxides and amorphous boron/active carbon/NaN{sub 3} with the assistance of metallic Na and elemental S. In-situ temperature monitoring showed that the reaction temperature could increase quickly to {approx}850 Degree-Sign C, once the autoclave was heated to 100 Degree-Sign C. Such a rapid temperature increase was attributed to the intense exothermic reaction between Na and S, which assisted the formation of borides, carbides and nitrides. The as-obtained products were characterized by XRD, SEM, TEM, and HRTEM techniques. Results in this report will greatly benefit the future extension of this approach to other compounds. - Graphical abstract: An additive-assisted approach is successfully developed for the syntheses of borides, carbides and nitrides micro/nanocrystals with the assistance of the exothermic reaction between Na and S. Highlights: Black-Right-Pointing-Pointer An additive-assisted synthesis strategy is developed for a number of borides, carbides and nitrides. Black-Right-Pointing-Pointer The reaction mechanism is demonstrated by the case of SiC nanowires. Black-Right-Pointing-Pointer The formation of SiC nanowires is initiated by the exothermic reaction of Na and S.

  7. Improving the Adhesion Resistance of the Boride Coatings to AISI 316L Steel Substrate by Diffusion Annealing

    NASA Astrophysics Data System (ADS)

    Campos-Silva, I.; Bernabé-Molina, S.; Bravo-Bárcenas, D.; Martínez-Trinidad, J.; Rodríguez-Castro, G.; Meneses-Amador, A.

    2016-07-01

    In this study, new results about the practical adhesion resistance of boride coating/substrate system formed at the surface of AISI 316 L steel and improved by means of a diffusion annealing process are presented. First, the boriding of AISI 316 L steel was performed by the powder-pack method at 1173 K with different exposure times (4-8 h). The diffusion annealing process was conducted on the borided steels at 1273 K with 2 h of exposure using a diluent atmosphere of boron powder mixture. The mechanical behavior of the boride coating/substrate system developed by both treatments was established using Vickers and Berkovich tests along the depth of the boride coatings, respectively. Finally, for the entire set of experimental conditions, the scratch tests were performed with a continuously increasing normal force, in which the practical adhesion resistance of the boride coating/substrate system was represented by the critical load. The failure mechanisms developed over the surface of the scratch tracks were analyzed; the FeB-Fe2B/substrate system exhibited an adhesive mode, while the Fe2B/substrate system obtained by the diffusion annealing process showed predominantly a cohesive failure mode.

  8. The coexistence of silicon borides with boron-saturated silicon: Metastability of SiB{sub 3}

    SciTech Connect

    Aselage, T.L.

    1998-07-01

    The silicon-rich end of the Si-B phase diagram, defining the silicon boride(s) that coexist in equilibrium with boron-saturated silicon, is poorly known. Understanding this equilibrium has implications for the processing of p{sup +} silicon wafers, whose boron concentrations are near the solubility limit. Additionally, silicon boride precipitates produced by boron-ion-implantation and annealing of crystalline silicon have recently been shown to be efficient internal getters of transition metal ions. The experiments described in this paper probe the stability of these silicon borides. A phase with a boron-carbide-like structure, SiB{sub 3}, grows from boron-saturated silicon in both the solid and the liquid state. However, SiB{sub 3} is not found to be stable in either circumstance. Rather, SiB{sub 3} is a metastable phase whose formation is driven by the relative ease of its nucleation and growth. The silicon boride that exists in stable equilibrium with boron-saturated silicon is SiB{sub 6}. A qualitative understanding of the metastability of SiB{sub 3} comes from recognizing the conflict between the bonding requirements of icosahedral borides such as SiB{sub 3} and the size mismatch between silicon and boron atoms. {copyright} {ital 1998 Materials Research Society.}

  9. Selection of peptides binding to metallic borides by screening M13 phage display libraries

    PubMed Central

    2014-01-01

    Background Metal borides are a class of inorganic solids that is much less known and investigated than for example metal oxides or intermetallics. At the same time it is a highly versatile and interesting class of compounds in terms of physical and chemical properties, like semiconductivity, ferromagnetism, or catalytic activity. This makes these substances attractive for the generation of new materials. Very little is known about the interaction between organic materials and borides. To generate nanostructured and composite materials which consist of metal borides and organic modifiers it is necessary to develop new synthetic strategies. Phage peptide display libraries are commonly used to select peptides that bind specifically to metals, metal oxides, and semiconductors. Further, these binding peptides can serve as templates to control the nucleation and growth of inorganic nanoparticles. Additionally, the combination of two different binding motifs into a single bifunctional phage could be useful for the generation of new composite materials. Results In this study, we have identified a unique set of sequences that bind to amorphous and crystalline nickel boride (Ni3B) nanoparticles, from a random peptide library using the phage display technique. Using this technique, strong binders were identified that are selective for nickel boride. Sequence analysis of the peptides revealed that the sequences exhibit similar, yet subtle different patterns of amino acid usage. Although a predominant binding motif was not observed, certain charged amino acids emerged as essential in specific binding to both substrates. The 7-mer peptide sequence LGFREKE, isolated on amorphous Ni3B emerged as the best binder for both substrates. Fluorescence microscopy and atomic force microscopy confirmed the specific binding affinity of LGFREKE expressing phage to amorphous and crystalline Ni3B nanoparticles. Conclusions This study is, to our knowledge, the first to identify peptides that

  10. Friction and wear of radiofrequency-sputtered borides, silicides, and carbides

    NASA Technical Reports Server (NTRS)

    Brainard, W. A.; Wheeler, D. R.

    1978-01-01

    The friction and wear properties of several refractory compound coatings were examined. These compounds were applied to 440 C bearing steel surfaces by radiofrequency (RF) sputtering. The refractory compounds were the titanium and molybdenum borides, the titanium and molybdenum silicides, and the titanium, molybdenum, and boron carbides. Friction testing was done with a pin-on-disk wear apparatus at loads from 0.1 to 5.0 newtons. Generally, the best wear properties were obtained when the coatings were bias sputtered onto 440 C disks that had been preoxidized. Adherence was improved because of the better bonding of the coatings to the iron oxide formed during preoxidation. As a class the carbides provided wear protection to the highest loads. Titanium boride coatings provided low friction and good wear properties to moderate loads.

  11. Synthesis and Characterization of an Alumina Forming Nanolaminated Boride: MoAlB

    NASA Astrophysics Data System (ADS)

    Kota, Sankalp; Zapata-Solvas, Eugenio; Ly, Alexander; Lu, Jun; Elkassabany, Omar; Huon, Amanda; Lee, William E.; Hultman, Lars; May, Steve J.; Barsoum, Michel W.

    2016-05-01

    The ‘MAlB’ phases are nanolaminated, ternary transition metal borides that consist of a transition metal boride sublattice interleaved by monolayers or bilayers of pure aluminum. However, their synthesis and properties remain largely unexplored. Herein, we synthesized dense, predominantly single-phase samples of one such compound, MoAlB, using a reactive hot pressing method. High-resolution scanning transmission electron microscopy confirmed the presence of two Al layers in between a Mo-B sublattice. Unique among the transition metal borides, MoAlB forms a dense, mostly amorphous, alumina scale when heated in air. Like other alumina formers, the oxidation kinetics follow a cubic time-dependence. At room temperature, its resistivity is low (0.36–0.49 μΩm) and – like a metal – drops linearly with decreasing temperatures. It is also a good thermal conductor (35 Wm‑1K‑1 at 26 °C). In the 25–1300 °C temperature range, its thermal expansion coefficient is 9.5 × 10‑6 K‑1. Preliminary results suggest the compound is stable to at least 1400 °C in inert atmospheres. Moderately low Vickers hardness values of 10.6 ± 0.3 GPa, compared to other transition metal borides, and ultimate compressive strengths up to 1940 ± 103 MPa were measured at room temperature. These results are encouraging and warrant further study of this compound for potential use at high temperatures.

  12. Synthesis and Characterization of an Alumina Forming Nanolaminated Boride: MoAlB.

    PubMed

    Kota, Sankalp; Zapata-Solvas, Eugenio; Ly, Alexander; Lu, Jun; Elkassabany, Omar; Huon, Amanda; Lee, William E; Hultman, Lars; May, Steve J; Barsoum, Michel W

    2016-01-01

    The 'MAlB' phases are nanolaminated, ternary transition metal borides that consist of a transition metal boride sublattice interleaved by monolayers or bilayers of pure aluminum. However, their synthesis and properties remain largely unexplored. Herein, we synthesized dense, predominantly single-phase samples of one such compound, MoAlB, using a reactive hot pressing method. High-resolution scanning transmission electron microscopy confirmed the presence of two Al layers in between a Mo-B sublattice. Unique among the transition metal borides, MoAlB forms a dense, mostly amorphous, alumina scale when heated in air. Like other alumina formers, the oxidation kinetics follow a cubic time-dependence. At room temperature, its resistivity is low (0.36-0.49 μΩm) and - like a metal - drops linearly with decreasing temperatures. It is also a good thermal conductor (35 Wm(-1)K(-1) at 26 °C). In the 25-1300 °C temperature range, its thermal expansion coefficient is 9.5 × 10(-6 )K(-1). Preliminary results suggest the compound is stable to at least 1400 °C in inert atmospheres. Moderately low Vickers hardness values of 10.6 ± 0.3 GPa, compared to other transition metal borides, and ultimate compressive strengths up to 1940 ± 103 MPa were measured at room temperature. These results are encouraging and warrant further study of this compound for potential use at high temperatures. PMID:27220751

  13. Synthesis and Characterization of an Alumina Forming Nanolaminated Boride: MoAlB

    PubMed Central

    Kota, Sankalp; Zapata-Solvas, Eugenio; Ly, Alexander; Lu, Jun; Elkassabany, Omar; Huon, Amanda; Lee, William E.; Hultman, Lars; May, Steve J.; Barsoum, Michel W.

    2016-01-01

    The ‘MAlB’ phases are nanolaminated, ternary transition metal borides that consist of a transition metal boride sublattice interleaved by monolayers or bilayers of pure aluminum. However, their synthesis and properties remain largely unexplored. Herein, we synthesized dense, predominantly single-phase samples of one such compound, MoAlB, using a reactive hot pressing method. High-resolution scanning transmission electron microscopy confirmed the presence of two Al layers in between a Mo-B sublattice. Unique among the transition metal borides, MoAlB forms a dense, mostly amorphous, alumina scale when heated in air. Like other alumina formers, the oxidation kinetics follow a cubic time-dependence. At room temperature, its resistivity is low (0.36–0.49 μΩm) and – like a metal – drops linearly with decreasing temperatures. It is also a good thermal conductor (35 Wm−1K−1 at 26 °C). In the 25–1300 °C temperature range, its thermal expansion coefficient is 9.5 × 10−6 K−1. Preliminary results suggest the compound is stable to at least 1400 °C in inert atmospheres. Moderately low Vickers hardness values of 10.6 ± 0.3 GPa, compared to other transition metal borides, and ultimate compressive strengths up to 1940 ± 103 MPa were measured at room temperature. These results are encouraging and warrant further study of this compound for potential use at high temperatures. PMID:27220751

  14. Direct Hydrogenation Magnesium Boride to Magnesium Borohydride: Demonstration of >11 Weight Percent Reversible Hydrogen Storage

    SciTech Connect

    Severa, Godwin; Ronnebro, Ewa; Jensen, Craig M.

    2010-11-16

    We here for the first time demonstrate direct hydrogenation of magnesium boride, MgB2, to magnesium borohydride, Mg(BH4)2 at 900 bar H2-pressures and 400°C. Upon 14.8wt% hydrogen release, the end-decomposition product of Mg(BH4)2 is MgB2, thus, this is a unique reversible path here obtaining >11wt% H2 which implies promise for a fully reversible hydrogen storage material.

  15. Heteroleptic naphthalo-phthalocyaninates of lutetium: synthesis and spectral and conductivity properties.

    PubMed

    Dubinina, Tatiana V; Kosov, Anton D; Petrusevich, Elizaveta F; Maklakov, Sergey S; Borisova, Nataliya E; Tomilova, Larisa G; Zefirov, Nikolay S

    2015-05-01

    Novel heteroleptic naphthalo-phthalocyaninates of lutetium possessing a symmetrical substituted naphthalocyanine deck were synthesized on the basis of two preformed synthetic blocks: naphthalocyanine ligand and lutetium phthalocyaninates. The compounds obtained were characterized by (1)H NMR and high-resolution MALDI-TOF/TOF mass spectrometry. The correlation between the nature of the substituents and the spectral properties of the target complexes was determined by the introduction of electron-donating (aryl-, aryloxy-) or electron-withdrawing (chloro-) substituents into the phthalocyanine deck. In addition, the nature of peripheral substituents was shown not to affect drastically the phthalocyanine conductivity and activation energy. Conductivity properties depend on thin film morphology which, in turn, relies on intermolecular π-π interactions. PMID:25826576

  16. Distinct surface hydration behaviors of boron-rich boride thin film coatings

    NASA Astrophysics Data System (ADS)

    Lu, Xinhong; Liu, Wei; Ouyang, Jun; Tian, Yun

    2014-08-01

    In this work, the surface boron chemical states and surface hydration behaviors of the as-deposited and annealed boron-rich boride thin film coatings, including AlMgB14, TiB2 and AlMgB14-TiB2, were systematically studied by use of X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The XPS results indicate that boron at annealed AlMgB14 film surface can be oxidized; surprisingly, such oxidation does not lead to the formation of boric acid in ambient air. Instead, boric acid can be produced at the surface of annealed TiB2 film and AlMgB14-TiB2 film. It is shown, via the water contact angle measurements, that these boride films exhibit distinct surface wettability characteristics, which are believed to result in the observed surface hydration processes. Furthermore, we found anatase TiO2 formation plays a major role in the surface wetting behaviors for these boride films.

  17. Structure of superhard tungsten tetraboride: a missing link between MB2 and MB12 higher borides.

    PubMed

    Lech, Andrew T; Turner, Christopher L; Mohammadi, Reza; Tolbert, Sarah H; Kaner, Richard B

    2015-03-17

    Superhard metals are of interest as possible replacements with enhanced properties over the metal carbides commonly used in cutting, drilling, and wear-resistant tooling. Of the superhard metals, the highest boride of tungsten--often referred to as WB4 and sometimes as W(1-x)B3--is one of the most promising candidates. The structure of this boride, however, has never been fully resolved, despite the fact that it was discovered in 1961--a fact that severely limits our understanding of its structure-property relationships and has generated increasing controversy in the literature. Here, we present a new crystallographic model of this compound based on refinement against time-of-flight neutron diffraction data. Contrary to previous X-ray-only structural refinements, there is strong evidence for the presence of interstitial arrangements of boron atoms and polyhedral bonding. The formation of these polyhedral--slightly distorted boron cuboctahedra--appears to be dependent upon the defective nature of the tungsten-deficient metal sublattice. This previously unidentified structure type has an intermediary relationship between MB2 and MB12 type boride polymorphs. Manipulation of the fractionally occupied metal and boron sites may provide insight for the rational design of new superhard metals. PMID:25733870

  18. Structure of superhard tungsten tetraboride: A missing link between MB2 and MB12 higher borides

    PubMed Central

    Lech, Andrew T.; Turner, Christopher L.; Mohammadi, Reza; Tolbert, Sarah H.; Kaner, Richard B.

    2015-01-01

    Superhard metals are of interest as possible replacements with enhanced properties over the metal carbides commonly used in cutting, drilling, and wear-resistant tooling. Of the superhard metals, the highest boride of tungsten—often referred to as WB4 and sometimes as W1–xB3—is one of the most promising candidates. The structure of this boride, however, has never been fully resolved, despite the fact that it was discovered in 1961—a fact that severely limits our understanding of its structure–property relationships and has generated increasing controversy in the literature. Here, we present a new crystallographic model of this compound based on refinement against time-of-flight neutron diffraction data. Contrary to previous X-ray–only structural refinements, there is strong evidence for the presence of interstitial arrangements of boron atoms and polyhedral bonding. The formation of these polyhedra—slightly distorted boron cuboctahedra—appears to be dependent upon the defective nature of the tungsten-deficient metal sublattice. This previously unidentified structure type has an intermediary relationship between MB2 and MB12 type boride polymorphs. Manipulation of the fractionally occupied metal and boron sites may provide insight for the rational design of new superhard metals. PMID:25733870

  19. Properties of Ce-activated alkali-lutetium double phosphate scintillators

    SciTech Connect

    Wiśniewski, D.; Wojtowicz, A. J.; Boatner, Lynn A

    2010-01-01

    The scintillation properties of Ce-activated alkali-lutetium double phosphate single crystals that vary with the alkali ion type and activation level are summarized and compared. The materials investigated here have been identified as fast and efficient scintillators for the detection of x-ray and radiation, and in case of Li3Lu(PO4)2:Ce, for thermal neutron detection as well.

  20. Lutetium(iii) aqua ion: On the dynamical structure of the heaviest lanthanoid hydration complex

    NASA Astrophysics Data System (ADS)

    Sessa, Francesco; Spezia, Riccardo; D'Angelo, Paola

    2016-05-01

    The structure and dynamics of the lutetium(iii) ion in aqueous solution have been investigated by means of a polarizable force field molecular dynamics (MD). An 8-fold square antiprism (SAP) geometry has been found to be the dominant configuration of the lutetium(iii) aqua ion. Nevertheless, a low percentage of 9-fold complexes arranged in a tricapped trigonal prism (TTP) geometry has been also detected. Dynamic properties have been explored by carrying out six independent MD simulations for each of four different temperatures: 277 K, 298 K, 423 K, 632 K. The mean residence time of water molecules in the first hydration shell at room temperature has been found to increase as compared to the central elements of the lanthanoid series in agreement with previous experimental findings. Water exchange kinetic rate constants at each temperature and activation parameters of the process have been determined from the MD simulations. The obtained structural and dynamical results suggest that the water exchange process for the lutetium(iii) aqua ion proceeds with an associative mechanism, in which the SAP hydration complex undergoes temporary structural changes passing through a 9-fold TTP intermediate. Such results are consistent with the water exchange mechanism proposed for heavy lanthanoid atoms.

  1. Lutetium(iii) aqua ion: On the dynamical structure of the heaviest lanthanoid hydration complex.

    PubMed

    Sessa, Francesco; Spezia, Riccardo; D'Angelo, Paola

    2016-05-28

    The structure and dynamics of the lutetium(iii) ion in aqueous solution have been investigated by means of a polarizable force field molecular dynamics (MD). An 8-fold square antiprism (SAP) geometry has been found to be the dominant configuration of the lutetium(iii) aqua ion. Nevertheless, a low percentage of 9-fold complexes arranged in a tricapped trigonal prism (TTP) geometry has been also detected. Dynamic properties have been explored by carrying out six independent MD simulations for each of four different temperatures: 277 K, 298 K, 423 K, 632 K. The mean residence time of water molecules in the first hydration shell at room temperature has been found to increase as compared to the central elements of the lanthanoid series in agreement with previous experimental findings. Water exchange kinetic rate constants at each temperature and activation parameters of the process have been determined from the MD simulations. The obtained structural and dynamical results suggest that the water exchange process for the lutetium(iii) aqua ion proceeds with an associative mechanism, in which the SAP hydration complex undergoes temporary structural changes passing through a 9-fold TTP intermediate. Such results are consistent with the water exchange mechanism proposed for heavy lanthanoid atoms. PMID:27250314

  2. Corrosion behavior of titanium boride composite coating fabricated on commercially pure titanium in Ringer's solution for bioimplant applications.

    PubMed

    Sivakumar, Bose; Singh, Raghuvir; Pathak, Lokesh Chandra

    2015-03-01

    The boriding of commercially pure titanium was performed at 850°C, 910°C, and 1050°C for varied soaking periods (1, 3 and 5h) to enhance the surface properties desirable for bioimplant applications. The coating developed was characterized for the evolution of phases, microstructure and morphology, microhardness, and consequent corrosion behavior in the Ringer's solution. Formation of the TiB2 layer at the outermost surface followed by the TiB whiskers across the borided CpTi is unveiled. Total thickness of the composite layer on the substrates borided at 850, 910, and 1050°C for 5h was found to be 19.1, 26.4, and 18.2μm respectively which includes <3μm thick TiB2 layer. The presence of TiB2 phase was attributed to the high hardness ~2968Hv15gf of the composite coating. The anodic polarization studies in the simulated body fluid unveiled a reduction in the pitting corrosion resistance after boriding the CpTi specimens. However, this value is >0.55VSCE (electrochemical potential in in-vivo physiological environment) and hence remains within the safe region. Both the untreated and borided CpTi specimens show two passive zones associated with different passivation current densities. Among the CpTi borided at various times and temperatures, a 3h treated shows better corrosion resistance. The corrosion of borided CpTi occurred through the dissolution of TiB2. PMID:25579920

  3. PREFACE: The 16th International Symposium on Boron, Borides and Related Materials (ISBB 2008)

    NASA Astrophysics Data System (ADS)

    Tanaka, Takaho

    2009-07-01

    This volume of Journal of Physics: Conference Series contains invited and contributed peer-reviewed papers that were presented at the 16th International Symposium on Boron, Borides and Related Materials (ISBB 2008), which was held on 7-12 September 2008, at Kunibiki Messe, Matsue, Japan. This triennial symposium has a half-century long history starting from the 1st meeting in 1959 at Asbury Park, New Jersey. We were very pleased to organize ISBB 2008, which gathered chemists, physicists, materials scientists as well as diamond and high-pressure researchers. This meeting had a strong background in the boron-related Japanese research history, which includes the discovery of superconductivity in MgB2 and development of Nd-Fe-B hard magnets and of YB66 soft X-ray monochromator. The scope of ISBB 2008 spans both basic and applied interdisciplinary research that is centered on boron, borides and related materials, and the collection of articles defines the state of the art in research on these materials. The topics are centered on: 1. Preparation of new materials (single crystals, thin films, nanostructures, ceramics, etc) under normal or extreme conditions. 2. Crystal structure and chemical bonding (new crystal structures, nonstoichiometry, defects, clusters, quantum-chemical calculations). 3. Physical and chemical properties (band structure, phonon spectra, superconductivity; optical, electrical, magnetic, emissive, mechanical properties; phase diagrams, thermodynamics, catalytic activity, etc) in a wide range of temperatures and pressures. 4. Applications and prospects (thermoelectric converters, composites, ceramics, coatings, etc) There were a few discoveries of new materials, such as nanomaterials, and developments in applications. Many contributions were related to 4f heavy Fermion systems of rare-earth borides. Exotic mechanisms of magnetism and Kondo effects have been discussed, which may indicate another direction of development of boride. Two special sessions

  4. Synthesis of Lutetium Phosphate/Apoferritin Core-Shell Nanoparticles for Potential Applications in Radioimmunoimaging and Radioimmunotherapy of Cancers

    SciTech Connect

    Wu, Hong; Engelhard, Mark H.; Wang, Jun; Fisher, Darrell R.; Lin, Yuehe

    2008-04-01

    We report a novel approach for synthesizing LuPO4/apoferritin core-shell nanoparticles based on an apoferritin template, conjugated to the protein biotin. To prepare the nanoparticle conjugates, we used non-radioactive lutetium as a model target or surrogate for radiolutetium (177Lu). The central cavity, multi-channel structure, and chemical properties of apoferritin are well-suited for sequentially diffusing lutetium and phosphate ions into the cavity--resulting in a stable core-shell composite. We characterized the synthesized LuPO4/apoferritin nanoparticle using transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS). We tested the pre-targeting capability of biotin-modified lutetium/apoferritin nanoparticle using streptavidin-modified magnetic beads and streptavidin-modified fluorescein isothiocyanate (FITC) tracer. This paper presents a simple, fast, and efficient method for synthesizing LuPO4/apoferritin nanoparticle conjugates with biotin for potential applications in radioimmunotherapy and radioimmunoimaging of cancer.

  5. Synthesis and Characterization of Low-Cost Superhard Transition-Metal Borides

    NASA Astrophysics Data System (ADS)

    Kaner, Richard

    2013-06-01

    The increasing demand for high-performance cutting and forming tools, along with the shortcomings of traditional tool materials such as diamond (unable to cut ferrous materials), cubic boron nitride (expensive) and tungsten carbide (relatively-low hardness), has motivated the search for new superhard materials for these applications. This has led us to a new class of superhard materials, dense refractory transition-metal borides, which promise to address some of the existing problems of conventional superhard materials. For example, we have synthesized rhenium diboride (ReB2) using arc melting at ambient pressure. This superhard material has demonstrated an excellent electrical conductivity and superior mechanical properties, including a Vickers hardness of 48.0 GPa (under an applied load of 0.49 N). To further increase the hardness and lower the materials costs, we have begun exploring high boron content metal borides including tungsten tetraboride (WB4) . We have synthesized WB4 by arc melting and studied its hardness and high-pressure behavior. With a similar Vickers hardness (43.3 GPa under a load of 0.49 N) and bulk modulus (326-339 GPa) to ReB2, WB4 offers a lower cost alternative and has the potential to be used in cutting tools. To further enhance the hardness of this superhard metal, we have created the binary and ternary solid solutions of WB4 with Cr, Mn and Ta, the results of which show a hardness increase of up to 20 percent. As with other metals, these metallic borides can be readily cut and shaped using electric discharge machining (EDM).

  6. Physical, chemical, and catalytic properties of borided cobalt Fischer-Tropsch catalysts

    SciTech Connect

    Wang, J.

    1987-01-01

    Unsupported and alumina-supported borided cobalt catalysts were prepared by chemical reduction of anhydrous cobalt acetate at 25/sup 0/C using B/sub 2/H/sub 6//THF or NaBH/sub 4//diglyme solution as the reducing agent. These catalysts were further activated in H/sub 2/ at 250/sup 0/C prior to use. The physical and chemical properties of these catalysts were characterized by chemical analysis, BET surface area measurements, H/sub 2/ and CO adsorption measurements, X-ray Diffraction, and Temperature Programmed Desorption of CO. The catalytic properties of these catalysts for hydrogenation of CO to hydrocarbons were investigated at 160 - 300/sup 0/C, 1 and 10 atm, and H/sub 2//CO ratio of 2 in a differential conversion range of less than 8%. The data show that unsupported, Na-free, borided cobalt is much more active than Na-containing borided cobalt and pure cobalt on a site basis. Similarly, CoB/Al/sub 2/O/sub 3/ is more than an order of magnitude more active than Co/Al/sub 2/O/sub 3/ is more than an order of magnitude more active than Co/Al/sub 2/O/sub 3/ but has similar selectivity; its selectivity for C/sub 5//sup +/ hydrocarbons, however, is very high (> 75 wt%) at low reaction temperatures (e.g. 170/sup 0/C) or at low H/sub 2//CO ratios (e.g. less than or equal to 1). The observed changes in catalytic and adsorption behavior are consistent with an electron-donor model in which boron atoms donate electrons to cobalt. Na was found to lower catalytic activity of cobalt while increasing selectivity for light hydrocarbons, olefins, and CO/sub 2/ products.

  7. Indentation strength of ultraincompressible rhenium boride, carbide, and nitride from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Zang, Chenpeng; Sun, Hong; Tse, John S.; Chen, Changfeng

    2012-07-01

    Using a recently developed first-principles approach for determining indentation strength [Z. Pan, H. Sun, and C. Chen, Phys. Rev. Lett.0031-9007 PRLTAO10.1103/PhysRevLett.98.135505 98, 135505 (2007); Z. Pan, H. Sun, and C. Chen, Phys. Rev. Lett.0031-9007 PRLTAO10.1103/PhysRevLett.102.055503 102, 055503 (2009)], we performed calculations of the ideal strength of hexagonal Re, Re3N, Re2N, Re2C, Re2B, and ReB2 in various shear deformation directions beneath the Vickers indentor. Our results show that the normal compressive pressure beneath the indentor weakens the strength of these electron-rich rhenium boride, carbide, and nitride compounds that belong to a distinct class of ultraincompressible and ultrahard materials. The reduction of indentation strength in these materials stems from lateral bond and volume expansions driven by the normal compressive pressure mediated by the high-density valence electrons in these structures. We compare the calculated indentation strength to the Poisson's ratio, which measures the lateral structural expansion, for the rhenium boride, carbide, and nitride compounds as well as diamond and cubic boron nitride. Our analysis indicates that although the normal pressure beneath the indentor generally leads to more significant reduction of indentation strength in materials with larger Poisson's ratios, crystal and electronic structures also play important roles in determining the structural response under indentation. The present study reveals structural deformation modes and the underlying atomistic mechanisms in transition-metal boride, carbide, and nitride compounds under the Vickers indentation. The results are distinctive from those of the traditional covalent superhard materials. The insights obtained from this work have important implications for further exploration and design of ultrahard materials.

  8. Metal-boride catalysts for indirect liquefaction. Quarterly technical progress report, December 1, 1982-February 28, 1983

    SciTech Connect

    Bartholomew, C.H.

    1983-03-15

    Four iron-boride catalysts were prepared. Washing with methanol did not change the iron phase composition as did water. Potassium borohydride reduction produces essentially the same iron phases as sodium borohydride reduction. Solution phase reductions with NH/sub 3/BH/sub 3/ were not productive. Reduction of ferric citrate with sodium borohydride produced a highly magnetic Fe/sub 2/B which was easily washed. Reduction of cobalt boride catalysts at a low temperature resulted in a catalyst with unusual selectivities in CO hydrogenation, i.e. the product contained more than 95% C/sub 5/-C/sub 16/ hydrocarbons. However, this catalyst deactivated rapidly.

  9. Phase I trial of motexafin-lutetium-mediated interstitial photodynamic therapy in patients with locally recurrent prostate cancer

    NASA Astrophysics Data System (ADS)

    Stripp, Diana C. H.; Mick, Rosemarie; Zhu, Timothy C.; Whittington, Richard; Smith, Debbie; Dimofte, Andreea; Finlay, Jarod C.; Miles, Jeremy; Busch, Theresa M.; Shin, Daniel; Kachur, Alex; Tochner, Zelig A.; Malkowicz, S. Bruce; Glatstein, Eli; Hahn, Stephen M.

    2004-06-01

    Therapeutic options for patients with locally recurrent prostate cancer after treatment with radiation therapy are limited. An ongoing Phase I trial of interstitial photodynamic therapy (PDT) with the photosensitizer motexafin lutetium (MLu) was initiated in year 2000 for men with locally recurrent prostate cancer. The primary objective of this trial is to determine the maximally tolerated dose of motexafin lutetium-mediated PDT. Twelve men with biopsy-proven recurrent prostate cancer and no evidence of distant metastatic disease have been enrolled. Pre-treatment evaluation included an MRI of the prostate, bone scan, laboratory studies, cystoscopy, and transrectal ultrasound. Treatment plans were generated based upon the ultrasound findings. PDT dose was escalated by increasing the motexafin lutetium dose, increasing the 732 nm light dose, and decreasing the drug-light interval. Motexafin lutetium doses ranged from 0.5 to 2 mg/kg administered IV 3, 6, or 24 hours prior to 732 nm light delivery. The light dose measured in real time with in situ spherical detectors was 25-100 J/cm2 for all patients. Light was delivered through optical fibers inserted through a transperineal brachytherapy template in the operating room and optical property measurements were made before and after light therapy. Prostate biopsies were obtained before and after light delivery for spectrofluorometric measurements of photosensitizer uptake. Twelve patients have completed protocol treatment on eight dose levels without dose-limiting toxicity. Grade I PDT-related genitourinary symptoms were observed. One patient had Grade II urinary urgency that was urinary catheter-related. No rectal or other GI PDT-related toxicities were observed. Measurements of motexafin lutetium in prostate tissue demonstrated the presence of photosensitizer at all dose levels. Conclusions: Motexafin lutetium-mediated PDT designed to treat comprehensively the entired prostate gland has been well-tolerated at the doses

  10. Electroplating of the superconductive boride MgB2 from molten salts

    NASA Astrophysics Data System (ADS)

    Abe, Hideki; Yoshii, Kenji; Nishida, Kenji; Imai, Motoharu; Kitazawa, Hideaki

    2005-02-01

    An electroplating technique of the superconductive boride MgB2 onto graphite substrates is reported. Films of MgB2 with a thickness of tens micrometer were fabricated on the planar and curved surfaces of graphite substrates by means of electrolysis on a mixture of magnesium chloride, potassium chloride, sodium chloride, and magnesium borate fused at 600 °C under an Ar atmosphere. The electrical resistivity and magnetization measurements revealed that the electroplated MgB2 films undergo a superconducting transition with the critical temperature (Tc) of 36 K.

  11. Improved carbides and new borides for HVOF and their coating properties

    SciTech Connect

    Froning, M.J.; Keller, H.

    1995-12-31

    In the presented paper, investigations on HVOF coatings produced from a new family of powders will be discussed. The influence of microstructure, composition and production methods will be discussed in view of powder properties and resulting coating properties. New boride powders and coatings will be compared with regard to their properties deposition, efficiency, hardness, surface roughness, bond strength, and wear against commercial WC-Co and cr3C2-NiCr coatings. Additionally, improved WC- and CrC-based powders and coatings will be compared with regard to oxidation and erosion resistance.

  12. Infiltration processing of boron carbide-, boron-, and boride-reactive metal cermets

    DOEpatents

    Halverson, Danny C.; Landingham, Richard L.

    1988-01-01

    A chemical pretreatment method is used to produce boron carbide-, boron-, and boride-reactive metal composites by an infiltration process. The boron carbide or other starting constituents, in powder form, are immersed in various alcohols, or other chemical agents, to change the surface chemistry of the starting constituents. The chemically treated starting constituents are consolidated into a porous ceramic precursor which is then infiltrated by molten aluminum or other metal by heating to wetting conditions. Chemical treatment of the starting constituents allows infiltration to full density. The infiltrated precursor is further heat treated to produce a tailorable microstructure. The process at low cost produces composites with improved characteristics, including increased toughness, strength.

  13. Growth of epitaxial bismuth and gallium substituted lutetium iron garnet films by pulsed laser deposition

    SciTech Connect

    Leitenmeier, Stephan; Heinrich, Andreas; Lindner, Joerg K. N.; Stritzker, Bernd

    2006-04-15

    Epitaxial bismuth and gallium substituted lutetium iron garnet thin films have been grown on (100) oriented gadolinium gallium garnet Gd{sub 3}Ga{sub 5}O{sub 12} substrates by pulsed laser deposition. The films have been studied using x-ray diffraction, high resolution x-ray diffraction, Rutherford backscattering spectroscopy, transmission electron microscopy, and electron diffraction. We obtained smooth films with thicknesses between 0.3 and 1.0 {mu}m showing good crystalline quality and epitaxial growth.

  14. Light-emitting diode versus laser irradiation phototherapy with lutetium texaphyrin (PCI-0123)

    NASA Astrophysics Data System (ADS)

    Woodburn, Kathryn W.; Young, Stuart W.; Qing, Fan; Miles, Dale R.; Thiemann, Patricia A.

    1997-05-01

    Lutetium texaphyrin (PCI-0123) is presently in clinical trials for the treatment of neoplasms. An argon-pumped dye laser has mostly been used to generate light for PCI-0123 photoactivation. However, lasers are expensive and produce a limited area of illumination, so the efficacy of light emitting diodes (LEDs) was investigated. An LED array was developed so that the spectral emission matched the far red absorption spectrum of PCI-0123. A preclinical PDT efficacy study comparing the laser and the LED was undertaken using EMT6-bearing animals. The LED and laser light sources were statistically comparable in eradicating the murine mammary sarcomas using PCI-0123 as the photosensitizer.

  15. Thermodynamic modeling of chemical equilibria in liquid-liquid extraction of lutetium

    SciTech Connect

    Sreelatha, S.; Sai, P.S.T.; Prasada Rao, T.; Narayanan, C.S.; Damodaran, A.D. )

    1991-12-01

    The extraction equilibrium data of lutetium from sodium succinate solution with Aliquat 336 in benzene is systematically investigated. The aqueous phase metal complexation and polymerization in the organic phase are taken into account in obtaining extraction coefficients, stability constants, hydrolysis constants, solubility product, and extraction constants. A thermodynamic model of the above equilibrium extraction data is developed for use in computer simulation of the extraction process. The correlations are based on chemical mass action principles in which the metal complexation in the aqueous phase, polymerization in the organic phase, precipitation in the aqueous phase, and aqueous phase activity coefficients are considered. Extraction behavior of other lanthanides from a succinate medium is also discussed.

  16. Amorphous nickel boride membrane on a platinum–nickel alloy surface for enhanced oxygen reduction reaction

    PubMed Central

    He, Daping; Zhang, Libo; He, Dongsheng; Zhou, Gang; Lin, Yue; Deng, Zhaoxiang; Hong, Xun; Wu, Yuen; Chen, Chen; Li, Yadong

    2016-01-01

    The low activity of the oxygen reduction reaction in polymer electrolyte membrane fuel cells is a major barrier for electrocatalysis, and hence needs to be optimized. Tuning the surface electronic structure of platinum-based bimetallic alloys, a promising oxygen reduction reaction catalyst, plays a key role in controlling its interaction with reactants, and thus affects the efficiency. Here we report that a dealloying process can be utilized to experimentally fabricate the interface between dealloyed platinum–nickel alloy and amorphous nickel boride membrane. The coating membrane works as an electron acceptor to tune the surface electronic structure of the platinum–nickel catalyst, and this composite catalyst composed of crystalline platinum–nickel covered by amorphous nickel boride achieves a 27-times enhancement in mass activity relative to commercial platinum/carbon at 0.9 V for the oxygen reduction reaction performance. Moreover, this interactional effect between a crystalline surface and amorphous membrane can be readily generalized to facilitate the 3-times higher catalytic activity of commercial platinum/carbon. PMID:27503412

  17. Amorphous nickel boride membrane on a platinum-nickel alloy surface for enhanced oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    He, Daping; Zhang, Libo; He, Dongsheng; Zhou, Gang; Lin, Yue; Deng, Zhaoxiang; Hong, Xun; Wu, Yuen; Chen, Chen; Li, Yadong

    2016-08-01

    The low activity of the oxygen reduction reaction in polymer electrolyte membrane fuel cells is a major barrier for electrocatalysis, and hence needs to be optimized. Tuning the surface electronic structure of platinum-based bimetallic alloys, a promising oxygen reduction reaction catalyst, plays a key role in controlling its interaction with reactants, and thus affects the efficiency. Here we report that a dealloying process can be utilized to experimentally fabricate the interface between dealloyed platinum-nickel alloy and amorphous nickel boride membrane. The coating membrane works as an electron acceptor to tune the surface electronic structure of the platinum-nickel catalyst, and this composite catalyst composed of crystalline platinum-nickel covered by amorphous nickel boride achieves a 27-times enhancement in mass activity relative to commercial platinum/carbon at 0.9 V for the oxygen reduction reaction performance. Moreover, this interactional effect between a crystalline surface and amorphous membrane can be readily generalized to facilitate the 3-times higher catalytic activity of commercial platinum/carbon.

  18. Amorphous nickel boride membrane on a platinum-nickel alloy surface for enhanced oxygen reduction reaction.

    PubMed

    He, Daping; Zhang, Libo; He, Dongsheng; Zhou, Gang; Lin, Yue; Deng, Zhaoxiang; Hong, Xun; Wu, Yuen; Chen, Chen; Li, Yadong

    2016-01-01

    The low activity of the oxygen reduction reaction in polymer electrolyte membrane fuel cells is a major barrier for electrocatalysis, and hence needs to be optimized. Tuning the surface electronic structure of platinum-based bimetallic alloys, a promising oxygen reduction reaction catalyst, plays a key role in controlling its interaction with reactants, and thus affects the efficiency. Here we report that a dealloying process can be utilized to experimentally fabricate the interface between dealloyed platinum-nickel alloy and amorphous nickel boride membrane. The coating membrane works as an electron acceptor to tune the surface electronic structure of the platinum-nickel catalyst, and this composite catalyst composed of crystalline platinum-nickel covered by amorphous nickel boride achieves a 27-times enhancement in mass activity relative to commercial platinum/carbon at 0.9 V for the oxygen reduction reaction performance. Moreover, this interactional effect between a crystalline surface and amorphous membrane can be readily generalized to facilitate the 3-times higher catalytic activity of commercial platinum/carbon. PMID:27503412

  19. Electrochromic and gas adsorption properties of Langmuir-Blodgett films of lutetium bisphthalocyanine complexes

    SciTech Connect

    Rodriguez-Mendez, M.L.; Aroca, R. ); DeSaja, J.A. )

    1993-07-01

    The electrochromic behaviour, spectroscopic properties and gas chemisorption of ultra thin films of lutetium octa-4-phenyldiphthalocyanine (LuPc[sub 2][sup Ph]), and the lutetium octa-3-bromo-octa-5-tert-butylphthalocyanine (LuPc[sub 2][sup tBr]) are reported. Electrochromism was observed for Langmuir-Blodgett (LB) and films cast onto indium tin oxide (ITO) coated glass electrodes in aqueous KClO[sub 4] solution. Mixed LB films supported on ITO glass electrodes were more stable to repetitive cycling than cast films. Films of LuPc[sub 2][sup Ph] and LuPc[sub 2][sup tBr] were sensitive to electron-acceptor gases as observed by the changes in the electronic absorption spectra and the surface-enhanced resonance Raman scattering (SERRS) spectra. The presence of electron-withdrawing bromine atoms in the phthalocyanine ring increased the rate of desorption for chemisorbed electron-acceptor molecules. 10 refs., 8 figs., 3 tabs.

  20. Atomic and electronic structures of lutetium oxide Lu{sub 2}O{sub 3}

    SciTech Connect

    Kaichev, V. V.; Asanova, T. I.; Erenburg, S. B.; Perevalov, T. V.; Shvets, V. A.; Gritsenko, V. A.

    2013-02-15

    The chemical composition, electronic structure, structure, and physical properties a lutetium oxide Lu{sub 2}O{sub 3} film are studied by X-ray photoelectron spectroscopy, ellipsometry, and X-ray absorption spectroscopy. The short-range order in Lu{sub 2}O{sub 3} is found to correspond to its cubic modification. The binding energies of the 1s and 2p levels of oxygen and the 4d{sub 5/2} and 4f{sub 7/2} levels of lutetium are 529.2, 5.0 and 7.4, 195.9 eV, respectively. The energy gap determined from the electron energy loss spectrum of the film is 5.9 eV. The electron energy loss spectra have two peaks at 17.4 and 22.0 eV, which can be attributed to the excitation of bulk plasma oscillations. The dispersion of the refractive index is measured by spectral ellipsometry. The refractive index is shown to increase from 1.82 at 1.5 eV to 2.18 at 5.0 eV, and the high-frequency permittivity of Lu{sub 2}O{sub 3} is 3.31.

  1. On the photoelectron velocity-map imaging of lutetium monoxide anion LuO{sup −}

    SciTech Connect

    Liu, Zhiling; Xie, Hua; Qin, Zhengbo; Cong, Ran; Wu, Xia; Tang, Zichao Fan, Hongjun; Li, Quanjiang

    2014-01-21

    We report a combined photoelectron velocity-map imaging spectroscopy and density functional theory investigation on lutetium monoxide anion. Transition between the X {sup 1}Σ{sup +} anion electronic ground state and the neutral X {sup 2}Σ{sup +} electronic ground state is observed. Vibrationally resolved spectra were obtained at four different photon energies, providing a wealth of spectroscopic information for the electronic ground states of the anionic lutetium monoxide and corresponding neutral species. Franck-Condon simulations of the ground-state transition are performed to assign vibrational structure in the spectra and to assist in identifying the observed spectral bands. The electronic ground state of LuO{sup −} is found to have a vibrational frequency of 743 ± 10 cm{sup −1} and an equilibrium bond length of 1.841 Å. The electron affinity of LuO is measured to be 1.624 ± 0.002 eV. The fundamental frequency of ground-state LuO is estimated to be 839 ± 10 cm{sup −1}.

  2. Investigation of composition and chemical state of elements in iron boride by the method of X-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Alyoshin, V. G.; Kharlamov, A. I.; Prokopenko, V. M.

    1981-06-01

    The composition and chemical state of iron and boron in the surface layer of iron boride under different kinds of pretreatment of samples have been investigated by the method of X-ray photo-electron spectroscopy. It has been found that in the initial sample there is oxygen chemically combined with iron and boron atoms. Upon heating (450°C) in hydrogen, in argon, and in vacuo there occurs removal of oxygen only from iron atoms (no pure iron was found to be formed). Boron oxidizes and there probably appears a new surface combination of boron with oxygen in which the bonding energy of 1 s electrons is higher than that in B 2O 3. Treatment of the iron boride surface with argon ions and with protons ensures uniform removal of oxygen from iron and boron atoms. It has been found that thermal treatment of iron boride leads to depletion of iron atoms from the sample surface layer, and pickling with argon ions and with protons leads to strong enrichment. Iron boride samples subjected to Ar + and H + bombardment tend to undergo significant oxidation when subsequently exposed to air at room temperature.

  3. Synthesis of transition metal borides layers under pulsed electron-beams treatment in a vacuum for surface hardening of instrumental steels

    NASA Astrophysics Data System (ADS)

    Milonov, A. S.; Danzheev, B. A.; Smirnyagina, N. N.; Dasheev, D. E.; Kim, T. B.; Semenov, A. P.

    2015-11-01

    The saturation of the surface layers of metals and alloys with boron is conducted for increasing their surface hardness, wear resistance, etc. Multicomponent layers containing in its composition borides of refractory metals, as a rule, are formed by the methods of chemical- thermal processing in the interaction of boriding component with refractory one or by the method of saturation of refractory metal impurities or alloy with boron. In this work, we studied the features of vanadium and iron borides formation on the surface of instrumental steels U8A and R18 under the influence of intense electron beams in continuous and pulse modes.

  4. Preparation and sintering of refractory metal borides, carbides and nitrides of high purity

    SciTech Connect

    Sane, A.Y.

    1987-09-15

    The method of preparing a consolidated and purified Group IVb, Vb, or VIb refractory metal boride, carbide, nitride, or mixture, combination or cermet thereof by means of aided, reduced pressure and elevated temperature conditions is described. It consists of: (a) establishing a composition for a second stage reaction step of reaction sintering and adapted for enhanced production of desired product; (b) providing sintering aid at least in part together with the composition and resting the composition upon the sintering aid, which aid is solid at normal pressure and temperatures and aids via the vapor phase at the pressure and temperature conditions of the second stage reaction step; (c) reducing the pressure around the composition; (d) heating the composition at a temperature for sintering; while (e) establishing sintering aid atmosphere in contact with the composition; and (f) maintaining the heating for a time sufficient to consolidate the composition, and thereby prepare a consolidate and purified product.

  5. Valence fluctuations of europium in the boride Eu4Pd29+x B8

    NASA Astrophysics Data System (ADS)

    Gumeniuk, Roman; Schnelle, Walter; Ahmida, Mahmoud A.; Abd-Elmeguid, Mohsen M.; Kvashnina, Kristina O.; Tsirlin, Alexander A.; Leithe-Jasper, Andreas; Geibel, Christoph

    2016-03-01

    We synthesized a high-quality sample of the boride Eu4Pd29+x B8 (x  =  0.76) and studied its structural and physical properties. Its tetragonal structure was solved by direct methods and confirmed to belong to the Eu4Pd29B8 type. All studied physical properties indicate a valence fluctuating Eu state, with a valence decreasing continuously from about 2.9 at 5 K to 2.7 at 300 K. Maxima in the T dependence of the susceptibility and thermopower at around 135 K and 120 K, respectively, indicate a valence fluctuation energy scale on the order of 300 K. Analysis of the magnetic susceptibility evidences some inconsistencies when using the ionic interconfigurational fluctuation (ICF) model, thus suggesting a stronger relevance of hybridization between 4f and valence electrons compared to standard valence-fluctuating Eu systems.

  6. Identification of delamination failure of boride layer on common Cr-based steels

    NASA Astrophysics Data System (ADS)

    Taktak, Sukru; Tasgetiren, Suleyman

    2006-10-01

    Adhesion is an important aspect in the reliability of coated components. With low-adhesion of interfaces, different crack paths may develop depending on the local stress field at the interface and the fracture toughness of the coating, substrate, and interface. In the current study, an attempt has been made to identify the delamination failure of coated Cr-based steels by boronizing. For this reason, two commonly used steels (AISI H13, AISI 304) are considered. The steels contain 5.3 and 18.3 wt.% Cr, respectively. Boriding treatment is carried out in a slurry salt bath consisting of borax, boric acid, and ferrosilicon at a temperature range of 800 950 °C for 3, 5, and 7 h. The general properties of the boron coating are obtained by mechanical and metallographic characterization tests. For identification of coating layer failure, some fracture toughness tests and the Daimler-Benz Rockwell-C adhesion test are used.

  7. A new tetragonal boride phase in FeAl+B type alloys

    SciTech Connect

    Pierron, X.; Baker, I.

    1997-12-31

    The structure and composition of a previously unreported second phase were investigated in both Fe-43Al-0.12B and Fe-48Al-0.12B alloys. Energy dispersive x-ray and electron energy loss spectroscopy showed that the precipitates contained boron and were enriched in iron. This new boride phase had a tetragonal symmetry, with a{sub t} = 4a{sub B2} and c{sub t} = a{sub B2}, where a{sub B2} is the matrix lattice parameter. The effect of iron content and heat treatments on the microstructure of those two boron-doped FeAl alloys are discussed.

  8. Valence fluctuations of europium in the boride Eu4Pd(29+x)B8.

    PubMed

    Gumeniuk, Roman; Schnelle, Walter; Ahmida, Mahmoud A; Abd-Elmeguid, Mohsen M; Kvashnina, Kristina O; Tsirlin, Alexander A; Leithe-Jasper, Andreas; Geibel, Christoph

    2016-03-23

    We synthesized a high-quality sample of the boride Eu4Pd(29+x)B8 (x  =  0.76) and studied its structural and physical properties. Its tetragonal structure was solved by direct methods and confirmed to belong to the Eu4Pd29B8 type. All studied physical properties indicate a valence fluctuating Eu state, with a valence decreasing continuously from about 2.9 at 5 K to 2.7 at 300 K. Maxima in the T dependence of the susceptibility and thermopower at around 135 K and 120 K, respectively, indicate a valence fluctuation energy scale on the order of 300 K. Analysis of the magnetic susceptibility evidences some inconsistencies when using the ionic interconfigurational fluctuation (ICF) model, thus suggesting a stronger relevance of hybridization between 4f and valence electrons compared to standard valence-fluctuating Eu systems. PMID:26895077

  9. Cobalt-Boride: An efficient and robust electrocatalyst for Hydrogen Evolution Reaction

    NASA Astrophysics Data System (ADS)

    Gupta, Suraj; Patel, Nainesh; Miotello, Antonio; Kothari, D. C.

    2015-04-01

    This work presents Cobalt-Boride (Co-B) as a non-noble, efficient and robust electrocatalyst for Hydrogen Evolution Reaction (HER) active in aqueous solution of wide pH values. In neutral solution, amorphous Co-B nanoparticles (30-50 nm size) generate high current density (10 mA/cm2) at low overpotential (250 mV) with Tafel slope of 75 mV/dec following Volmer-Heyrovsky reaction mechanism. Highly active Co surface sites created by electronic transfer from B to Co (as inferred from XPS analysis and supported by theoretical calculations) are responsible for this significant HER activity in wide range of pH (4-9) values. Stability and reusability tests also demonstrate the robust nature of the catalyst.

  10. Vacuum Ultraviolet Field Emission Lamp Consisting of Neodymium Ion Doped Lutetium Fluoride Thin Film as Phosphor

    PubMed Central

    Yanagihara, Masahiro; Tsuji, Takayuki; Yusop, Mohd Zamri; Tanemura, Masaki; Nagami, Tomohito; Fukuda, Kentaro; Suyama, Toshihisa; Yokota, Yuui; Yanagida, Takayuki; Yoshikawa, Akira

    2014-01-01

    A vacuum ultraviolet (VUV) field emission lamp was developed by using a neodymium ion doped lutetium fluoride (Nd3+ : LuF3) thin film as solid-state phosphor and carbon nanofiber field electron emitters. The thin film was synthesized by pulsed laser deposition and incorporated into the lamp. The cathodoluminescence spectra of the lamp showed multiple emission peaks at 180, 225, and 255 nm. These emission spectra were in good agreement with the spectra reported for the Nd3+ : LuF3 crystal. Moreover, application of an acceleration voltage effectively increased the emission intensity. These results contribute to the performance enhancement of the lamp operating in the VUV region. PMID:25302320

  11. Photoelectric conversion and electrochromic properties of lutetium tetrakis(tert-butyl)bisphthalocyaninate

    SciTech Connect

    Hu, Andrew Teh; Hu Tenyi; Liu Lungchang

    2003-12-10

    Both photoelectric and electrochromic effects on lutetium tetrakis(tert-butyl)bisphthalocyaninate (Lu(TBPc){sub 2}) have been carried out in this study. Lu(TBPc){sub 2} is known for its electrochromic performance, but its photoelectric effect has not mentioned in the literature. The electrochromic properties of Lu(TBPc){sub 2} have been measured by cyclic voltammetry (CV) and UV-Vis spectrometer at the same time. It takes less than 1.5 s for the color to change from red to green under 0.9 V. Its cycle life is at least over 500 times. Furthermore, we also investigate its photoelectric conversion properties. Its photoelectric cell exhibits a positive photo-electricity conversion effect with a short-circuit photocurrent (46.4 {mu}A/cm{sup 2}) under illumination of white light (1.201 mW/cm{sup 2})

  12. Photoemission spectroscopy study of the lanthanum lutetium oxide/silicon interface

    SciTech Connect

    Nichau, A.; Schnee, M.; Schubert, J.; Bernardy, P.; Hollaender, B.; Buca, D.; Mantl, S.; Besmehn, A.; Breuer, U.; Rubio-Zuazo, J.; Castro, G. R.; Muecklich, A.; Borany, J. von

    2013-04-21

    Rare earth oxides are promising candidates for future integration into nano-electronics. A key property of these oxides is their ability to form silicates in order to replace the interfacial layer in Si-based complementary metal-oxide field effect transistors. In this work a detailed study of lanthanum lutetium oxide based gate stacks is presented. Special attention is given to the silicate formation at temperatures typical for CMOS processing. The experimental analysis is based on hard x-ray photoemission spectroscopy complemented by standard laboratory experiments as Rutherford backscattering spectrometry and high-resolution transmission electron microscopy. Homogenously distributed La silicate and Lu silicate at the Si interface are proven to form already during gate oxide deposition. During the thermal treatment Si atoms diffuse through the oxide layer towards the TiN metal gate. This mechanism is identified to be promoted via Lu-O bonds, whereby the diffusion of La was found to be less important.

  13. Refractory Boride Formation and Microstructure Evolution during Solidification of Titanium-Boron and Titanium Aluminum-Boron Alloys

    NASA Astrophysics Data System (ADS)

    Hyman, Mark Edward

    1990-01-01

    gamma-TiAl alloys targeted for use as a structural material in advanced aerospace applications lack adequate creep strength at high temperatures. Incorporation of hard refractory second phase particles (e.g. TiB _2) exhibiting large aspect ratios (i.e. needles) can increase creep strength by constraining the plastic flow of the matrix during high temperature service. Matrix microstructure evolution and refractory boride formation in binary Ti-B and Ti-(25-52) at% Al and <= ~ 6 at% B alloys during conventional solidification is examined. The effects of rapid solidification processing (RSP) on microstructure evolution and boride morphology in ternary alloys is examined in electromagnetically levitated droplets processed via gas and splat quenching. A liquidus projection near the Ti-Al edge binary is deduced from a combination of computer modelling efforts and experimental evidence. The primary fields of crystallization sequentially traversed with increasing Al content starting from the Ti-B edge binary are: TiB to Ti_3B_4 to TiB_2 and beta to alpha to gamma for B-rich (i.e. ~5 at% B) and dilute alloys, respectively. A monovariant line of the type, L to M + TiB_2 (where M = beta, alpha , and gamma) was found to run slightly below the ~1 at% B isoconcentration line near the equiatomic TiAl composition. Matrix microstructure evolution and boride formation in these ternary alloys can be explained using the proposed liquidus projection for the Ti-Al-B system. TiB_2 forms in Ti-Al-B alloys (i.e. >= 35 at% Al) with various morphologies--blocky, plate/needle and flakes--and are extensively characterized by TEM and SEM. Their growth mechanisms leading to their various morphologies is discussed. Aside from the boride phases formed, the solidification microstructures of the Ti-Al -B alloys of interest showed essentially the same constituent phases as those of binary Ti-Al alloys of similar composition. Characterization of supercooled ternary droplets dilute in B (i.e. <=1 at% B

  14. PREFACE: The 16th International Symposium on Boron, Borides and Related Materials (ISBB 2008)

    NASA Astrophysics Data System (ADS)

    Tanaka, Takaho

    2009-07-01

    This volume of Journal of Physics: Conference Series contains invited and contributed peer-reviewed papers that were presented at the 16th International Symposium on Boron, Borides and Related Materials (ISBB 2008), which was held on 7-12 September 2008, at Kunibiki Messe, Matsue, Japan. This triennial symposium has a half-century long history starting from the 1st meeting in 1959 at Asbury Park, New Jersey. We were very pleased to organize ISBB 2008, which gathered chemists, physicists, materials scientists as well as diamond and high-pressure researchers. This meeting had a strong background in the boron-related Japanese research history, which includes the discovery of superconductivity in MgB2 and development of Nd-Fe-B hard magnets and of YB66 soft X-ray monochromator. The scope of ISBB 2008 spans both basic and applied interdisciplinary research that is centered on boron, borides and related materials, and the collection of articles defines the state of the art in research on these materials. The topics are centered on: 1. Preparation of new materials (single crystals, thin films, nanostructures, ceramics, etc) under normal or extreme conditions. 2. Crystal structure and chemical bonding (new crystal structures, nonstoichiometry, defects, clusters, quantum-chemical calculations). 3. Physical and chemical properties (band structure, phonon spectra, superconductivity; optical, electrical, magnetic, emissive, mechanical properties; phase diagrams, thermodynamics, catalytic activity, etc) in a wide range of temperatures and pressures. 4. Applications and prospects (thermoelectric converters, composites, ceramics, coatings, etc) There were a few discoveries of new materials, such as nanomaterials, and developments in applications. Many contributions were related to 4f heavy Fermion systems of rare-earth borides. Exotic mechanisms of magnetism and Kondo effects have been discussed, which may indicate another direction of development of boride. Two special sessions

  15. Interlayer utilization (including metal borides) for subsequent deposition of NSD films via microwave plasma CVD on 316 and 440C stainless steels

    NASA Astrophysics Data System (ADS)

    Ballinger, Jared

    Diamond thin films have promising applications in numerous fields due to the extreme properties of diamonds in conjunction with the surface enhancement of thin films. Biomedical applications are numerous including temporary implants and various dental and surgical instruments. The unique combination of properties offered by nanostructured diamond films that make it such an attractive surface coating include extreme hardness, low obtainable surface roughness, excellent thermal conductivity, and chemical inertness. Regrettably, numerous problems exist when attempting to coat stainless steel with diamond generating a readily delaminated film: outward diffusion of iron to the surface, inward diffusion of carbon limiting necessary surface carbon precursor, and the mismatch between the coefficients of thermal expansion yielding substantial residual stress. While some exotic methods have been attempted to overcome these hindrances, the most common approach is the use of an intermediate layer between the stainless steel substrate and the diamond thin film. In this research, both 316 stainless steel disks and 440C stainless steel ball bearings were tested with interlayers including discrete coatings and graded, diffusion-based surface enhancements. Titanium nitride and thermochemical diffusion boride interlayers were both examined for their effectiveness at allowing for the growth of continuous and adherent diamond films. Titanium nitride interlayers were deposited by cathodic arc vacuum deposition on 440C bearings. Lower temperature diamond processing resulted in improved surface coverage after cooling, but ultimately, both continuity and adhesion of the nanostructured diamond films were unacceptable. The ability to grow quality diamond films on TiN interlayers is in agreement with previous work on iron and low alloy steel substrates, and the similarly seen inadequate adhesion strength is partially a consequence of the lacking establishment of an interfacial carbide phase

  16. Pt-B System Revisited: Pt2B, a New Structure Type of Binary Borides. Ternary WAl12-Type Derivative Borides.

    PubMed

    Sologub, Oksana; Salamakha, Leonid; Rogl, Peter; Stöger, Berthold; Bauer, Ernst; Bernardi, Johannes; Giester, Gerald; Waas, Monika; Svagera, Robert

    2015-11-16

    On the basis of a detailed study applying X-ray single-crystal and powder diffraction, differential scanning calorimetry, and scanning electron microscopy analysis, it was possible to resolve existing uncertainties in the Pt-rich section (≥65 atom % Pt) of the binary Pt-B phase diagram above 600 °C. The formation of a unique structure has been observed for Pt2B [X-ray single-crystal data: space group C2/m, a = 1.62717(11) nm, b = 0.32788(2) nm, c = 0.44200(3) nm, β = 104.401(4)°, RF2 = 0.030]. Within the homogeneity range of "Pt3B", X-ray powder diffraction phase analysis prompted two structural modifications as a function of temperature. The crystal structure of "hT-Pt3B" complies with the hitherto reported structure of anti-MoS2 [space group P63/mmc, a = 0.279377(2) nm, c = 1.04895(1) nm, RF = 0.075, RI = 0.090]. The structure of the new "[Formula: see text]T-Pt3B" is still unknown. The formation of previously reported Pt∼4B has not been confirmed from binary samples. Exploration of the Pt-rich section of the Pt-Cu-B system at 600 °C revealed a new ternary compound, Pt12CuB6-y [X-ray single-crystal data: space group Im3̅, a = 0.75790(2) nm, y = 3, RF2 = 0.0129], which exhibits the filled WAl12-type structure accommodating boron in the interstitial trigonal-prismatic site 12e. The isotypic platinum-aluminum-boride was synthesized and studied. The solubility of copper in binary platinum borides has been found to attain ∼7 atom % Cu for Pt2B but to be insignificant for "[Formula: see text]T-Pt3B". The architecture of the new Pt2B structure combines puckered layers of boron-filled and empty [Pt6] octahedra (anti-CaCl2-type fragment) alternating along the x axis with a double layer of boron-semifilled [Pt6] trigonal prisms interbedded with a layer of empty tetrahedra and tetragonal pyramids (B-deficient α-T[Formula: see text]I fragment). Assuming boron vacancies ordering (space group R3), the Pt12CuB6-y structure exhibits serpentine-like columns of edge

  17. Pre-irradiation spatial distribution and stability of boride particles in rapidly solidified boron-doped stainless steels

    SciTech Connect

    Kanani, N.; Arnberg, L.; Harling, O.K.

    1981-01-01

    The time temperature behavior of boride particles has been studied in rapidly solidified ultra low carbon and nitrogen modified 316 stainless steel with 0.088% boron and 0.45% zirconium. The results show that the as-splat-cooled specimens exhibit precipitates at the grain boundaries and triple junctions. For temperatures up to about 750/sup 0/C no significant microstructural changes occur for short heat treatment times. In the temperature range of 750 to 950/sup 0/C, however, particles typically 100 to 500 A in diameter containing Zr and B are formed within the grains. Higher temperatures enhance the formation of such particles and give rise to particle networks. The results show that a fine and uniform distribution of the boride particles almost exclusively within the grains can be achieved if proper annealing conditions are chosen. This type of distribution is an important requirement for the homogeneous production of helium during neutron irradiation in fast reactors.

  18. Synthesis and characterization of nitrogen-phosphorus-based fire retardants modified by boride/propanetriol flyeidyl ether complex

    NASA Astrophysics Data System (ADS)

    Kang, Haijiao; Ma, Linrong; Zhang, Shifeng; Li, Jianzhang

    2015-07-01

    A Boride/propanetriol glyeidyl ether (B/PTGE) complex was employed to intensify the fire resistance capabilities of nitrogen-phosphorus (NP) fire retardants by reacting with phosphoric acid and urea to yield nitrogen-phosphorus-boron-PTGE fire retardants. The effects of NPB-PTGE fire retardants on wooden properties were characterized by limit oxygen index (LOI), cone calorimetry, X-ray Diffraction (XRD) and scanning electron microscopy (SEM). The results depict that the fire resistance of the B/PTGE complex modified by NP-based fire retardants was improved significantly. The PTGE was at 10% boride at 2%, and the treated wood has the LOI of 52%, which is 11.46% higher compared with woods treated with NP fire retardant.

  19. Features of the spectral dependences of transmittance of organic semiconductors based on tert-butyl substituted lutetium phthalocyanine molecules

    SciTech Connect

    Belogorokhov, I. A.; Tikhonov, E. V.; Dronov, M. A.; Belogorokhova, L. I.; Ryabchikov, Yu. V.; Tomilova, L. G.; Khokhlov, D. R.

    2011-11-15

    Vibronic properties of organic semiconductors based on tert-butyl substituted phthalocyanine lutetium diphthalocyanine molecules are studied by IR and Raman spectroscopy. It is shown that substitution of several carbon atoms in initial phthalocyanine (Pc) ligands with {sup 13}C isotope atoms causes a spectral shift in the main absorption lines attributed to benzene, isoindol, and peripheral C-H groups. A comparison of spectral characteristics showed that the shift can vary from 3 to 1 cm{sup -1}.

  20. Auto-ionization in lutetium iodide complexes: effect of the Iioic radius on lanthanide-iodide binding.

    PubMed

    Giesbrecht, Garth R; Gordon, John C; Clark, David L; Scott, Brian L

    2004-02-01

    Reaction of lutetium metal with 1.5 equiv of elemental iodine in 2-propanol leads to the isolation of LuI(3)(HO(i)Pr)(4) (1). An X-ray crystal structure reveals an ionic structure with well-separated [LuI(2)(HO(i)Pr)(4)] cations and [I] anions. Dissolution of 1 in pyridine generates the unusual alkoxide species [LuI(O(i)Pr)(py)(5)][I] (2) with the elimination of HI. An X-ray crystal structure of 2 confirmed the ionic nature of the compound, with the cationic portion of the complex exhibiting a seven-coordinated lutetium center with trans-disposed iodo and alkoxide ligands and five pyridine molecules equally displaced within the equatorial plane. Exposure of 2 to iodotrimethylsilane yields the expected triiodide species [LuI(2)(py)(5)][I] (3), which may also be prepared by refluxing commercially available LuI(3) in THF, followed by crystallization from a THF/pyridine mixture. The solid-state structure of 3 is similar to that of 2, with the alkoxide ligand having been replaced by an iodide. The formation of ionic structures 1-3 as opposed to the higher-coordinated neutral species may be traced to the small lutetium center and the presence of relatively strong Lewis bases within the coordination sphere of the metal. PMID:14753829

  1. Suppression of Boride Formation in Transient Liquid Phase Bonding of Pairings of Parent Superalloy Materials with Different Compositions and Grain Structures and Resulting Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Steuer, Susanne; Singer, Robert F.

    2014-07-01

    Two Ni-based superalloys, columnar grained Alloy 247 and single-crystal PWA1483, are joined by transient liquid phase bonding using an amorphous brazing foil containing boron as a melting point depressant. At lower brazing temperatures, two different morphologies of borides develop in both base materials: plate-like and globular ones. Their ratio to each other is temperature dependent. With very high brazing temperatures, the deleterious boride formation in Alloy 247 can be totally avoided, probably because the three-phase-field moves to higher alloying element contents. For the superalloy PWA1483, the formation of borides cannot be completely avoided at high brazing temperatures as incipient melting occurs. During subsequent solidification of these areas, Chinese-script-like borides precipitate. The mechanical properties (tensile tests at room and elevated temperatures and short-term creep rupture tests at elevated temperatures) for brazed samples without boride precipitation are very promising. Tensile strengths and creep times to 1 pct strain are comparable, respectively, higher than the ones of the weaker parent material for all tested temperatures and creep conditions (from 90 to 100 pct rsp. 175 to 250 pct).

  2. Preliminary investigation of zirconium boride ceramals for gas-turbine blade applications

    NASA Technical Reports Server (NTRS)

    Hoffman, Charles A

    1953-01-01

    Zirconium boride ZrB2 ceramals were investigated for possible gas-turbine-blade application. Included in the study were thermal shock evaluations of disks, preliminary turbine-blade operation, and observations of oxidation resistance. Thermal shock disks of the following three compositions were studied: (a) 97.5 percent ZrB2 plus 2.5 percent B by weight; (b) 92.5 percent ZrB2 plus 7.5 percent B by weight; and (c) 100 percent ZrB2. Thermal shock disks were quenched from temperatures of 1800 degrees, 2000 degrees, 2200 degrees, and 2400 degrees F. The life of turbine blades containing 93 percent ZrB2 plus 7 percent B by weight was determined in gas-turbine tests. The blades were run at approximately 1600 degrees F and 15,000 to 26,000 rpm. The thermal shock resistance of the 97.5 percent ZrB2 plus 2.5 percent boron ceramals compares favorably with that of TiC plus Co and TiC plus Ni ceramals. Oxidation of the disks during the thermal shock evaluation was slight for the comparatively short time (8.3 hr) up through 2000 degrees F. Oxidation of a specimen was severe, however, after 100 hours at 2000 degrees F. The turbine blade performance evaluation of the 93 percent ZrB2 plus 7 percent B composition was preliminary in scope ; no conclusions can be drawn.

  3. Mechanical properties of laser-deposited composite boride coating using nanoindentation

    SciTech Connect

    Agarwal, A.; Dahotre, N.B.

    2000-02-01

    Nanoindentation proves to be an effective technique to measure mechanical properties of composite materials, as it has high spatial resolution that enables estimation of properties even from fine grains, particles, and precipitates. The elastic modulus, E, of the composite boride coating deposited on AISI 1010 steel using the laser surface engineering (LSE) process has been computed using the nanoindentation technique. The highest E value of 477.3 GPa was achieved for coating in a sample that contained 0.69 volume fraction of TiB{sub 2} particles in the coating after processing with the highest laser traverse speed of 33 mm/s. A comparison between the theoretical and experimental computation of the elastic modulus suggests that theoretical elastic modulus values are lower than computed elastic modulus, as the latter includes the effect of dissolution of fine TiB{sub 2} particles in Fe matrix and metastable phase formation such as Fe{sub a}B{sub b} and Ti{sub m}B{sub n}. Dissolution of fine TiB{sub 2} particles in the Fe matrix in the coating region has been corroborated by transmission electron microscope (TEM) micrographs and corresponding energy-dispersive spectroscope (EDS) analysis and selected area diffraction (SAD) pattern.

  4. High borides: determining the features and details of lattice dynamics from neutron spectroscopy

    NASA Astrophysics Data System (ADS)

    Alekseev, P. A.

    2015-04-01

    We review wide-ranging research that combines inelastic neutron scattering spectroscopy with phenomenological and ab initio calculations to study the lattice dynamics and specifics of the electron-phonon interaction in three-dimensional boron cluster network systems M B_6 and M B12 ( M= {La}, {Sm}, and {Yb}, {Lu}, {Zr}). A close similarity is found between the atomic vibration spectra of these systems, which is fundamentally due to a strong hierarchy of interatomic interaction in these systems and which manifests itself both in the shape of the low-energy phonon dispersion and in the position of the high-energy edge of the spectrum. Manifestations of strong electron-phonon interactions in the lattice vibration spectra of borides are studied in detail and their relation to the nature and features of the valence-unstable state of rare-earth ions is examined. Resonance nonadiabaticity and magnetovibration interaction effects in spin- and valence-fluctuating systems are given special attention.

  5. Electronic spectra and magnetic properties of RB6, RB12 and RB2C2 borides

    NASA Astrophysics Data System (ADS)

    Baranovskiy, A. E.; Grechnev, G. E.; Logosha, A. V.; Svechkarev, I. V.; Filippov, V. B.; Shitsevalova, N. Yu.; Oga, O. J.; Eriksson, O.

    2006-01-01

    The electronic structures of R B6, R B12 and R B2C2 borides are studied ab initio by using the full-potential linear muffin-tin orbital method. This study includes the promising materials for spin electronics with reported high temperature ferromagnetism, namely, doped divalent hexaborides CaB6, SrB6, BaB6, and the CaB2C2 compound, as well as Kondo semiconductors, SmB6 and YbB12. For CaB6 and SrB6 a semiconducting band structure has been obtained, whereas a semimetallic ground state is revealed for CaB2C2 and doped hexaborides. For YB6, LaB6, CaB2C2 and the semimetallic Ba1-x Lax B6 alloys we have performed spin-polarized band structure calculations in an external field to evaluate the induced spin and orbital magnetic moments. These calculations indicate a feasibility of the field-induced weak ferromagnetic phase in CaB2C2 and the La doped hexaborides. The LSDA and GGA calculations for different spin configurations of YbB12 point to a possibility of antiferromagnetic coupling between Yb3+ ions. For SmB6 and YbB12 our LSDA, GGA, and LSDA+U calculations have not revealed the hybridization gap for configurations with trivalent Sm3+ and Yb3+.

  6. Charge-Driven Structural Transformation and Valence Versatility of Boron Sheets in Magnesium Borides

    NASA Astrophysics Data System (ADS)

    Zhao, Yufeng; Ban, Chunmei; Xu, Qiang; Wei, Suhuai; Dillon, Anne C.; National Renewable Energy Laboratory Team

    2011-03-01

    We show here that boron sheets exhibit highly versatile valence and the layered boron materials may hold the promise for a high energy-density magnesium-ion battery. Practically, boron is superior to previously known multi-valence materials, especially transition metal compounds, which are heavy, expensive, and often not benign. Based on Density Functional Theory simulations, we have predicted a series of stable magnesium borides MgBx with a broad range of stoichiometries, 2 x <= 16, by removing magnesium atoms from MgB2. The layered boron structures are preserved through an in-plane topological transformation between the hexagonal lattice domains and triangular domains. The process can be reversibly switched as the charge transfer changes with Mg insertion/extraction. The mechanism of such a charge-driven transformation originates from the versatile valence state of boron in its planar form. The discovery of these new physical phenomena suggests the design of a high-capacity magnesium-boron battery. Funded by the U.S. Department of Energy under subcontract number DE-AC36-08GO28308 through: DOE Office of Energy Efficiency and Renewable Energy Office of the Vehicle Technologies Program.

  7. Physical properties of zircon and scheelite lutetium orthovanadate: Experiment and first-principles calculation

    SciTech Connect

    Huang, Zuocai; Zhang, Lei; Pan, Wei

    2013-09-15

    Pure zircon and scheelite LuVO{sub 4} were prepared by solid state reaction and high-pressure route, respectively. Structure, elastic constants, lattice dynamics and thermodynamics of LuVO{sub 4} polymorphs were studied by experiments and first principles calculation. Calculations here are in good agreement with the experimental results. The phonon dispersions of LuVO{sub 4} polymorphs were studied by the linear response method. The calculated phonon dispersions show that zircon and scheelite LuVO{sub 4} phases are dynamically stable. Raman-active frequencies were measured and assigned to different modes according to the calculations. The internal frequencies shift downward after phase transition from zircon to scheelite. Born effective charge tensors elements for both phases are analyzed. The finite temperature thermodynamic properties of LuVO{sub 4} polymorphs were calculated from the obtained phonon density of states by quasi-harmonic approach. - Graphical abstract: Lutetium orthovanadate polymorphs were synthesized by SSR and HP methods and their physical and chemical properties, including lattice dynamical properties, were determined by DFT calculations and experiments. Display Omitted - Highlights: • Pure zircon and scheelite LuVO{sub 4} polymorphs were synthesized by solid state reaction and high-pressure route. • Chemical and physical properties of LuVO4 polymorphs were studied by experiments and first principles calculation. • Raman-active frequencies were measured and assigned to different modes according to the calculations. • Lattice dynamics of polymorphs were discussed in details.

  8. Structural, elastic and vibrational properties of nanocrystalline lutetium gallium garnet under high pressure.

    PubMed

    Monteseguro, V; Rodríguez-Hernández, P; Ortiz, H M; Venkatramu, V; Manjón, F J; Jayasankar, C K; Lavín, V; Muñoz, A

    2015-04-14

    An ab initio study of the structural, elastic and vibrational properties of the lutetium gallium garnet (Lu3Ga5O12) under pressure has been performed in the framework of the density functional theory, up to 95 GPa. Pressure dependence of the elastic constants and the mechanical stability are analyzed, showing that the garnet structure is mechanically unstable above 87 GPa. Lattice-dynamics calculations in bulk at different pressures have been performed and compared with Raman scattering measurements of the nanocrystalline Tm(3+)-doped Lu3Ga5O12 up to 60 GPa. The theoretical frequencies and pressure coefficients of the Raman active modes for bulk Lu3Ga5O12 are in good agreement with the experimental data measured for the nano-crystals. The contributions of the different atoms to the vibrational modes have been analyzed based on the calculated total and partial phonon density of states. The vibrational modes have been discussed in relation to the internal and external modes of the GaO4 tetrahedron and the GaO6 octahedron. The calculated infrared modes and their pressure dependence are also reported. Our results show that with this nano-garnet size the sample has essentially bulk properties. PMID:25767835

  9. Parameters for the RM1 Quantum Chemical Calculation of Complexes of the Trications of Thulium, Ytterbium and Lutetium

    PubMed Central

    Filho, Manoel A. M.; Dutra, José Diogo L.; Rocha, Gerd B.; Simas, Alfredo M.

    2016-01-01

    The RM1 quantum chemical model for the calculation of complexes of Tm(III), Yb(III) and Lu(III) is advanced. Subsequently, we tested the models by fully optimizing the geometries of 126 complexes. We then compared the optimized structures with known crystallographic ones from the Cambridge Structural Database. Results indicate that, for thulium complexes, the accuracy in terms of the distances between the lanthanide ion and its directly coordinated atoms is about 2%. Corresponding results for ytterbium and lutetium are both 3%, levels of accuracy useful for the design of lanthanide complexes, targeting their countless applications. PMID:27223475

  10. Parameters for the RM1 Quantum Chemical Calculation of Complexes of the Trications of Thulium, Ytterbium and Lutetium.

    PubMed

    Filho, Manoel A M; Dutra, José Diogo L; Rocha, Gerd B; Simas, Alfredo M; Freire, Ricardo O

    2016-01-01

    The RM1 quantum chemical model for the calculation of complexes of Tm(III), Yb(III) and Lu(III) is advanced. Subsequently, we tested the models by fully optimizing the geometries of 126 complexes. We then compared the optimized structures with known crystallographic ones from the Cambridge Structural Database. Results indicate that, for thulium complexes, the accuracy in terms of the distances between the lanthanide ion and its directly coordinated atoms is about 2%. Corresponding results for ytterbium and lutetium are both 3%, levels of accuracy useful for the design of lanthanide complexes, targeting their countless applications. PMID:27223475

  11. Investigation of high pressure phase transition and electronic properties of Lutetium Nitride

    NASA Astrophysics Data System (ADS)

    Singh, Sanjay Kumar; Verma, U. P.

    2015-09-01

    In the present manuscript we have investigated the structural, electronic and phase transition properties of the heaviest lanthanide lutetium nitride (LuN) compound using an ab initio calculations based on the density functional theory with Perdrew, Burke and Ernzerhof generalized gradient approximation (PBE-GGA) and Engel-Vosko(EV)-GGA as implemented in WIEN2k code. The basic ground state properties viz., lattice constants (a), bulk modulus (B0) and its pressure derivative (B0’) and total energy (E0) are calculated. The calculated values of lattice constant is 4.76 Å which is in good agreement with experimental value a= 4.76 A and other theoretical value. The relative stabilities of LuN at high pressures in the NaCl (B1), CsCl (B2), zinc blende (B3) and body centred tetragonal (BCT) structures are analysed. At compressed volumes, this compound is found to favour the CsCl phase rather the body centred tetragonal phase and zinc blende as observed in other lanthanum pnictides, which has been predicted by the total energy minimization. Under compression LuN undergoes a transition from NaCl to CsCl type structure at around 250.81 GPa with a volume collapse of 3.75%. To see the effect of functional we have also computed the band structure in B1 and B2 structure. Obtained result on band structure shows that LuN are semimetal by GGA while depicts semiconducting behaviour by EV-GGA. It shows metallic nature in B2 phase.

  12. Photodynamic therapy trials with lutetium texaphyrin (Lu-Tex) in patients with locally recurrent breast cancer

    NASA Astrophysics Data System (ADS)

    Renschler, Markus F.; Yuen, Alan R.; Panella, Timothy J.; Wieman, Thomas J.; Dougherty, Shona; Esserman, Laura; Panjehpour, Masoud; Taber, Scott W.; Fingar, Victor H.; Lowe, Elizabeth; Engel, Julie S.; Lum, Bert; Woodburn, Kathryn W.; Cheong, Wai-Fung; Miller, Richard A.

    1998-05-01

    Photodynamic therapy (PDT) of locally recurrent breast cancer has been limited to treatment of small lesions because of non- selective necrosis of adjacent normal tissues in the treatment field. Lutetium Texaphyrin (PCI-0123, Lu-Tex) is a photosensitizer with improved tumor localization that is activated by 732 nm light, which can penetrate through larger tumors. We have evaluated Lu-Tex in a Phase I trial and in an ongoing Phase II trial in women with locally recurrent breast cancer with large tumors who have failed radiation therapy. Patients received Lu-Tex intravenously by rapid infusion 3 hours before illumination of cutaneous or subcutaneous lesions. In Phase I, Lu-Tex doses were escalated from 0.6 to 7.2 mg/kg in 7 cohorts. Sixteen patients with locally recurrent breast cancer lesions were treated. Dose limiting toxicities above 5.5 mg/kg were pain in the treatment field during therapy, and dysesthesias in light exposed areas. No necrosis of normal tissues in the treated field was noticed. Responses were observed in 60% of evaluable patients [n equals 15, 27% complete remission (CR), 33% partial remission (PR)], with 63% of lesions responding (n equals 73: 45% CR, 18% PR). In Phase II, 25 patients have been studied to date, receiving two treatments ranging from 1.0 to 3.0 mg/kg at a 21 day interval. Treatment fields up to 480 cm2 in size were treated successfully and activity has been observed. Patients have experienced pain at the treatment site but no tissue necrosis. These studies demonstrate the feasibility of Lu-Tex PDT to large chest wall areas in women who have failed radiation therapy for the treatment of locally recurrent breast cancer. Treatment conditions are currently being optimized in the ongoing Phase II trials.

  13. Structural and electrochemical properties of lutetium bis-octachloro-phthalocyaninate nanostructured films. Application as voltammetric sensors.

    PubMed

    Alessio, P; Apetrei, C; Rubira, R J G; Constantino, C J L; Medina-Plazal, C; De Saja, J A; Rodríguez-Méndez, M L

    2014-09-01

    Thin films of the bis[2,3,9,10,16,17,23,24-octachlorophthalocyaninate] lutetium(III) complex (LuPc2Cl32) have been prepared by the Langmuir-Blodgett and the Langmuir-Schaefer (LS) techniques. The influence of the chlorine substituents in the structure of the films and in their spectroscopic, electrochemical and sensing properties has been evaluated. The π-A isotherms exhibit a monolayer stability greater than the observed in the unsubstituted analogue (LuPc2), being easily transferred to solid substrates, also in contrast to LuPc2. The LB and LS films present a linear growth forming stratified layers, monitored by UV-VIS absorption spectroscopy. The latter also revealed the presence of LuPc2Cl32 in the form of monomers and aggregates in both films. The FTIR data showed that the LuPc2Cl32 molecules present a non-preferential arrangement in both films. Monolayers of LB and LS were deposited onto 6 nm Ag island films to record surface-enhanced resonance Raman scattering (SERRS), leading to enhancement factors close to 2 x 10(3). Finally, LB and LS films deposited onto ITO glass have been successfully used as voltammetric sensors for the detection of catechol. The improved electroactivity of the LB and LS films has been confirmed by the reduction of the overpotential of the oxidation of catechol. The enhancement of the electrocatalytic effect observed in LB and LS films is the result of the nanostructured arrangement of the surface which increases the number of active sites. The sensors show a limit of detection in the range of 10(-5) mol/L. PMID:25924327

  14. Nano-Borides and Silicide Dispersed Composite Coating on AISI 304 Stainless Steel by Laser-Assisted HVOF Spray Deposition

    NASA Astrophysics Data System (ADS)

    Sharma, Prashant; Majumdar, Jyotsna Dutta

    2014-10-01

    The study concerned a detailed microstructural investigation of nano-borides (Cr2B and Ni3B) and nano-silicide (Ni2Si) dispersed γ-nickel composite coating on AISI 304 stainless steel by HVOF spray deposition of the NiCrBSi precursor powder and subsequent laser surface melting. A continuous wave diode laser with an applied power of 3 kW and scan speed of 20 mm/s in argon shroud was employed. The characterization of the surface in terms of microstructure, microtexture, phases, and composition were carried out and compared with the as-coated (high-velocity oxy-fuel sprayed) surface. Laser surface melting led to homogenization and refinement of microstructures with the formation of few nano-silicides of nickel along with nano-borides of nickel and chromium (Ni3B, Cr2B, and Cr2B3). A detailed microtexture analysis showed the presence of no specific texture in the as-sprayed and laser-melted surface of Cr2B and Ni3B phases. The average microhardness was improved to 750-900 VHN as compared to 250 VHN of the as-received substrate. Laser surface melting improved the microhardness further to as high as 1400 VHN due to refinement of microstructure and the presence of silicides.

  15. A new coprecipitation methodology with lutetium hydroxide for preconcentration of heavy metal ions in herbal plant samples.

    PubMed

    Soylak, Mustafa; Murat, Ipek

    2014-01-01

    A new coprecipitation methodology that used lutetium hydroxide as a precipitant for Cu(II), Pb(II), Mn(II), Co(II), Cd(II), Fe(III), and Ni(II) ions in herbal plant and water samples for analysis by atomic absorption spectrometry has been investigated. The parameters such as pH, amount of lutetium, and volume of aqueous sample were optimized for the recovery of these seven metals. The effects of concomitant ions on the separation-preconcentration of analytes were also checked. The validation of the procedure was checked with addition recovery tests and analysis of Standard Reference Material 1570a-Trace Elements in Spinach Leaves and TMDA-70 fortified lake water Certified Reference Material. The LODs for analyte ions were in the range of 1.7-7.2 microg/L. The application of the present procedure was successfully performed for the analysis of analyte contents of herbal plant samples from Turkey. PMID:25145156

  16. Piano-Stool Lutetium Amido and Imido Compounds Supported by a Constrained Bis(oxazoline)cyclopentadienyl Ligand.

    PubMed

    Lampland, Nicole L; Zhu, Jing; Hovey, Megan; Jana, Barun; Ellern, Arkady; Sadow, Aaron D

    2015-07-20

    {Bo(M)Cp(tet)}Lu(CH2Ph)2 (1; Bo(M)Cp(tet) = MeC(Ox(Me2))2C5Me4; Ox(Me2) = 4,4-dimethyl-2-oxazoline) was prepared in 95% yield from the reaction of Bo(M)Cp(tet)H and Lu(CH2Ph)3THF3. Compound 1 reacts with 1 or 2 equiv of H2NCH2R (R = C6H5, 1-C10H7) to give the corresponding imido complexes [{Bo(M)Cp(tet)}LuNCH2R]2 (R = C6H5 (2a), 1-C10H7 (2b)) or amido complexes {Bo(M)Cp(tet)}Lu(NHCH2R)2 (R = C6H5 (3a), 1-C10H7 (3b)). Once isolated, the imido species are insoluble in nonprotic organic solvents. Crystallographic characterization reveals dimeric [{Bo(M)Cp(tet)}LuNCH2(1-C10H7)]2 in the solid state. The reaction of 1 and NH3B(C6F5)3 affords crystallographically characterized {Bo(M)Cp(tet)}Lu{NHB(C6F5)2}C6F5. This species is proposed to form via a transient lutetium imido, which undergoes C6F5 migration to the lutetium center. PMID:26110352

  17. Piano-stool lutetium amido and imido compounds supported by a constrained bis(oxazoline)cyclopentadienyl ligand

    DOE PAGESBeta

    Lampland, Nicole L.; Zhu, Jing; Hovey, Megan; Jana, Barun; Ellern, Arkady; Sadow, Aaron D.

    2015-06-25

    {BoMCptet}Lu(CH2Ph)2 (1; BoMCptet = MeC(OxMe2 2C5Me4; OxMe2 = 4,4-dimethyl-2-oxazoline) was prepared in 95% yield from the reaction of BoMCptetH and Lu(CH2Ph)3THF3. Compound 1 reacts with 1 or 2 equiv of H2NCH2R (R = C6H5, 1-C10H7) to give the corresponding imido complexes [{BoMCptet}LuNCH2R]2 (R = C6H5 (2a), 1-C10H7 (2b)) or amido complexes {BoMCptet}Lu(NHCH2R)2 (R = C6H5 (3a), 1-C10H7 (3b)). When isolated, the imido species are insoluble in nonprotic organic solvents. Crystallographic characterization reveals dimeric [{BoMCptet}LuNCH2(1-C10H7)]2 in the solid state. The reaction of 1 and NH3B(C6F5)3 affords crystallographically characterized {BoMCptet}Lu{NHB(C6F5)2}C6F5. This species is proposed to form via a transient lutetium imido, whichmore » undergoes C6F5 migration to the lutetium center.« less

  18. Anti-biofouling polymer-decorated lutetium-based nanoparticulate contrast agents for in vivo high-resolution trimodal imaging.

    PubMed

    Liu, Zhen; Dong, Kai; Liu, Jianhua; Han, Xueli; Ren, Jinsong; Qu, Xiaogang

    2014-06-25

    Nanomaterials have gained considerable attention and interest in the development of novel and high-resolution contrast agents for medical diagnosis and prognosis in clinic. A classical urea-based homogeneous precipitation route that combines the merits of in situ thermal decomposition and surface modification is introduced to construct polyethylene glycol molecule (PEG)-decorated hybrid lutetium oxide nanoparticles (PEG-UCNPs). By utilizing the admirable optical and magnetic properties of the yielded PEG-UCNPs, in vivo up-conversion luminescence and T1 -enhanced magnetic resonance imaging of small animals are conducted, revealing obvious signals after subcutaneous and intravenous injection, respectively. Due to the strong X-ray absorption and high atomic number of lanthanide elements, X-ray computed-tomography imaging based on PEG-UCNPs is then designed and carried out, achieving excellent imaging outcome in animal experiments. This is the first example of the usage of hybrid lutetium oxide nanoparticles as effective nanoprobes. Furthermore, biodistribution, clearance route, as well as long-term toxicity are investigated in detail after intravenous injection in a murine model, indicating the overall safety of PEG-UCNPs. Compared with previous lanthanide fluorides, our nanoprobes exhibit more advantages, such as facile construction process and nearly total excretion from the animal body within a month. Taken together, these results promise the use of PEG-UCNPs as a safe and efficient nanoparticulate contrast agent for potential application in multimodal imaging. PMID:24610806

  19. The Wyckoff positional order and polyhedral intergrowth in the M3B2- and M5B3-type boride precipitated in the Ni-based superalloys.

    PubMed

    Hu, X B; Zhu, Y L; Sheng, N C; Ma, X L

    2014-01-01

    Ni-based single superalloys play a crucial role in the hottest parts of jet engines. However, due to the complex geometry and macro-segregation during the solidification process, the cast defect such as stray grains is inevitable. Therefore, the transient liquid phase (TLP) bonding which can join several small single crystalline castings together is gradually believed to be an effective method for improving the yields of production of the complex components. The melting point depressant element B is always added into the interlayer filler material. Consequently, borides including the M3B2 and M5B3 phase usually precipitate during the TLP bonding process. So a comprehensive knowledge of the fine structural characteristics of the borides is very critical for an accurate evaluation of the TLP bonding process. In this work, by means of the aberration-corrected transmission electron microscopy, we show, at an atomic scale, the Wyckoff positional order phenomenon of the metal atoms in the unit cell of M3B2- and M5B3-type boride. Meanwhile, the defect along the (001) plane of the above two types of boride are determined to be the polyhedral intergrowth with complex configurations. PMID:25482386

  20. Surface decoration through electrostatic interaction leading to enhanced reactivity: Low temperature synthesis of nanostructured chromium borides (CrB and CrB{sub 2})

    SciTech Connect

    Menaka,; Kumar, Bharat; Kumar, Sandeep; Ganguli, A.K.

    2013-04-15

    The present study describes a novel low temperature route at ambient pressure for the synthesis of nanocrystalline chromium borides (CrB and CrB{sub 2}) without using any flux or additives. The favorable and intimate mixing of nanoparticles of chromium acetate (Cr source) and boron forms an active chromium–boron precursor which decomposes at much lower temperature (400 °C) to form CrB (which is ∼1000 °C less than the known ambient pressure synthesis). The chromium acetate nanoparticles (∼5 nm) decorate the larger boron particles (150–200 nm) due to electrostatic interactions resulting from opposing surface charges of boron (zeta potential:+48.101 mV) and chromium acetate (zeta potential:−4.021 mV) in ethanolic medium and is evident in the TEM micrographs. The above method leads to the formation of pure CrB film like structure at 400 °C and nanospheres (40–60 nm) at 600 °C. Also, chromium diboride (CrB{sub 2}) nanoparticles (25 nm) could be obtained at 1000 °C. - Graphical abstract: Variation of surface charge of reactants, precursor and the products, chromium borides (CrB and CrB{sub 2}). Highlights: ► Novel borothermal reduction process for synthesis of chromium boride. ► Significant lowering of reaction temperature to obtain nanocrystalline chromium boride. ► Enhanced reactivity due to appropriate surface interactions.

  1. The Wyckoff positional order and polyhedral intergrowth in the M3B2- and M5B3-type boride precipitated in the Ni-based superalloys

    PubMed Central

    Hu, X. B.; Zhu, Y. L.; Sheng, N. C.; Ma, X. L.

    2014-01-01

    Ni-based single superalloys play a crucial role in the hottest parts of jet engines. However, due to the complex geometry and macro-segregation during the solidification process, the cast defect such as stray grains is inevitable. Therefore, the transient liquid phase (TLP) bonding which can join several small single crystalline castings together is gradually believed to be an effective method for improving the yields of production of the complex components. The melting point depressant element B is always added into the interlayer filler material. Consequently, borides including the M3B2 and M5B3 phase usually precipitate during the TLP bonding process. So a comprehensive knowledge of the fine structural characteristics of the borides is very critical for an accurate evaluation of the TLP bonding process. In this work, by means of the aberration-corrected transmission electron microscopy, we show, at an atomic scale, the Wyckoff positional order phenomenon of the metal atoms in the unit cell of M3B2- and M5B3-type boride. Meanwhile, the defect along the (001) plane of the above two types of boride are determined to be the polyhedral intergrowth with complex configurations. PMID:25482386

  2. The Wyckoff positional order and polyhedral intergrowth in the M3B2- and M5B3-type boride precipitated in the Ni-based superalloys

    NASA Astrophysics Data System (ADS)

    Hu, X. B.; Zhu, Y. L.; Sheng, N. C.; Ma, X. L.

    2014-12-01

    Ni-based single superalloys play a crucial role in the hottest parts of jet engines. However, due to the complex geometry and macro-segregation during the solidification process, the cast defect such as stray grains is inevitable. Therefore, the transient liquid phase (TLP) bonding which can join several small single crystalline castings together is gradually believed to be an effective method for improving the yields of production of the complex components. The melting point depressant element B is always added into the interlayer filler material. Consequently, borides including the M3B2 and M5B3 phase usually precipitate during the TLP bonding process. So a comprehensive knowledge of the fine structural characteristics of the borides is very critical for an accurate evaluation of the TLP bonding process. In this work, by means of the aberration-corrected transmission electron microscopy, we show, at an atomic scale, the Wyckoff positional order phenomenon of the metal atoms in the unit cell of M3B2- and M5B3-type boride. Meanwhile, the defect along the (001) plane of the above two types of boride are determined to be the polyhedral intergrowth with complex configurations.

  3. Structural and Physical Properties Diversity of New CaCu5-Type Related Europium Platinum Borides

    PubMed Central

    2013-01-01

    Three novel europium platinum borides have been synthesized by arc melting of constituent elements and subsequent annealing. They were characterized by X-ray powder and single-crystal diffraction: EuPt4B, CeCo4B type, P6/mmm, a = 0.56167(2) nm, c = 0.74399(3) nm; Eu3Pt7B2, Ca3Al7Cu2 type as an ordered variant of PuNi3, R3̅m, a = 0.55477(2) nm, c = 2.2896(1) nm; and Eu5Pt18B6–x, a new unique structure type, Fmmm, a = 0.55813(3) nm, b = 0.95476(5) nm, c = 3.51578(2) nm. These compounds belong to the CaCu5 family of structures, revealing a stacking sequence of CaCu5-type slabs with different structural units: CaCu5 and CeCo3B2 type in EuPt4B; CeCo3B2 and Laves MgCu2 type in Eu3Pt7B2; and CaCu5-, CeCo3B2-, and site-exchange ThCr2Si2-type slabs in Eu5Pt18B6–x. The striking motif in the Eu5Pt18B6–x structure is the boron-centered Pt tetrahedron [BPt4], which build chains running along the a axis and plays a decisive role in the structure arrangement by linking the terminal fragments of repeating blocks of fused Eu polyhedra. Physical properties of two compounds, EuPt4B and Eu3Pt7B2, were studied. Both compounds were found to order magnetically at 36 and 57 K, respectively. For EuPt4B a mixed-valence state of the Eu atom was confirmed via magnetic and specific heat measurements. Moreover, the Sommerfeld value of the specific heat of Eu3Pt7B2 was found to be extraordinarily large, on the order of 0.2 J/mol K2. PMID:23540751

  4. Lutetium oxyorthosilicate block detector readout by avalanche photodiode arrays for high resolution animal PET

    NASA Astrophysics Data System (ADS)

    Pichler, B. J.; Swann, B. K.; Rochelle, J.; Nutt, R. E.; Cherry, S. R.; Siegel, S. B.

    2004-09-01

    Avalanche photodiodes (APDs) have proven to be useful as light detectors for high resolution positron emission tomography (PET). Their compactness makes these devices excellent candidates for replacing bulky photomultiplier tubes (PMTs) in PET systems where space limitations are an issue. The readout of densely packed, 10 × 10 lutetium oxyorthosilicate (LSO) block detectors (crystal size 2.0 × 2.0 × 12 mm3) with custom-built monolithic 3 × 3 APD arrays was investigated. The APDs had a 5 × 5 mm2 active surface and were arranged on a 6.25 mm pitch. The dead space on the edges of the array was 1.25 mm. The APDs were operated at a bias voltage of approximately 380 V for a gain of 100 and a dark current of 10 nA per APD. The standard deviation in gain between the APDs in the array ranged from 1.8 to 6.5% as the gain was varied from 50 to 108. A fast, low-noise, multi-channel charge sensitive preamplifier application-specific integrated circuit (ASIC) was developed for the APD readout. The amplifier had a rise time of 8 ns, a noise floor of 515 e- rms and a 9 e- pF-1 noise slope. An acquired flood image showed that all 100 crystals from the block detector could be resolved. Timing measurements with single-channel LSO-APD detectors, as well as with the array, against a plastic scintillator and PMT assembly showed a time resolution of 1.2 ns and 2.5 ns, respectively. The energy resolution measured with a single 4.0 × 4.0 × 10 mm3 LSO crystal, wrapped in four-layer polytetrafluoroethylene (PTFE) tape and coupled with optical grease on a single APD of the array, yielded 15% (full width at half maximum, FWHM) at 511 keV. Stability tests over 9 months of operation showed that the APD arrays do not degrade appreciably. These results demonstrate the ability to decode densely packed LSO scintillation blocks with compact APD arrays. The good timing and energy resolution makes these detectors suitable for high resolution PET.

  5. Influence of cations on the complexation yield of DOTATATE with yttrium and lutetium: a perspective study for enhancing the 90Y and 177Lu labeling conditions.

    PubMed

    Asti, Mattia; Tegoni, Matteo; Farioli, Daniela; Iori, Michele; Guidotti, Claudio; Cutler, Cathy S; Mayer, Pat; Versari, Annibale; Salvo, Diana

    2012-05-01

    The DOTA macrocyclic ligand can form stable complexes with many cations besides yttrium and lutetium. For this reason, the presence of competing cationic metals in yttrium-90 and lutetium-177 chloride solutions can dramatically influence the radiolabeling yield. The aim of this study was to evaluate the coordination yield of yttrium- and lutetium-DOTATATE complexes when the reaction is performed in the presence of varying amounts of competing cationic impurities. In the first set of experiments, the preparation of the samples was performed by using natural yttrium and lutetium (20.4 nmol). The molar ratio between DOTATATE and these metals was 1 to 1. Metal competitors (Pb(2+), Zn(2+), Cu(2+), Fe(3+), Al(3+), Ni(2+), Co(2+), Cr(3+)) were added separately to obtain samples with varying molar ratio with respect to yttrium or lutetium (0.1, 0.5, 1, 2 and 10). The final solutions were analyzed through ultra high-performance liquid chromatography with an UV detector. In the second set of experiments, an amount of (90)Y or (177)Lu chloride (6 MBq corresponding to 3.3 and 45 pmol, respectively) was added to the samples, and a radio-thin layer chromatography analysis was carried out. The coordination of Y(3+) and Lu(3+) was dramatically influenced by low levels of Zn(2+), Cu(2+) and Co(2+). Pb(2+) and Ni(2+) were also shown to be strong competitors at higher concentrations. Fe(3+) was expected to be a strong competitor, but the effect on the incorporation was only partly dependent on its concentration. Al(3+) and Cr(3+) did not compete with Y(3+) and Lu(3+) in the formation of DOTATATE complexes. PMID:22172388

  6. On the use of X-ray absorption spectroscopy to elucidate the structure of lutetium adenosine mono- and triphosphate complexes.

    PubMed

    Mostapha, S; Berthon, C; Fontaine-Vive, F; Gaysinski, M; Guérin, L; Guillaumont, D; Massi, L; Monfardini, I; Solari, P L; Thomas, O P; Charbonnel, M C; Den Auwer, C

    2014-02-01

    Although the physiological impact of the actinide elements as nuclear toxicants has been widely investigated for half a century, a description of their interactions with biological molecules remains limited. It is however of primary importance to better assess the determinants of actinide speciation in cells and more generally in living organisms to unravel the molecular processes underlying actinide transport and deposition in tissues. The biological pathways of this family of elements in case of accidental contamination or chronic natural exposure (in the case of uranium rich soils for instance) are therefore a crucial issue of public health and of societal impact. Because of the high chemical affinity of those actinide elements for phosphate groups and the ubiquity of such chemical functions in biochemistry, phosphate derivatives are considered as probable targets of these cations. Among them, nucleotides and in particular adenosine mono- (AMP) and triphosphate (ATP) nucleotides occur in more chemical reactions than any other compounds on the earth's surface, except water, and are therefore critical target molecules. In the present study, we are interested in trans-plutonium actinide elements, in particular americium and curium that are more rarely considered in environmental and bioaccumulation studies than early actinides like uranium, neptunium and plutonium. A first step in this strategy is to work with chemical analogues like lanthanides that are not radioactive and therefore allow extended physical chemical characterization to be conducted that are difficult to perform with radioactive materials. We describe herein the interaction of lutetium(III) with adenosine AMP and ATP. With AMP and ATP, insoluble amorphous compounds have been obtained with molar ratios of 1:2 and 1:1, respectively. With an excess of ATP, with 1:2 molar ratio, a soluble complex has been obtained. A combination of spectroscopic techniques (IR, NMR, ESI-MS, EXAFS) together with quantum

  7. Raman scattering in organic semiconductors based on erbium biphthalocyanine molecules and chlorine-containing europium-lutetium triphthalocyanine molecules

    SciTech Connect

    Belogorokhov, I. A.; Mamichev, D. A.; Dronov, M. A.; Pushkarev, V. E.; Tomilova, L. G.; Khokhlov, D. R.

    2010-08-15

    The Raman spectra of semiconductor structures based on erbium biphthalocyanine molecules and chlorine-substituted europium-lutetium triphthalocyanine molecules are studied on excitation with Ar{sup +} laser radiation at the wavelength 514 nm. The data on the spectral position of Raman intensity peaks related to vibronic states of the basic molecular groups forming the semiconductor are obtained. Raman lines irrelevant to the known vibronic states of the basic phthalocyanine molecular groups are observed in the ranges 100-500 and 500-900 cm{sup -1}. It is shown that, in the spectra of triphthalocyanine, some lines are structurally complex and shifted with respect to the characteristic lines of molecular groups by several inverse centimeters.

  8. Solvation properties and behaviour of lutetium(III) in aqueous solution—A quantum mechanical charge field (QMCF) study

    NASA Astrophysics Data System (ADS)

    Hitzenberger, Manuel; Hofer, Thomas S.; Weiss, Alexander K. H.

    2013-09-01

    This work presents the first ab initio molecular dynamics study of trivalent lutetium in aqueous solution. The hybrid quantum and molecular mechanics simulation has been carried out on Hartree-Fock level and the results were compared to extended X-ray absorption fine structure and X-ray diffraction data. In addition to the structural characterisation via radial and angular distribution functions, the influence of the ion on the surrounding solvent was further investigated by local-density-corrected three-body distribution functions and frequency calculations. The obtained results for the mean Lu-O bond distance and force constant were in very good agreement with the literature. Furthermore, deeper insight into the dynamics and geometry of the solvation shell and the number of involved solvent molecules was obtained.

  9. In situ chemichromic studies of interactions between a lutetium bis-octaalkyl-substituted phthalocyanine and selected biological cofactors

    PubMed Central

    Pal, C.; Cammidge, A. N.; Cook, M. J.; Sosa-Sanchez, J. L.; Sharma, A. K.; Ray, A. K.

    2012-01-01

    Spin-coated films, approximately 100 nm thick, of a newly synthesized bis[octakis(octyl)phthalocyaninato] lutetium(III) complex on ultrasonically cleaned glass substrates exhibit pronounced chemichromic behaviour with potential application in healthcare. In situ kinetic optical absorption spectroscopic measurements show that the phthalocyanine Q-band is red shifted by 60 nm upon oxidation arising from exposure to bromine vapour. Recovery to the original state is achieved by the treatment of the oxidized films with nicotinamide adenine dinucleotide and l-ascorbic acid (vitamin C) in an aqueous solution containing 1.5 M lithium perchlorate. The neutralization process is found to be governed by first-order kinetics. The linear increase of the reduction rate with increasing concentration of cofactors provides a basis for calibration of analyte concentrations ranging from 3.5 mM down to 0.03 mM. PMID:21676969

  10. Processing development of 4 tantalum carbide-hafnium carbide and related carbides and borides for extreme environments

    NASA Astrophysics Data System (ADS)

    Gaballa, Osama Gaballa Bahig

    Carbides, nitrides, and borides ceramics are of interest for many applications because of their high melting temperatures and good mechanical properties. Wear-resistant coatings are among the most important applications for these materials. Materials with high wear resistance and high melting temperatures have the potential to produce coatings that resist degradation when subjected to high temperatures and high contact stresses. Among the carbides, Al4SiC4 is a low density (3.03 g/cm3), high melting temperature (>2000°C) compound, characterized by superior oxidation resistance, and high compressive strength. These desirable properties motivated this investigation to (1) obtain high-density Al4SiC4 at lower sintering temperatures by hot pressing, and (2) to enhance its mechanical properties by adding WC and TiC to the Al4SiC4. Also among the carbides, tantalum carbide and hafnium carbide have outstanding hardness; high melting points (3880°C and 3890°C respectively); good resistance to chemical attack, thermal shock, and oxidation; and excellent electronic conductivity. Tantalum hafnium carbide (Ta4HfC 5) is a 4-to-1 ratio of TaC to HfC with an extremely high melting point of 4215 K (3942°C), which is the highest melting point of all currently known compounds. Due to the properties of these carbides, they are considered candidates for extremely high-temperature applications such as rocket nozzles and scramjet components, where the operating temperatures can exceed 3000°C. Sintering bulk components comprised of these carbides is difficult, since sintering typically occurs above 50% of the melting point. Thus, Ta4 HfC5 is difficult to sinter in conventional furnaces or hot presses; furnaces designed for very high temperatures are expensive to purchase and operate. Our research attempted to sinter Ta4HfC5 in a hot press at relatively low temperature by reducing powder particle size and optimizing the powder-handling atmosphere, milling conditions, sintering

  11. Piano-stool lutetium amido and imido compounds supported by a constrained bis(oxazoline)cyclopentadienyl ligand

    SciTech Connect

    Lampland, Nicole L.; Zhu, Jing; Hovey, Megan; Jana, Barun; Ellern, Arkady; Sadow, Aaron D.

    2015-06-25

    {BoMCptet}Lu(CH2Ph)2 (1; BoMCptet = MeC(OxMe2 2C5Me4; OxMe2 = 4,4-dimethyl-2-oxazoline) was prepared in 95% yield from the reaction of BoMCptetH and Lu(CH2Ph)3THF3. Compound 1 reacts with 1 or 2 equiv of H2NCH2R (R = C6H5, 1-C10H7) to give the corresponding imido complexes [{BoMCptet}LuNCH2R]2 (R = C6H5 (2a), 1-C10H7 (2b)) or amido complexes {BoMCptet}Lu(NHCH2R)2 (R = C6H5 (3a), 1-C10H7 (3b)). When isolated, the imido species are insoluble in nonprotic organic solvents. Crystallographic characterization reveals dimeric [{BoMCptet}LuNCH2(1-C10H7)]2 in the solid state. The reaction of 1 and NH3B(C6F5)3 affords crystallographically characterized {BoMCptet}Lu{NHB(C6F5)2}C6F5. This species is proposed to form via a transient lutetium imido, which undergoes C6F5 migration to the lutetium center.

  12. On the transferability of electron density in binary vanadium borides VB, V3B4 and VB2.

    PubMed

    Terlan, Bürgehan; Akselrud, Lev; Baranov, Alexey I; Borrmann, Horst; Grin, Yuri

    2015-12-01

    Binary vanadium borides are suitable model systems for a systematic analysis of the transferability concept in intermetallic compounds due to chemical intergrowth in their crystal structures. In order to underline this structural relationship, topological properties of the electron density in VB, V3B4 and VB2 reconstructed from high-resolution single-crystal X-ray diffraction data as well as derived from quantum chemical calculations, are analysed in terms of Bader's Quantum Theory of Atoms in Molecules [Bader (1990). Atoms in Molecules: A Quantum Theory, 1st ed. Oxford: Clarendon Press]. The compounds VB, V3B4 and VB2 are characterized by a charge transfer from the metal to boron together with two predominant atomic interactions, the shared covalent B-B interactions and the polar covalent B-M interactions. The resembling features of the crystal structures are well reflected by the respective B-B interatomic distances as well as by ρ(r) values at the B-B bond critical points. The latter decrease with an increase in the corresponding interatomic distances. The B-B bonds show transferable electron density properties at bond critical points depending on the respective bond distances. PMID:26634735

  13. Mechanism and kinetics of sodium borohydride hydrolysis over crystalline nickel and nickel boride and amorphous nickel-boron nanoparticles

    NASA Astrophysics Data System (ADS)

    Wu, Zhijie; Mao, Xikang; Zi, Qin; Zhang, Rongrong; Dou, Tao; Yip, Alex C. K.

    2014-12-01

    The initial hydrogen generation turnover rates during the hydrolysis of sodium borohydride over nickel catalysts (crystalline nickel (Ni), crystalline nickel boride (Ni3B), and amorphous nickel-boron (Ni-B) nanoparticles) were measured to investigate the reaction kinetics and mechanisms by varying the reactant concentrations and reaction temperatures. Nickel catalysts with and without boron follow different hydrolysis pathways; hydroxide ions are involved in the activation of reactant molecules over Ni3B and Ni-B catalysts. This study explicitly reports the zero-order and first-order reaction kinetics with respect to the reactant concentration over Ni, Ni3B and Ni-B catalysts. The initial hydrogen generation turnover rates and activation energies determined from the experimental data indicate that the amorphous Ni-B nanoparticles exhibit the highest turnover rate and lowest activation energy for the hydrolysis of borohydride among the investigated catalysts. This study provides a general strategy for the development of borohydride hydrolysis catalysts via the modification of a metal catalyst using boron, which causes the crystalline structure to become amorphous and leads to electron-rich, highly undercoordinated metal atoms at the surface.

  14. Transition metal carbides, nitrides and borides, and their oxygen containing analogs useful as water gas shift catalysts

    DOEpatents

    Thompson, Levi T.; Patt, Jeremy; Moon, Dong Ju; Phillips, Cory

    2003-09-23

    Mono- and bimetallic transition metal carbides, nitrides and borides, and their oxygen containing analogs (e.g. oxycarbides) for use as water gas shift catalysts are described. In a preferred embodiment, the catalysts have the general formula of M1.sub.A M2.sub.B Z.sub.C O.sub.D, wherein M1 is selected from the group consisting of Mo, W, and combinations thereof; M2 is selected from the group consisting of Fe, Ni, Cu, Co, and combinations thereof; Z is selected from the group consisting of carbon, nitrogen, boron, and combinations thereof; A is an integer; B is 0 or an integer greater than 0; C is an integer; O is oxygen; and D is 0 or an integer greater than 0. The catalysts exhibit good reactivity, stability, and sulfur tolerance, as compared to conventional water shift gas catalysts. These catalysts hold promise for use in conjunction with proton exchange membrane fuel cell powered systems.

  15. Precipitation of Niobium Boride Phases at the Base Metal/Weld Metal Interface in Dissimilar Weld Joints

    NASA Astrophysics Data System (ADS)

    Výrostková, Anna; Kepič, Ján; Homolová, Viera; Falat, Ladislav

    2015-07-01

    In this work, the analysis of failure mechanism in the heat affected zone is described in dissimilar weld joints between advanced martensitic steel T92 and Ni-base weld metal. The joints were treated with two different post-weld heat treatments and tested. For the creep, tensile, and Charpy impact tests, the samples with interfacially located notch were used. Moreover long term aging at 625 °C was applied before the tensile and notch toughness tests. Decohesion fractures ran along carbides at the T92 BM/WM interfaces in case of the modified PWHT, whereas type IV cracking was the prevailing failure mechanism after the classical PWHT in the creep test. In the notch tensile and Charpy impact tests, with the notch at T92 base metal/weld metal interface, fractures ran along the interface with a hard phase on the fracture surface along with the ductile dimple and brittle quasi-cleavage fracture. The phase identified as niobium boride (either NbB and/or Nb3B2) was produced during welding at the end of the solidification process. It was found in the welds regardless of the post-weld heat treatment and long-term aging.

  16. Spectroscopic refractive indices of monoclinic single crystal and ceramic Lutetium oxyorthosilicate (LSO) from 200 to 850 nm

    SciTech Connect

    Jellison Jr, Gerald Earle; Specht, Eliot D; Boatner, Lynn A; Singh, David J; Melcher, Charles L

    2012-01-01

    The four real values of the dielectric function tensor of the monoclinic crystal Lu2SiO5 or lutetium oxyorthosilicate (LSO) have been determined using generalized ellipsometry from 200 to 850 nm. The three principal values are fit to the Sellmeier model, and they indicate that the band gap of LSO is less than ~9 eV. The off-diagonal element 12 is non-zero over the entire spectrum, but it is very close to zero for wavelengths longer than ~400 nm, indicating that structurally monoclinic LSO is nearly optically orthorhombic in this wavelength region. The spectroscopic dielectric functions of three isotropic ceramic LSO samples are presented, which are consistent with the dielectric functions of single-crystal LSO when the effects of porosity are included. As a comparison, the dielectric functions are also determined using relativistic electronic structure and optical calculations based on the recently developed potential functional of Tran and Blaha (Phys. Rev. Lett. 102, 226401 (2009).)

  17. Higher borides and oxygen-enriched Mg-B-O inclusions as possible pinning centers in nanostructural magnesium diboride and the influence of additives on their formation

    NASA Astrophysics Data System (ADS)

    Prikhna, Tatiana; Gawalek, Wolfgang; Savchuk, Yaroslav; Tkach, Vasiliy; Danilenko, Nikolay; Wendt, Michael; Dellith, Jan; Weber, Harold; Eisterer, Michael; Moshchil, Viktor; Sergienko, Nina; Kozyrev, Artem; Nagorny, Peter; Shapovalov, Andrey; Melnikov, Vladimir; Dub, Sergey; Litzkendorf, Doris; Habisreuther, Tobias; Schmidt, Christa; Mamalis, Athanasios; Sokolovsky, Vladimir; Sverdun, Vladimir; Karau, Fridrich; Starostina, Alexandra

    2010-10-01

    The study of high pressure (2 GPa) synthesized MgB 2-based materials allows us to conclude that higher borides (with near MgB 12 stoichiometry) and oxygen-enriched Mg-B-O inclusions can be pinning centers in nanostructural magnesium diboride matrix (with average grain sizes of 15-37 nm). It has been established that additions of Ti or SiC as well as manufacturing temperature can affect the size, amount and distribution of these inclusions in the material structure and thus, influence critical current density. The superconducting behavior of materials with near MgB 12 stoichiometry of matrix is discussed.

  18. Site-preferential design of itinerant ferromagnetic borides: experimental and theoretical investigation of MRh6B3 (M = Fe, Co).

    PubMed

    Misse, Patrick R N; Gillessen, Michael; Fokwa, Boniface P T

    2011-10-17

    Single-phase polycrystalline samples of the compounds MRh(6)B(3) (M = Fe, Co) as well as single crystals of CoRh(6)B(3) have been synthesized by arc-melting the elements under a purified argon atmosphere in a water-cooled copper crucible. The characterization of the new phases was achieved by using single-crystal and powder X-ray diffraction as well as EDX measurements. The two phases are isotypic and crystallize in the hexagonal Th(7)Fe(3) structure type (space group P6(3)mc, no. 186, Z = 2). In this structure, the magnetically active atoms (Fe, Co) are preferentially found on only one of the three available rhodium sites, and together with rhodium they build a three-dimensional network of interconnected (Rh/M)(3) triangles. Magnetic properties investigations show that both phases order ferromagnetically below Curie temperatures of 240 K (for FeRh(6)B(3)) and 150 K (for CoRh(6)B(3)). First-principles DFT calculations correctly reproduce not only the lattice parameters but also the ground state magnetic ordering in the two phases. These calculations also show that the long-range magnetic ordering in both phases occurs via indirect ferromagnetic coupling between the iron atoms mediated by rhodium. This magnetic structural model also predicts the saturation magnetizations to be 4.02 μ(B) for FeRh(6)B(3) (3.60 μ(B) found experimentally) and 2.75 μ(B) for CoRh(6)B(3). Furthermore, both phases are predicted to be metallic conductors as expected for these intermetallic borides. PMID:21905755

  19. Effect of higher borides and inhomogeneity of oxygen distribution on critical current density of undoped and doped magnesium diboride

    NASA Astrophysics Data System (ADS)

    Prikhna, T. A.; Gawalek, W.; Tkach, V. M.; Danilenko, N. I.; Savchuk, Ya M.; Dub, S. N.; Moshchil, V. E.; Kozyrev, A. V.; Sergienko, N. V.; Wendt, M.; Melnikov, V. S.; Dellith, J.; Weber, H.; Eisterer, M.; Schmidt, Ch; Habisreuther, T.; Litzkendorf, D.; Vajda, J.; Shapovalov, A. P.; Sokolovsky, V.; Nagorny, P. A.; Sverdun, V. B.; Kosa, J.; Karau, F.; Starostina, A. V.

    2010-06-01

    The effect of doping with Ti, Ta, SiC in complex with synthesis temperature on the amount and distribution of structural inhomogeneities in MgB2 matrix of high-pressure-synthesized-materials (2 GPa) which can influence pinning: higher borides (MgB12) and oxygen-enriched Mg-B-O inclusions, was established and a mechanism of doping effect on jc increase different from the generally accepted was proposed. Near theoretically dense SiC-doped material exhibited jc= 106 A/cm2 in 1T field and Hirr =8.5 T at 20 K. The highest jc in fields above 9, 6, and 4 T at 10, 20, and 25 K, respectively, was demonstrated by materials synthesized at 2 GPa, 600 °C from Mg and B without additions (at 20 K jc= 102 A/cm2 in 10 T field). Materials synthesized from Mg and B taken up to 1:20 ratio were superconductive. The highest jc (6×104 A/cm2 at 20 K in zero field, Hirr= 5 T) and the amount of SC phase (95.3% of shielding fraction), Tc being 37 K were demonstrated by materials having near MgB12 composition of the matrix. The materials with MgB12 matrix had a doubled microhardness of that with MgB2 matrix (25±1.1 GPa and 13.08±1.07 GPa, at a load of 4.9 N, respectively).

  20. Anomalous effect of vanadium boride seeding on thermoelectric properties of YB{sub 22}C{sub 2}N

    SciTech Connect

    Prytuliak, A.; Maruyama, S.; Mori, T.

    2013-05-15

    Highlights: ► We doped YB{sub 22}C{sub 2}N; the long awaited n-type counterpart to p-type boron carbide. ► VB{sub 2} seeding of YB{sub 22}C{sub 2}N showed striking results. ► Thermal treatment effects led to VB{sub 2} being intrinsically doped. ► Large increase of both Seebeck coefficient and electrical conductivity was obtained. - Abstract: Vanadium boride seeded YB{sub 22}C{sub 2}N were synthesized and the thermoelectric properties investigated. YB{sub 22}C{sub 2}N is representative of the series of rare earth borocarbonitrides which is the potential long awaited n-type counterpart to p-type boron carbide. VB{sub 2} seeded samples of YB{sub 22}C{sub 2}N were prepared using VB{sub 2} directly as an initial additive and V{sub 2}O{sub 3} which also results in formation of vanadium diboride in the final product. The resistivity and Seebeck coefficient of samples were measured in the temperature range of 323 K to 1073 K. A dramatic effect of thermal treatment on the Seebeck coefficient of VB{sub 2} seeded samples was observed, and it is indicated that there is possible partial intrinsic doping of vanadium into YB{sub 22}C{sub 2}N. VB{sub 2} is revealed to be a promising additive to improve the thermoelectric properties of YB{sub 22}C{sub 2}N. An enhancement of more than 220% of the maximum absolute value of the Seebeck coefficient was obtained while the resistivity was also reduced considerably.

  1. Feasibility of repeated sequential treatments of RIF-1 tumors with photodynamic therapy (PDT) using lutetium texaphyrin (PCI-0123)

    NASA Astrophysics Data System (ADS)

    Miles, Dale R.; Parker, Lynn M.; Thiemann, Patricia A.; Woodburn, Kathryn W.; Young, Stuart W.

    1997-05-01

    Lutetium texaphyrin (PCI-0123) is currently in clinical trials as a PDT agent for the treatment of cancer patients. The drug is cleared rapidly from the plasma, and photoirradiation can be performed shortly after drug administration.T He photosensitizer as yet does not appear to elicit any significant skin photosensitivity. These characteristics favor frequent multiple PDT treatments with PCI-0123. In order to support repeated PDT treatments in the clinic, the safety of multiple drug dosing was studied in rats and mice. In rats, each group received 5 consecutive daily intravenous administrations of 5, 15, 30, or 60 mg/kg/day of PCI-0123. There were no deaths in any of the groups, and no drug-related effects were detected in the 5 mg/kg/day group. In mice, there were no observable signs of toxicity after consecutive daily administration of 10 micrometers ol/kg/day of PCI-0123 for 13 days. The feasibility and efficacy of repeated PDT treatments were assessed in C3H mice bearing RIF-1 tumors. Repeated PDT proved to be superior to a single PDT treatment. Repeated PDT treatments were well tolerated. Seven PDT treatments were administered over a nine day period without significant toxicity while achieving good therapeutic responses. All six groups receiving repeated PDT treatments showed an improved response compared to groups receiving a single PDT cycle, and the improvement was statistically significant for five of these groups. Sixty-two percent of mice receiving four sequential daily treatments were cured, and daily treatments were superior to regimens with longer intervals between PDT cycles.

  2. Single crystal studies on Co-containing {tau}-borides Co{sub 23-x}M{sub x}B{sub 6} (M=Al, Ga, Sn, Ti, V, Ir) and the boron-rich {tau}-boride Co{sub 12.3}Ir{sub 8.9}B{sub 10.5}

    SciTech Connect

    Kotzott, Dominik; Ade, Martin; Hillebrecht, Harald

    2009-03-15

    Single crystals of the cubic {tau}-Borides Co{sub 23-x}M{sub x}B{sub 6} (M=Al, Ga, Sn) were synthesised from the elements at temperatures between 1200 and 1500 deg. C. According to the structure refinements one (Ga, Sn: 8c) or two (Al: 4a and 8c) of the four independent metal sites show a mixed occupation Co/M resulting in the compositions Co{sub 20.9}Al{sub 2.1}B{sub 6}, Co{sub 21.9}Ga{sub 1.1}B{sub 6}, and Co{sub 21.4}Sn{sub 1.6}B{sub 6}, respectively. Melts with Indium gave access to Co{sub 23}B{sub 6} as the first binary {tau}-boride (Fm3-barm,a=10.4618(13) A, 104 refl., 14 param., R{sub 1}(F)=0.0132, wR{sub 2}(F{sup 2})=0.0210). With M=Ir mixed occupations occur for all sites and the boron content varies. The composition for the boron-poor single crystal was Co{sub 16.2}Ir{sub 6.8}B{sub 6}. A higher Ir-content enables the uptake of additional boron resulting in a composition Co{sub 12.3}Ir{sub 8.9}B{sub 10.5}. This can be explained be the substitution of metal atoms on the 8c-site by B{sub 4}-tetrahedra. A boron-rich phase was observed for the first time for a {tau}-boride of cobalt. All compositions were confirmed by EDX measurements. - Graphical Abstract: Single crystal investigations on {tau}-borides Co/M/B with M = Al, Ga, In, Sn, V, Ti, Ir explained the substitution processes. Furthermore the yielded the first binary boride, Co{sub 23}B{sub 6}, and a boron-rich Co{sub 12.3}Ir{sub 8.9}B{sub 10.5} containing B{sub 4}-tetrahedra.

  3. A Simple Kinetic Model for the Growth of Fe2B Layers on AISI 1026 Steel During the Powder-pack Boriding

    NASA Astrophysics Data System (ADS)

    Flores-Rentería, M. A.; Ortiz-Domínguez, M.; Keddam, M.; Damián-Mejía, O.; Elias-Espinosa, M.; Flores-González, M. A.; Medina-Moreno, S. A.; Cruz-Avilés, A.; Villanueva-Ibañez, M.

    2015-02-01

    This work focused on the determination of boron diffusion coefficient through the Fe2B layers on AISI 1026 steel using a mathematical model. The suggested model solves the mass balance equation at the (Fe2B/substrate) interface. This thermochemical treatment was carried out in the temperature range of 1123-1273 K for a treatment time ranging from 2 to 8 h. The generated boride layers were characterized by different experimental techniques such as light optical microscopy, scanning electron microscopy, XRD analysis and the Daimler-Benz Rockwell-C indentation technique. As a result, the boron activation energy for AISI 1026 steel was estimated as 178.4 kJ/mol. Furthermore, this kinetic model was validated by comparing the experimental Fe2B layer thickness with the predicted one at a temperature of 1253 K for 5 h of treatment. A contour diagram relating the layer thickness to the boriding parameters was proposed to be used in practical applications.

  4. Monoclonal antibody-based therapy of a human tumor xenograft with a 177lutetium-labeled immunoconjugate

    SciTech Connect

    Schlom, J.; Siler, K.; Milenic, D.E.; Eggensperger, D.; Colcher, D.; Miller, L.S.; Houchens, D.; Cheng, R.; Kaplan, D.; Goeckeler, W. )

    1991-06-01

    {sup 177}Lutetium ({sup 177}Lu) is a member of the family of elements known as lanthanides or rare earths. Monoclonal antibody (MAb) CC49, a murine IgG1, which is reactive with the tumor-associated antigen, TAG-72, has been shown previously to react with a wide range of human carcinomas; CC49 reacts to a different epitope on the TAG-72 molecule than MAb B72.3 and has a higher binding affinity. We report here the first use of a {sup 177}Lu-labeled immunoconjugate, {sup 177}Lu-CC49, in an experimental therapy model for human carcinoma. {sup 177}Lu-CC49 was shown to delay the growth of established LS-174T human colon carcinomas in athymic mice at a single dose of 50 microCi. Overt toxicity was observed with the administration of approximately 500 microCi of {sup 177}Lu-CC49 in which 5 of 9 mice died of apparent marrow toxicity. A single administration of 200 or 350 microCi of {sup 177}Lu-CC49, however, was shown to eliminate established tumors through the 77-day observation period after MAb administration. Dose fractionation experiments revealed that at least 750 microCi of {sup 177}Lu-CC49 (250 microCi/week for 3 consecutive weeks) was well tolerated in that 9 of 10 mice survived. Moreover, this dose schedule was able to eliminate the growth of relatively large (300 mm3) human colon tumor xenografts in 90% of the animals treated. Single-dose and dose fractionation studies were also carried out with an isotype-matched control MAb, {sup 177}Lu-MOPC-21. In all dose schedules, a large differential was seen between the therapeutic effects of the {sup 177}Lu-CC49 versus that of the {sup 177}Lu-control MAb. The merits and limitations of the use of {sup 177}Lu-labeled immunoconjugates (in particular, {sup 177}Lu-CC49) are discussed in terms of potential novel therapeutics for human carcinoma.

  5. Beta emitters rhenium-188 and lutetium-177 are equally effective in radioimmunotherapy of HPV-positive experimental cervical cancer.

    PubMed

    Phaeton, Rebecca; Jiang, Zewei; Revskaya, Ekaterina; Fisher, Darrell R; Goldberg, Gary L; Dadachova, Ekaterina

    2016-01-01

    Cervical cancer caused by the infection with the human papillomavirus (HPV) remains the fourth leading killer of women worldwide. Therefore, more efficacious treatments are needed. We are developing radioimmunotherapy (RIT) of HPV-positive cervical cancers by targeting E6 and E7 viral oncoproteins expressed by the cancer cells with the radiolabeled monoclonal antibodies (mAbs). To investigate the influence of different radionuclides on the RIT efficacy-we performed RIT of experimental cervical cancer with Rhenium-188 ((188) Re) and Lutetium-177 ((177) Lu)-labeled mAb C1P5 to E6. The biodistribution of (188) Re- and (177) Lu-labeled C1P5 was performed in nude female mice bearing CasKi cervical cancer xenografts and the radiation dosimetry calculations for the tumors and organs were carried out. For RIT the mice were treated with 7.4 MBq of either (188) Re-C1P5 or (177) Lu-C1P5 or left untreated, and observed for their tumor size for 28 days. The levels of (188) Re- and (177) Lu-C1P5 mAbs-induced double-strand breaks in CasKi tumors were compared on days 5 and 10 post treatment by staining with anti-gamma H2AX antibody. The radiation doses to the heart and lungs were similar for both (177) Lu-C1P5 and (188) Re-C1P5. The dose to the liver was five times higher for (177) Lu-C1P5. The doses to the tumor were 259 and 181 cGy for (177) Lu-C1P5 and (188) Re-C1P5, respectively. RIT with either (177) Lu-C1P5 or (188) Re-C1P5 was equally effective in inhibiting tumor growth when each was compared to the untreated controls (P = 0.001). On day 5 there was a pronounced staining for gamma H2AX foci in (177) Lu-C1P5 group only and on day 10 it was observed in both (177) Lu-C1P5 and (188) Re-C1P5 groups. (188) Re- and (177) Lu-labeled mAbs were equally effective in arresting the growth of CasKi cervical tumors. Thus, both of these radionuclides are candidates for the clinical trials of this approach in patients with advanced, recurrent or metastatic cervical cancer. PMID:26625938

  6. X-Ray photoelectron spectroscopy study of radiofrequency-sputtered titanium, carbide, molybdenum carbide, and titanium boride coatings and their friction properties

    NASA Technical Reports Server (NTRS)

    Brainard, W. A.; Wheeler, D. R.

    1977-01-01

    Radiofrequency sputtered coatings of titanium carbide, molybdenum carbide and titanium boride were tested as wear resistant coatings on stainless steel in a pin on disk apparatus. X-ray photoelectron spectroscopy (XPS) was used to analyze the sputtered films with regard to both bulk and interface composition in order to obtain maximum film performance. Significant improvements in friction behavior were obtained when properly biased films were deposited on deliberately preoxidized substrates. XPS depth profile data showed thick graded interfaces for bias deposited films even when adherence was poor. The addition of 10 percent hydrogen to the sputtering gas produced coatings with thin poorly adherent interfaces. Results suggest that some of the common practices in the field of sputtering may be detrimental to achieving maximum adherence and optimum composition for these refractory compounds.

  7. Metallic Borides, La2Re3B7 and La3Re2B5, Featuring Extensive Boron-Boron Bonding.

    PubMed

    Bugaris, Daniel E; Malliakas, Christos D; Chung, Duck Young; Kanatzidis, Mercouri G

    2016-02-15

    La2Re3B7 and La3Re2B5 have been synthesized in single-crystalline form from a molten La/Ni eutectic at 1000 °C in the first example of the flux crystal growth of ternary rare-earth rhenium borides. Both compounds crystallize in their own orthorhombic structure types, with La2Re3B7 (space group Pcca) having lattice parameters a = 7.657(2) Å, b = 6.755(1) Å, and c = 11.617(2) Å, and La3Re2B5 (space group Pmma) having lattice parameters a = 10.809(2) Å, b = 5.287(1) Å, and c = 5.747(1) Å. The compounds possess three-dimensional framework structures that are built up from rhenium boride polyhedra and boron-boron bonding. La3Re2B5 features fairly common B2 dumbbells, whereas La2Re3B7 has unique one-dimensional subunits composed of alternating triangular B3 and trans-B4 zigzag chain fragments. Also observed in La3Re2B5 is an unusual coordination of B by an octahedron of La atoms. Electronic band structure calculations predict that La2Re3B7 is a semimetal, which is observed in the electrical resistivity data as measured on single crystals, with behavior obeying the Bloch-Grüneisen model and a room-temperature resistivity ρ300 K of ∼375 μΩ cm. The electronic band structure calculations also suggest that La3Re2B5 is a regular metal. PMID:26812202

  8. Hydrothermal synthesis and characterization of the lutetium borate-nitrate Lu2B2O5(NO3)2·2H2O

    NASA Astrophysics Data System (ADS)

    Ortner, Teresa S.; Wurst, Klaus; Hejny, Clivia; Huppertz, Hubert

    2016-01-01

    The lutetium diborate-dinitrate Lu2B2O5(NO3)2·2H2O was discovered through a hydrothermal synthesis from Lu(NO3)3·H2O and H3BO3. The compound crystallizes in the space group P 1 ̅ (no. 2) with the lattice parameters a=789.52(5), b=988.62(6), c=1460.33(8) pm, α=90.83(1), β=101.75(1), and γ=110.02(1)° (Z=4). Isolated [B2O5]4- units show coplanar alignment and the coordinating [NO3]- groups are stacked perpendicular to the borate plane. Thereby, a novel, open arrangement solely built up from diborate and nitrate groups at a 1:1 ratio is formed. Additionally, Lu2B2O5(NO3)2·2H2O is characterized by vibrational spectroscopy (IR/Raman).

  9. Pressed boride cathodes

    NASA Technical Reports Server (NTRS)

    Wolski, W.

    1985-01-01

    Results of experimental studies of emission cathodes made from lanthanum, yttrium, and gadolinium hexaborides are presented. Maximum thermal emission was obtained from lanthanum hexaboride electrodes. The hexaboride cathodes operated stably under conditions of large current density power draw, at high voltages and poor vacuum. A microtron electron gun with a lanthanum hexaboride cathode is described.

  10. Fabrication and microstructure of cerium doped lutetium aluminum garnet (Ce:LuAG) transparent ceramics by solid-state reaction method

    SciTech Connect

    Li, Junlang; Xu, Jian; Shi, Ying; Qi, Hongfang; Xie, Jianjun; Lei, Fang

    2014-07-01

    Highlights: • We fabricate Ce doped lutetium aluminum garnet ceramics by solid-state method. • The raw materials include Lu{sub 2}O{sub 3} nanopowders synthesized by co-precipitation method. • The density of the transparent ceramics reach 99.7% of the theoretical value. • The optical transmittance of the bulk ceramic at 550 nm was 57.48%. • Some scattering centers decrease the optical characteristic of the ceramic. - Abstract: Polycrystalline Ce{sup 3+} doped lutetium aluminum garnet (Ce:LuAG) transparent ceramics fabricated by one step solid-state reaction method using synthetic nano-sized Lu{sub 2}O{sub 3}, commercial α-Al{sub 2}O{sub 3} and CeO{sub 2} powders were investigated in this paper. The green compacts shaped by the mixed powders were successfully densified into Ce:LuAG transparent ceramics after vacuum sintering at 1750 °C for 10 h. The in-line optical transmittance of the Ce:LuAG ceramic made by home-made Lu{sub 2}O{sub 3} powders could reach 57.48% at 550 nm, which was higher than that of the ceramic made by commercial Lu{sub 2}O{sub 3} powders (22.96%). The microstructure observation showed that light scattering centers caused by micro-pores, aluminum segregation and refraction index inhomogeneities induced the decrease of optical transparency of the Ce:LuAG ceramics, which should be removed and optimized in the future work.

  11. The electronic structure, mechanical and thermodynamic properties of Mo{sub 2}XB{sub 2} and MoX{sub 2}B{sub 4} (X = Fe, Co, Ni) ternary borides

    SciTech Connect

    He, TianWei; Jiang, YeHua E-mail: jfeng@seas.harvard.edu; Zhou, Rong; Feng, Jing E-mail: jfeng@seas.harvard.edu

    2015-08-21

    The mechanical properties, electronic structure and thermodynamic properties of the Mo{sub 2}XB{sub 2} and MoX{sub 2}B{sub 4} (X = Fe, Co, Ni) ternary borides were calculated by first-principles methods. The elastic constants show that these ternary borides are mechanically stable. Formation enthalpy of Mo{sub 2}XB{sub 2} and MoX{sub 2}B{sub 4} (X = Fe, Co, Ni) ternary borides are at the range of −118.09 kJ/mol to −40.14 kJ/mol. The electronic structures and chemical bonding characteristics are analyzed by the density of states. Mo{sub 2}FeB{sub 2} has the largest shear and Young's modulus because of its strong chemical bonding, and the values are 204.3 GPa and 500.3 GPa, respectively. MoCo{sub 2}B{sub 4} shows the lowest degree of anisotropy due to the lack of strong direction in the bonding. The Debye temperature of MoFe{sub 2}B{sub 4} is the largest among the six phases, which means that MoFe{sub 2}B{sub 4} possesses the best thermal conductivity. Enthalpy shows an approximately linear function of the temperature above 300 K. The entropy of these compounds increase rapidly when the temperature is below 450 K. The Gibbs free energy decreases with the increase in temperature. MoCo{sub 2}B{sub 4} has the lowest Gibbs free energy, which indicates the strongest formation ability in Mo{sub 2}XB{sub 2} and MoX{sub 2}B{sub 4} (X = Fe, Co, Ni) ternary borides.

  12. Ternary Borides Cr2AlB2, Cr3AlB4, and Cr4AlB6: The First Members of the Series (CrB2)nCrAl with n = 1, 2, 3 and a Unifying Concept for Ternary Borides as MAB-Phases.

    PubMed

    Ade, Martin; Hillebrecht, Harald

    2015-07-01

    Single crystals of the ternary borides Cr2AlB2, Cr3AlB4, Cr4AlB6, MoAlB, WAlB, Mn2AlB2, and Fe2AlB2 were grown from the elements with an excess of Al. Structures were refined by X-ray methods on the basis of single crystal data. All compounds crystallize in orthorhombic space groups. In each case boron atoms show the typical trigonal prisms BM6. The BM6-units are linked by common rectangular faces forming B-B-bonds. Thus, zigzag chains of boron atoms are obtained for MoAlB, WAlB, and M2AlB2 (M = Cr, Mn, Fe); chains of hexagons for Cr3AlB4; and double chains of hexagons for Cr4AlB6. The same subunits are known for the binary borides CrB, Cr3B4, Cr2B3, and β-WB, too. The boride partial structures are separated by single layers of Al-atoms in the case of the chromium compounds and double layers for WAlB, i.e., W2Al2B2. All crystal structures can be described using a unified building set principle with quadratic 4(4)-nets of metal atoms. The different compositions and crystal structures are obtained by different numbers of metal layers in the corresponding parts according to the formula (MB)2Aly(MB2)x. This principle is an extension of a scheme which was developed for the boridecarbides of niobium. Furthermore, there is a close similarity to the group of ternary carbides MAl(MC)n, so-called MAX-phases. Therefore, they might be named as "MAB-phases". The pronounced two-dimensionality and the mixture of strong covalent and metallic interactions make MAB-phases to promising candidates for interesting material properties. All compositions were confirmed by EDX measurements. Additionally, microhardness measurements were performed. PMID:26069993

  13. Stability and crystal chemistry of the ternary borides M2(Ni21-xMx)B6 (M tbnd Ti, Zr, Hf)

    NASA Astrophysics Data System (ADS)

    Artini, C.; Provino, A.; Valenza, F.; Pani, M.; Cacciamani, G.

    2016-01-01

    A crystallochemical study was undertaken to investigate the structural stability and the compositional extent of the ternary borides M2(Ni21-xMx)B6 (M tbnd Ti, Zr, Hf). This phase often occurs during the production of MB2 joints by means of Ni-B brazing alloys. Samples with the nominal compositions M2Ni21B6 and M3Ni20B6 were synthesized by arc melting and characterized by optical and electron microscopy, and X-ray diffraction. Crystal structure refinements were performed by the Rietveld method. The compositional boundaries of the ternary phases were experimentally determined and found strictly related to the M/Ni size ratio. The stability of this structure is mainly determined by the capability of the structure to expand under the effect of the Ni substitution by the M atom. The CALPHAD modeling of the three M-Ni-B ternary systems in the Ni-rich corner of the phase diagram, performed on the basis of the obtained structural data, shows a good agreement with experimental results.

  14. An XPS study of the adherence of refractory carbide, silicide, and boride RF-sputtered wear-resistant coatings. [X-ray Photoelectron Spectroscopy of steel surfaces

    NASA Technical Reports Server (NTRS)

    Brainard, W. A.; Wheeler, D. R.

    1978-01-01

    Radio frequency sputtering was used to deposit refractory carbide, silicide, and boride coatings on 440-C steel substrates. Both sputter etched and pre-oxidized substrates were used and the films were deposited with and without a substrate bias. The composition of the coatings was determined as a function of depth by X-ray photoelectron spectroscopy combined with argon ion etching. Friction and wear tests were conducted to evaluate coating adherence. In the interfacial region there was evidence that bias may produce a graded interface for some compounds. Biasing, while generally improving bulk film stoichiometry, can adversely affect adherence by removing interfacial oxide layers. Oxides of all film constituents except carbon and iron were present in all cases but the iron oxide coverage was only complete on the preoxidized substrates. The film and iron oxides were mixed in the MoSi2 and Mo2C films but layered in the Mo2B5 films. In the case of mixed oxides, preoxidation enhanced film adherence. In the layered case it did not.

  15. Microstructural Characterization and Wear Behavior of Nano-Boride Dispersed Coating on AISI 304 Stainless Steel by Hybrid High Velocity Oxy-Fuel Spraying Laser Surface Melting

    NASA Astrophysics Data System (ADS)

    Sharma, Prashant; Majumdar, Jyotsna Dutta

    2015-07-01

    The current study concerns the detailed microstructural characterization and investigation of wear behavior of nano-boride dispersed coating developed on AISI 304 stainless steel by high velocity oxy-fuel spray deposition of nickel-based alloy and subsequent laser melting. There is a significant refinement and homogenization of microstructure with improvement in microhardness due to laser surface melting (1200 VHN as compared to 945 VHN of as-sprayed and 250 VHN of as-received substrate). The high temperature phase stability of the as-coated and laser melted surface has been studied by differential scanning calorimeter followed by detailed phase analysis at room and elevated temperature. There is a significant improvement in wear resistance of laser melted surface as compared to as-sprayed and the as-received one due to increased hardness and reduced coefficient of friction. The mechanism of wear has been investigated in details. Corrosion resistance of the coating in a 3.56 wt pct NaCl solution is significantly improved (4.43 E-2 mm/year as compared to 5 E-1 mm/year of as-sprayed and 1.66 mm/year of as-received substrate) due to laser surface melting as compared to as-sprayed surface.

  16. Synthesis, crystal structure, and physical properties of a new boride Ga2Ni21B20 with a modified Zn2Ni21B20-type structure

    NASA Astrophysics Data System (ADS)

    Zheng, Qiang; Gumeniuk, Roman; Schnelle, Walter; Prots, Yurii; Burkhardt, Ulrich; Leithe-Jasper, Andreas

    2016-05-01

    A ternary boride Ga2Ni21B20, with modified Zn2Ni21B20-type structure (space group I4/mmm, and lattice parameters a = 7.2164(1) Å, c = 14.2715(4) Å), was synthesized from the constituent elements. Single crystal diffraction data reveal Ni at 8f site splitting into 16m position with nearly half occupancy. In this structure, [Ni6B20] cages share ligand boron atoms with [Ga2B4Ni9] hexa-capped square prisms, forming two dimensional layers. Layers are interconnected via Ga-Ni interactions and build up a three-dimensional framework. Quasi-two-dimensional infinite planar nets formed by intercrossed Ni atoms are embedded. Ga2Ni21B20 is a metallic Pauli paramagnet, in agreement with electronic structure calculations, resulting in 8.2 states eV-1 f.u-1 at the Fermi level.

  17. Indirect Production of No Carrier Added (NCA) (177)Lu from Irradiation of Enriched (176)Yb: Options for Ytterbium/Lutetium Separation.

    PubMed

    Dash, Ashutosh; Chakravarty, Rubel; Knapp, Furn F Russ; Pillai, Ambikalmajan M R

    2015-01-01

    This article presents a concise review of the production of no-carrier-added (NCA) (177)Lu by the 'indirect' route by irradiating ytterbium-176 ((176)Yb)-enriched targets. The success of this production method depends on the ability to separate the microscopic amounts of NCA (177)Lu from bulk irradiated ytterbium targets. The presence of Yb(+3) from the target in the final processed (177)Lu will adversely affect the quality of (177)Lu by decreasing the specific activity and competing with Lu(+3) complexation since ytterbium will follow the same coordination chemistry. Ytterbium and lutetium are adjacent members of the lanthanide family with very similar chemical properties which makes the separation of one from the other a challenging task. This review provides a summary of the methods developed for the separation and purification of NCA (177)Lu from neutron irradiated (176)Yb-enriched targets, a critical assessment of recent developments and a discussion of the current status of this (177)Lu production method. PMID:25771377

  18. Electron microscopy studies of lutetium doped erbium silicide (Er{sub 0.9}Lu{sub 0.1}){sub 5}Si{sub 4}

    SciTech Connect

    Cao, Q. Chumbley, L.S.

    2011-08-15

    Examination of bulk microstructures of lutetium doped erbium silicide (Er{sub 0.9}Lu{sub 0.1}){sub 5}Si{sub 4} (space group: Pnma) using scanning and transmission electron microscopy (SEM, TEM) reveals the existence of thin plates of a hexagonal phase (space group: P6{sub 3}/mcm) where the stoichiometric ratio in moles between the rare earths and Si is 5 to 3, i. e the 5:3 phase. The orientation relationship between the matrix and the plates was determined as [010]{sub m} {approx} -parallel [-1010]{sub p.} This observation adds credence to the assumption that all linear features noted in alloys of the rare-earth intermetallic family R{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} are of the stoichiometric ratio 5:3 and possess a common orientation relationship with the parent 5:4 alloys. - Highlights: {yields} The linear features observed in the (Er{sub 0.9}Lu{sub 0.1}){sub 5}Si{sub 4} sample are hexagonal 5:3 plates. {yields} Thickness of 5:3 plates in 5:4 alloys made by tri-arc pulling is greater than made by arc-melting. {yields} The orientation relationship between 5:3 plates and the matrix is [010]{sub m} {approx} ||[-1010]{sub p}.

  19. History of ``NANO''-Scale VERY EARLY Solid-State (and Liquid-State) Physics/Chemistry/Metallurgy/ Ceramics; Interstitial-Alloys Carbides/Nitrides/Borides/...Powders and Cermets, Rock Shocks, ...

    NASA Astrophysics Data System (ADS)

    Maiden, Colin; Siegel, Edward

    History of ``NANO'': Siegel-Matsubara-Vest-Gregson[Mtls. Sci. and Eng. 8, 6, 323(`71); Physica Status Solidi (a)11,45(`72)] VERY EARLY carbides/nitrides/borides powders/cermets solid-state physics/chemistry/metallurgy/ ceramics FIRST-EVER EXPERIMENTAL NANO-physics/chemistry[1968 ->Physica Status Solidi (a)11,45(`72); and EARLY NANO-``physics''/NANO-``chemistry'' THEORY(after: Kubo(`62)-Matsubara(`60s-`70s)-Fulde (`65) [ref.: Sugano[Microcluster-Physics, Springer('82 `98)

  20. Crystal structures and compressibility of novel iron borides Fe{sub 2}B{sub 7} and Fe{sub x}B{sub 50} synthesized at high pressure and high temperature

    SciTech Connect

    Bykova, E.; Gou, H.; Bykov, M.; Hanfland, M.; Dubrovinsky, L.; Dubrovinskaia, N.

    2015-10-15

    We present here a detailed description of the crystal structures of novel iron borides, Fe{sub 2}B{sub 7} and Fe{sub x}B{sub 50} with various iron content (x=1.01(1), 1.04(1), 1.32(1)), synthesized at high pressures and high temperatures. As revealed by high-pressure single-crystal X-ray diffraction, the structure of Fe{sub 2}B{sub 7} possesses short incompressible B–B bonds, which make it as stiff as diamond in one crystallographic direction. The volume compressibility of Fe{sub 2}B{sub 7} (the bulk modulus K{sub 0}= 259(1.8) GPa, K{sub 0}′= 4 (fixed)) is even lower than that of FeB{sub 4} and comparable with that of MnB{sub 4}, known for high bulk moduli among 3d metal borides. Fe{sub x}B{sub 50} adopts the structure of the tetragonal δ-B, in which Fe atoms occupy an interstitial position. Fe{sub x}B{sub 50} does not show considerable anisotropy in the elastic behavior. - Graphical abstract: Crystal structures of novel iron borides, Fe{sub 2}B{sub 7} and Fe{sub x}B{sub 50} (x=1.01(1), 1.04(1), 1.32(1)). - Highlights: • Novel iron borides, Fe{sub 2}B{sub 7} and Fe{sub x}B{sub 50}, were synthesized under HPHT conditions. • Fe{sub 2}B{sub 7} has a unique orthorhombic structure (space group Pbam). • Fe{sub 2}B{sub 7} possesses short incompressible B–B bonds that results in high bulk modulus. • Fe{sub x}B{sub 50} adopts the structure of the tetragonal δ-B composed of B{sub 12} icosahedra. • In Fe{sub x}B{sub 50} intraicosahedral bonds are stiffer than intericosahedral ones.

  1. Ternary borides Nb7Fe3B8 and Ta7Fe3B8 with Kagome-type iron framework.

    PubMed

    Zheng, Qiang; Gumeniuk, Roman; Borrmann, Horst; Schnelle, Walter; Tsirlin, Alexander A; Rosner, Helge; Burkhardt, Ulrich; Reissner, Michael; Grin, Yuri; Leithe-Jasper, Andreas

    2016-06-21

    Two new ternary borides TM7Fe3B8 (TM = Nb, Ta) were synthesized by high-temperature thermal treatment of samples obtained by arc-melting. This new type of structure with space group P6/mmm, comprises TM slabs containing isolated planar hexagonal [B6] rings and iron centered TM columns in a Kagome type of arrangement. Chemical bonding analysis in Nb7Fe3B8 by means of the electron localizability approach reveals two-center interactions forming the Kagome net of Fe and embedded B, while weaker multicenter bonding present between this net and Nb atoms. Magnetic susceptibility measurements reveal antiferromagnetic order below TN = 240 K for Nb7Fe3B8 and TN = 265 K for Ta7Fe3B8. Small remnant magnetization below 0.01μB per f.u. is observed in the antiferromagnetic state. The bulk nature of the magnetic transistions was confirmed by the hyperfine splitting of the Mössbauer spectra, the sizable anomalies in the specific heat capacity, and the kinks in the resistivity curves. The high-field paramagnetic susceptibilities fitted by the Curie-Weiss law show effective paramagnetic moments μeff≈ 3.1μB/Fe in both compounds. The temperature dependence of the electrical resistivity also reveals metallic character of both compounds. Density functional calculations corroborate the metallic behaviour of both compounds and demonstrate the formation of a sizable local magnetic moment on the Fe-sites. They indicate the presence of both antiferro- and ferrromagnetic interactions. PMID:27216270

  2. Lutetium oxyorthosilicate (LSO) intrinsic activity correction and minimal detectable target activity study for SPECT imaging with a LSO-based animal PET scanner.

    PubMed

    Yao, Rutao; Ma, Tianyu; Shao, Yiping

    2008-08-21

    This work is part of a feasibility study to develop SPECT imaging capability on a lutetium oxyorthosilicate (LSO) based animal PET system. The SPECT acquisition was enabled by inserting a collimator assembly inside the detector ring and acquiring data in singles mode. The same LSO detectors were used for both PET and SPECT imaging. The intrinsic radioactivity of (176)Lu in the LSO crystals, however, contaminates the SPECT data, and can generate image artifacts and introduce quantification error. The objectives of this study were to evaluate the effectiveness of a LSO background subtraction method, and to estimate the minimal detectable target activity (MDTA) of image object for SPECT imaging. For LSO background correction, the LSO contribution in an image study was estimated based on a pre-measured long LSO background scan and subtracted prior to the image reconstruction. The MDTA was estimated in two ways. The empirical MDTA (eMDTA) was estimated from screening the tomographic images at different activity levels. The calculated MDTA (cMDTA) was estimated from using a formula based on applying a modified Currie equation on an average projection dataset. Two simulated and two experimental phantoms with different object activity distributions and levels were used in this study. The results showed that LSO background adds concentric ring artifacts to the reconstructed image, and the simple subtraction method can effectively remove these artifacts-the effect of the correction was more visible when the object activity level was near or above the eMDTA. For the four phantoms studied, the cMDTA was consistently about five times of the corresponding eMDTA. In summary, we implemented a simple LSO background subtraction method and demonstrated its effectiveness. The projection-based calculation formula yielded MDTA results that closely correlate with that obtained empirically and may have predicative value for imaging applications. PMID:18670052

  3. Lutetium oxyorthosilicate (LSO) intrinsic activity correction and minimal detectable target activity study for SPECT imaging with a LSO-based animal PET scanner

    NASA Astrophysics Data System (ADS)

    Yao, Rutao; Ma, Tianyu; Shao, Yiping

    2008-08-01

    This work is part of a feasibility study to develop SPECT imaging capability on a lutetium oxyorthosilicate (LSO) based animal PET system. The SPECT acquisition was enabled by inserting a collimator assembly inside the detector ring and acquiring data in singles mode. The same LSO detectors were used for both PET and SPECT imaging. The intrinsic radioactivity of 176Lu in the LSO crystals, however, contaminates the SPECT data, and can generate image artifacts and introduce quantification error. The objectives of this study were to evaluate the effectiveness of a LSO background subtraction method, and to estimate the minimal detectable target activity (MDTA) of image object for SPECT imaging. For LSO background correction, the LSO contribution in an image study was estimated based on a pre-measured long LSO background scan and subtracted prior to the image reconstruction. The MDTA was estimated in two ways. The empirical MDTA (eMDTA) was estimated from screening the tomographic images at different activity levels. The calculated MDTA (cMDTA) was estimated from using a formula based on applying a modified Currie equation on an average projection dataset. Two simulated and two experimental phantoms with different object activity distributions and levels were used in this study. The results showed that LSO background adds concentric ring artifacts to the reconstructed image, and the simple subtraction method can effectively remove these artifacts—the effect of the correction was more visible when the object activity level was near or above the eMDTA. For the four phantoms studied, the cMDTA was consistently about five times of the corresponding eMDTA. In summary, we implemented a simple LSO background subtraction method and demonstrated its effectiveness. The projection-based calculation formula yielded MDTA results that closely correlate with that obtained empirically and may have predicative value for imaging applications.

  4. Peptide receptor radionuclide therapy of treatment-refractory metastatic thyroid cancer using 90Yttrium and 177Lutetium labeled somatostatin analogs: toxicity, response and survival analysis

    PubMed Central

    Budiawan, Hendra; Salavati, Ali; Kulkarni, Harshad R; Baum, Richard P

    2014-01-01

    The overall survival rate of non-radioiodine avid differentiated (follicular, papillary, medullary) thyroid carcinoma is significantly lower than for patients with iodine-avid lesions. The purpose of this study was to evaluate toxicity and efficacy (response and survival) of peptide receptor radionuclide therapy (PRRT) in non-radioiodine-avid or radioiodine therapy refractory thyroid cancer patients. Sixteen non-radioiodine-avid and/or radioiodine therapy refractory thyroid cancer patients, including follicular thyroid carcinoma (n = 4), medullary thyroid carcinoma (n = 8), Hürthle cell thyroid carcinoma (n = 3), and mixed carcinoma (n = 1) were treated with PRRT by using 90Yttrium and/or 177Lutetium labeled somatostatin analogs. 68Ga somatostatin receptor PET/CT was used to determine the somatostatin receptor density in the residual tumor/metastatic lesions and to assess the treatment response. Hematological profiles and renal function were periodically examined after treatment. By using fractionated regimen, only mild, reversible hematological toxicity (grade 1) or nephrotoxicity (grade 1) were seen. Response assessment (using EORTC criteria) was performed in 11 patients treated with 2 or more (maximum 5) cycles of PRRT and showed disease stabilization in 4 (36.4%) patients. Two patients (18.2%) showed partial remission, in the remaining 5 patients (45.5%) disease remained progressive. Kaplan-Meier analysis resulted in a mean survival after the first PRRT of 4.2 years (95% CI, range 2.9-5.5) and median progression free survival of 25 months (inter-quartiles: 12-43). In non-radioiodine-avid/radioiodine therapy refractory thyroid cancer patients, PRRT is a promising therapeutic option with minimal toxicity, good response rate and excellent survival benefits. PMID:24380044

  5. Ternary rare earth metal boride carbides containing two-dimensional boron carbon network: The crystal and electronic structure of R2B4C (R=Tb, Dy, Ho, Er)

    NASA Astrophysics Data System (ADS)

    Babizhetskyy, Volodymyr; Zheng, Chong; Mattausch, Hansjürgen; Simon, Arndt

    2007-12-01

    The ternary rare earth boride carbides R2B4C (R=Tb, Dy, Ho, Er) have been synthesized by reacting the elements at temperatures between 1800 and 2000K. The crystal structure of Dy2B4C has been determined from single-crystal X-ray diffraction data. It crystallizes in a new structure type in the orthorhombic space group Immm (a=3.2772(6) Å, b=6.567(2) Å, c=7.542(1) Å, Z=2, R1=0.035 (wR2=0.10) for 224 reflections with Io>2σ(Io)). Boron atoms form infinite chains of fused B6 rings in [100] joined with carbon atoms into planar, two-dimensional networks which alternate with planar sheets of rare earth metal atoms. The electronic structure of Dy2B4C was also analyzed using the tight-binding extended Hückel method.

  6. Ternary boride product and process

    NASA Technical Reports Server (NTRS)

    Clougherty, Edward V. (Inventor)

    1976-01-01

    A hard, tough, strong ceramic body is formed by hot pressing a mixture of a powdered metal and a powdered metal diboride. The metal employed is zirconium, titanium or hafnium and the diboride is the diboride of a different member of the same group of zirconium, titanium or hafnium to form a ternary composition. During hot pressing at temperatures above about 2,000.degree.F., a substantial proportion of acicular ternary monoboride is formed.

  7. Atomic site preferences and its effect on magnetic structure in the intermetallic borides M{sub 2}Fe(Ru{sub 0.8}T{sub 0.2}){sub 5}B{sub 2} (M=Sc, Ti, Zr; T=Ru, Rh, Ir)

    SciTech Connect

    Brgoch, Jakoah; Mahmoud, Yassir A.; Miller, Gordon J.

    2012-12-15

    The site preference for a class of intermetallic borides following the general formula M{sub 2}Fe(Ru{sub 0.8}T{sub 0.2}){sub 5}B{sub 2} (M=Sc, Ti, Zr; T=Ru, Rh, Ir), has been explored using ab initio and semi-empirical electronic structure calculations. This intermetallic boride series contains two potential sites, the Wyckoff 2c and 8j sites, for Rh or Ir to replace Ru atoms. Since the 8j site is a nearest neighbor to the magnetically active Fe atom, whereas the 2c site is a next nearest neighbor, the substitution pattern should play an important role in the magnetic structure of these compounds. The substitution preference is analyzed based on the site energy and bond energy terms, both of which arise from a tight-binding evaluation of the electronic band energy, and are known to influence the locations of atoms in extended solids. According to these calculations, the valence electron-rich Rh and Ir atoms prefer to occupy the 8j site, a result also corroborated by experimental evidence. Additionally, substitution of Rh or Ir at the 8j site results in a modification of the magnetic structure that ultimately results in larger local magnetic moment on the Fe atoms. - Graphical abstract: The site preference for electron rich atoms to occupy the 8j (gray) site is identified in these intermetallic borides, while the magnetic structure is modified as a function of the substituted atoms band center. Highlights: Black-Right-Pointing-Pointer We identify the energetics dictating the site preference in a series of intermetallic borides. Black-Right-Pointing-Pointer Establish substitution rules for use in future directed synthetic preparations. Black-Right-Pointing-Pointer Identified changes in magnetic structure that accompany the site preference.

  8. Synthesis and crystal structures of the new metal-rich ternary borides Ni{sub 12}AlB{sub 8}, Ni{sub 12}GaB{sub 8} and Ni{sub 10.6}Ga{sub 0.4}B{sub 6}-examples for the first B{sub 5} zig-zag chain fragment

    SciTech Connect

    Ade, Martin; Kotzott, Dominik; Hillebrecht, Harald

    2010-08-15

    Single crystals of the new borides Ni{sub 12}AlB{sub 8}, and Ni{sub 10.6}Ga{sub 0.4}B{sub 6} were synthesized from the elements and characterized by XRD and EDXS measurements. The crystal structures were refined on the basis of single crystal data. Ni{sub 12}AlB{sub 8} (oC252, Cmce, a=10.527(2), b=14.527(2), c=14.554(2) A, Z=12, 1350 reflections, 127 parameters, R{sub 1}(F)=0.0284, wR{sub 2}(F{sup 2})=0.0590) represents a new structure type with isolated B atoms and B{sub 5} fragments of a B-B zig-zag chain. Because the pseudotetragonal metric crystals are usually twinned. Ni{sub 10.6}Ga{sub 0.4}B{sub 6} (oP68, Pnma, a=12.305(2), b=2.9488(6), c=16.914(3) A, Z=4, 1386 reflections, 86 parameters, R{sub 1}(F)=0.0394, wR{sub 2}(F{sup 2})=0.104) is closely related to binary Ni borides. The structure contains B-B zig-zag chains and isolated B atoms. Ni{sub 12}GaB{sub 8} is isotypical to the Al-compound (a=10.569(4), b=14.527(4) and c=14.557(5) A). - Graphical abstract: Pentameric B{sub 5}-units are longest fragments of a B-B zig-zag chain ever characterized in a boride. They are found in the structures of Ni{sub 12}AlB{sub 8} and Ni{sub 12}GaB{sub 8}. The compounds are formed on annealing boron-rich {tau}-borides like Ni{sub 20}AlB{sub 14}.

  9. First-principles study of structural stability, elastic and electronic properties of ternary rare earth-transition metal—Borides and carbides (RTxZ, R=Sc, Y, and La, T=Pt and Pd, Z=B and C, and x=2, 3, and 4)

    NASA Astrophysics Data System (ADS)

    Yao, Tiankai; Wang, Yachun; Li, Hui; Lian, Jie; Zhang, Jingwu; Gou, Huiyang

    2013-12-01

    Using first-principles total energy calculations (CASTEP code), the structural stability, elastic, and electronic properties of ternary rare earth-transition metal borides and carbides (RTxZ, R=Sc, Y, and La, T=Pt and Pd, Z=B and C, and x=2, 3, and 4) compounds were studied. Results show that RT3Z compounds with tetragonal P4mm structure are energetically more favorable than usually cubic perovskite-type structure. Furthermore, RT3Z with perovskite structure is found to be mechanically unstable with the negative C44. Formation enthalpy calculations indicate that Pt-based borides are easier to be synthesized compared with Pd-based ones and counterpart carbides, respectively. Elastic constants, bulk moduli, shear moduli, Young's moduli, and Poisson's ratio of studied compounds have been calculated. Also, all the studied compounds show ductile behavior. Moreover, total and partial density of states (DOSs) and bonding charge density were employed to elucidate the bonding features of these compounds. The results reveal that the covalency between Pt-5d and Z-2p as well as T-nd (n=4 for Pd and 5 for Pt) and B-2p states, are the cause of the relatively higher elastic moduli of Pt-based compounds and R-T-borides, respectively.

  10. Electronic structure and bonding of the 3d transition metal borides, MB, M =Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu through all electron ab initio calculations

    NASA Astrophysics Data System (ADS)

    Tzeli, Demeter; Mavridis, Aristides

    2008-01-01

    The electronic structure and bonding of the ground and some low-lying states of all first row transition metal borides (MB), ScB, TiB, VB, CrB, MnB, FeB, CoB, NiB, and CuB have been studied by multireference configuration interaction (MRCI) methods employing a correlation consistent basis set of quintuple cardinality (5Z). It should be stressed that for all the above nine molecules, experimental results are essentially absent, whereas with the exception of ScB and CuB the remaining seven species are studied theoretically for the first time. We have constructed full potential energy curves at the MRCI/5Z level for a total of 27 low-lying states, subsequently used to extract binding energies, spectroscopic parameters, and bonding schemes. In addition, some 20 or more states for every MB species have been examined at the MRCI/4Z level of theory. The ground state symmetries and corresponding binding energies (in kcal/mol) are Σ-5(ScB), 76; Δ6(TiB), 65; Σ+7(VB), 55; Σ+6(CrB), 31; Π5(MnB), 20; Σ-4(FeB), 54; Δ3(CoB), 66; Σ+2(NiB), 79; and Σ+1(CuB), 49.

  11. New ternary rare-earth metal boride carbides R{sub 15}B{sub 4}C{sub 14} (R=Y, Gd-Lu) containing BC{sub 2} units: Crystal and electronic structures, magnetic properties

    SciTech Connect

    Babizhetskyy, Volodymyr; Simon, Arndt; Mattausch, Hansjuergen; Hiebl, Kurt; Zheng Chong

    2010-10-15

    The ternary rare-earth boride carbides R{sub 15}B{sub 4}C{sub 14} (R=Y, Gd-Lu) were prepared from the elements by arc-melting followed by annealing in silica tubes at 1270 K for 1 month. The crystal structures of Tb{sub 15}B{sub 4}C{sub 14} and Er{sub 15}B{sub 4}C{sub 14} were determined from single crystal X-ray diffraction data. They crystallize in a new structure type in space group P4/mnc (Tb{sub 15}B{sub 4}C{sub 14}: a=8.1251(5) A, c=15.861(1) A, Z=2, R{sub 1}=0.041 (wR{sub 2}=0.088) for 1023 reflections with I{sub o}>2{sigma}(I{sub o}); Er{sub 15}B{sub 4}C{sub 14}: a=7.932(1) A, c=15.685(2) A, Z=2, R{sub 1}=0.037 (wR{sub 2}=0.094) for 1022 reflections with I{sub o}>2{sigma}(I{sub o})). The crystal structure contains discrete carbon atoms and bent CBC units in octahedra and distorted bicapped square antiprisms, respectively. In both structures the same type of disorder exists. One R atom position needs to be refined as split atom position with a ratio 9:1 indicative of a 10% substitution of the neighboring C{sup 4-} by C{sub 2}{sup 4-}. The actual composition has then to be described as R{sub 15}B{sub 4}C{sub 14.2}. The isoelectronic substitution does not change the electron partition of R{sub 15}B{sub 4}C{sub 14} which can be written as (R{sup 3+}){sub 15}(C{sup 4-}){sub 6}(CBC{sup 5-}){sub 4{center_dot}}e{sup -}. The electronic structure was studied with the extended Hueckel method. The investigated compounds Tb{sub 15}B{sub 4}C{sub 14}, Dy{sub 15}B{sub 4}C{sub 14} and Er{sub 15}B{sub 4}C{sub 14} are hard ferromagnets with Curie temperatures T{sub C}=145, 120 and 50 K, respectively. The coercive field B{sub C}=3.15 T for Dy{sub 15}B{sub 4}C{sub 14} is quite remarkable. - Graphical abstract: The ternary rare earth boride carbides R{sub 15}B{sub 4}C{sub 14} (R=Y, Gd-Lu) were prepared from the elements by arc-melting followed by annealing in silica tubes at 1270 K for 1 month. Tb{sub 15}B{sub 4}C{sub 14} is a new member of the rare-earth metal boride carbide

  12. Ternary rare earth metal boride carbides containing two-dimensional boron-carbon network: The crystal and electronic structure of R{sub 2}B{sub 4}C (R=Tb, Dy, Ho, Er)

    SciTech Connect

    Babizhetskyy, Volodymyr Zheng Chong; Mattausch, Hansjuergen; Simon, Arndt

    2007-12-15

    The ternary rare earth boride carbides R{sub 2}B{sub 4}C (R=Tb, Dy, Ho, Er) have been synthesized by reacting the elements at temperatures between 1800 and 2000K. The crystal structure of Dy{sub 2}B{sub 4}C has been determined from single-crystal X-ray diffraction data. It crystallizes in a new structure type in the orthorhombic space group Immm (a=3.2772(6) A, b=6.567(2) A, c=7.542(1) A, Z=2, R1=0.035 (wR{sub 2}=0.10) for 224 reflections with I{sub o}>2{sigma}(I{sub o})). Boron atoms form infinite chains of fused B{sub 6} rings in [100] joined with carbon atoms into planar, two-dimensional networks which alternate with planar sheets of rare earth metal atoms. The electronic structure of Dy{sub 2}B{sub 4}C was also analyzed using the tight-binding extended Hueckel method. - Graphical abstract: Dy{sub 2}B{sub 4}C crystallizes a new structure type where planar 6{sup 3}-Dy metal atom layers alternate with planar non-metal layers consisting of ribbons of fused B{sub 6} hexagons bridged by carbon atoms. Isostructural analogues with Tb, Ho and Er have also been characterized.

  13. In{sub 3}Ir{sub 3}B, In{sub 3}Rh{sub 3}B and In{sub 5}Ir{sub 9}B{sub 4}, the first indium platinum metal borides

    SciTech Connect

    Kluenter, Wilhelm; Jung, Walter . E-mail: walter.jung@uni-koeln.de

    2006-09-15

    The first indium platinum metal borides have been synthesized and structurally characterized by single crystal X-ray diffraction data. In{sub 3}Ir{sub 3}B and In{sub 3}Rh{sub 3}B are isotypic. They crystallize with the hexagonal space group P6-bar 2m and Z=1. The lattice constants are a=685.78(1)pm, c=287.30(1)pm for In{sub 3}Ir{sub 3}B and a=678.47(3)pm, c=288.61(6)pm for In{sub 3}Rh{sub 3}B. The structure which is derived from the Fe{sub 2}P type is characterized by columns of boron centered triangular platinum metal prisms inserted in a three-dimensional indium matrix. The indium atoms are on split positions. In{sub 5}Ir{sub 9}B{sub 4} (hexagonal, space group P6-bar 2m, a=559.0(2)pm, c=1032.6(3)pm, Z=1) crystallizes with a structure derived from the CeCo{sub 3}B{sub 2} type. The structure can be interpreted as a layer as well as a channel structure. In part the indium atoms are arranged at the vertices of a honeycomb net (Schlaefli symbol 6{sup 3}) separating slabs consisting of double layers of triangular Ir{sub 6}B prisms, and in part they form a linear chain in a hexagonal channel formed by iridium prisms and indium atoms of the honeycomb lattice.

  14. New ternary rare-earth metal boride carbides R15B 4C 14 ( R=Y, Gd-Lu) containing BC 2 units: Crystal and electronic structures, magnetic properties

    NASA Astrophysics Data System (ADS)

    Babizhetskyy, Volodymyr; Simon, Arndt; Mattausch, Hansjürgen; Hiebl, Kurt; Zheng, Chong

    2010-10-01

    The ternary rare-earth boride carbides R15B 4C 14 ( R=Y, Gd-Lu) were prepared from the elements by arc-melting followed by annealing in silica tubes at 1270 K for 1 month. The crystal structures of Tb 15B 4C 14 and Er 15B 4C 14 were determined from single crystal X-ray diffraction data. They crystallize in a new structure type in space group P4/ mnc (Tb 15B 4C 14: a=8.1251(5) Å, c=15.861(1) Å, Z=2, R1=0.041 (w R2=0.088) for 1023 reflections with Io>2 σ( Io); Er 15B 4C 14: a=7.932(1) Å, c=15.685(2) Å, Z=2, R1=0.037 (w R2=0.094) for 1022 reflections with Io>2 σ( Io)). The crystal structure contains discrete carbon atoms and bent CBC units in octahedra and distorted bicapped square antiprisms, respectively. In both structures the same type of disorder exists. One R atom position needs to be refined as split atom position with a ratio 9:1 indicative of a 10% substitution of the neighboring C 4- by C 24-. The actual composition has then to be described as R15B 4C 14.2. The isoelectronic substitution does not change the electron partition of R15B 4C 14 which can be written as ( R3+) 15(C 4-) 6(CBC 5-) 4•e -. The electronic structure was studied with the extended Hückel method. The investigated compounds Tb 15B 4C 14, Dy 15B 4C 14 and Er 15B 4C 14 are hard ferromagnets with Curie temperatures TC=145, 120 and 50 K, respectively. The coercive field BC=3.15 T for Dy 15B 4C 14 is quite remarkable.

  15. Single crystal studies on boron-rich {tau}-borides Ni{sub 23-x}M{sub x}B{sub 6} (M=Zn, Ga, In, Sn, Ir)-The surprising occurrence of B{sub 4}-tetraheda as a normal case?

    SciTech Connect

    Kotzott, Dominik; Ade, Martin; Hillebrecht, Harald

    2010-10-15

    Single crystals of the cubic {tau}-borides Ni{sub 23-x}M{sub x}B{sub 6} (M=Zn, Ga, In, Sn, Ir) were synthesised from the elements at temperatures between 1200 and 1500 {sup o}C. The structure refinements show that the existence of boron-rich phases is quite common. Starting from the idealised composition Ni{sub 20}M'{sub 3}B{sub 6} a part of the metal atoms on site 8c is substituted by B{sub 4} tetrahedra. For M'=Ga a complete exchange seems to be possible leading to the composition Ni{sub 20}GaB{sub 14}. For M'=Zn and Sn the formation of solid solutions is less extended. For M'=In no exchange is observed but an unusual pattern of Ni/In distribution is observed. With M=Ir mixed occupations occur for all sites and the boron content varies, too. All compositions were confirmed by EDX measurements. - Graphical abstract: Crystal structure of {tau}-Borides M{sub 23}B{sub 6}; M1: M{sub 8}-cubes, M2: M{sub 12}-cuboctahedra centred by M3, isolated M-atoms: M4; grey circles: boron, black circles: metal atoms.

  16. Boron induced structure modifications in Pd-Cu-B system: new Ti2Ni-type derivative borides Pd3Cu3B and Pd5Cu5B2.

    PubMed

    Sologub, Oksana; Salamakha, Leonid P; Eguchi, Gaku; Stöger, Berthold; Rogl, Peter F; Bauer, Ernst

    2016-03-21

    The formation of two distinct derivative structures of Ti2Ni-type, interstitial Pd3Cu3B and substitutive Pd5Cu5B2, has been elucidated in Pd-Cu-B alloys from analysis of X-ray single crystal and powder diffraction data and supported by SEM. The metal atom arrangement in the new boride Pd3Cu3B (space group Fd3m, W3Fe3C-type structure, a = 1.1136(3) nm) follows the pattern of atom distribution in the CdNi-type structure. Pd5Cu5B2 (space group F(4)3m, a = 1.05273(5) nm) exhibits a non-centrosymmetric substitutive derivative of the Ti2Ni-type structure. The reduction of symmetry on passing from Ti2Ni-type structure to Pd5Cu5B2 corresponds to the loss of an inversion centre delivered by an ordered occupation of the Ni position (32e) by dissimilar atoms, Cu and B. In both structures, the boron atom centers Pd forming [BPd6] octahedra in Pd3Cu3B and [BPd6] trigonal prisms in Pd5Cu5B2. Neither a perceptible homogeneity range nor mutual solid solubility was observed for two compounds at 600 °C, while in as cast conditions Pd5Cu5B2 exhibits an extended homogeneity range formed by a partial substitution of Cu atoms (in 24f) by Pd (Pd5+xCu5-xB2, 0 ≤x≤ 1). Electrical resistivity measurements performed on Pd3Cu3B as well as on Pd-poor and Pd-rich termini of Pd5+xCu5-xB2 annealed at 600 °C and in as cast conditions respectively demonstrated the absence of any phase transitions for this compounds in the temperature region from 0.3 K to 300 K. PMID:26875687

  17. New examples of ternary rare-earth metal boride carbides containing finite boron carbon chains: The crystal and electronic structure of RE15B6C20 (RE=Pr, Nd)

    NASA Astrophysics Data System (ADS)

    Babizhetskyy, Volodymyr; Mattausch, Hansjürgen; Simon, Arndt; Hiebl, Kurt; Ben Yahia, Mouna; Gautier, Régis; Halet, Jean-François

    2008-08-01

    The ternary rare-earth metal boride carbides RE15B6C20 (RE=Pr, Nd) were synthesized by co-melting the elements. They exist above 1270 K. Their crystal structures were determined from single-crystal X-ray diffraction data. Both crystallize in the space group P1¯, Z=1, a=8.3431(8) Å, b=9.2492(9) Å, c=8.3581(8) Å, α=84.72(1)°, β=89.68(1)°, γ =84.23(1)° (R1=0.041 (wR2=0.10) for 3291 reflections with Io>2σ(Io)) for Pr15B6C20, and a=8.284(1) Å, b=9.228(1) Å, c=8.309(1) Å, α=84.74(1)°, β=89.68(1)°, γ=84.17(2)° (R1=0.033 (wR2=0.049) for 2970 reflections with Io>2σ(Io)) for Nd15B6C20. Their structure consists of a three-dimensional framework of rare-earth metal atoms resulting from the stacking of slightly corrugated and distorted square nets, leading to cavities filled with unprecedented B2C4 finite chains, disordered C3 entities and isolated carbon atoms, respectively. Structural and theoretical analyses suggest the ionic formulation (RE3+)15([B2C4]6-)3([C3]4-)2(C4-)2·11ē. Accordingly, density functional theory calculations indicate that the compounds are metallic. Both structural arguments as well as energy calculations on different boron vs. carbon distributions in the B2C4 chains support the presence of a CBCCBC unit. Pr15B6C18 exhibits antiferromagnetic order at TN=7.9 K, followed by a meta-magnetic transition above a critical external field B>0.03 T. On the other hand, Nd15B6C18 is a ferromagnet below TC≈40 K.

  18. (Pt1-xCux)3Cu2B and Pt9Cu3B5, the first examples of copper platinum borides. Observation of superconductivity in a novel boron filled β-Mn-type compound

    NASA Astrophysics Data System (ADS)

    Salamakha, Leonid P.; Sologub, Oksana; Stöger, Berthold; Michor, Herwig; Bauer, Ernst; Rogl, Peter F.

    2015-09-01

    New ternary copper platinum borides have been synthesized by arc melting of pure elements followed by annealing at 600 °C. The structures have been studied by X-ray single crystal and powder diffraction. (Pt1-xCux)3Cu2B (x=0.33) forms a B-filled β-Mn-type structure (space group P4132; a=0.6671(1) nm). Cu atoms are distributed preferentially on the 8c atom sites, whereas the 12d site is randomly occupied by Pt and Cu atoms (0.670(4) Pt±0.330(4) Cu). Boron is located in octahedral voids of the parent β-Mn-type structure. Pt9Cu3B5 (space group P-62m; a=0.9048(3) nm, c=0.2908(1) nm) adopts the Pt9Zn3B5-δ-type structure. It has a columnar architecture along the short translation vector exhibiting three kinds of [Pt6] trigonal prism columns (boron filled, boron semi-filled and empty) and Pt channels with a pentagonal cross section filled with Cu atoms. The striking structural feature is a [Pt6] cluster in form of an empty trigonal prism at the origin of the unit cell, which is surrounded by coupled [BPt6] and [Pt6] trigonal prisms, rotated perpendicularly to the central one. There is no B-B contact as well as Cu-B contact in the structure. The relationships of Pt9Cu3B5 structure with the structure of Ti1+xOs2-xRuB2 as well as with the structure families of metal sulfides and aluminides have been elucidated. (Pt1-xCux)3Cu2B (x=0.3) (B-filled β-Mn-type structure) is a bulk superconductor with a transition temperature of about 2.06 K and an upper critical field μ0HC2(0)WHH of 1.2 T, whereas no superconducting transition has been observed up to 0.3 K in Pt9Cu3B5 (Pt9Zn3B5-δ-type structure) from electrical resistivity measurements.

  19. Synthesis, crystal structure investigation and magnetism of the complex metal-rich boride series Cr{sub x}(Rh{sub 1-y}Ru{sub y}){sub 7-x}B{sub 3} (x=0.88-1; y=0-1) with Th{sub 7}Fe{sub 3}-type structure

    SciTech Connect

    Misse, Patrick R.N.; Mbarki, Mohammed; Fokwa, Boniface P.T.

    2012-08-15

    Powder samples and single crystals of the new complex boride series Cr{sub x}(Rh{sub 1-y}Ru{sub y}){sub 7-x}B{sub 3} (x=0.88-1; y=0-1) have been synthesized by arc-melting the elements under purified argon atmosphere on a water-cooled copper crucible. The products, which have metallic luster, were structurally characterized by single-crystal and powder X-ray diffraction as well as EDX measurements. Within the whole solid solution range the hexagonal Th{sub 7}Fe{sub 3} structure type (space group P6{sub 3}mc, no. 186, Z=2) was identified. Single-crystal structure refinement results indicate the presence of chromium at two sites (6c and 2b) of the available three metal Wyckoff sites, with a pronounced preference for the 6c site. An unexpected Rh/Ru site preference was found in the Ru-rich region only, leading to two different magnetic behaviors in the solid solution: The Rh-rich region shows a temperature-independent (Pauli) paramagnetism whereas an additional temperature-dependent paramagnetic component is found in the Ru-rich region. - Graphical abstract: The new complex boride series Cr{sub x}(Rh{sub 1-y}Ru{sub y}){sub 7-x}B{sub 3} (x=0.88-1; y=0-1) has been synthesized by arc melting the elements under purified argon atmosphere. Beside the 3d/4d site preference within the whole solid solution, an unexpected Rh/Ru site preference was found in the Ru-rich region only, leading to two different magnetic behaviors: The Rh-rich region shows a temperature-independent (Pauli) paramagnetism whereas an additional temperature-dependent paramagnetic component is found in the Ru-rich region. Highlights: Black-Right-Pointing-Pointer Synthesis of a new boride series fulfilling Vegard Acute-Accent s rule. Black-Right-Pointing-Pointer 3d/4d site preference. Black-Right-Pointing-Pointer Unexpected Ru/Rh site preference. Black-Right-Pointing-Pointer Rh-rich region is Pauli paramagnetic. Black-Right-Pointing-Pointer Ru-rich region is Pauli and temperature-dependent paramagnetic.

  20. The complex metal-rich boride Ti{sub 1+x}Rh{sub 2-x+y}Ir{sub 3-y}B{sub 3} (x=0.68, y=1.06) with a new structure type containing B{sub 4} zigzag fragments: Synthesis, crystal chemistry and theoretical calculations

    SciTech Connect

    Goerens, Christian; Fokwa, Boniface P.T.

    2012-08-15

    Polycrystalline samples and single crystals of the new complex boride Ti{sub 1+x}Rh{sub 2-x+y}Ir{sub 3-y}B{sub 3} (x=0.68; y=1.06) were synthesized by arc-melting the elements in a water-cooled copper crucible under an argon atmosphere and characterized by X-Ray diffraction as well as EDX measurements. The crystal structure was refined on the basis of single crystal data. The new phase, which represents a new structure type containing trans zigzag B{sub 4} fragments as well as isolated boron atoms crystallizes in the orthorhombic space group Pbam (Nr. 55) with the lattice parameters a=8.620(1) A, b=14.995(2) A and c=3.234(1) A. First-principles density functional theory calculations using the Vienna ab-initio simulation package (VASP) were performed on an appropriate structural model (using a supercell approach) and the experimental crystallographic data could be reproduced accurately. Based on this model, the density of states and crystal orbital Hamilton population (for bonding analysis) were calculated, using the linear muffin-tin orbital atomic sphere approximation (LMTO-ASA) method. According to these calculations, this metal-rich compound should be metallic, as expected. Furthermore, very strong boron-boron interactions are observed in the trans zigzag B{sub 4} fragment, which induce a clear differentiation of two types of metal-boron contacts with different strength. The observed three-dimensional metal-metal interaction is in good agreement with the predicted metallic behavior. - graphical abstract: The structure of Ti{sub 1.68(2)}Rh{sub 2.38(6)}Ir{sub 1.94(4)} B{sub 3}, a new structure type containing planar trans zigzag B{sub 4} units, is another example which illustrates the tendency of metal-rich borides to form B-B bonds with increasing boron content. Beside the B{sub 4} fragment it exhibits one-dimensional chains of titanium atoms and hold one-dimensional strings of face-sharing empty tetrahedral and square pyramidal clusters (see figure). Highlights

  1. Motexafin lutetium in graft coronary artery disease

    NASA Astrophysics Data System (ADS)

    Woodburn, Kathryn W.; Rodriquez, Shari L.; Yamaguchi, Atsushi; Hayase, Motoya; Robbins, Robert C.; Kessel, David

    2000-03-01

    Graft coronary artery disease (GCAD) is the chief complication following cardiac transplantation. Presently, there are limited treatment options. Insights into more expedient diagnosis and amelioration, if only partially, of GCAD are fervently sought. The selectivity of Antrin Injection (Lu-Tex) with subsequent photoactivation has been evaluated in several preclinical atherosclerosis models. The inhibitory effect of Lu-Tex induced photosensitization was demonstrated with human bypass coronary smooth muscle cells. The biodistribution of Lu-Tex was evaluated in a rat model of heterotopic cardiac allografts 60 days following transplantation. Lu-Tex was retained in the cardiac allograft, exhibiting a five-fold increase in retention between the allograft and native heart. These findings lead us to suggest that further studies are warranted to ascertain the merits of Lu-Tex for the diagnosis and possible attenuation of chronic graft vascular disease.

  2. Combustion synthesis of boride and other composites

    DOEpatents

    Halverson, Danny C.; Lum, Beverly Y.; Munir, Zuhair A.

    1989-01-01

    A self-sustaining combustion synthesis process for producing hard, tough, lightweight B.sub.4 C/TiB.sub.2 composites is based on the thermodynamic dependence of adiabatic temperature and product composition on the stoichiometry of the B.sub.4 C and TiB.sub.2 reactants. For lightweight products the composition must be relatively rich in the B.sub.4 C component. B.sub.4 C-rich composites are obtained by varying the initial temperature of the reactants. The product is hard, porous material whose toughness can be enhanced by filling the pores with aluminum or other metal phases using a liquid metal infiltration process. The process can be extended to the formation of other composites having a low exothermic component.

  3. Combustion synthesis of boride and other composites

    DOEpatents

    Halverson, D.C.; Lum, B.Y.; Munir, Z.A.

    1988-07-28

    A self-sustaining combustion synthesis process for producing hard, tough, lightweight B/sub 4/C/TiB/sub 2/ composites is described. It is based on the thermodynamic dependence of adiabatic temperature and product composition on the stoichiometry of the B/sub 4/C and TiB/sub 2/ reactants. For lightweight products the composition must be relatively rich in the B/sub 4/C component. B/sub 4/C-rich composites are obtained by varying the initial temperature of the reactants. The product is hard, porous material whose toughness can be enhanced by filling the pores with aluminum or other metal phases using a liquid metal infiltration process. The process can be extended to the formation of other composites having a low exothermic component. 9 figs., 4 tabs.

  4. Thermal analysis, phase equilibria, and superconducting properties in magnesium boride and carbon doped magnesium boride

    NASA Astrophysics Data System (ADS)

    Bohnenstiehl, Scot David

    In this work, the low temperature synthesis of MgB2 from Mg/B and MgH2/B powder mixtures was studied using Differential Scanning Calorimetry (DSC). For the Mg/B powder mixture, two exothermic reaction events were observed and the first reaction event was initiated by the decomposition of Mg(OH)2 on the surface of the magnesium powder. For the MgH 2/B powder mixture, there was an endothermic event at ˜375 °C (the decomposition of MgH2 into H2 and Mg) and an exothermic event ˜600 °C (the reaction of Mg and B). The Kissinger analysis method was used to estimate the apparent activation energy of the Mg and B reaction using DSC data with different furnace ramp rates. The limitations of MgB2 low temperature synthesis led to the development of a high pressure induction furnace that was constructed using a pressure vessel and an induction heating power supply. The purpose was to not only synthesize more homogeneous MgB2 samples, but also to determine whether MgB2 melts congruently or incongruently. A custom implementation of the Smith Thermal Analysis method was developed and tested on aluminum and AlB2, the closest analogue to MgB2. Measurements on MgB2 powder and a high purity Mg/B elemental mixture confirmed that MgB2 melts incongruently and decomposes into a liquid and MgB4 at ˜1445 °C at 10 MPa via peritectic decomposition. Another measurement using a Mg/B elemental mixture with impure boron suggested that ˜0.7 wt% carbon impurity in the boron raised the incongruent melting temperature to ˜1490-1500 °C. Lastly, the solubility limit for carbon in MgB2 was studied by making samples from B4C and Mg at 1530 °C, 1600 °C and 1700 °C in the high pressure furnace. All three samples had three phases: Mg, MgB2C2, and carbon doped MgB2. The MgB 2C2 and carbon doped MgB2 grain size increased with temperature and the 1700 °C sample had needle-like grains for both phases. The presence of the ternary phase, MgB2C2, suggested that the maximum doping limit for carbon in MgB2 had been reached. The 1530 °C sample was characterized by Electron Probe Microanalysis at the University of Oregon and the average carbon concentration was estimated to be ˜5.9 at%. Further investigation using TEM found MgO inclusions in the 1530 °C sample which were not detected with X-ray diffraction.

  5. Synthesis, crystal structure investigation and magnetism of the complex metal-rich boride series Crx(Rh1-yRuy)7-xB3 (x=0.88-1; y=0-1) with Th7Fe3-type structure

    NASA Astrophysics Data System (ADS)

    Misse, Patrick R. N.; Mbarki, Mohammed; Fokwa, Boniface P. T.

    2012-08-01

    Powder samples and single crystals of the new complex boride series Crx(Rh1-yRuy)7-xB3 (x=0.88-1; y=0-1) have been synthesized by arc-melting the elements under purified argon atmosphere on a water-cooled copper crucible. The products, which have metallic luster, were structurally characterized by single-crystal and powder X-ray diffraction as well as EDX measurements. Within the whole solid solution range the hexagonal Th7Fe3 structure type (space group P63mc, no. 186, Z=2) was identified. Single-crystal structure refinement results indicate the presence of chromium at two sites (6c and 2b) of the available three metal Wyckoff sites, with a pronounced preference for the 6c site. An unexpected Rh/Ru site preference was found in the Ru-rich region only, leading to two different magnetic behaviors in the solid solution: The Rh-rich region shows a temperature-independent (Pauli) paramagnetism whereas an additional temperature-dependent paramagnetic component is found in the Ru-rich region.

  6. (Pt{sub 1–x}Cu{sub x}){sub 3}Cu{sub 2}B and Pt{sub 9}Cu{sub 3}B{sub 5}, the first examples of copper platinum borides. Observation of superconductivity in a novel boron filled β-Mn-type compound

    SciTech Connect

    Salamakha, Leonid P.; Sologub, Oksana; Stöger, Berthold; Michor, Herwig; Bauer, Ernst; Rogl, Peter F.

    2015-09-15

    New ternary copper platinum borides have been synthesized by arc melting of pure elements followed by annealing at 600 °C. The structures have been studied by X-ray single crystal and powder diffraction. (Pt{sub 1−x}Cu{sub x}){sub 3}Cu{sub 2}B (x=0.33) forms a B-filled β-Mn-type structure (space group P4{sub 1}32; a=0.6671(1) nm). Cu atoms are distributed preferentially on the 8c atom sites, whereas the 12d site is randomly occupied by Pt and Cu atoms (0.670(4) Pt±0.330(4) Cu). Boron is located in octahedral voids of the parent β-Mn-type structure. Pt{sub 9}Cu{sub 3}B{sub 5} (space group P-62m; a=0.9048(3) nm, c=0.2908(1) nm) adopts the Pt{sub 9}Zn{sub 3}B{sub 5–δ}-type structure. It has a columnar architecture along the short translation vector exhibiting three kinds of [Pt{sub 6}] trigonal prism columns (boron filled, boron semi-filled and empty) and Pt channels with a pentagonal cross section filled with Cu atoms. The striking structural feature is a [Pt{sub 6}] cluster in form of an empty trigonal prism at the origin of the unit cell, which is surrounded by coupled [BPt{sub 6}] and [Pt{sub 6}] trigonal prisms, rotated perpendicularly to the central one. There is no B–B contact as well as Cu–B contact in the structure. The relationships of Pt{sub 9}Cu{sub 3}B{sub 5} structure with the structure of Ti{sub 1+x}Os{sub 2−x}RuB{sub 2} as well as with the structure families of metal sulfides and aluminides have been elucidated. (Pt{sub 1–x}Cu{sub x}){sub 3}Cu{sub 2}B (x=0.3) (B-filled β-Mn-type structure) is a bulk superconductor with a transition temperature of about 2.06 K and an upper critical field μ{sub 0}H{sub C2}(0){sup WHH} of 1.2 T, whereas no superconducting transition has been observed up to 0.3 K in Pt{sub 9}Cu{sub 3}B{sub 5} (Pt{sub 9}Zn{sub 3}B{sub 5–δ}-type structure) from electrical resistivity measurements. - Highlights: • First two copper platinum borides, (Pt{sub 0.67}Cu{sub 0.33}){sub 3}Cu{sub 2}B and Pt{sub 9}Cu{sub 3}B

  7. Investigation of magnetic properties and electronic structure of layered-structure borides AlT{sub 2}B{sub 2} (T=Fe, Mn, Cr) and AlFe{sub 2–x}Mn{sub x}B{sub 2}

    SciTech Connect

    Chai, Ping; Stoian, Sebastian A.; Tan, Xiaoyan; Dube, Paul A.; Shatruk, Michael

    2015-04-15

    magnetic properties of these materials. - Graphical abstract: We follow a gradual evolution of magnetic properties in a series of ternary borides AlT{sub 2}B{sub 2}, from non-magnetic AlCr{sub 2}B{sub 2} and AlMn{sub 2}B{sub 2} to ferromagnetic AlFe{sub 2}B{sub 2}. - Highlights: • AlT{sub 2}B{sub 2} (T=Fe, Mn, Cr) and AlFe{sub 2−x}Mn{sub x}B{sub 2} were prepared by arc‐melting. • Bulk ferromagnetism of AlFe{sub 2}B{sub 2} is gradually suppressed by the introduction of Mn. • AlMn{sub 2}B{sub 2} and AlCr{sub 2}B{sub 2} do not exhibit magnetic ordering. • Nonmagnetic (Mn‐rich) and ferromagnetic (Fe‐rich) clustering in AlFe{sub 2–x}Mn{sub x}B{sub 2}. • Ferromagnetism is suppressed due to weakening of antibonding T–T interactions.

  8. Electrochromic lutetium phthalocyanine films for in situ detection of NADH

    NASA Astrophysics Data System (ADS)

    Basova, Tamara; Gürek, Ayşe Gül; Ahsen, Vefa; Ray, Asim

    2013-01-01

    A simple and sensitive method for the detection of NADH on a glass substrate modified with spin coated electrochromic [(C6H13S)8Pc]2Lu is presented. The modification of a [(C6H13S)8Pc]2Lu sensing layer was achieved chemically. The functionalized layer shows an efficient activity towards the NADH at conc. as low as 1 × 10-5 M. The in situ UV-Vis and Raman measurements were carried out to study the interaction of oxidized films with NADH. The electrochromic behaviour of [(C6H13S)8Pc]2Lu thin films was examined in detail under various conditions. The spin coated films deposited on glass substrate were chemically oxidized and were found to change the colour. The oxidized films were believed to be reduced to its natural form on interaction with NADH. The colour of the film changed from green to brownish-purple after interaction with NADH. Reversible electrochromism was observed, leading reusable sensor film. The transformation of the oxidised phthalocyanine films into neutral form was monitored by both in situ UV-Vis and Raman techniques.

  9. Lutetium-177 Labeled Bombesin Peptides for Radionuclide Therapy.

    PubMed

    Reynolds, Tamila Stott; Bandari, Rajendra P; Jiang, Zongrun; Smith, Charles J

    2016-01-01

    The rare-earth radionuclides that decay by beta particle (β-) emission are considered to be ideal in the context of targeted radiotherapy. The rare-earth isotopes exist primarily in the 3+ oxidation state and are considered to be hard metal centers, requiring multidentate, hard donor ligands such as the poly(aminocarboxylates) for in vivo kinetic inertness. 177Lu is a rare-earth radionuclide that is produced in moderate specific activity (740 GBq/mg) by direct neutron capture of enriched 176Lu via the 176Lu(n,γ)177Lu nuclear reaction. 177Lu has a half-life of 6.71 d, decays by beta emission (Ebmax = 0.497 MeV), and emits two imagable photons (113keV, 3% and 208kev, 11%). High specific activity, no-carrier-added 177Lu can also be prepared by an indirect neutron capture nuclear reaction on a 176Yb target. Herein, we report upon bombesin (BBN) peptides radiolabeled with 177Lu. The impetus driving many of the research studies that we have described in this review is that the high-affinity gastrin releasing peptide receptor (GRPR, BBN receptor subtype 2, BB2) has been identified in tissue biopsy samples and immortalized cell lines of many human cancers and is an ideal biomarker for targeting early-stage disease. Early on, the ability of GRPR agonists to be rapidly internalized coupled with a high incidence of GRPR expression on various neoplasias was a driving force for the design and development of new diagnostic and therapeutic agents targeting GRP receptor-positive tumors. Recent reports, however, show compelling evidence that radiopharmaceutical design and development based upon antagonist-type ligand frameworks clearly bears reexamination. Last of all, the ability to target multiple biomarkers simultaneously via a heterodimeric targeting ligand has also provided a new avenue to investigate the dual targeting capacity of bivalent radioligands for improved in vivo molecular imaging and treatment of specific human cancers. In this report, we describe recent advances in 177Lu-labeled bombesin peptides for targeted radiotherapy that includes agonist, antagonist, and multivalent cell-targeting agents. In vitro, in vivo translational, and in vivo human clinical investigations are described. PMID:25771366

  10. Lutetium-177 Labeled Peptides: The European Institute of Oncology Experience.

    PubMed

    Carollo, Angela; Papi, Stefano; Chinol, Marco

    2016-01-01

    Peptide receptor radionuclide therapy (PRRT) using radiolabeled somatostatin analogues has shown encouraging results in various somatostatin receptor positive tumors. Partial remission rates up to 30% have been documented as well as significant improvements in quality of life and survival. This treatment takes advantage of the high specific binding of the radiolabeled peptide to somatostatin receptors overexpressed by the tumors thus being more effective on the tumor cells with less systemic side-effects. The development of macrocyclic chelators conjugated to peptides made possible the stable binding with various radionuclides. In particular 177Lu features favourable physical characteristics with a half-life of 6.7 days, emission of β- with energy of 0.5 MeV for treatment and γ-emissions suitable for imaging. The present contribution describes the learning process achieved at the European Institute of Oncology (IEO) since the first application of 90Y labeled peptides to the therapy of neuroendocrine tumors back in 1997. Continuous improvements led to the preparation of a safe 177Lu labeled peptide for human use. Our learning curve began with the identification of the optimal characteristics of the isotope paying attention to its chemical purity and specific activity along with the optimization of the parameters involved in the radiolabeling procedure. Also the radiation protection issues have been improved along the years and recently more and more attention has been devoted to the pharmaceutical aspects involved in the preparation. The overall issue of the quality has now been completed by drafting an extensive documentation with the goal to deliver a safe and reliable product to our patients. PMID:25771368

  11. Lutetium-labelled peptides for therapy of neuroendocrine tumours.

    PubMed

    Kam, B L R; Teunissen, J J M; Krenning, E P; de Herder, W W; Khan, S; van Vliet, E I; Kwekkeboom, D J

    2012-02-01

    Treatment with radiolabelled somatostatin analogues is a promising new tool in the management of patients with inoperable or metastasized neuroendocrine tumours. Symptomatic improvement may occur with (177)Lu-labelled somatostatin analogues that have been used for peptide receptor radionuclide therapy (PRRT). The results obtained with (177)Lu-[DOTA(0),Tyr(3)]octreotate (DOTATATE) are very encouraging in terms of tumour regression. Dosimetry studies with (177)Lu-DOTATATE as well as the limited side effects with additional cycles of (177)Lu-DOTATATE suggest that more cycles of (177)Lu-DOTATATE can be safely given. Also, if kidney-protective agents are used, the side effects of this therapy are few and mild and less than those from the use of (90)Y-[DOTA(0),Tyr(3)]octreotide (DOTATOC). Besides objective tumour responses, the median progression-free survival is more than 40 months. The patients' self-assessed quality of life increases significantly after treatment with (177)Lu-DOTATATE. Lastly, compared to historical controls, there is a benefit in overall survival of several years from the time of diagnosis in patients treated with (177)Lu-DOTATATE. These findings compare favourably with the limited number of alternative therapeutic approaches. If more widespread use of PRRT can be guaranteed, such therapy may well become the therapy of first choice in patients with metastasized or inoperable neuroendocrine tumours. PMID:22388631

  12. Investigation of the fracture mechanics of boride composites

    NASA Technical Reports Server (NTRS)

    Clougherty, E. V.; Pober, R. L.; Kaufman, L.

    1972-01-01

    Significant results were obtained in fabrication studies of the role of metallic additives of Zr, Ti, Ni, Fe and Cr on the densification of ZrB2. All elemental additions lower the processing temperatures required to effect full densification of ZrB2. Each addition effects enhanced densification by a clearly distinguishable and different mechanism and the resulting fabricated materials are different. A significant improvement in strength and fracture toughness was obtained for the ZrB2/Ti composition. Mechanical characterization studies for the ZrB2/SiC/C composites and the new ZrB2/Metal materials produced data relevant to the effect of impacting load on measured impact energies, a specimen configuration for which controlled fracture could occur in a suitably hard testing apparatus, and fracture strength data. Controlled fracture--indicative of measurable fracture toughness--was obtained for the ZrB2-SiC-C composite, and a ZrB2/Ti composite fabricated from ZrB2 with an addition of 30 weight per cent Ti. The increased strength and toughness of the ZrB2/Ti composite is consistent with the presence of a significantly large amount of a fine grained acicular phase formed by reaction of Ti with ZrB2 during processing.

  13. Magnesium boride superconductors: Processing, characterization and enhancement of critical fields

    NASA Astrophysics Data System (ADS)

    Bhatia, Mohit

    In this work, the basic formation of in-situ MgB2, and how variations in the formation process influence the electrical and magnetic properties of this material was studied. Bulk MgB2 samples were prepared by stoichiometric, elemental powder mixing and compaction followed by heat-treatment. Strand samples were prepared by a modified powder-in-tube technique with subsequent heat-treatment. The influence of various heat-treatment schedules on the formation reaction was studied. Two different optimum heat-treatment windows were indentified, namely, low-temperature heat-treatment (below the melting point of Mg i.e. between 620--650°C) and high-temperature heat-treatment (>650°C) for the preparation of MgB2 with good transport properties. XRD was used to confirm phase formation and microstructural variations were studied with the help of SEM. Following a study of the reaction temperature regimes, the focus turned to critical field enhancement via doping with various compounds targeting either the Mg or the B sites. The effects of these dopants on the superconducting properties, in particular the critical fields, were studied. Large increases in irreversibility field, muoH irr, and upper critical field, Bc2, of bulk and strand superconducting MgB2 were achieved by separately adding SiC, amorphous C, and selected metal diborides (NaB2, ZrB 2, TiB2) in bulk samples and three different sizes of SiC (˜200 nm, 30 nm and 15 nm) in strand samples. Lattice spacing shifts and resistivity measurements (on some samples) were consistent with dopant introduction to the lattice. It was also found that both muoH irr and Bc2 depend on the sensing current level which may be an indication of current path percolations. These increases in the Bc2 were also complimented by an increase in the transport Jcs, especially for the SiC doped samples. It was important to differentiate between the effects on the transport properties arising from possible particulate enhanced flux pinning from that due to Bc2 enhancements, associated with smaller length scale disorder. Flux pinning analysis performed on SiC doped samples showed that while some small level of particulate-enhanced pinning was present, the majority of the pinning was associated with a grain boundary mechanism, suggesting that transport Jc increases were predominantly Bc2 related. Lastly, since the residual resistivity of a material is directly related to the electron scattering and hence Bc2, it can therefore be used as a measure to confirm the dopant introduction into the lattice. Normal-state resistivities were measured for various binary and doped MgB2 samples as a function of temperature. These resistivities were modeled based on the Bloch-Gruneissen equations. This allowed extraction of the residual resistivities, Debye temperatures and current carrying volume fractions for these samples, as well as providing information on the electron-phonon coupling constant. The residual resistivity was found to increase by a factor of three, Debye temperature decreased and the electron-phonon coupling constant increased marginally for the SiC doped samples as compared to the binary sample. This change in rho0 and theta D confirmed the XRD evidence that the dopants were increasing mu oHirr and Bc2 by substituting on the B and Mg sites of the crystalline lattice.

  14. Charge transfer and negative curvature energy in magnesium boride nanotubes

    NASA Astrophysics Data System (ADS)

    Tang, Hui; Ismail-Beigi, Sohrab

    2016-07-01

    Using first-principles calculations based on density functional theory, we study the energetics and charge transfer effects in MgBx nanotubes and two-dimensional (2D) sheets. The behavior of adsorbed Mg on 2D boron sheets is found to depend on the amount of electron transfer between the two subsystems. The amount is determined by both the density of adsorbed Mg as well as the atomic-scale structure of the boron subsystem. The degree of transfer can lead to repulsive or attractive Mg-Mg interactions. In both cases, model MgBx nanotubes built from 2D MgBx sheets can display negative curvature energy: a relatively unusual situation in nanosystems where the energy cost to curve the parent 2D sheet into a small-diameter nanotube is negative. Namely, the small-diameter nanotube is energetically preferred over the corresponding flat sheet. We also discuss how these findings may manifest themselves in experimentally synthesized MgBx nanotubes.

  15. Designing thin film materials — Ternary borides from first principles

    PubMed Central

    Euchner, H.; Mayrhofer, P.H.

    2015-01-01

    Exploiting the mechanisms responsible for the exceptional properties of aluminum based nitride coatings, we apply ab initio calculations to develop a recipe for designing functional thin film materials based on ternary diborides. The combination of binary diborides, preferring different structure types, results in supersaturated metastable ternary systems with potential for phase transformation induced effects. For the exemplary cases of MxW1 − xB2 (with M = Al, Ti, V) we show by detailed ab initio calculations that the respective ternary solid solutions are likely to be experimentally accessible by modern depositions techniques. PMID:26082562

  16. Investigation of Non-Magnetic Iron in LUTETIUM(2)IRON(3)SILICON(5) - Superconductors.

    NASA Astrophysics Data System (ADS)

    Xu, Youwen

    1987-03-01

    A focussed study on the effect of transition metal substitution for Fe in the compounds {rm Lu_2(Fe_{1-x}T_{x}) _3Si}_5 (Where T = Cr, Mn, Co, Ni Cu, and Ru) is reported. The effect of these transition metals on the superconducting transition temperature shows that Cr, Co, Ni and Ru all act as non-magnetic impurities. By fitting the experimental data {rm T _{c}/T_{co}} to Kaiser's equation, a good agreement with Kaiser's theory is obtained. The rate of suppression due to Co substitution is similar to that of Ru. Superconductivity persists ({rm T_{c}} = 0.49K) even when 10 at.% Co is substituted for Fe. In contrast, Mn and Cu act as magnetic impurities and suppress {rm T_{c}} in a way described by the theory of Abrikosov and Gor'kov. The molar magnetic susceptibility of {rm Lu_2Fe_3Si}_5 does not follow a Curie-Weiss law, but rather increases slightly as temperature increases. The addition of Ru lowers the value of chi{rm (T) }, but the overall shape of chi {rm (T)} is unchanged. In contrast, the substitution of the nominally magnetic transition metals Cr, Mn, Co and Ni for Fe causes chi{ rm (T)} to become more Curie-Weiss like. The magnetic susceptibility of the compound { rm Lu_2Co_3Si}_5 follows the Curie-Weiss law, while that of the compound {rm Lu_2Ru_3Si}_5 is diamagnetic. The electrical resistivity rho{ rm (T)} of the compound { rm Lu_2Fe_3Si}_5 is approximately quadratic in T at temperatures below 50 K and proportional to lnT at temperature above 100 K. The low temperature heat capacity data of the Co- and Ru-containing samples are similar and both fit to equations gamma{_ {s}T+beta_{s}T}^3 below {rm T_{c} } and gamma{_ {n}T+beta_{n}T^3+ alpha_{n}T}^5 above {rm T_{c}} in agreement with the heat capacity measurement by C. B. Vining for the compound {rm Lu_2Fe_3Si}_5. Increasing the concentration of Co or Ru lowers the Debye temperature and the electronic density of states at the Fermi level of the compounds and enhances the linear term in the superconducting state heat capacity. The reduced specific heat jump between {rm C_{s}} and {rm C_{n}} at {rm T_{c} } follows neither the BCS prediction nor the Abrikosov and Gor'kov's theory. All of the data in this investigation show that the strong covalent bonding between the iron and the silicon atoms in this complex crystal structure is related directly to the unusual behavior of these 3d transition metals in the compounds {rm Lu_2(Fe_ {1-x}T_{x})_3Si} _5. ftn * DOE Report IS-T-1280. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Energy.

  17. Lutetium-177-labeled gastrin releasing peptide receptor binding analogs: a novel approach to radionuclide therapy.

    PubMed

    Panigone, S; Nunn, A D

    2006-12-01

    Optimization of therapy for individual patients remains a goal of clinical practice. Radionuclide imaging can identify those patients who may benefit from subsequent targeted therapy by providing regional information on the distribution of the target. An ideal situation may be when the imaging and the therapeutic compounds are the same agent. Two antibodies ([ [90Y]ibritumomab, [131I]tositumomab) are now approved for the systemic radiotherapy of non-Hodgkin's lymphoma. The main hurdle is to deliver higher absorbed doses to the more refractory solid tumors paying particular regard to the bone marrow toxicity. The low dose is thought to be a result of the large size of antibodies slowing delivery to the target. Peptides having high affinity to receptors expressed on cancer cells are a promising alternative. They are usually rapidly excreted from the body through renal and/or hepatobiliary excretion thus creating a prolonged accumulation of the radioactivity in the kidneys, which represents a recognized issue for systemic radiotherapy. The first radiopeptide developed was a somatostatin analogue, which led to a major breakthrough in the field. Beside the kidney issue, somatostatin use remains limited to few cancers that express receptors in sufficiently large quantities, mainly neuroendocrine tumors. The gastrin releasing peptide (GRP) receptor is an attractive target for development of new radiopeptides with diagnostic and therapeutic potential. This is based upon the functional expression of GRP receptors in several of the more prevalent cancers including prostate, breast, and small cell lung cancer. This review covers the efforts currently underway to develop new and clinically promising GRP-receptor specific molecules labeled with imageable and therapeutic radionuclides. PMID:17043628

  18. Implementation of radiation image detector based on lutetium and gadolinium phosphors

    NASA Astrophysics Data System (ADS)

    Lee, Y.; Shin, J.; Oh, K.; Noh, S.; Kim, D.; Kim, J.; Hong, J.; Park, S.; Kim, J.; Nam, S.

    2013-03-01

    The clinical use of radiation image detectors is influenced by the degree to which patients are exposed to radiation. Phosphors are being used as the radiation receptor materials in a number of radiation imaging systems for the detection of radiation. Rare earth phosphors such as those of Gd, Y, Lu, and La are attracting attention in particular as they exhibit improved properties. However, there has not been any research on the conditions for the synthesis of these phosphors, including the optimal concentrations in which the sensitizer should be added to them. Therefore, in this study, the optimal conditions for the phosphor synthesis were determined by analyzing the characteristics of the phosphors fabricated using various sensitizer concentrations. The deposition method used to form films of the synthesized phosphors was screen printing. This technique is suitable for large-area deposition and allowed for imaging to be performed in conjunction with a complementary metal-oxide semiconductor (CMOS) image detector. The phosphors synthesized were Gd2O3:Eu and Lu2O3:Eu, and the sensitizer used was citric acid, which was added in varying concentrations (0.00-0.05 g) to the phosphors during synthesis. Films of the phosphors 5 × 5 cm in size, which was the size of the active area of the CMOS image sensor, and 100-250 μm in thickness were formed. The structural characteristics of the phosphors were determined through X-ray diffraction analyses and scanning electron microscopy, and the optical characteristics through photoluminescence (PL) measurements. A CMOS-based X-ray detector was manufactured by attaching the phosphor films to the CMOS image sensor and evaluating the modulation transfer functions of the images obtained. The results showed that of all the phosphor samples synthesized, the Gd2O3:Eu and Lu2O3:Eu samples synthesized using 0.02 g of citric acid exhibited the best luminescence characteristics.

  19. Optical property of Ce3+-doped lutetium lithium fluoride for the short-wavelength device application

    NASA Astrophysics Data System (ADS)

    Shimizu, Toshihiko; Yamanoi, Kohei; Arita, Ren; Hori, Tatsuhiro; Fukuda, Kazuhito; Minami, Yuki; Cadatal-Raduban, Marilou; Sarukura, Nobuhiko; Fukuda, Tsuguo; Nagasono, Mitsuru; Ishikawa, Tetsuya

    2014-10-01

    We report on the optical properties of Ce:LLF excited by the 61-nm wavelength emission of the SPring-8 compact self amplification of spontaneous emission source (SCSS) test accelerator, which is a prototype self-amplified stimulated emission (SASE)-type free electron laser (FEL) that emits extreme ultraviolet (EUV) radiation. Ce:LLF fluorescence at 308 nm and 322 nm wavelength was observed using a streak camera. The temporal profile exhibited a 62.1-ns fast decay component and 8.63-ns slow decay component. This double exponential behavior is observed with EUV-FEL excitation and is due to the de-excitation process involving several relaxation steps because of the energetically long distance and intricate band structure between the excitation and emission states. The double exponential nature of fluorescence decay is not observable with low-energy excitation sources; hence, our results show the importance of novel light sources, such as the FEL, for the development and characterization of new materials.

  20. Physical properties of zircon and scheelite lutetium orthovanadate: Experiment and first-principles calculation

    NASA Astrophysics Data System (ADS)

    Huang, Zuocai; Zhang, Lei; Pan, Wei

    2013-09-01

    Pure zircon and scheelite LuVO4 were prepared by solid state reaction and high-pressure route, respectively. Structure, elastic constants, lattice dynamics and thermodynamics of LuVO4 polymorphs were studied by experiments and first principles calculation. Calculations here are in good agreement with the experimental results. The phonon dispersions of LuVO4 polymorphs were studied by the linear response method. The calculated phonon dispersions show that zircon and scheelite LuVO4 phases are dynamically stable. Raman-active frequencies were measured and assigned to different modes according to the calculations. The internal frequencies shift downward after phase transition from zircon to scheelite. Born effective charge tensors elements for both phases are analyzed. The finite temperature thermodynamic properties of LuVO4 polymorphs were calculated from the obtained phonon density of states by quasi-harmonic approach.

  1. Low temperature XAFS investigation on the lutetium binding changes during the 2-line ferrihydrite alteration process.

    PubMed

    Dardenne, K; Schäfer, T; Lindqvist-Reis, P; Denecke, M A; Plaschke, M; Rothe, J; Kim, J I

    2002-12-01

    The time dependent changes of Lu speciation (used as Am(III) homologue), initially sorbed onto 2-line ferrihydrite at pH 5.9, during tempering (70 degrees C) to stable crystalline transformation products, goethite and hematite, is studied. Microscopies (AFM, SEM), XRD and FTIR spectroscopy confirm transformation to both goethite and hematite, with a predominance of hematite. XRD investigation of another transformation series at pH 8.0 (75 degrees C, [Lu(III)initial] 7 times higher) shows that the cell volume of hematite increases, suggesting the incorporation of Lu in the crystal structure. Extended X-ray absorption fine structure (EXAFS) (pH 5.9 series, 70 degrees C) reveals a shortening of the Lu-O bond distance and an increase in asymmetry of the first shell with increasing tempering time in the intermediate temper time samples. The intensity of the second peak in the Fourier transform (FT) of the EXAFS increases and splits into two components. The EXAFS data of the end product can be modeled well using a hematite-like cluster, with an isotropic expansion of distances to account for incorporation of Lu into the hematite structure. These results demonstrate that the Lu is incorporated in the crystal lattice of the transformation product, as opposed to being occluded or remaining a sorbed species on the surface. PMID:12523425

  2. 68Gallium- and 90Yttrium-/ 177Lutetium: "theranostic twins" for diagnosis and treatment of NETs.

    PubMed

    Werner, Rudolf A; Bluemel, Christina; Allen-Auerbach, Martin S; Higuchi, Takahiro; Herrmann, Ken

    2015-01-01

    Abundant expression of somatostatin receptors (SSTR) is frequently identified in differentiated neuroendocrine tumors and may serve as potential target for diagnostic imaging and treatment. This article discusses the "theranostic approach" of SSTR-targeting compounds including an overview of its role for diagnosis, staging and restaging, discussing its way to being established in clinical routine, and giving an outlook about further potentially relevant developments. PMID:25139472

  3. Structural and dielectric properties of the lutetium (Lu) and yttrium (Y) doped nickel ferrite

    SciTech Connect

    Ugendar, Kodam Markandeyulu, G.

    2014-04-24

    The structural and dielectric characteristics of NiFe{sub 1.925}R{sub 0.075}O{sub 4} (R=Lu,Y) were investigated. The material crystallize in the cubic inverse spinel phase with a very small amount of RFeO{sub 3} (R=Lu,Y) as the additional phase. Frequency variation of the dielectric constant shows the dispersion that can be modeled with a modified Debye's function, which considers the possibility of more than one ion, contributing to the relaxation. Impedance spectroscopic analysis indicates the different relaxation mechanisms, bulk grain and grain-boundary contributions to the electrical conductivity and capacitance of these materials.

  4. Formation of molybdenum boride cermet coating by the detonation spray process

    NASA Astrophysics Data System (ADS)

    Yang, Gao; Zu-Kun, Hei; Xiaolei, Xu; Gang, Xin

    2001-09-01

    The effects of the powder particle size and the acetylene/oxygen gas flow ratio during the detonation spray process on the amount of molybdenum phase, porosity, and hardness of the coatings using MoB powder were investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), etc. The results show that the presence of metallic molybdenum in the coating results from decomposition of MoB powder during thermal spray. The compositions of the coatings are metallic Mo, MoB, and Mo2B, which are different from the phases of the original powder. The amount of molybdenum phase increases monotonously with the oxygen/acetylene ratio, but the increasing rate for the fine powder is faster than that for the coarse powder. The porosity and hardness of the coating are related to the amount of molybdenum phase. The phase constitution of the coating is discussed.

  5. Superconductivity and spin fluctuations in the actinoid-platinum metal borides {Th ,U } Pt3B

    NASA Astrophysics Data System (ADS)

    Bauer, E.; Royanian, E.; Michor, H.; Sologub, O.; Scheidt, E.-W.; Gonçalves, A. P.; Bursik, J.; Wolf, W.; Reith, D.; Blaas-Schenner, C.; Moser, R.; Podloucky, R.; Rogl, P.

    2015-07-01

    Investigating the phase relations of the system {Th ,U } -Pt-B at 900 °C the formation of two compounds has been observed: cubic ThPt3B with P m 3 ¯m structure as a representative of the perovskites, and tetragonal UPt3B with P 4 m m structure being isotypic to the noncentrosymmetric structure of CePt3B . The crystal structures of the two compounds are defined by combined x-ray diffraction and transmission electron microscopy. Characterization of physical properties for ThPt3B reveals a superconducting transition at 0.75 K and an upper critical field at T =0 exceeding 0.4 T. For nonsuperconducting UPt3B a metallic resistivity behavior was found in the entire temperature range; at very low temperatures spin fluctuations become evident and the resistivity ρ (T ) follows non-Fermi liquid characteristics, ρ =ρ0+A T n with n =1.6 . Density functional theory (DFT) calculations were performed for both compounds for both types of structures. They predict that the experimentally claimed cubic structure of ThPt3B is thermodynamically not stable in comparison to a tetragonal phase, with a very large enthalpy difference of 25 kJ/mol, which cannot be explained by the formation energy of B vacancies. However, the presence of random boron vacancies possibly stabilizes the cubic structure via a local strain compensation mechanism during the growth of the crystal. For UPt3B the DFT results agree well with the experimental findings.

  6. Improving Hardness and Toughness of Boride Composites Based on AIMgB14

    SciTech Connect

    Justin Steven Peters

    2007-12-01

    The search for new super-hard materials has usually focused on strongly bonded, highly symmetric crystal structures similar to diamond. The two hardest single-phase materials, diamond and cubic boron nitride (cBN), are metastable, and both must be produced at high temperatures and pressures, which makes their production costly. In 2000, a superhard composite based on a low-symmetry, boron-rich compound was reported. Since then, many advances have been made in the study of this AlMgB{sub 14}-TiB{sub 2} composite. The composite has been shown to exhibit hardness greater than either of its constituent phases, relying on its sub-micron microstructure to provide hardening and strengthening mechanisms. With possible hardness around 40 GPa, an AlMgB{sub 14} - 60 vol% TiB{sub 2} approaches the hardness of cBN, yet is amenable to processing under ambient pressure conditions. There are interesting aspects of both the AlMgB{sub 14} and TiB{sub 2} phases. AlMgB{sub 14} is comprised of a framework of boron, mostly in icosahedral arrangements. It is part of a family of 12 known compounds with the same boron lattice, with the metal atoms replaced by Li, Na, Y or a number of Lanthanides. Another peculiar trait of this family of compounds is that every one contains a certain amount of intrinsic vacancies on one or both of the metal sites. These vacancies are significant, ranging from 3 to 43% of sites depending on the composition. TiB{sub 2} is a popular specialty ceramic material due to its high hardness, moderate toughness, good corrosion resistance, and high thermal and electrical conductivity. The major drawback is the difficulty of densification of pure TiB2 ceramics. A combination of sintering aids, pressure, and temperatures of 1800 C are often required to achieve near full density articles. The AlMgB{sub 14} - TiB{sub 2} composites can achieve 99% density from hot-pressing at 1400 C. This is mostly due to the preparation of powders by a high-energy milling technique known as mechanical alloying. The resulting fine powders have high activity, and Fe from wear debris acts as a sintering aid. Mechanical alloying improves the sinterability of the composite material, it has the same effect on pure TiB{sub 2}. TiB{sub 2} processed by high-energy milling has been found to achieve 99% theoretical density at 1400 C with the addition of {approx}1 wt% Fe. Both the AlMgB{sub 14} - TiB{sub 2} composites and pure TiB{sub 2} produced from these methods have enhanced mechanical properties due to their fine microstructures. These materials show exceptional promise in the field of wear resistance. This includes cutting tools, erosion resistant coatings, and low-friction sliding contacts to name a few. Under certain wear conditions, the composite material can show performance on par with that of current high-end cBN and WC materials tailored for wear resistance. The composite material also exhibits low reactivity with Ti alloys, a pre-requisite for effective machining of these alloys, a trait that few hard materials possess.

  7. Iron cobalt boride and iron zirconium silicide-based nanocomposite soft magnetic alloys and application

    NASA Astrophysics Data System (ADS)

    Long, Jianguo

    Nanocrystalline composite soft magnetic materials, which consist of nanoscale crystalline ferromagnetic phases (typical 10 nm) homogeneously dispersed in an amorphous matrix are derived from crystallizing amorphous ribbons. The excellent soft magnetic properties, such as extremely low coercivities, high permeabilities, low energy losses, etc, have attracted the major interest and research activity in both academic community and industrial community in the past two decades. In this thesis, two classes of nanocrystalline composite soft magnetic alloys are developed from their amorphous precursors, accompanying the analysis on their sturctural evolution, thermal kinetics and variou magnetic properties. FeCoB based nanocrystalline composite soft magnetic alloy is developed, in collaboration with Magnetics Division at Spang & Company, for application in high frequency and high temperature. This class of nanocrystalline composite alloy has the nominal composition (FeCo)80Nb4[BGe(Si)] 15Cu1. The crystallization products are bcc FeCo for primary crystallization at 410°C and (FeCoNb)23B 6 for second crystallization. The average grain size is below 10 nm after annealed at 500°C for 1 hour. After transverse field annealing at its primary crystallization temperature, the core loss significantly decreased to the value which can comparable with other commercial soft magnetic alloy. Another class of nanocrystalline composite soft magnetic alloy is Fe based and Boron free alloy. This class of soft magnetic alloy with the nominal composition Fe79ZrxSi20- xCu1 was developed for low cost on raw materials. The nanocrystalline phase alpha-Fe(Si) with average grain size 10 nm was observed in this kind alloy annealed at 460°C for 1 hour. Cu acts as the nucleation agent for making the precipitated nanocrystals uniform and very fine. The measurement of core loss shows the alloy annealed at 460°C for 2 hour has the relatively core loss which can be comparable that of other commericial nanocrystalline soft magnetic alloy. Moreover, the analysis on hysteresis behavior and magnetic domain under different annealing conditions are discussed. The Preisach Distribution evaluated by first order reverse curves (FORCs) indicates the reversible process is dominant when the grain size at the sample is close to 10 nm. The irreversible part should be ascribed to the pinning sites by the grain boundaries which is significant when the large grains exist in the sample.

  8. Elastic stability and electronic structure of tantalum boride investigated via first-principles density functional calculations

    NASA Astrophysics Data System (ADS)

    Chen, Hai-Hua; Bi, Yan; Cheng, Yan; Ji, Guangfu; Cai, Lingcang

    2012-10-01

    The elastic properties, electronic structure and thermodynamic behavior of the TaB have been investigated for the first time in this work. Using first-principles plane-wave ultrasoft-pseudopotential density functional theory (DFT), the ground state properties and equation of state of TaB have been obtained. The average zero-pressure bulk modulus of TaB is 302 GPa. By analyzing the elastically anisotropic behavior and the relative structure parameters of TaB, we found that the crystal cell along the b-axis was more compressible than along the a and c axes. The calculated ratio of bulk modulus and shear modulus (B/G) for TaB is 1.58, demonstrating that TaB is rather brittle. From the elastic stiffness constants, we found that TaB in the Cmcm phase is mechanically stable. The calculated hardness of TaB is 28.6 GPa which is close to the previous data. Moreover, using the Gibbs 2 model, the thermodynamic properties such as the thermal expansion and Debye temperature of TaB have been obtained firstly. At the ambient temperature, the Debye temperatures of TaB are 792 K and 845 K from GGA calculation and LDA calculation, respectively.

  9. Microstructure and mechanical properties of titanium alloys reinforced with titanium boride

    NASA Astrophysics Data System (ADS)

    Hill, Davion M.

    Microstructure features in TiB-reinforced titanium alloys are correlated with mechanical properties. Both laser deposition and arc melting are used to fabricate test alloys where microstructure evolution with heat treatment is examined. SEM and TEM investigations of microstructure are coupled with 3D reconstruction to provide an adequate picture of phases in these alloys. Mechanical properties are then studied. Wear testing of several test alloys is presented, followed by hardness and modulus measurements of individual phases via micro- and nano-indentation as well as a novel micro-compression technique. Bulk mechanical properties are then tested in Ti-6Al-4V and Ti-555 (Ti-5Al-5V-5Mo-3Cr-1Fe) with varying amounts of boron. Image processing methods are then applied to high resolution back-scattered scanning electron microscope images to quantify microstructure features in the tensile test specimens, and these values are then correlated with mechanical properties.

  10. Wetting of boride cathode coatings by low-melting-point cryolite and liquid aluminum

    NASA Astrophysics Data System (ADS)

    Kataev, A. A.; Karimov, K. R.; Chernov, Ya. B.; Kulik, N. P.; Malkov, V. B.; Antonov, B. D.; Vovkotrub, E. G.; Zaikov, Yu. P.

    2010-08-01

    The liquid meniscus that forms on a solid sample in contact with a melt is weighed to determine the angles of wetting of the following three types of cathode coatings by aluminum and low-melting-point cryolite with a high potassium fluoride content: a hot-pressed titanium diboride sample, borated steel, and borated-aluminized steel. Information on the corrosion resistance of these materials in liquid electrolysis bath media is obtained.

  11. Semi-permanent lutetium modifier for the determination of beryllium in urine by electrothermal atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Burguera, J. L.; Burguera, M.; Rondón, C.; Carrero, P.

    1999-11-01

    The determination of beryllium using electrothermal atomic absorption spectrometry with deuterium background correction in the presence of various isomorphous metals and Mg(NO 3) 2 was studied. While, Eu, Ir and Sm had no effect on the transient signals, the addition of Lu and Mg(NO 3) 2 improved the sensitivity of the beryllium signal with respect to that obtained in the absence of modifier. Although, Mg(NO 3) 2 has improved the signal with respect to its sensitivity, it also increased the tail and the background (BG) signals, specially when urine samples are under study. Whereas, when Lu was used the analytical signal is virtually free of BG interference indicating that the urine matrix interference was almost eliminated. Besides, the addition of 6 μg of Lu ensured that the signals were effectively constant for five firings following the furnace program, which included: three drying, and the pyrolysis, atomization, cleaning and cooling steps. The effect of some components, likely to interfere in the accurate determination of beryllium (such as: Al, Ca, Cl, Co, Cr, Fe, Mg and Mn) were investigated. At the physiological levels, most of these elements had no effect, except in the case of chloride when Mg(NO 3) 2 was used as modifier. In this case, the tolerance limit was of 3000 mg Cl - l -1. The characteristic masses were 1.19, 0.45 and 0.48 pg, when integrated absorbance was measured for beryllium without the addition of any modifier and in the presence of Lu and Mg(NO 3) 2, respectively. The limits of detection (3σ) were 85, 19 and 58 fg, respectively. The accuracy and precision with the use of Lu and Mg(NO 3) 2 was tested for the direct determination of beryllium in urine samples. Quantification was performed with aqueous standards. The results obtained for the determination of beryllium in reference materials (Trace Elements in Urine), together with good recovery of spiked analyte, using either Lu or Mg(NO 3) 2 modification demonstrate the applicability of the procedure to the analysis of real samples. However, Lu provided the most accurate results. Also, the addition of Lu enhanced the precision of the measurements to levels of 1.8% relative standard deviation instead of 5.6 and 3.3% for the case of beryllium alone and with the addition of Mg(NO 3) 2.

  12. NEW ABUNDANCE DETERMINATIONS OF CADMIUM, LUTETIUM, AND OSMIUM IN THE r-PROCESS ENRICHED STAR BD +17 3248 {sup ,}

    SciTech Connect

    Roederer, Ian U.; Sneden, Christopher; Lawler, James E.; Cowan, John J.

    2010-05-01

    We report the detection of Cd I (Z = 48), Lu II (Z = 71), and Os II (Z = 76) in the metal-poor star BD +17 3248. These abundances are derived from an ultraviolet spectrum obtained with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. This is the first detection of these neutron-capture species in a metal-poor star enriched by the r process. We supplement these measurements with new abundances of Mo I, Ru I, and Rh I derived from an optical spectrum obtained with the High Resolution Echelle Spectrograph on Keck. Combined with previous abundance derivations, 32 neutron-capture elements have been detected in BD +17 3248, the most complete neutron-capture abundance pattern in any metal-poor star to date. The light neutron-capture elements (38 {<=} Z {<=} 48) show a more pronounced even-odd effect than expected from current solar system r-process abundance predictions. The age for BD +17 3248 derived from the Th II/Os II chronometer is in better agreement with the age derived from other chronometers than the age derived from Th II/Os I. New Hf II abundance derivations from transitions in the ultraviolet are lower than those derived from transitions in the optical, and the lower Hf abundance is in better agreement with the scaled solar system r-process distribution.

  13. Lanthanum(III) and Lutetium(III) in Nitrate-Based Ionic Liquids: A Theoretical Study of Their Coordination Shell.

    PubMed

    Bodo, Enrico

    2015-09-01

    By using ab initio molecular dynamics, we investigate the solvent shell structure of La(3+) and Lu(3+) ions immersed in two ionic liquids, ethylammonium nitrate (EAN) and its hydroxy derivative (2-ethanolammonium nitrate, HOEAN). We provide the first study of the coordination properties of these heavy metal ions in such a highly charged nonacqueous environment. We find, as expected, that the coordination in the liquid is mainly due to nitrate anions and that, due to the bidentate nature of the ligand, the complexation shell of the central ion has a nontrivial geometry and a coordination number in terms of nitrate molecules that apparently violates the decrease of ionic radii along the lanthanides series, since the smaller Lu(3+) ion seems to coordinate six nitrate molecules and the La(3+) ion only five. A closer inspection of the structural features obtained from our calculations shows, instead, that the first shell of oxygen atoms is more compact for Lu(3+) than for La(3+) and that the former coordinates 8 oxygen atoms while the latter 10 in accord with the typical lanthanide's trend along the series and that their first solvation shells have a slight irregular and complex geometrical pattern. When moving to the HOEAN solutions, we have found that the solvation of the central ion is possibly also due to the cation itself through the oxygen atom on the side chain. Also, in this liquid, the coordination numbers in terms of oxygen atoms in both solvents is 10 for La(3+) and 8 for Lu(3+). PMID:26291240

  14. Electronic structure of interstitial hydrogen in lutetium oxide from DFT+U calculations and comparison study with μ SR spectroscopy

    NASA Astrophysics Data System (ADS)

    da Silva, E. Lora; Marinopoulos, A. G.; Vieira, R. B. L.; Vilão, R. C.; Alberto, H. V.; Gil, J. M.; Lichti, R. L.; Mengyan, P. W.; Baker, B. B.

    2016-07-01

    The electronic structure of hydrogen impurity in Lu2O3 was studied by first-principles calculations and muonium spectroscopy. The computational scheme was based on two methods which are well suited to treat defect calculations in f -electron systems: first, a semilocal functional of conventional density-functional theory (DFT) and secondly a DFT+U approach which accounts for the on-site correlation of the 4 f electrons via an effective Hubbard-type interaction. Three different types of stable configurations were found for hydrogen depending upon its charge state. In its negatively charged and neutral states, hydrogen favors interstitial configurations residing either at the unoccupied sites of the oxygen sublattice or at the empty cube centers surrounded by the lanthanide ions. In contrast, the positively charged state stabilized only as a bond configuration, where hydrogen binds to oxygen ions. Overall, the results between the two methods agree in the ordering of the formation energies of the different impurity configurations, though within DFT+U the charge-transition (electrical) levels are found at Fermi-level positions with higher energies. Both methods predict that hydrogen is an amphoteric defect in Lu2O3 if the lowest-energy configurations are used to obtain the charge-transition, thermodynamic levels. The calculations of hyperfine constants for the neutral interstitial configurations show a predominantly isotropic hyperfine interaction with two distinct values of 926 MHz and 1061 MHz for the Fermi-contact term originating from the two corresponding interstitial positions of hydrogen in the lattice. These high values are consistent with the muonium spectroscopy measurements which also reveal a strongly isotropic hyperfine signature for the neutral muonium fraction with a magnitude slightly larger (1130 MHz) from the ab initio results (after scaling with the magnetic moments of the respective nuclei).

  15. Etching studies on lutetium yttrium orthosilicate LuxY2-xSiO5:Ce (LYSO) scintillator crystals

    NASA Astrophysics Data System (ADS)

    Péter, Á.; Berze, N.; Lengyel, K.; Lörincz, E.

    2010-11-01

    Surface dissolution has been investigated on {100}, {010}, {001}, {110} and {101} oriented Lu1.6Y0.4SiO5:Ce crystal samples by using orthophosphoric acid up to 180°C. Depending on the etching temperature and surface orientation smooth or bunched surfaces were produced. In order to study the effect of the etching process on the scintillation properties temperature dependent optical absorption measurements were carried out up to 236°C. It was found that depending on the post-growth history of the sample, etching may influence the scintillation mechanism by modifying the concentration of shallow traps.

  16. New Nd{sup 3+}:CaLu{sub 2}F{sub 8} laser crystal containing lutetium

    SciTech Connect

    Kaminskii, Alexandr A; Butashin, A V; Li, L E; Jaque, D; Garsia, Sole J

    1999-05-31

    A new Nd{sup 3+}:CaLu{sub 2}F{sub 8} fluoride laser crystal with a disordered structure was produced. A preliminary investigation was made of its absorption and luminescence characteristics, and cw lasing ({sup 4}F{sub 3/2} {yields} {sup 4}I{sub 11/2} channel) of the Nd{sup 3+} activator ions was achieved. (letters to the editor)

  17. EF5 and Motexafin Lutetium in Detecting Tumor Cells in Patients With Abdominal or Non-Small Cell Lung Cancer

    ClinicalTrials.gov

    2013-01-15

    Advanced Adult Primary Liver Cancer; Carcinoma of the Appendix; Fallopian Tube Cancer; Gastrointestinal Stromal Tumor; Localized Extrahepatic Bile Duct Cancer; Localized Gallbladder Cancer; Localized Gastrointestinal Carcinoid Tumor; Localized Resectable Adult Primary Liver Cancer; Localized Unresectable Adult Primary Liver Cancer; Metastatic Gastrointestinal Carcinoid Tumor; Ovarian Sarcoma; Ovarian Stromal Cancer; Primary Peritoneal Cavity Cancer; Recurrent Adult Primary Liver Cancer; Recurrent Adult Soft Tissue Sarcoma; Recurrent Colon Cancer; Recurrent Extrahepatic Bile Duct Cancer; Recurrent Gallbladder Cancer; Recurrent Gastric Cancer; Recurrent Gastrointestinal Carcinoid Tumor; Recurrent Non-small Cell Lung Cancer; Recurrent Ovarian Epithelial Cancer; Recurrent Ovarian Germ Cell Tumor; Recurrent Pancreatic Cancer; Recurrent Rectal Cancer; Recurrent Small Intestine Cancer; Recurrent Uterine Sarcoma; Regional Gastrointestinal Carcinoid Tumor; Small Intestine Adenocarcinoma; Small Intestine Leiomyosarcoma; Small Intestine Lymphoma; Stage 0 Non-small Cell Lung Cancer; Stage I Adult Soft Tissue Sarcoma; Stage I Colon Cancer; Stage I Gastric Cancer; Stage I Non-small Cell Lung Cancer; Stage I Ovarian Epithelial Cancer; Stage I Ovarian Germ Cell Tumor; Stage I Pancreatic Cancer; Stage I Rectal Cancer; Stage I Uterine Sarcoma; Stage II Adult Soft Tissue Sarcoma; Stage II Colon Cancer; Stage II Gastric Cancer; Stage II Non-small Cell Lung Cancer; Stage II Ovarian Epithelial Cancer; Stage II Ovarian Germ Cell Tumor; Stage II Pancreatic Cancer; Stage II Rectal Cancer; Stage II Uterine Sarcoma; Stage III Adult Soft Tissue Sarcoma; Stage III Colon Cancer; Stage III Gastric Cancer; Stage III Ovarian Epithelial Cancer; Stage III Ovarian Germ Cell Tumor; Stage III Pancreatic Cancer; Stage III Rectal Cancer; Stage III Uterine Sarcoma; Stage IIIA Non-small Cell Lung Cancer; Stage IIIB Non-small Cell Lung Cancer; Stage IV Adult Soft Tissue Sarcoma; Stage IV Colon Cancer; Stage IV Gastric Cancer; Stage IV Non-small Cell Lung Cancer; Stage IV Ovarian Epithelial Cancer; Stage IV Ovarian Germ Cell Tumor; Stage IV Pancreatic Cancer; Stage IV Rectal Cancer; Stage IV Uterine Sarcoma; Unresectable Extrahepatic Bile Duct Cancer; Unresectable Gallbladder Cancer

  18. Discrete zero-phonon Cr3+ lines in the spectra of Terbium-Yttrium-Lutetium Aluminum garnets solid solutions: Lattice compression and dilation

    NASA Astrophysics Data System (ADS)

    Feofilov, S. P.; Kulinkin, A. B.; Ovanesyan, K. L.; Petrosyan, A. G.

    2016-01-01

    The zero-phonon electronic transitions in Cr3+ impurity ions in a series of Tb3zY3-3zAl5O12 (0

  19. Studies on the Labeling of Ethylenediaminetetramethylene Phosphonic Acid, Methylene Diphosphonate, Sodium Pyrophosphate and Hydroxyapatite with Lutetium-177 for use in Nuclear Medicine.

    PubMed

    Abbasi, Imtiaz Ahmed

    2015-01-01

    For the treatment of skeletal metastasis, a therapeutic radionuclide tagged with a bone seeking ligand is required, while for radiation synovectomy (RS), a therapeutic radionuclide irreversibly attached to pre-formed particles of appropriate size is required. Radio lanthanides are mostly therapeutic, and ligands containing phosphate groups are predominantly bone seekers. Exploiting these facts, number of new therapeutic radiopharmaceuticals could be developed. Labeling of four phosphate containing materials was pursued in the present study. It was hypothesized that various (177)Lu-labeled bone-seeking complexes such as (177)Lu-ethylenediaminetetramethylene phosphonic acid (EDTMP), (177)Lu-methylene diphosphonate (MDP) and (177)Lu-pyrophosphate (PYP) could be developed as agents for palliative radiotherapy of bone pain due to skeletal metastases, and (177)Lu-Hydroxyapatite (HA) could be developed as an agent for radiosynovectomy of small joints. Lyophilized kit vials of EDTMP, MDP and sodium pyrophosphate (Na-PYP) were formulated. HA particles were synthesized locally and purity was checked by high-performance liquid chromatography (HPLC). (177)Lu was labeled with EDTMP, MDP, PYP, and HA and the behavior of all was studied by radio-thin layer chromatography (TLC) radio-HPLC and radio-electrophoresis. Radio-TLC confirmed the labeling. HPLC analysis too verified the labeling. Radio-electrophoresis results depicted peaks for (177)Lu-MDP, (177)Lu-EDTMP and (177)Lu-PYP at 3.37 ± 0.06 cm, 5.53 ± 0.15 cm and 7.03 ± 0.06 cm respectively confirming negative charge on each specie as all migrated toward positive anode. All 3 methods verified the labeling. The study demonstrated that EDTMP, MDP and PYP form stable complexes with (177)Lu in injectable solution form. HA particulates could too be labeled with (177)Lu with high radiochemical yields (>98%) in suspension form. Former three could be utilized as bone-pain palliation agents for the treatment of bone metastases, and the later could be applied for the treatment of Rheumatoid arthritis of small joints. The study has also indicated the possibility of developing other numerous radiolanthanide analogs with the potentials of possible use in radiation therapy. PMID:26097419

  20. Variable Emission Changes in Bi3+/Ln3+ (Ln = Eu, Sm, Dy) Co-doped Lutetium Vanadates (LuVO4)

    NASA Astrophysics Data System (ADS)

    Zheng, Yuhui; Hu, Jing; Deng, Surong; Gao, Jinwei; Wang, Qianming

    2016-06-01

    High-purity LuVO4: Ln3+/Bi3+ (Ln = Eu, Sm, Dy) phosphors with tetragonal zircon structures were successfully synthesized. The reactions have been carried out by multiple irradiations with very high efficiency. Transmission electron microscope images showed that the phosphors had rod-like structures with average lengths of about 200 nm. The host absorption edge of LuVO4: Ln3+/Bi3+ (Ln = Eu, Sm) shifted to the longer wavelength side. Furthermore, the red emission of Eu3+ ion and the orange emission of Sm3+ ion are remarkably enhanced by encapsulating Bi3+ in LuVO4 system, whereas in the case of LuVO4: Dy3+/Bi3+, the host absorption and the yellow emission from dysprosium have been suppressed in the presence of Bi3+. These novel findings will facilitate their use in the display field.

  1. Growth and characterization of Bi, Pr- and Bi, Sc-substituted lutetium iron garnet films with planar magnetization for magneto-optic visualization

    NASA Astrophysics Data System (ADS)

    Syvorotka, Igor M.; Ubizskii, Sergii B.; Kucera, Miroslav; Kuhn, Marcus; Vértesy, Zofia

    2001-04-01

    The series of epitaxial garnet films of general composition Lu3-x-yBixPryFe5- zAlzO12 and Lu3-xBixFe5-y- zScyAlzO12 were grown on (111) oriented GGG (gadolinium gallium garnet) substrates by the liquid phase epitaxy. Their magnetic and magneto-optical properties were studied using both experimental techniques and modelling. All obtained films demonstrated generally a magnetic anisotropy close to the easy-plane type. The Pr-containing films exhibited large negative uniaxial anisotropy and significant cubic anisotropy. The latter causes a distortion of magnetization curves in samples magnetized in a direction normal to the film plane, especially at low temperatures. The large negative uniaxial anisotropy of Pr-substituted iron garnets allows us to increase the saturation field up to 0.5 T at liquid nitrogen temperature. The Sc-doped films displayed small positive uniaxial anisotropy that did not exceed the shape anisotropy. The magnetization curves of these films did not show any distortion due to the cubic anisotropy. The suitability of Pr- and Sc-doped garnets that meet the requirements for indicator layers for magneto-optic visualization at liquid nitrogen temperature is discussed.

  2. Studies on the Labeling of Ethylenediaminetetramethylene Phosphonic Acid, Methylene Diphosphonate, Sodium Pyrophosphate and Hydroxyapatite with Lutetium-177 for use in Nuclear Medicine

    PubMed Central

    Abbasi, Imtiaz Ahmed

    2015-01-01

    For the treatment of skeletal metastasis, a therapeutic radionuclide tagged with a bone seeking ligand is required, while for radiation synovectomy (RS), a therapeutic radionuclide irreversibly attached to pre-formed particles of appropriate size is required. Radio lanthanides are mostly therapeutic, and ligands containing phosphate groups are predominantly bone seekers. Exploiting these facts, number of new therapeutic radiopharmaceuticals could be developed. Labeling of four phosphate containing materials was pursued in the present study. It was hypothesized that various 177Lu-labeled bone-seeking complexes such as 177Lu-ethylenediaminetetramethylene phosphonic acid (EDTMP), 177Lu-methylene diphosphonate (MDP) and 177Lu-pyrophosphate (PYP) could be developed as agents for palliative radiotherapy of bone pain due to skeletal metastases, and 177Lu-Hydroxyapatite (HA) could be developed as an agent for radiosynovectomy of small joints. Lyophilized kit vials of EDTMP, MDP and sodium pyrophosphate (Na-PYP) were formulated. HA particles were synthesized locally and purity was checked by high-performance liquid chromatography (HPLC). 177Lu was labeled with EDTMP, MDP, PYP, and HA and the behavior of all was studied by radio-thin layer chromatography (TLC) radio-HPLC and radio-electrophoresis. Radio-TLC confirmed the labeling. HPLC analysis too verified the labeling. Radio-electrophoresis results depicted peaks for 177Lu-MDP, 177Lu-EDTMP and 177Lu-PYP at 3.37 ± 0.06 cm, 5.53 ± 0.15 cm and 7.03 ± 0.06 cm respectively confirming negative charge on each specie as all migrated toward positive anode. All 3 methods verified the labeling. The study demonstrated that EDTMP, MDP and PYP form stable complexes with 177Lu in injectable solution form. HA particulates could too be labeled with 177Lu with high radiochemical yields (>98%) in suspension form. Former three could be utilized as bone-pain palliation agents for the treatment of bone metastases, and the later could be applied for the treatment of Rheumatoid arthritis of small joints. The study has also indicated the possibility of developing other numerous radiolanthanide analogs with the potentials of possible use in radiation therapy. PMID:26097419

  3. Spectroscopy and laser operation of Sm(3+)-doped lithium lutetium tetrafluoride (LiLuF(4)) and strontium hexaaluminate (SrAl(12)O(19)).

    PubMed

    Marzahl, Daniel-Timo; Metz, Philip Werner; Kränkel, Christian; Huber, Günter

    2015-08-10

    We report on laser operation in the orange and red spectral range in samarium (Sm(3+))-doped fluoride and oxide crystals at 300 K. Sm(3+)-doped LiLuF(4) (LLF) and SrAl(12)O(19) (SRA) crystals were grown by the Czochralski-technique and utilized for spectroscopic investigations and laser experiments. The spin-forbidden transitions of Sm(3+)exhibit low cross sections the order of 10(-21) cm(2), but high radiative upper state lifetimes of several ms in both crystal systems. Under 2ω-OPSL-pumping at 480 nm, orange laser operation was achieved with Sm:LLF and Sm,Mg:SRA at lasing wavelengths of 606 nm and 593 nm, respectively. Furthermore laser oscillation was demonstrated at 648 nm in the red and 703 nm in the deep red spectral range with Sm:LLF and Sm,Mg:SRA, respectively. Output power levels of several 10 mW were obtained at slope efficiencies of up to 15 %. Most of the realized lasers were operating in a strongly modulated or even self-pulsing regime. PMID:26367962

  4. Etudes optiques de nouveaux materiaux laser: Des orthosilicates dopes a l'ytterbium: Le yttrium (lutetium,scandium) pentoxide de silicium

    NASA Astrophysics Data System (ADS)

    Denoyer, Aurelie

    La decouverte et l'elaboration de nouveaux materiaux laser solides suscitent beaucoup d'interet parmi la communaute scientifique. En particulier les lasers dans la gamme de frequence du micron debouchent sur beaucoup d'applications, en telecommunication, en medecine, dans le domaine militaire, pour la, decoupe des metaux (lasers de puissance), en optique non lineaire (doublage de frequence, bistabilite optique). Le plus couramment utilise actuellement est le Nd:YAG dans cette famille de laser, mais des remplacants plus performants sont toujours recherches. Les lasers a base d'Yb3+ possedent beaucoup d'avantages compares aux lasers Nd3+ du fait de leur structure electronique simple et de leur deterioration moins rapide. Parmi les matrices cristallines pouvant accueillir l'ytterbium, les orthosilicates Yb:Y 2SiO5, Yb:Lu2SiO5 et Yb:Sc2SiO 5 se positionnent tres bien, du fait de leur bonne conductivite thermique et du fort eclatement de leur champ cristallin necessaire a l'elaboration de lasers quasi-3 niveaux. De plus l'etude fine et systematique des proprietes microscopiques de nouveaux materiaux s'avere toujours tres interessante du point de vue de la recherche fondamentale, c'est ainsi que de nouveaux modeles sont concus (par exemple pour le champ cristallin) ou que de nouvelles proprietes inhabituelles sont decouvertes, menant a de nouvelles applications. Ainsi d'autres materiaux dopes a l'ytterbium sont connus pour leurs proprietes de couplage electron-phonon, de couplage magnetique, d'emission cooperative ou encore de bistabilite optique, mais ces proprietes n'ont encore jamais ete mises en evidence dans Yb:Y 2SiO5, Yb:Lu2SiO5 et Yb:Sc2SiO 5. Ainsi, cette these a pour but l'etude des proprietes optiques et des interactions microscopiques dans Yb:Y2SiO 5, Yb:Lu2SiO5 et Yb:Sc2SiO5. Nous utilisons principalement les techniques d'absorption IR et de spectroscopie Raman pour determiner les excitations du champ cristallin et les modes de vibration dans le materiau. Des mesures optiques sous champ magnetique ont egalement ete effectuees dans le but de caracteriser le comportement de ces excitations lorsqu'elles sont soumises a l'effet Zeeman. La resonance paramagnetique electronique a permis de completer cette etude de l'eclatement Zeeman suivant toutes les orientations du cristal. Enfin la fluorescence par excitation selective et la fluorescence induite par Raman FT, completent la description des niveaux d'energie et revelent l'existence d'emission cooperative de deux ions Yb3+ et de transferts d'energie. Les resultats de cette these apportent une contribution originale dans le domaine des nouveaux materiaux lasers par l'etude et la comprehension des interactions fines et des proprietes microscopiques d'un materiau en particulier. Ils debouchent a la fois sur des applications possibles dans le domaine de l'optique et des lasers, et sur la comprehension d'aspects fondamentaux. Cette these a prouve l'interet de ces matrices pour leur utilisation comme lasers solides: un fort eclatement du champ cristallin favorable a l'elaboration de laser quasi-3 niveaux, et de larges bandes d'absorption (dues a un fort couplage electron-phonon et a des raies satellites causees par une interaction d'echange entre deux ions Yb3+) qui permettent la generation d'impulsions laser ultra-courtes, l'accordabilite du laser, etc. De plus la miniaturisation des lasers est possible pour l'optique integree grace a des couches minces synthetisees par epitaxie en phase liquide dont nous avons demontre la tres bonne qualite structurale et l'ajustement possible de certains parametres. Nous avons reconstruit le tenseur g du niveau fondamental (qui donne des informations precieuses sur les fonctions d'onde), ceci dans le but d'aider les theoriciens a concevoir un modele de champ cristallin valide. Plusieurs mecanismes de transferts d'energie ont ete mis en evidence: un mecanisme de relaxation d'un site vers l'autre, un mecanisme d'emission cooperative, et un mecanisme d'excitation de l'Yb3+ par le Tm3+ (impurete presente dans le materiau). Ces transferts sont plutot nefastes pour la fabrication d'un laser mais sont interessants pour l'optique non lineaire (doublage de frequence, memoires optiques). Enfin, plusieurs elements (le couplage magnetique de paire, le couplage electron-phonon et l'emission cooperative) nous ont permis de conclure sur le caractere covalent de la matrice. Nous avons d'ailleurs demontre ici le role de la covalence dans l'emission cooperative, transition habituellement attribuee aux interactions multipolaires electriques.

  5. Variable Emission Changes in Bi3+/Ln3+ (Ln = Eu, Sm, Dy) Co-doped Lutetium Vanadates (LuVO4)

    NASA Astrophysics Data System (ADS)

    Zheng, Yuhui; Hu, Jing; Deng, Surong; Gao, Jinwei; Wang, Qianming

    2016-02-01

    High-purity LuVO4: Ln3+/Bi3+ (Ln = Eu, Sm, Dy) phosphors with tetragonal zircon structures were successfully synthesized. The reactions have been carried out by multiple irradiations with very high efficiency. Transmission electron microscope images showed that the phosphors had rod-like structures with average lengths of about 200 nm. The host absorption edge of LuVO4: Ln3+/Bi3+ (Ln = Eu, Sm) shifted to the longer wavelength side. Furthermore, the red emission of Eu3+ ion and the orange emission of Sm3+ ion are remarkably enhanced by encapsulating Bi3+ in LuVO4 system, whereas in the case of LuVO4: Dy3+/Bi3+, the host absorption and the yellow emission from dysprosium have been suppressed in the presence of Bi3+. These novel findings will facilitate their use in the display field.

  6. Phase II study of lutetium-177 labeled anti-prostate-specific membrane antigen (PSMA) monoclonal antibody J591 for metastatic castration-resistant prostate cancer

    PubMed Central

    Tagawa, Scott T.; Milowsky, Matthew I.; Morris, Michael; Vallabhajosula, Shankar; Christos, Paul; Akhtar, Naveed H.; Osborne, Joseph; Goldsmith, Stanley J.; Larson, Steve; Taskar, Neeta Pandit; Scher, Howard I.; Bander, Neil H.; Nanus, David M.

    2013-01-01

    Purpose To assess the efficacy of a single infusion of radiolabeled anti-prostate specific membrane antigen monoclonal antibody J591 (177Lu-J591) by PSA decline, measurable disease response, and survival. Experimental Design In this dual-center phase II study, 2 cohorts with progressive metastatic castration-resistant prostate cancer received one dose of 177Lu-J591 (15 patients at 65 mCi/m2, 17 at 70 mCi/m2) with radionuclide imaging. Expansion cohort (n=15) received 70 mCi/m2 to verify response rate and examine biomarkers. Results 47 patients who progressed after hormonal therapies (55.3% also received prior chemotherapy) received 177Lu-J591. 10.6% experienced ≥ 50% decline in PSA, 36.2% experienced ≥ 30% decline, and 59.6% experienced any PSA decline following their single treatment. One of 12 with measurable disease experienced a partial radiographic response (8 with stable disease). Sites of prostate cancer metastases were targeted in 44 of 47 (93.6%) as determined by planar imaging. All experienced reversible hematologic toxicity with grade 4 thrombocytopenia occurring in 46.8% (29.8% received platelet transfusions) without significant hemorrhage. 25.5% experienced grade 4 neutropenia with 1 episode of febrile neutropenia. The phase I maximum tolerated dose (70 mCi/m2) resulted in more 30% PSA declines (46.9% vs 13.3%, p=0.048) and longer survival (21.8 vs 11.9 months, p=0.03), but also more grade 4 hematologic toxicity and platelet transfusions. No serious non-hematologic toxicity occurred. Those with poor PSMA imaging were less likely to respond. Conclusion A single dose of 177Lu-J591 was well-tolerated with reversible myelosuppression. Accurate tumor targeting and PSA responses were seen with evidence of dose-response. Imaging biomarkers appear promising. PMID:23714732

  7. Synthesis of ferromagnetic nanoparticles, formic acid oxidation catalyst nanocomposites, and late-transition metal-boride intermetallics by unique synthetic methods and single-source precursors

    NASA Astrophysics Data System (ADS)

    Wellons, Matthew S.

    The design, synthesis, and characterization of magnetic alloy nanoparticles, supported formic acid oxidation catalysts, and superhard intermetallic composites are presented. Ferromagnetic equatomic alloy nanoparticles of FePt, FePd, and CoPt were synthesized utilizing single-source heteronuclear organometallic precursors supported on an inert water-soluble matrix. Direct conversion of the precursor-support composite to supported ferromagnetic nanoparticles occurs under elevated temperatures and reducing conditions with metal-ion reduction and minimal nanoparticle coalescence. Nanoparticles were easily extracted from the support by addition of water and characterized in structure and magnetic properties. Palladium and platinum based nanoparticles were synthesized with microwave-based and chemical metal-ion reduction strategies, respectively, and tested for catalytic performance in a direct formic acid fuel cell (DFAFC). A study of palladium carbide nanocomposites with various carbonaceous supports was conducted and demonstrated strong activity comparable to commercially available palladium black, but poor catalytic longevity. Platinum-lead alloy nanocomposites synthesized with chemical reduction and supported on Vulcan carbon demonstrated strong activity, excellent catalytic longevity, and were subsequently incorporated into a prototype DFAFC. A new method for the synthesis of superhard ceramics on polymer substrates called Confined Plasma Chemical Deposition (CPCD) was developed. The CPCD method utilizes a tuned Free Electron Laser to selectively decompose the single-source precursor, Re(CO)4(B3H8), in a plasma-like state resulting in the superhard intermetallic ReB2 deposited on polymer substrates. Extension of this method to the synthesis of other hard of superhard ceramics; WB4, RuB2, and B4C was demonstrated. These three areas of research show new synthetic methods and novel materials of technological importance, resulting in a substantial advance in their respective fields.

  8. CaNi/sub 12/B/sub 6/: a new boride of the SrNi/sub 12/B/sub 6/ structure type

    SciTech Connect

    Leshko, L.V.; Kuz'ma, Yu.B.

    1987-11-01

    The structure of CaNi/sub 12/B/sub 6/ has been examined from the diffraction pattern (DRON-3.0, Cu K/sub ..cap alpha../ radiation). When the pattern had been indexed to the hexagonal system, the cell parameters were found as ..cap alpha.. = 9.542 (3); c = 7.420 (3) A. The coordinates of the Ca and Ni atoms were refined via the PMNK program with an SM-4 computer, with the initial coordinates those for the metal atoms in SrNi/sub 12/B/sub 6/. The coordinates of the boron atoms were not refined, being taken the same as in SrNi/sub 12/B/sub 6/. The final values for the coordinates (space group R3m) are Ca at 3 (..cap alpha..) 000, B = 3.3 (5) A/sup 2/; 18 Nil at 18 (g) (x = 0.369(2)), B = 0.7(1) A/sup 2/; 18Ni2 at 18 (h) (x = 0.426(1), z = 0.031(2)), B = 0.5(1) A/sup 2/; 18B at 18 (h) (x = 0.191, z = 0.042), B = 3.3(5) A/sup 2/. The intensities were calculated for these coordinates, reliability factor R = 0.108

  9. Superconductivity in a New Pseudo-Binary Li2B(Pd1-xPtx)3 (x=0--1) Boride System

    NASA Astrophysics Data System (ADS)

    Badica, Petre; Kondo, Takaaki; Togano, Kazumasa

    2005-03-01

    Recently we have found superconductivity in a cubic antiperovskite-like compound Li2BPd3. A new pseudo-binary complete solid solution Li2B(Pd1-xPtx)3, x=0--1 with similar structure has been synthesized and observation of superconductivity in the entire x-range is reported. Our results strongly suggest that superconductivity is of bulk type. Critical temperature Tc is decreasing approximately linearly with amount (x) of Pt from 7.2-8 K for Li2BPd3 to 2.2-2.8 K for Li2BPt3. From isothermal magnetization (M-H) measurements, lower critical fields Hc1 (138 Oe/x=0, 38 Oe/x=1), upper critical fields Hc2WHH (3.4 T/x=0, 1 T/x=1), coherence length ξ(0) (9.8 nm/x=0, 17.9 nm/x=1) and penetration depth λ(0) (190 nm/x=0, 364 nmx=1) were estimated and shown to follow approximately linear dependencies with x, either. Structure and superconducting similarities with MgCNi3, viewed as a bridge between low and high Tc superconductors are increasing the expectations that Li2B(Pd1-xPtx)3, x=0--1 superconductor can be included in the same class of ‘intermediate’ superconductors. For x=0--1 a weak fish-tail effect was observed at low and intermediate fields. Apart from this effect, some samples for x=1 have shown magnetization jumps at fields close to Hc2.

  10. Synthesis and crystal structure of Mg{sub 2}B{sub 24}C, a new boron-rich boride related to 'tetragonal boron I'

    SciTech Connect

    Adasch, Volker; Hess, Kai-Uwe; Vojteer, Natascha; Hillebrecht, Harald . E-mail: harald.hillebrecht@ac.uni-freiburg.de

    2006-07-15

    Single crystals of Mg{sub 2}B{sub 24}C, a new boron-rich boridecarbide of magnesium, were synthesized as black needles and columns by reaction of the elements in Ta ampoules and BN crucibles at 1300 deg. C. The crystal structure was determined by X-ray diffraction (P-4n2, a=8.9391(13)A, c=5.0745(10)A, Z=2, 713 reflections, 64 variables, R{sub 1}(F)=0.0235, wR{sub 2}(I)=0.0591). It is closely related to 'tetragonal boron I' and can be described as a tetragonal rod packing of corner-linked B{sub 12} icosahedra with C and Mg atoms in the voids. Each B{sub 12} icosahedron has 2 B-C bonds and 10 exohedral bonds to other icosahedra, 2 within the rod and 4x2 to neighbouring rods. The isolated C atoms are 4-fold coordinated forming distorted tetrahedra. Mg is placed on two crystallographically independent positions within the three-dimensional B{sub 12}C network. Mg{sub 2}B{sub 24}C is the first example for a compound related to 'tetragonal boron I' with a stoichiometric composition.

  11. Identification of specific phonon contributions in BCS-type superconductivity of boride-carbide crystals with a layer-like structure

    NASA Astrophysics Data System (ADS)

    Uzunok, H. Y.; Tütüncü, H. M.; Özer, S.; Ugˇur, Ş.; Srivastava, G. P.

    2015-03-01

    We report on an ab initio study of the BCS-type superconductivity in the intermetallic borocarbides YPd2B2C, YPt2B2C and LaPt2B2C with a layer-like structure. The largest contribution to the electron-phonon coupling constant λ is identified to come from transverse acoustic phonons at a zone-edge, arising from the atomic vibrations in the boron-transition metal layer. A detailed examination of the atomic geometry in the boron-transition metal layer, the electron-phonon coupling constant λ, and the logarithmically averaged phonon frequency ωln helps explain the relatively higher superconducting temperature Tc of YPd2B2C (20.6 K) compared to that of YPt2B2C (11.3 K) and LaPt2B2C (10.40 K).

  12. Structural arrangements of the ternary metal boride carbide compounds MB 2C 4 ( M=Mg, Ca, La and Ce) from first-principles theory

    NASA Astrophysics Data System (ADS)

    Fang, Chang-Ming; Bauer, Joseph; Saillard, Jean-Yves; Halet, Jean-François

    2007-09-01

    The structural arrangements of the ternary metal borocarbides MB 2C 4 ( M=Mg, Ca; La and Ce) are investigated using density-functional theory (DFT) calculations within the generalized gradient approximation (GGA). Results indicate that these compounds adopt a layered structure consisting of graphite-like B 2C 4 layers alternating with metal sheets. Within the hexagonal layers, the coloring with the -C-C-C-B-C-B- sequence is energetically more stable than that with the -C-C-C-C-B-B- one. The electronic structures of these compounds, mainly determined by the B 2C 4 sheets, can be rationalized with the simple valence electron distribution M2+[B 2C 4] 2-xe -, with the metals essentially acting as two-electron donors with respect to the boron-carbon network, the other x electrons remaining in the relatively narrow d and/or f bands of the metals. Accordingly, MB 2C 4 are narrow band-gap semiconductors (Δ E≈0.2-0.4 eV) with M=Mg and Ca. On the other hand, with M=La and Ce, the compounds are conducting with a relatively high density of states at the Fermi level predominantly metal in character with substantial B/C π* antibonding state admixture.

  13. Effect of double addition of V and Cr on the properties of Mo2NiB2 ternary boride-based cermets

    NASA Astrophysics Data System (ADS)

    Shiota, Yuusuke; Miyajima, Yuuta; Fujima, Takuya; Takagi, Ken-ichi

    2009-06-01

    The effect of double addition of V and Cr on the mechanical properties and microstructure of Mo2NiB2 base cermet was investigated. Total additional amount of V and Cr was fixed to 12.5 mass% and the fraction between the two additives was varied. Transverse rupture strength (TRS) and Rockwell A-scale hardness (HRA) were measured on the cermets and discussed together with their microstructure obtained by X-ray diffraction (XRD) and backscattered electron images (COMP). Addition of 2.5-mass% Cr and 10-mass% V showed the highest mechanical properties. Microstructural analysis revealed that brittle orthoronbic-M5B3 phase was formed in high V fraction. The corrosion resistance of the cermets against hydrochloric acid was superior to that of JIS SUS 304. The resistance against nitric acid decreased with decreasing Cr content and was lower than that of SUS 304.

  14. Quantitative Electron-Excited X-Ray Microanalysis of Borides, Carbides, Nitrides, Oxides, and Fluorides with Scanning Electron Microscopy/Silicon Drift Detector Energy-Dispersive Spectrometry (SEM/SDD-EDS) and NIST DTSA-II.

    PubMed

    Newbury, Dale E; Ritchie, Nicholas W M

    2015-10-01

    A scanning electron microscope with a silicon drift detector energy-dispersive X-ray spectrometer (SEM/SDD-EDS) was used to analyze materials containing the low atomic number elements B, C, N, O, and F achieving a high degree of accuracy. Nearly all results fell well within an uncertainty envelope of ±5% relative (where relative uncertainty (%)=[(measured-ideal)/ideal]×100%). Quantification was performed with the standards-based "k-ratio" method with matrix corrections calculated based on the Pouchou and Pichoir expression for the ionization depth distribution function, as implemented in the NIST DTSA-II EDS software platform. The analytical strategy that was followed involved collection of high count (>2.5 million counts from 100 eV to the incident beam energy) spectra measured with a conservative input count rate that restricted the deadtime to ~10% to minimize coincidence effects. Standards employed included pure elements and simple compounds. A 10 keV beam was employed to excite the K- and L-shell X-rays of intermediate and high atomic number elements with excitation energies above 3 keV, e.g., the Fe K-family, while a 5 keV beam was used for analyses of elements with excitation energies below 3 keV, e.g., the Mo L-family. PMID:26365439

  15. Synthesis and characterization of titanium carbide, titanium boron carbonitride, titanium boride/titanium carbide and titanium carbide/chromium carbide multilayer coatings by reactive and ion beam assisted, electron beam-physical vapor deposition (EB-PVD)

    NASA Astrophysics Data System (ADS)

    Wolfe, Douglas Edward

    The purpose of the present work was to investigate the synthesis of titanium carbide, TiBCN, TiB2/TiC and TiC/Cr23C6 multilayer coatings by several methods of electron beam-physical vapor deposition (EB-PVD) and examine the affects of various processing parameters on the properties and microstructures of the coatings. TiC was successfully deposited by reactive ion beam assisted (RIBA), EB-PVD and the results were compared to various titanium carbide coatings deposited by a variety of techniques. The affects of substrate temperature and ion beam current density were correlated with composition, hardness, changes in the lattice parameter, degree of crystallographic texture, residual stress, surface morphology, and microstructure. The average Vicker's hardness number was found to increase with increasing ion beam current density and increase over the substrate temperature range of 250°C to 650°C. The average Vicker's hardness number decreased at a substrate temperature of 750°C as a result of texturing and microstructure. The present investigation shows that the average Vicker's hardness number is not only a function of the composition, but also the microstructure including the degree of crystallographic texture. TiB2/TiC multilayer coatings were deposited by argon ion beam assisted, EB-PVD with varying number of total layers to two different film thicknesses under slightly different deposition conditions. In both cases, the hardness of the coatings increased with increasing number of total layers. The adhesion of the coatings ranged from 30 N to 50 N, with the better adhesion values obtained with the thinner coatings. The crystallographic texture coefficients of both the TiC and TiB2 layers were found to change with increasing number of total layers. The multilayer design was found to significantly affect the microstructure and grain size of the deposited coatings. The fracture toughness was found to decrease with increasing number of total layers and was attributed to the increase in hardness and reduction in the total amount of compressive stress. TiBCN coatings were synthesized by the co-evaporation of titanium, titanium diboride, and carbon (through tungsten) while simultaneously bombarding the substrate surface with a mixture of argon and nitrogen ionized gas which has not been performed to the author's knowledge. The bulk composition was determined by EPMA and suggests that TiBCN has a wide compositional range similar to TiN and TiC. The TiBCN coatings were determined to be nano-crystalline with a cubic crystallographic structure. The average Vicker's hardness number of the TiBCN coatings ranged from 2777 VHN0.050 to 3343 VHN0.050 with the highest value reported for the higher concentrations of boron. The adhesion of the coatings to WC-6wt.Co-0.3wt.%TaC was found to increase from 20 N to 52 N with decreasing compressive stress. Lastly, multilayer titanium carbide and chromium carbide coatings with varying individual layer thickness were synthesized by the co-evaporation of Ti, Cr and C through tungsten at elevated temperatures. The average Vicker's hardness number was found to increase from 1302 VHN0.050 to 2052 VHN0.050 by changing the individual layer thickness of the multilayers. In addition, the grain size, measured compressive stress, and fracture toughness values all decreased with decreasing individual layer thickness.

  16. Structural arrangements of the ternary metal boride carbide compounds MB{sub 2}C{sub 4} (M=Mg, Ca, La and Ce) from first-principles theory

    SciTech Connect

    Fang Changming Bauer, Joseph; Saillard, Jean-Yves; Halet, Jean-Francois

    2007-09-15

    The structural arrangements of the ternary metal borocarbides MB{sub 2}C{sub 4} (M=Mg, Ca; La and Ce) are investigated using density-functional theory (DFT) calculations within the generalized gradient approximation (GGA). Results indicate that these compounds adopt a layered structure consisting of graphite-like B{sub 2}C{sub 4} layers alternating with metal sheets. Within the hexagonal layers, the coloring with the -C-C-C-B-C-B- sequence is energetically more stable than that with the -C-C-C-C-B-B- one. The electronic structures of these compounds, mainly determined by the B{sub 2}C{sub 4} sheets, can be rationalized with the simple valence electron distribution M{sup 2+}[B{sub 2}C{sub 4}]{sup 2-}xe{sup -}, with the metals essentially acting as two-electron donors with respect to the boron-carbon network, the other x electrons remaining in the relatively narrow d and/or f bands of the metals. Accordingly, MB{sub 2}C{sub 4} are narrow band-gap semiconductors ({delta}E{approx}0.2-0.4 eV) with M=Mg and Ca. On the other hand, with M=La and Ce, the compounds are conducting with a relatively high density of states at the Fermi level predominantly metal in character with substantial B/C{pi}* antibonding state admixture. - Graphical abstract: Density-functional theory calculations on the structural arrangements of the ternary metal borocarbides MB{sub 2}C{sub 4} (M=Mg, Ca; La and Ce) indicate that these compounds adopt a layered structure consisting of graphite-like B{sub 2}C{sub 4} layers alternating with metal sheets. Within the hexagonal layers, the coloring with the -C-C-C-B-C-B- sequence is energetically more stable than that with the -C-C-C-C-B-B- one.

  17. Zr{sub 2}Ir{sub 6}B with an eightfold superstructure of the cubic perovskite-like boride ZrIr{sub 3}B{sub 0.5}: Synthesis, crystal structure and bonding analysis

    SciTech Connect

    Hermus, Martin; Fokwa, Boniface P.T.

    2010-04-15

    Single phase powder samples and single crystals of Zr{sub 2}Ir{sub 6}B were successfully synthesized by arc-melting the elements in a water-cooled copper crucible under an argon atmosphere. Superstructure reflections were observed both on powder and on single crystal diffraction data, leading to an eightfold superstructure of ZrIr{sub 3}B{sub x} phase. The new phase, which has a metallic luster, crystallizes in space group Fm3-barm (no. 225) with the lattice parameters a=7.9903(4) A, V=510.14(4) A{sup 3}. Its crystal structure was refined on the basis of powder as well as single crystal data. The single crystal refinement converged to R{sub 1}=0.0239 and wR{sub 2}=0.0624 for all 88 unique reflections and 6 parameters. Zr{sub 2}Ir{sub 6}B is isotypic to Ti{sub 2}Rh{sub 6}B and its structure can be described as a defect double perovskite, A{sub 2}BB'O{sub 6}, where the A site is occupied by zirconium, the B site by boron, the O site by iridium but the B' site is vacant, leading to the formation of empty and boron-filled octahedral Ir{sub 6} clusters. According to the result of tight-binding electronic structure calculations, Ir-B and Ir-Zr interactions are mainly responsible for the structural stability of the phase. According to COHP bonding analysis, the strongest bonding occurs for the Ir-B contacts, and the Ir-Ir bonding within the empty clusters is two times stronger than that in the BIr{sub 6} octahedra. - Graphical abstract: Zr{sub 2}Ir{sub 6}B crystallizes with an eightfold superstructure of the already reported simple cubic perovskite ZrIr{sub 3}B{sub x}. According to the result of tight-binding electronic structure calculations, Ir-B and Ir-Zr interactions are mainly responsible for its structural stability, and the Ir-Ir bonding within the empty Ir{sub 6} clusters is two times stronger than that in the BIr{sub 6} octahedra.

  18. Borohydride complexes of europium(ii) and ytterbium(ii) and their conversion to metal borides. Structures of (l)4YbBh42 (L = Ch3Cn, C5H5N). (Reannouncement with new availability information)

    SciTech Connect

    White, J.P.; Deng, H.; Shore, S.G.

    1991-12-31

    Borohydride complexes of numerous metal ions are known. We have found that acetonitrile and pyridine are exceptionally good ligands for lathanide(II) ions. They promote formation of complexes with boron hydride and carborane anions. Use of these amines allows isolation of complexes that would otherwise be insoluble or unstable in other solvents. When these amines are employed as solvents, stable lanthanide(II) borohydride complexes can be isolated.

  19. Nickel and titanium nanoboride composite coating

    NASA Astrophysics Data System (ADS)

    Efimova, K. A.; Galevsky, G. V.; Rudneva, V. V.; Kozyrev, N. A.; Orshanskaya, E. G.

    2015-09-01

    Electrodeposition conditions, structural-physical and mechanical properties (microhardness, cohesion with a base, wear resistance, corrosion currents) of electroplated composite coatings on the base of nickel with nano and micro-powders of titanium boride are investigated. It has been found out that electro-crystallization of nickel with boride nanoparticles is the cause of coating formation with structural fragments of small sizes, low porosity and improved physical and mechanical properties. Titanium nano-boride is a component of composite coating, as well as an effective modifier of nickel matrix. Nano-boride of the electrolyte improves efficiency of the latter due to increased permissible upper limit of the cathodic current density.

  20. Measurement of high energy neutrons via Lu(n,xn) reactions

    SciTech Connect

    Henry, E.A.; Becker, J.A.; Archer, D.E.; Younes, W.; Stoyer, M.A.; Slaughter, D.

    1997-07-01

    High energy neutrons can be assayed by the use of the nuclear diagnostic material lutetium. We are measuring the (n,xn) cross sections for natural lutetium in order to develop it as a detector material. We are applying lutetium to diagnose the high energy neutrons produced in test target/blanket systems appropriate for the Accelerator Production of Tritium Project. 3 refs., 5 figs., 1 tab.

  1. A Study on the Microstructures and Toughness of Fe-B Cast Alloy Containing Rare Earth

    NASA Astrophysics Data System (ADS)

    Yi, Dawei; Zhang, Zhiyun; Fu, Hanguang; Yang, Chengyan; Ma, Shengqiang; Li, Yefei

    2015-02-01

    This study investigates the effect of cerium on the microstructures, mechanical properties of medium carbon Fe-B cast alloy. The as-cast microstructure of Fe-B cast alloy consists of the eutectic boride, pearlite, and ferrite. Compared with the coarse eutectic borides in the unmodified alloy, the eutectic boride structures in the modified alloy are greatly refined. Cerium promotes the formation of Ce2O3 phase. Ce2O3 can act as effective heterogeneous nuclei of primary austenite, and refine austenite and boride. After heat treatment, the impact toughness of the modified alloy is higher than that of the unmodified alloy because there are more broken borides in the modified alloy. Meanwhile, the fracture mechanism of medium carbon Fe-B alloy is depicted and analyzed by using fractography.

  2. Methods of repairing a substrate

    NASA Technical Reports Server (NTRS)

    Riedell, James A. (Inventor); Easler, Timothy E. (Inventor)

    2011-01-01

    A precursor of a ceramic adhesive suitable for use in a vacuum, thermal, and microgravity environment. The precursor of the ceramic adhesive includes a silicon-based, preceramic polymer and at least one ceramic powder selected from the group consisting of aluminum oxide, aluminum nitride, boron carbide, boron oxide, boron nitride, hafnium boride, hafnium carbide, hafnium oxide, lithium aluminate, molybdenum silicide, niobium carbide, niobium nitride, silicon boride, silicon carbide, silicon oxide, silicon nitride, tin oxide, tantalum boride, tantalum carbide, tantalum oxide, tantalum nitride, titanium boride, titanium carbide, titanium oxide, titanium nitride, yttrium oxide, zirconium boride, zirconium carbide, zirconium oxide, and zirconium silicate. Methods of forming the ceramic adhesive and of repairing a substrate in a vacuum and microgravity environment are also disclosed, as is a substrate repaired with the ceramic adhesive.

  3. Gadolinium: Central Metal of the Lanthanoids

    ERIC Educational Resources Information Center

    Laing, Michael

    2009-01-01

    The physical and chemical properties of gadolinium are compared with those of the other lanthanoids. Some properties are intermediate between those of lanthanum and lutetium; some between those of barium and hafnium; and others (unexpectedly) between those of ytterbium and lutetium. Both the remarkably high molar heat capacity of the metal and the…

  4. Microstructure and properties of borocarburized and laser-modified 17CrNi6-6 steel

    NASA Astrophysics Data System (ADS)

    Kulka, M.; Makuch, N.; Pertek, A.; Piasecki, A.

    2012-06-01

    Two-step process: carburizing followed by boriding was applied to the formation of borocarburized layers. The boride layer formed on the substrate of changeable chemical and phase composition (e.g. borocarburized layer) was called "gradient boride layer", in contrast to "typical boride layer", formed on the substrate of constant chemical and phase composition. Until now, the typical heat treatment of borocarburized layer consisted of treatment through hardening: quenching in oil and low-temperature tempering. In this paper, instead of treatment through hardening, laser-heat treatment was employed. The properties of such layer were compared to the properties of typical carburized layer. Three zones characterized the microstructure of laser-modified borocarburized layer: iron borides (FeB+Fe 2B) of modified morphology, hardened carburized zone (heat affected zone) and carburized layer without heat treatment. X-ray microanalysis indicated the increased boron concentration close to the surface due to the occurrence of a mixture of FeB and Fe 2B borides. Near to the hardened carburized zone, Fe 2B phase occurred in the laser-modified boride zone. Laser-heat treated borocarburized layer was characterized by higher microhardness at the surface than that obtained in case of carburized layer. It was caused by the iron borides (FeB+Fe 2B) occurrence at the surface, as a consequence of boriding process. However, the carburized layer was characterized by considerably larger hardened zone. Higher abrasive wear resistance, but lower low-cycle fatigue strength in comparison with the carburized layer, characterized the gradient boride layer formed by borocarburizing and laser surface modification. The indentation craters obtained on the surface of laser-heat treated borocarburized layer revealed sufficient cohesion (HF3 standard). The use of laser-modified borocarburized layers may be advantageous under conditions of high abrasive wear of mating parts. In case of parts, which

  5. Thermal expansion and lattice dynamics of RB66 compounds at low temperatures

    SciTech Connect

    Novikov, V V; Avdashchenko, D V; Mitroshenkov, N V; Matovnikov, A V; Budko, Serguei L

    2014-10-01

    Thermal characteristics of the phonon and magnon subsystems of icosahedral borides RB66 (R = Gd, Tb, Dy, Ho, Eu, or Lu) have been studied based on the obtained experimental data on the thermal expansion of the borides and the earlier results on their heat capacity in the range of 2–300 K. The contribution to the expansion of borides containing paramagnetic R 3+ ions, which is characteristic of transition to the spin-glass state, has been revealed. The phonon spectrum moments of RB66 compounds and the Grüneisen parameters have been calculated.

  6. NEUTRONIC REACTOR FUEL COMPOSITION

    DOEpatents

    Thurber, W.C.

    1961-01-10

    Uranium-aluminum alloys in which boron is homogeneously dispersed by adding it as a nickel boride are described. These compositions have particular utility as fuels for neutronic reactors, boron being present as a burnable poison.

  7. Ceramic material suitable for repair of a space vehicle component in a microgravity and vacuum environment, method of making same, and method of repairing a space vehicle component

    NASA Technical Reports Server (NTRS)

    Riedell, James A. (Inventor); Easler, Timothy E. (Inventor)

    2009-01-01

    A precursor of a ceramic adhesive suitable for use in a vacuum, thermal, and microgravity environment. The precursor of the ceramic adhesive includes a silicon-based, preceramic polymer and at least one ceramic powder selected from the group consisting of aluminum oxide, aluminum nitride, boron carbide, boron oxide, boron nitride, hafnium boride, hafnium carbide, hafnium oxide, lithium aluminate, molybdenum silicide, niobium carbide, niobium nitride, silicon boride, silicon carbide, silicon oxide, silicon nitride, tin oxide, tantalum boride, tantalum carbide, tantalum oxide, tantalum nitride, titanium boride, titanium carbide, titanium oxide, titanium nitride, yttrium oxide, zirconium diboride, zirconium carbide, zirconium oxide, and zirconium silicate. Methods of forming the ceramic adhesive and of repairing a substrate in a vacuum and microgravity environment are also disclosed, as is a substrate repaired with the ceramic adhesive.

  8. Interfacial reactions between titanium and borate glass

    SciTech Connect

    Brow, R.K.; Saha, S.K.; Goldstein, J.I.

    1992-12-31

    Interfacial reactions between melts of several borate glasses and titanium have been investigated by analytical scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (XPS). A thin titanium boride interfacial layer is detected by XPS after short (30 minutes) thermal treatments. ASEM analyses after longer thermal treatments (8--120 hours) reveal boron-rich interfacial layers and boride precipitates in the Ti side of the interface.

  9. Comment on 'A planar refractive x-ray lens made of nanocrystalline diamond'[J. Appl. Phys. 108, 123107 (2010)

    SciTech Connect

    Kroon, R. E.

    2013-05-28

    The material LuAG (lutetium aluminium garnet) has been confused with LAG (lanthanum aluminium garnet). In general, aluminium garnet phases only occur for the smaller trivalent metal cations and LAG is not known to have been synthesized.

  10. Microstructural development in transient liquid-phase bonding

    NASA Astrophysics Data System (ADS)

    Gale, W. F.; Wallach, E. R.

    1991-10-01

    The applicability of conventional models of the transient liquid-phase (TLP) bonding process to the joining of nickel using ternary Ni-Si-B insert metals is considered in this article. It is suggested that diffusion of boron out of the liquid and into the solid substrate before the equilibration of the liquid and solid phases can result in the development of significant boron concentrations in the substrate. This, in turn, leads to the precipitation of boride phases in the substrate during holding at bonding temperatures below the binary nickel-boron eutectic temperature. The formation of boride phases during holding at the bonding temperature is of importance, because first, it is not predicted by the standard models of the TLP process, and second, the borides are not removed by prolonged holding at the bonding temperature and therefore may influence the in-service properties of the joint. In contrast, when bonding above the binary nickel-boron eutectic temperature, localized liquation of the substrate takes place. This liquid region resolidifies following prolonged holding and does not result in the formation of persistent boride phases. Experimental support is presented for the formation of borides during bonding, and characterization of the boride phases formed in the substrate is described.

  11. Influence of laser alloying with boron and niobium on microstructure and properties of Nimonic 80A-alloy

    NASA Astrophysics Data System (ADS)

    Makuch, N.; Piasecki, A.; Dziarski, P.; Kulka, M.

    2015-12-01

    Ni-base superalloys were widely used in aeronautics, chemical and petrochemical industries due to their high corrosion resistance, high creep and rupture strength at high temperature. However, these alloys were not considered for applications in which conditions of appreciable mechanical wear were predominant. The diffusion boriding provided suitable protection against wear. Unfortunately, this process required long duration and high temperature. In this study, instead of the diffusion process, the laser alloying with boron and niobium was used in order to produce the hard and wear resistant layer on Nimonic 80A-alloy. The laser-alloying was carried out as a two-step process. First, the external cylindrical surface of specimens was pre-placed with a paste containing boron and niobium. Then, the pre-placed coating and the thin surface layer of the substrate were re-melted by a laser beam. The high laser beam power (P=1.56 kW) and high averaging irradiance (E=49.66 kW/cm2) provided the thick laser re-melted zone. The laser-borided layers were significantly thicker (470 μm) in comparison with the layers obtained as a consequence of the diffusion boriding. Simultaneously, the high overlapping of multiple laser tracks (86%) caused that the laser-alloyed layer was uniform in respect of the thickness. The produced layer consisted of nickel borides (Ni3B, Ni2B, Ni4B3, NiB), chromium borides (CrB, Cr2B), niobium borides (NbB2, NbB) and Ni-phase. The presence of hard borides caused the increase in microhardness up to 1000 HV in the re-melted zone. However, the measured values were lower than those-characteristic of niobium borides, chromium borides and nickel borides. The presence of the soft Ni-phase in re-melted zone was the reason for such a situation. After laser alloying, the significant increase in abrasive wear resistance was also observed. The mass wear intensity factor, as well as the relative mass loss of the laser-alloyed specimens, was over 10 times smaller in

  12. A study on the formation of solid state nanoscale materials using polyhedral borane compounds

    NASA Astrophysics Data System (ADS)

    Romero, Jennifer V.

    The formation of boron containing materials using a variety of methods was explored. The pyrolysis of a metal boride precursor solution can be accomplished using a one-source method by combining TiCl4, B10H 14 and CH3CN in one reaction vessel and pyrolyzing it at temperatures above 900 °C. Amorphous dark blue colored films were obtained after the pyrolysis reactions. Well-defined spherical shaped grains or particles were observed by SEM. The amorphous films generated contained titanium, however, the determination of the boron content of the films was inconclusive. This one pot method making metal boride thin films has the advantage of being able to dictate the stoichiometry of the reactants. Another part of this work represents the first report of both the use of metal boride materials and the use of a titanium-based compound for the formation of nanotubes. This method provides a facile method for generating well-formed boron-containing carbon nanotubes in a "one-pot" process through an efficient aerosol process. The formation of metal boride corrosion resistant layers was also explored. It was shown that metallic substrates can be effectively boronized using paste mixtures containing boron carbide and borax. The formation of a Fe4B 2 iron boride phase was achieved, however, this iron boride phase does not give enough corrosion protection. The formation of a corrosion resistant metal boride coating with strong adhesion was accomplished by boronization of a thermal sprayed nickel layer on the surface of steel. Surfactants were explored as possible nanoreactors in which metal boride nanoparticles could be formed to use as nanotube growth catalyst via room temperature reaction. Different surfactants were used, but none of them successfully generated very well dispersed metal boride nanoparticles. Nanoparticles with varying shapes and sizes were generated which were highly amorphous. The carboxylic acid derivative of closo-C2B 10 cages was explored as a ligand in the

  13. A novel RE-chrome-boronizing technology assisted by fast multiple rotation rolling treatment at low temperature

    NASA Astrophysics Data System (ADS)

    Yuan, Xing-dong; Xu, Bin; Cai, Yu-cheng

    2015-12-01

    The boride layer was fabricated on the surface of carbon steel by a novel RE-Chrome-Boronizing technology assisted by fast multiple rotation rolling (FMRR) treatment at low temperature. The microstructure of the boride layer was characterized by using scanning electron microscopy (SEM). The microstructure of the top surface layer of substrate was characterized by transmission electron microscopy (TEM) and high resolution rransmission electron microscopy (HRTEM). Experimental results showed that a nanostructured layer with grain size of approximately 30 nm was obtained; the amorphous phase and high-density dislocations were observed in upper-layer of FMRR samples, which led to the reduction of diffusion activation energy of boron atoms. Boride layers fabricated on the FMRR samples are continuous, dense, uniform, and low in brittleness. The penetrating rate was enhanced significantly when the FMRR samples were Cr-Rare earth-boronized at 650 °C for 6 h. The thickness of the boride layer of FMRR samples on carbon steel was approximately 25 μm when the duration was 60 min, which was approximately 1.5 times higher than the original sample. The boride layer consisted of mainly Fe2B, and adheres well to the metallic substrate.

  14. Thermodynamical and thermoelectric properties of boron doped YPd3 and YRh3

    NASA Astrophysics Data System (ADS)

    Dwivedi, Shalini; Sharma, Ramesh; Sharma, Yamini

    2016-05-01

    The structural, electronic, thermal, and optical properties of borides of cubic non-magnetic YX3 (X=Rh, Pd) compounds and their borides which crystallize in the AuCu3 structure have been studied using the density functional theory (DFT). The flat bands in the vicinity of EF which are associated with superconductivity appear in YPd3 and YRh3 band structures. However, the B s-states enhance the flat band only in YRh3B. The optical properties clearly show that boron insertion modifies the absorption and transmittance. The YX3 alloys and their borides exhibit valuable changes in the thermopower and ZT. It is observed that the properties of the Y-X intermetallics change significantly for the Y-Rh and Y-Pd alloys and the presence of single boron atom modifies the properties to a great extent.

  15. Method of boronizing transition-metal surfaces

    SciTech Connect

    Koyama, K.; Shimotake, H.

    1981-08-28

    A method is presented for preparing a boride layer on a transition metal substrate for use in corrosive environments or as a harden surface in machine applications. This method is particularly useful in treating current collectors for use within a high temperature and corrosive electrochemical cell environment. A melt of a alkali metal boride tetrafluoride salt including such as KF to lower its melting point is prepared including a dissolved boron containing material, for instance NiB, MnB/sub 2/, or CrB/sub 2/. A transition metal to be coated is immersed in the melt at a temperature of no more than 700/sup 0/C and a surface boride layer of that transition metal is formed within a period of about 24 hours on the substrate surface.

  16. Silicon carbide sintered body manufactured from silicon carbide powder containing boron, silicon and carbonaceous additive

    NASA Technical Reports Server (NTRS)

    Tanaka, Hidehiko

    1987-01-01

    A silicon carbide powder of a 5-micron grain size is mixed with 0.15 to 0.60 wt% mixture of a boron compound, i.e., boric acid, boron carbide (B4C), silicon boride (SiB4 or SiB6), aluminum boride, etc., and an aluminum compound, i.e., aluminum, aluminum oxide, aluminum hydroxide, aluminum carbide, etc., or aluminum boride (AlB2) alone, in such a proportion that the boron/aluminum atomic ratio in the sintered body becomes 0.05 to 0.25 wt% and 0.05 to 0.40 wt%, respectively, together with a carbonaceous additive to supply enough carbon to convert oxygen accompanying raw materials and additives into carbon monoxide.

  17. Synthesis and Characterization of TiB2 Reinforced Aluminium Matrix Composites: A Review

    NASA Astrophysics Data System (ADS)

    Kumar, Narendra; Gautam, Gaurav; Gautam, Rakesh Kumar; Mohan, Anita; Mohan, Sunil

    2015-09-01

    Aluminium-matrix composites (AMCs) are developed to meet the demands of light weight high performance materials in aerospace, automotive, marine and other applications. The properties of AMCs can be tailored suitably by combinations of matrix, reinforcement and processing route. AMCs are one of the most attractive alternatives for the manufacturing of light weight and high strength parts due to their low density and high specific strength. There are various techniques for preparing the AMCs with different reinforcement particles. In AMCs, the reinforcements are usually in the form of metal oxides, carbides, borides, nitrides and their combination. Among the various reinforcements titanium di-boride (TiB2) is of much interest due to its excellent stiffness, hardness, and wear resistance. This paper attempts to provide an overview to explore the possibilities of synthesizing titanium di-boride reinforced AMCs with different techniques. The mechanical and tribological properties of these composites have been emphasized to project these as tribo-materials.

  18. Investigation of the structure and properties of boron-containing coatings obtained by electron-beam treatment

    SciTech Connect

    Krivezhenko, Dina S. Drobyaz, Ekaterina A. Bataev, Ivan A. Chuchkova, Lyubov V.

    2015-10-27

    An investigation of surface-hardened materials obtained by cladding with an electron beam injected into the air atmosphere was carried out. Structural investigations of coatings revealed that an increase in boron carbide concentration in a saturating mixture contributed to a rise of a volume fraction of iron borides in coatings. The maximum hardened depth reached 2 mm. Hardened layers were characterized by the formation of heterogeneous structure which consisted of iron borides and titanium carbides distributed uniformly in the eutectic matrix. Areas of titanium boride conglomerations were detected. It was found that an increase in the boron carbide content led to an enhancement in hardness of the investigated materials. Friction testing against loosely fixed abrasive particles showed that electron-beam cladding of powder mixtures containing boron carbides, titanium, and iron in air atmosphere allowed enhancing a resistance of materials hardened in two times.

  19. Wear resistance of composite coatings produced by thermal spraying

    SciTech Connect

    Klinskaya, N.A.

    1995-12-31

    Injection of refractory additions (carbides, borides, oxides etc.) into self-fluxing alloys is a well-known technique for their hardening. Nevertheless the matter of influence of refractory components on the structure and characteristics of composite coatings is not studied well enough. This paper presents the results of investigations of gas thermal coatings (plasma and detonation ones) on the base of stellite with refractory components in the form of borides such as CrB{sub 2}, TiB{sub 2}, (TiCr)B{sub 2}. This study is concerned with the influence of refractory additions (carbides, borides, oxides) on the wear resistance sprayed coatings based on self-fluxing alloys NiCrBSi and CoCrBSi.

  20. Influence of heat treatment on microstructure and hot crack susceptibility of laser-drilled turbine blades made from Rene 80

    SciTech Connect

    Osterle, W. Krause, S.; Neidel, A.; Oder, G.; Voelker, J.

    2008-11-15

    Turbine components from conventionally cast nickel-base alloy Rene 80 show different hot cracking susceptibilities depending on their heat treatment conditions leading to slightly different microstructures. Electron probe micro-analysis, focused ion beam technique and analytical transmission electron microscopy were applied to reveal and identify grain boundary precipitates and the {gamma}-{gamma}'-microstructure. The distribution of borides along grain boundaries was evaluated statistically by quantitative metallography. The following features could be correlated with an increase of cracking susceptibility: i) Increasing grain size, ii) increasing fraction of grain boundaries with densely spaced borides, iii) lack of secondary {gamma}'-particles in matrix channels between the coarse cuboidal {gamma}'-precipitates. The latter feature seems to be responsible for linking-up of cracked grain boundary precipitates which occurred as an additional cracking mechanism after one heat treatment, whereas decohesion at the boride-matrix-interface in the heat affected zone of laser-drilled holes was observed for both heat treatments.

  1. Method of boronizing transition metal surfaces

    DOEpatents

    Koyama, Koichiro; Shimotake, Hiroshi

    1983-01-01

    A method is presented for preparing a boride layer on a transition metal substrate for use in corrosive environments or as a harden surface in machine applications. This method is particularly useful in treating current collectors for use within a high temperature and corrosive electrochemical cell environment. A melt of a alkali metal boride tetrafluoride salt including such as KF to lower its melting point is prepared including a dissolved boron containing material, for instance NiB, MnB.sub.2, or CrB.sub.2. A transition metal to be coated is immersed in the melt at a temperature of no more than 700.degree. C. and a surface boride layer of that transition metal is formed within a period of about 24 hours on the substrate surface.

  2. Method of boronizing transition metal surfaces

    DOEpatents

    Koyama, Koichiro; Shimotake, Hiroshi.

    1983-08-16

    A method is presented for preparing a boride layer on a transition metal substrate for use in corrosive environments or as a harden surface in machine applications. This method is particularly useful in treating current collectors for use within a high temperature and corrosive electrochemical cell environment. A melt of a alkali metal boride tetrafluoride salt including such as KF to lower its melting point is prepared including a dissolved boron containing material, for instance NiB, MnB[sub 2], or CrB[sub 2]. A transition metal to be coated is immersed in the melt at a temperature of no more than 700 C and a surface boride layer of that transition metal is formed within a period of about 24 hours on the substrate surface. 4 figs.

  3. Influence of a corrosive-abrasive medium on the wear resistance of 12Kh18N10T steel with surface hardening

    SciTech Connect

    Golubets, V.M.; Kozub, V.V.; Shchuiko, Ya.V.; Pashechko, M.I.

    1987-11-01

    The authors study the wear and corrosion resistance of 12Kh18N10T steel after diffusion boriding, electrospark alloying, and combined hardening in a corrosive abrasive medium consisting of 50 percent sand and 3 percent NaCl with hydrochloric acid added to obtain a pH of 1. Metallographic analysis revealed a 40-micrometer-deep case with a microhardness of 6-8.5 GPa on the surface. X-ray diffraction established that the boride case consists of an FeB phase alloyed with chromium and nickel. Results are graphed.

  4. Electrically conductive containment vessel for molten aluminum

    DOEpatents

    Holcombe, C.E.; Scott, D.G.

    1984-06-25

    The present invention is directed to a containment vessel which is particularly useful in melting aluminum. The vessel of the present invention is a multilayered vessel characterized by being electrically conductive, essentially nonwettable by and nonreactive with molten aluminum. The vessel is formed by coating a tantalum substrate of a suitable configuration with a mixture of yttria and particulate metal 10 borides. The yttria in the coating inhibits the wetting of the coating while the boride particulate material provides the electrical conductivity through the vessel. The vessel of the present invention is particularly suitable for use in melting aluminum by ion bombardment.

  5. Electrically conductive containment vessel for molten aluminum

    DOEpatents

    Holcombe, Cressie E.; Scott, Donald G.

    1985-01-01

    The present invention is directed to a containment vessel which is particularly useful in melting aluminum. The vessel of the present invention is a multilayered vessel characterized by being electrically conductive, essentially nonwettable by and nonreactive with molten aluminum. The vessel is formed by coating a tantalum substrate of a suitable configuration with a mixture of yttria and particulate metal borides. The yttria in the coating inhibits the wetting of the coating while the boride particulate material provides the electrical conductivity through the vessel. The vessel of the present invention is particularly suitable for use in melting aluminum by ion bombardment.

  6. Association of broad icosahedral Raman bands with substitutional disorder in SiB{sub 3} and boron carbide

    SciTech Connect

    Aselage, T.L.; Tallant, D.R.

    1998-02-01

    The structure of silicon boride, SiB{sub 3}, is based on 12-atom, boron-rich icosahedra in which silicon atoms substitute for some boron atoms. Raman bands associated with vibrations of icosahedral atoms in SiB{sub 3} are quite broad, reflecting this substitutional disorder. Comparing the Raman spectra of other icosahedral borides with SiB{sub 3}, only boron carbides have similarly broad icosahedral Raman bands. The direct correlation of broad icosahedral Raman bands with substitutional disorder supports the proposition that carbon atoms replace icosahedral boron atoms in boron carbides of all compositions. {copyright} {ital 1998} {ital The American Physical Society}

  7. Investigations on Microstructures and Toughness of Fe-B Cast Alloy Containing Titanium and Nitrogen

    NASA Astrophysics Data System (ADS)

    Yi, Dawei; Zhang, Zhiyun; Fu, Hanguang; Yang, Chengyan

    2013-11-01

    The effects of titanium and nitrogen elements on the microstructure and impact toughness of the Fe-B alloy have been studied. The results show that the borides are refined after the additions of titanium and nitrogen elements. With the additions of titanium and nitrogen, titanium nitrides are formed in the Fe-B alloy. Titanium nitride can act as effective heterogeneous nuclei of primary austenite, and promote the refinement of austenite and boride. After heat treatment, the impact toughness of Fe-B alloys modified by titanium and nitrogen elements is higher than that of ordinary alloy.

  8. New Process for Grain Refinement of Aluminum. Final Report

    SciTech Connect

    Dr. Joseph A. Megy

    2000-09-22

    A new method of grain refining aluminum involving in-situ formation of boride nuclei in molten aluminum just prior to casting has been developed in the subject DOE program over the last thirty months by a team consisting of JDC, Inc., Alcoa Technical Center, GRAS, Inc., Touchstone Labs, and GKS Engineering Services. The Manufacturing process to make boron trichloride for grain refining is much simpler than preparing conventional grain refiners, with attendant environmental, capital, and energy savings. The manufacture of boride grain refining nuclei using the fy-Gem process avoids clusters, salt and oxide inclusions that cause quality problems in aluminum today.

  9. Brazing Inconel 625 Using Two Ni/(Fe)-Based Amorphous Filler Foils

    NASA Astrophysics Data System (ADS)

    Chen, Wen-Shiang; Shiue, Ren-Kae

    2012-07-01

    For MBF-51 filler, the brazed joint consists of interfacial grain boundary borides, coarse Nb6Ni16Si7, and Ni/Cr-rich matrix. In contrast, the VZ-2106 brazed joint is composed of interfacial Nb6Ni16Si7 precipitates as well as grain boundary borides, coarse Nb6Ni16Si7, and Ni/Cr/Fe-rich matrix. The maximum tensile strength of 443 MPa is obtained from the MBF-51 brazed specimen. The tensile strengths of VZ-2106 brazed joints are approximately 300 MPa. Both amorphous filler foils demonstrate potential in brazing IN-625 substrate.

  10. Photoeradication and imaging of atheromatous plaque with texaphyrins

    NASA Astrophysics Data System (ADS)

    Woodburn, Kathryn W.; Qing, Fan; Kessel, David; Young, Stuart W.

    1997-05-01

    Cardiovascular disease is the chief cause of death in the western world. Lutetium texaphyrin (PCI-0123) is a pure, synthetic, aqueous-soluble macrocycle that localizes in both cancerous lesions and atheromatous plaque. The lutetium texaphyrin complex is a potent photosensitizer in vivo, where it is activated by tissue-penetrating far red light (720 - 760 nm). Patient diagnosis and treatment planning are possible with PCI-0123 fluorescence imaging. In this study the localization and selective eradication of atheromatous plaque using PCI-0123 and photoangioplasty are discussed.

  11. Analysis of boron carbides' electronic structure

    NASA Technical Reports Server (NTRS)

    Howard, Iris A.; Beckel, Charles L.

    1986-01-01

    The electronic properties of boron-rich icosahedral clusters were studied as a means of understanding the electronic structure of the icosahedral borides such as boron carbide. A lower bound was estimated on bipolaron formation energies in B12 and B11C icosahedra, and the associated distortions. While the magnitude of the distortion associated with bipolaron formation is similar in both cases, the calculated formation energies differ greatly, formation being much more favorable on B11C icosahedra. The stable positions of a divalent atom relative to an icosahedral borane was also investigated, with the result that a stable energy minimum was found when the atom is at the center of the borane, internal to the B12 cage. If incorporation of dopant atoms into B12 cages in icosahedral boride solids is feasible, novel materials might result. In addition, the normal modes of a B12H12 cluster, of the C2B10 cage in para-carborane, and of a B12 icosahedron of reduced (D sub 3d) symmetry, such as is found in the icosahedral borides, were calculated. The nature of these vibrational modes will be important in determining, for instance, the character of the electron-lattice coupling in the borides, and in analyzing the lattice contribution to the thermal conductivity.

  12. Vapor pressure and evaporation rate of certain heat-resistant compounds in a vacuum at high temperatures

    NASA Technical Reports Server (NTRS)

    Bolgar, A. S.; Verkhoglyadova, T. S.; Samsonov, G. V.

    1985-01-01

    The vapor pressure and evaporation rate of borides of titanium, zirconium, and chrome; and of strontium and carbides of titanium, zirconium, and chrome, molybdenum silicide; and nitrides of titanium, niobium, and tantalum in a vacuum were studied. It is concluded that all subject compounds evaporate by molecular structures except AlB sub 12' which dissociates, losing the aluminum.

  13. Development of high temperature stable Ohmic and Schottky contacts on n-gallium nitride

    NASA Astrophysics Data System (ADS)

    Khanna, Rohit

    In this work the effort was made to towards develop and investigate high temperature stable Ohmic and Schottky contacts for n type GaN. Various borides and refractory materials were incorporated in metallization scheme to best attain the desired effect of minimal degradation of contacts when placed at high temperatures. This work focuses on achieving a contact scheme using different borides which include two Tungsten Borides (namely W2B, W2B 5), Titanium Boride (TiB2), Chromium Boride (CrB2) and Zirconium Boride (ZrB2). Further a high temperature metal namely Iridium (Ir) was evaluated as a potential contact to n-GaN, as part of continuing improved device technology development. The main goal of this project was to investigate the most promising boride-based contact metallurgies on GaN, and finally to fabricate a High Electron Mobility Transistor (HEMT) and compare its reliability to a HEMT using present technology contact. Ohmic contacts were fabricated on n GaN using borides in the metallization scheme of Ti/Al/boride/Ti/Au. The characterization of the contacts was done using current-voltage measurements, scanning electron microscopy (SEM) and Auger Electron Spectroscopy (AES) measurements. The contacts formed gave specific contact resistance of the order of 10-5 to 10-6 Ohm-cm2. A minimum contact resistance of 1.5x10-6 O.cm 2 was achieved for the TiB2 based scheme at an annealing temperature of 850-900°C, which was comparable to a regular ohmic contact of Ti/Al/Ni/Au on n GaN. When some of borides contacts were placed on a hot plate or in hot oven for temperature ranging from 200°C to 350°C, the regular metallization contacts degraded before than borides ones. Even with a certain amount of intermixing of the metallization scheme the boride contacts showed minimal roughening and smoother morphology, which, in terms of edge acuity, is crucial for very small gate devices. Schottky contacts were also fabricated and characterized using all the five boride

  14. Ultracapacitor current collector

    DOEpatents

    Jerabek, Elihu Calfin; Mikkor, Mati

    2001-10-16

    An ultracapacitor having two solid, nonporous current collectors, two porous electrodes separating the collectors, a porous separator between the electrodes and an electrolyte occupying the pores in the electrodes and separator. At least one of the current collectors comprises a conductive metal substrate coated with a metal nitride, carbide or boride coating.

  15. Magnetic properties and magnetic hardening mechansim of Pt-Co-B alloys

    NASA Technical Reports Server (NTRS)

    Qiu, Ning; Flanagan, F.; Wittig, James E.

    1994-01-01

    The intrinsic coercivity is found to be maximized in the Pt42Co45B13 ternary alloy which is undercooled and rapidly solidified (quenched using a 70 m/s wheel speed after undercooling), and then annealed (800 C for 2400 min). The same alloy, processed at slower cooling rates and annealed in the same way, has a much larger scale microstructure and a much lower resulting magnetic coercivity. The microstructure which would optimize the coercitvity of this coercivity of this ternary alloy is a completely ordered L1(sub zero) Pt-Co matrix with a submicron magnetic single-domion Co-boride precipitate. The L1(sub zero) phase is highly anistropic magnetically while the Co-boride precipate is somewhat less so. Annealing treatments designed to produced single-domain Co-boride precipitates enhance the coercivity. This suggests that the refined microstructures is responsible for the high coercivities found in the rapidly solidified and annealed alloy. The magnetic domain wall thickness for a Co-boride precipitate is determined from both experimental observation and theoretical calculation in order to evaluate its influence on the coercivity of the alloy. The effects of the pinning of domain walls and the barrier to the nucleation of reverse domains on the coercivity are discussed. Both microstrucutral analysis and theoretical calculation indicate that the high coercivities in the Pt42Co45B13 alloy are due to the difficult nucleation of reverse magnetic domains.

  16. Thermal emission property of solid solution Gd{sub 1-x}Nd{sub x}B{sub 6} (x=0, 0.6, 0.8)

    SciTech Connect

    Xing Zhang, Jiu; Hong Bao, Li; Lin Zhou, Shen E-mail: Baolihong_10@yahoo.com.cn

    2011-07-01

    In this paper, to further explore the excellent emission properties of rare earth boride cathode, herein we present the synthesis, characterization and properties of polycrystalline Nd{sub 1-x}Gd{sub x}B{sub 6} (x = 0, 0.6, 0.8) bulk via arc plasma and reactive SPS. (author)

  17. First international conference on surface engineering

    SciTech Connect

    Bucklow, I.A.

    1986-01-01

    This book contains 21 papers. Some of the titles are: The production of MCrAlHf diffusion coating in a single step pack process; Boride surface modifications; Surface boronising of metals and alloys; Hot zirconium cathode sputtered layers for useful surface modification; and Ceramics and cements in surface engineering.

  18. Boron Carbides As Thermo-electric Materials

    NASA Technical Reports Server (NTRS)

    Wood, Charles

    1988-01-01

    Report reviews recent theoretical and experimental research on thermoelectric materials. Recent work with narrow-band semiconductors demonstrated possibility of relatively high thermoelectric energy-conversion efficiencies in materials withstanding high temperatures needed to attain such efficiencies. Among promising semiconductors are boron-rich borides, especially boron carbides.

  19. Laser Boronizing of Stainless Steel with Direct Diode Laser

    NASA Astrophysics Data System (ADS)

    Kusuhara, Takayoshi; Morimoto, Junji; Abe, Nobuyuki; Tsukamoto, Masahiro

    Boronizing is a thermo-chemical surface treatment in which boron atoms are diffused into the surface of a work piece to form borides with the base material. When applied to the metallic materials, boronizing provides wear and abrasion resistance comparable to sintered carbides. However conventional boronizing is carried out at temperatures ranging from 800°C to 1050°C and takes from one to several hours. The structure and properties of the base material is influenced considerably by the high temperature and long treatment time. In order to avoid these drawbacks of conventional boronizing, laser-assisted boronizing is investigated which activates the conventional boronizing material and the work piece with a high density laser power. In this study, effect of laser characteristics was examined on the laser boronizing of stainless steel. After laser boronizing, the microstructure of the boride layer was analyzed with an optical microscope, electron probe micro analyser(EPMA) and X-ray diffractometer (XRD). The mechanical properties of borided layer were evaluated using Vickers hardness tester and sand erosion tester. Results showed that the boride layer was composed of NiB, CrB, FeB and Fe2B, and get wear resistance.

  20. Photovoltaic cell

    DOEpatents

    Gordon, Roy G.; Kurtz, Sarah

    1984-11-27

    In a photovoltaic cell structure containing a visibly transparent, electrically conductive first layer of metal oxide, and a light-absorbing semiconductive photovoltaic second layer, the improvement comprising a thin layer of transition metal nitride, carbide or boride interposed between said first and second layers.

  1. Analysis of boron carbides' electronic structure. Final technical report, 18 July 1984-17 August 1986

    SciTech Connect

    Howard, I.A.; Beckel, C.L.

    1986-08-01

    The electronic properties of boron-rich icosahedral clusters were studied as a means of understanding the electronic structure of the icosahedral borides such as boron carbide. A lower bound was estimated on bipolaron formation energies in B/sub 12/ and B/sub 11/C icosahedra, and the associated distortions. While the magnitude of the distortion associated with bipolaron formation is similar in both cases, the calculated formation energies differ greatly, formation being much more favorable on B11C icosahedra. The stable positions of a divalent atom relative to an icosahedral borane was also investigated, with the result that a stable energy minimum was found when the atom is at the center of the borane, internal to the B/sub 12/ cage. If incorporation of dopant atoms into B/sub 12/ cages in icosahedral boride solids is feasible, novel materials might result. In addition, the normal modes of a B/sub 12/H/sub 12/ cluster, of the C/sub 2/B/sub 10/ cage in para-carborane, and of a B/sub 12/ icosahedron of reduced (D sub 3d) symmetry, such as is found in the icosahedral borides, were calculated. The nature of these vibrational modes will be important in determining, for instance, the character of the electron-lattice coupling in the borides, and in analyzing the lattice contribution to the thermal conductivity.

  2. Characterization of natural zeolite clinoptilolite for sorption of contaminants

    NASA Astrophysics Data System (ADS)

    Xingu-Contreras, E.; García-Rosales, G.; García-Sosa, I.; Cabral-Prieto, A.; Solache-Ríos, M.

    2015-06-01

    The nanoparticles technology has received considerable attention for its potential applications in groundwater treatment for the removal of various pollutants as Cadmium. In this work, iron boride nanoparticles were synthesized in pure form and in presence of homo-ionized zeolite clinoptilolite, as support material. These materials were used for removing Cd (II) from aqueous solutions containing 10, 50, 100, 150, 200, 250, 300 and 400 mg/L. The characterization of these materials was made by using X-ray Diffraction, Scanning Electron Microscopy and Mössbauer Spectroscopy. Pure iron boride particles show a broad X-ray diffraction peak centered at 45∘ (2 𝜃), inferring the presence of nanocrystals of Fe2B as identified from Mössbauer Spectroscopy. The size of these Fe2B particles was within the range of 50 and 120 nm. The maximum sorption capacities for Cd (II) of iron boride particles and supported iron boride particles in homo-ionized zeolitic material were nearly 100 %. For homo-ionized zeolite and homo-ionized zeolite plus sodium borohydride was ≥ 95 %.

  3. Laser surface modification of carburized and borocarburized 15CrNi6 steel

    SciTech Connect

    Kulka, M. . E-mail: coolka@sol.put.poznan.pl; Pertek, A.

    2007-05-15

    The paper presents the results of laser heat treatment (LHT) of carburized and borocarburized 15CrNi6 low-carbon steel. Laser tracks were arranged by CO{sub 2} laser beam as multiple tracks formed in the shape of a helical line. The microstructure and properties of these diffusion layers were compared with those obtained after through-hardening. The microstructure after carburizing and LHT consists of adjacent characteristic zones: re-melted zone (coarse-grained martensite), carburized layer with heat affected zone (fine acicular martensite), carburized layer without heat treatment and the substrate (ferrite and pearlite). The highest measured microhardness (about 820 HV) was observed in re-melted and heat affected zones. The increase of distance from the surface was accompanied by a gradual decrease of microhardness up to 400 HV beneath the HAZ and up to 250 HV in the core of steel. The carburized layer after LHT exhibited a higher resistance to frictional wear compared to a carburized layer after through-hardening. The microstructure after borocarburizing and LHT consists of the following characteristic zones: iron borides of laser-modified morphology (FeB and Fe{sub 2}B), carburized layer with heat affected zone (martensite and alloyed cementite), carburized layer without heat treatment and the substrate (ferrite and pearlite). The highest microhardness was obtained in the iron boride zone. The microhardness of FeB boride extended up to 2200 HV and for the Fe{sub 2}B boride up to about 1300-1600 HV. With increased distance from the surface, the microhardness gradually decreases to 800 HV in HAZ, 400-450 HV in the carburized layer without heat treatment and to 250 HV in low-carbon substrate. The iron borides after LHT assume a globular shape, which leads to a lower texture and porosity of the borided layers. The increased resistance to friction wear of the borocarburized layers is certified in comparison with the borided layer after conventional heat treatment

  4. 40 CFR 421.271 - Specialized definitions.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... AND STANDARDS NONFERROUS METALS MANUFACTURING POINT SOURCE CATEGORY Primary Rare Earth Metals.... (b) The term rare earth metals refers to the elements scandium, yttrium, and lanthanum to lutetium, inclusive. (c) The term mischmetal refers to a rare earth metal alloy comprised of the natural mixture...

  5. 40 CFR 421.271 - Specialized definitions.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... AND STANDARDS NONFERROUS METALS MANUFACTURING POINT SOURCE CATEGORY Primary Rare Earth Metals.... (b) The term rare earth metals refers to the elements scandium, yttrium, and lanthanum to lutetium, inclusive. (c) The term mischmetal refers to a rare earth metal alloy comprised of the natural mixture...

  6. 40 CFR 421.271 - Specialized definitions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... AND STANDARDS NONFERROUS METALS MANUFACTURING POINT SOURCE CATEGORY Primary Rare Earth Metals.... (b) The term rare earth metals refers to the elements scandium, yttrium, and lanthanum to lutetium, inclusive. (c) The term mischmetal refers to a rare earth metal alloy comprised of the natural mixture...

  7. 40 CFR 421.271 - Specialized definitions.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... AND STANDARDS NONFERROUS METALS MANUFACTURING POINT SOURCE CATEGORY Primary Rare Earth Metals.... (b) The term rare earth metals refers to the elements scandium, yttrium, and lanthanum to lutetium, inclusive. (c) The term mischmetal refers to a rare earth metal alloy comprised of the natural mixture...

  8. Expanding Therapy for Neuroendocrine Tumors.

    PubMed

    2016-03-01

    Results from two phase III studies suggest that everolimus, an mTOR inhibitor, and (177)Lutetium-DOTATATE, a radiopharmaceutical, may be effective new options for patients with advanced neuroendocrine tumors of the gastrointestinal tract. Both therapies were well tolerated and significantly prolonged progression-free survival. PMID:26826165

  9. 40 CFR 421.271 - Specialized definitions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... definitions, abbreviations, and methods of analysis set forth in 40 CFR part 401 shall apply to this subpart. (b) The term rare earth metals refers to the elements scandium, yttrium, and lanthanum to lutetium... AND STANDARDS NONFERROUS METALS MANUFACTURING POINT SOURCE CATEGORY Primary Rare Earth...

  10. Yttrium and rare earth stabilized fast reactor metal fuel

    SciTech Connect

    Guon, J.; Grantham, L.F.; Specht, E.R.

    1992-05-12

    This patent describes an improved metal alloy reactor fuel consisting essentially of uranium, plutonium, and at least one element from the group consisting of yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium.

  11. Nuclear data sheets for A = 157

    SciTech Connect

    Helmer, R. G.

    1996-06-01

    The experimental results from the various reaction and decay studies leading to nuclides in the A=157 mass chain have been reviewed. These data are summarized and presented, together with adopted level schemes and properties. Data is presented for isotopes of dysprosium, erbium, europium, gadolinium, hafnium, holmium, lutetium, promethium, samarium, tantalum, terbium, thulium, ytterbium, and neodymium. 301 refs.

  12. Investigation of sulfur-tolerant catalysts for selective synthesis of hydrocarbon liquids from coal-derived gases. Annual technical progress report, September 19, 1980-September 18, 1981

    SciTech Connect

    Bartholomew, C.H.

    1981-10-31

    During the past contract year, considerable progress was made in characterization and activity/selectivity testing of iron and cobalt catalysts. Preparation of boride promoted cobalt and iron catalysts was refined and nearly completed. H/sub 2/ and CO adsorption and oxygen titration measurements were performed on a number of supported and unsupported catalysts, especially several boride promoted cobalt and iron catalysts. Activity/selectivity tests of 3 and 15% Fe/SiO/sub 2/ and Co/SiO/sub 2/ and of 6 borided cobalt and iron catalysts were completed. The product distributions for iron and cobalt boride catalysts are unusual and interesting. Boron promoted iron is more active and stable than iron/silica; cobalt boride has an unusually high selectivity for alcohols. Tests to determine effects of H/sub 2/S poisoning on activity/selectivity properties of 15% Co/SiO/sub 2/ indicate that a significant loss of activity occurs over a period of 24 to 28 h in the presence of 10 to 20 ppM H/sub 2/S. Product selectivity to liquids increased through a maximum during the gradual addition of sulfur. Reactant CO and H/sub 2/S interact partially to form COS which is less toxic than H/sub 2/S. H/sub 2/ and CO adsorption data were obtained for 3, 6 and 9% Co/ZSM-5 catalysts prepared and reactor tested by PETC. The unusual and interesting results suggest that metal-support interactions may have an important influence on reactant adsorption properties.

  13. Multi-component boron coatings on low carbon steel AISI 1018

    NASA Astrophysics Data System (ADS)

    Suwattananont, Naruemon

    Boronizing and metalizing are thermo-chemical surface hardening treatments in which boron and metal atoms diffuse into the metal substrate forming metallic boride layers, providing complex properties of B-Me-Fe system. To study multi-component boron coatings on low carbon steel AISI 1018, the simultaneous powder pack method of boronizing and metalizing was selected to perform the coatings. One B-Fe system and eight boron-metal (B-Me-Fe) systems from transition metals group IVB (Ti, Zr, HO, group VB (Nb, Ta), and group VIB (Cr, Mo, W) were studied. The system specimens were thereto-chemically treated at 950°C for 4 hours in a crucible containing powder mixture of boron source, transition metal powder, and activator. After the heat treatment process, the multi-component boron coatings were characterized by using optical microscope, microhardness tester, TGA, XRD, and Synchrotron microdiffraction. The coating morphology was observed and the coating thickness was measured as well as the microhardness across the depth of coating. The corrosion resistance of the coatings was evaluated by the continuous weighting method. The high temperature oxidation was also detected by isothermal method at a temperature range of 400-800°C for 24 hours. The Rietveld refinement method was used to examine the quantitative phase analysis, crystalline size, microstrain and lattice parameters of the multi-component boron coatings. The results have shown that adding transition metals into the B-Fe system caused the formation of solid solution of transition-metal borides. The distortion of crystal lattice parameters generated microstrain in the boride phase. The Synchrotron microdiffraction confirmed the presence of about 5-10 microns of transition-metal boride phase at the surface. Moreover, the additional transition metal can provide better corrosion and high temperature oxidation resistance to the B-Fe system, preventing the deboronizing and stabilizing the boride phases.

  14. NASA research on refractory compounds.

    NASA Technical Reports Server (NTRS)

    Gangler, J. J.

    1971-01-01

    The behavior and properties of the refractory carbides, nitrides, and borides are being investigated by NASA as part of its research aimed at developing superior heat resistant materials for aerospace applications. Studies of the zirconium-carbon-oxygen system show that zirconium oxycarbides of different compositions and lattice parameters can be formed between 1500 C and 1900 C and are stable below 1500 C. More applied studies show that hot working generally improves the microstructure and therefore the strength of TiC and NbC. Sintering studies on UN indicate that very high densities can be achieved. Hot pressing of cermets of HfN and HfC produces good mechanical properties for high temperature bearing applications. Attempts to improve the impact resistance of boride composites by the addition of a nickel or carbon yarn were not overly successful.

  15. YB48 the metal rich boundary of YB66; crystal growth and thermoelectric properties

    NASA Astrophysics Data System (ADS)

    Hossain, M. Anwar; Tanaka, Isao; Tanaka, Takaho; Khan, A. Ullah; Mori, Takao

    2015-12-01

    It was discovered that the well-known higher boride YB66, one of the first reported phonon glass electron crystals (PGEC), could be obtained in a much more metal-rich composition than previously thought possible. Using the floating zone growth method, YB48 single crystals with YB66 crystal structure could be obtained, and their thermoelectric properties measured. This expansion of the homogeneity range of the well-known YB66 compound is surprising and a new Y atomic site was discovered. YB48 exhibits much higher power factors than YB66 which increase rapidly with increasing temperature. The obtained dimensionless figure of merit of this compound at 990 K is approximately 30 times higher than that of previously reported YB66 samples, and higher than any other pristine higher boride. This discovery reveals YB48 as a promising high temperature thermoelectric material.

  16. Ceramic fibers from Si-B-C polymer precursors

    NASA Technical Reports Server (NTRS)

    Riccitiello, S. R.; Hsu, M. S.; Chen, T. S.

    1993-01-01

    Non-oxide ceramics such as silicon carbide (SiC), silicon nitride (Si3N4), and silicon borides (SiB4, SiB6) have thermal stability, oxidation resistance, hardness, and varied electrical properties. All these materials can be prepared in a fiber form from a suitable polymer precursor. The above mentioned fibers, when tested over a temperature range from 25 to 1400 C, experience degradation at elevated temperatures. Past work in ceramic materials has shown that the strength of ceramics containing both carbides and borides is sustained at elevated temperatures, with minimum oxidation. The work presented here describes the formation of ceramic fibers containing both elements, boron and silicon, prepared via the polymer precursor route previously reported by the authors, and discusses the fiber mechanical properties that are retained over the temperature range studied.

  17. Laser surface modification of boronickelized medium carbon steel

    NASA Astrophysics Data System (ADS)

    Bartkowska, Aneta; Pertek, Aleksandra; Kulka, Michał; Klimek, Leszek

    2015-11-01

    A two-step process was applied to produce the multicomponent boride layers. Boronickelizing consisted of nickel plating and diffusion boriding. Two different methods of heat treatment of boronickelized C45 steel were used: a typical through-hardening, and a laser surface modification with remelting. Microstructure and some mechanical properties of these layers were examined. Microstructural characterization was studied using optical microscope, Scanning Electron Microscope, energy-dispersive X-ray microanalysis, Electron Back-Scatter Diffraction and X-ray diffraction. The laser modification improved wear resistance, cohesion as well as low-cycle fatigue of the boronickelized layer. Compressive stresses, occurring after laser remelting, could be the reason for the advantageous mechanical behavior of the layer.

  18. Direct synthesis of magnesium borohydride

    DOEpatents

    Ronnebro, Ewa Carin Ellinor; Severa, Godwin; Jensen, Craig M.

    2012-04-03

    A method is disclosed for directly preparing an alkaline earth metal borohydride, i.e. Mg(BH.sub.4).sub.2, from the alkaline earth metal boride MgB.sub.2 by hydrogenating the MgB.sub.2 at an elevated temperature and pressure. The boride may also be doped with small amounts of a metal chloride catalyst such as TiCl.sub.3 and/or NiCl.sub.2. The process provides for charging MgB.sub.2 with high pressure hydrogen above at least 70 MPa while simultaneously heating the material to about 350.degree. C. to about 400.degree. C. The method is relatively simple and inexpensive and provides a reversible hydride compound having a hydrogen capacity of at least 11 wt %.

  19. Microstructure, microhardness, phase analysis and chemical composition of laser remelted FeB-Fe2B surface layers produced on Vanadis-6 steel

    NASA Astrophysics Data System (ADS)

    Bartkowska, Aneta; Swadźba, Radosław; Popławski, Mikołaj; Bartkowski, Dariusz

    2016-12-01

    The paper presents the study results of the diffusion boronized layer and their laser modification. Diffusion boronized processes were carried out on Vanadis-6 steel at 900 °C for 5 h. Boronized layers were characterized by dual-phase microstructure consisting of iron borides having a microhardness in the range from 1800 to 1400 HV. The laser heat treatment was carried out using CO2 laser after diffusion boronizing process. The research goals of this paper was analysis of microstructure, microhardness as well as phase and chemical composition of boronized layers after laser modification. Microstructure of boronized layer after laser modification consisted of remelted zone, heat affected zone and substrate. Remelted zone was characterized by microstructure consisted of boron-martensite eutectic. In this zone, the phases of borides and carbides were detected. Boronized layers after laser modification were characterized by the mild gradient of microhardness from surface to the substrate.

  20. Development of a method for fabricating metallic matrix composite shapes by a continuous mechanical process

    NASA Technical Reports Server (NTRS)

    Divecha, A. P.

    1974-01-01

    Attempts made to develop processes capable of producing metal composites in structural shapes and sizes suitable for space applications are described. The processes must be continuous and promise to lower fabrication costs. Special attention was given to the aluminum boride (Al/b) composite system. Results show that despite adequate temperature control, the consolidation characteristics did not improve as expected. Inadequate binder removal was identified as the cause responsible. An Al/c (aluminum-graphite) composite was also examined.

  1. Nonaqueous composition for slip casting or cold forming refractory material into solid shapes

    SciTech Connect

    Montgomery, L.C.

    1993-08-24

    A composition is described for slip casting or cold forming non-oxide refractory material(s) into solid shape comprising finely divided solid refractory materials selected from the group consisting of metal boride, refractory carbide, nitride, silicide and a refractory metal of tungsten, molybdenum, tantalum and chromium suspended in a nonaqueous liquid slip composition consisting essentially of a deflocculent composed of a vinyl chloride-vinyl acetate resin dissolved in an organic solvent.

  2. METHOD OF PROTECTING TANTALUM CRUCIBLES AGAINST REACTION WITH MOLTEN URANIUM

    DOEpatents

    Feder, H.M.; Chellew, N.R.

    1960-08-16

    Tantalum crucibles against reaction with molten uranium by contacting the surfaces to be protected with metallic boron (as powder, vapor, or suspension in a liquid-volatilenonreacting medium, such as acetone and petroleum oil) at about 1800 deg C in vacuum, discontinuing contact with the boron, and heating the crucibles to a temperature of between 1800 aad 2000 deg C, whereby the tantalum boride formed in the first heating step is converted to tantalum monoboride.

  3. Identification of thermodynamically stable ceramic reinforcement materials for iron aluminide matrices

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1990-01-01

    Aluminide-base intermetallic matrix composites are currently being considered as potential high-temperature materials. One of the key factors in the selection of a reinforcement material is its chemical stability in the matrix. In this study, chemical interactions between iron aluminides and several potential reinforcement materials, which include carbides, oxides, borides, and nitrides, are analyzed from thermodynamic considerations. Several chemically compatible reinforcement materials are identified for the iron aluminides with Al concentrations ranging from 40 to 50 at. pct.

  4. Wear Characteristics of Sintered Cermets

    NASA Astrophysics Data System (ADS)

    Bidulský, Róbert; Bidulská, Jana; Arenas, Freddy; Grande, Marco Actis

    2012-02-01

    The present paper deals with the tribological behaviour of the boride and carbide hardmetals evaluated by performing comparative dry sliding pin-on-disc experiments using normal contact loads. Analyses of the wear performance results, microstructural evaluation and processing conditions effect indicate that microstructure inhomogenities play an important role in abrasive wear behaviour of cermets. In term of grain size and chemical composition, the addition of VC also play an important role in increasing the wear resistance.

  5. Boron oxynitride nanoclusters on tungsten trioxide as a metal-free cocatalyst for photocatalytic oxygen evolution from water splitting.

    PubMed

    Xie, Ying Peng; Liu, Gang; Lu, Gao Qing Max; Cheng, Hui-Ming

    2012-02-21

    Here we show that B(2)O(3-x)N(x) nanoclusters can be formed on the surface of WO(3) particles by a combination of thermal oxidation of tungsten boride (WB) in air and the subsequent nitriding process in gaseous ammonia. The resultant nanoclusters are found to play an apparent role in improving the photocatalytic oxygen evolution of WO(3) by promoting the surface separation of photoexcited charge-carriers. PMID:22241455

  6. Computational analysis of stable hard structures in the Ti-B system.

    PubMed

    Li, Pengfei; Zhou, Rulong; Zeng, Xiao Cheng

    2015-07-22

    The lowest energy crystalline structures of various stoichiometric titanium boride (Ti-B) intermetallic compounds are sought based on density functional theory combined with the particle-swarm optimization (PSO) technique. Besides three established experimental structures, i.e., FeB-type TiB, AlB2-type, and Ta3B4-type Ti3B4, we predict additional six metastable phases at these stoichiometric ratios, namely, α- and β-phases for TiB, TiB2, and Ti3B4, respectively. Moreover, we predict the most stable crystalline structures of four new titanium boride compounds with different stoichiometric ratios: Ti2B-PSA, Ti2B3-PSB, TiB3-PSC, and TiB4-PSD. Notably, Ti2B-PSA is shown to have lower formation energy (thus higher stability) than the previously proposed Al2Cu-type Ti2B. The computed convex-hull and phonon dispersion relations confirm that all the newly predicted Ti-B intermetallic crystals are thermodynamically and dynamically stable. Remarkably, the predicted α-TiB2 and β-TiB2 show semi-metal-like electronic properties and possess high Vickers hardnesses (39.4 and 39.6 GPa), very close to the lower limit of superhard materials (40 GPa). Analyses of band structure, density of states, electronic localization function, and various elastic moduli provide further understanding of the electronic and mechanical properties of the intermetallic titanium borides. We hope the newly predicted hard intermetallic titanium borides coupled with desirable electronic properties and high elastic modulus will motivate future experimental synthesis for applications such as high-temperature structural materials. PMID:26125540

  7. Investigation of the thermophysical properties of high-melting materials with the aid of a complex of instruments

    NASA Technical Reports Server (NTRS)

    Bolgar, A. S.; Gordiyenko, S. P.; Guseva, Y. A.; Turchanin, A. G.; Fenochka, B. V.; Fesenko, V. V.

    1984-01-01

    The evaporation rate, vapor pressure, heats of evaporation reaction (sublimation, dissociation), enthalpy, electrical resistance, heat capacity, emissivity, and heat conductivity of various carbides, borides, sulfides, nitrides, selenides, and phosphides were investigated. A set of high temperature high vacuum devices, calorimeters (designed for operation at 400 to 1300 K and from 1200 K), and mass spectrometers, most of which were specially developed for these studies, is described.

  8. Composition and method for coke retardant during hydrocarbon processing

    SciTech Connect

    Reid, D.K.

    1988-02-09

    A process is described for inhibiting the formation and deposition of filamentous coke on metallic surfaces in contact with a hydrocarbon having a temperature of 600/sup 0/-1300/sup 0/F which comprises adding to the hydrocarbon a sufficient amount for the purpose of a boron compound selected from the group of boron oxide compounds, boric acid and metal borides, with the proviso that when boric acid is used, it is substantially free of water.

  9. Alumina-based ceramic composite

    DOEpatents

    Alexander, Kathleen B.; Tiegs, Terry N.; Becher, Paul F.; Waters, Shirley B.

    1996-01-01

    An improved ceramic composite comprising oxide ceramic particulates, nonoxide ceramic particulates selected from the group consisting of carbides, borides, nitrides of silicon and transition metals and mixtures thereof, and a ductile binder selected from the group consisting of metallic, intermetallic alloys and mixtures thereof is described. The ceramic composite is made by blending powders of the ceramic particulates and the ductile to form a mixture and consolidating the mixture of under conditions of temperature and pressure sufficient to produce a densified ceramic composite.

  10. On the development of a new pre-weld thermal treatment procedure for preventing heat-affected zone (HAZ) liquation cracking in nickel-base IN 738 superalloy

    NASA Astrophysics Data System (ADS)

    Ola, O. T.; Ojo, O. A.; Chaturvedi, M. C.

    2014-10-01

    Hot cracking in the heat-affected zone (HAZ) of precipitation strengthened nickel-base superalloys, such as IN 738, during fusion welding remains a major factor limiting reparability of nickel-base gas turbine components. The problem of HAZ intergranular cracking can be addressed by modifying the microstructure of the pre-weld material through thermal treatment, which requires significant understanding of the critical factors controlling cracking behaviour. The decomposition of Mo-Cr-W-and Cr-rich borides in the alloy, among other factors, has been observed to contribute significantly to non-equilibrium intergranular liquation and, hence, intergranular liquation cracking during welding. Gleeble physical simulation of HAZ microstructure has also shown that non-equilibrium liquation is more severe in the vicinity of decomposed borides in the alloy and can occur at temperatures as low as 1,150 °C. Although currently existing pre-weld heat treatments for IN 738 superalloy minimize the contributions of dissolution of second phases, including borides, to HAZ intergranular liquation, these heat treatments are not industrially feasible due to process-related difficulties. Therefore, a new industrially feasible and effective pre-weld thermal treatment process, designated as FUMT, was developed during the present research by controlling both the formation of borides and the segregation of boron at the grain boundaries in the pre-weld heat-treated material. This thermal treatment was observed to very significantly reduce intergranular HAZ cracking in welded IN 738 superalloy. The details of the development process and developed procedure are presented in this paper.

  11. Recent results in a search for inorganic scintillators for x- and gamma-ray detection

    SciTech Connect

    Moses, W.W.; Weber, M.J.; Derenzo, S.E.; Perry, D.; Berahl, P.

    1997-10-01

    We present recent results from an ongoing search for inorganic scintillators for gamma ray detection in which we measure the scintillation properties (luminous efficiency, decay time, and emission wavelength) of powdered samples excited by brief x-ray pulses. Recent promising candidates include cerium doped lutetium borate (LuBO{sub 3}) and the lutetium double phosphates K{sub 3}Lu(PO{sub 4}){sub 2} and Rb{sub 3}Lu(PO{sub 4}){sub 2}, which have luminous intensities above 25,000 photons/MeV. In order to find scintillators that are compatible with silicon photodetectors, we have tested over 1,100 samples using a photomultiplier tube with a GaAs:Cs photocathode, which is sensitive to emissions from 200-950 nm. While many samples exhibited strong emissions in the 600-900 nm range, all had decay times that were larger than 10 {mu}s.

  12. Evaluation of lanthanide salts as alternative stains to uranyl acetate.

    PubMed

    Hosogi, Naoki; Nishioka, Hideo; Nakakoshi, Masamichi

    2015-12-01

    Uranyl acetate (UAc) has been generally used not only as a superb staining reagent for ultrathin sections of plastic-embedded biological materials, but also as high-contrast negative stains for biological macromolecules such as particles of protein or virus. However, the use and purchase of radioactive UAc have been restricted. In this study, we determine the performance of ytterbium triacetate, lutetium triacetate, samarium triacetate and gadolinium triacetate as new staining reagents for biological electron microscopy. We observed chemically fixed spinach (Spinacia oleracea) leaves stained with these reagents. Ultrathin sections were stained with these reagents. Some of them were counterstained with lead citrate. The transmission electron microscopy contrast of spinach organelles was evaluated in sections exposed to the conventional stain and new stains. We show acetate salts of samarium, gadolinium, ytterbium and lutetium could be excellent substitutes for UAc for thin section staining and for negative staining. In addition, each reagent showed appreciable negative-staining effects. PMID:26374081

  13. Metal-Size Influence in Iso-Selective Lactide Polymerization**

    PubMed Central

    Bakewell, Clare; White, Andrew J P; Long, Nicholas J; Williams, Charlotte K

    2014-01-01

    Iso-selective initiators for the ring-opening polymerization (ROP) of rac-lactide are rare outside of Group 13. We describe the first examples of highly iso-selective lutetium initiators. The phosphasalen lutetium ethoxide complex shows excellent iso-selectivity, with a Pi value of 0.81–0.84 at 298 K, excellent rates, and high degrees of polymerization control. Conversely, the corresponding La derivative exhibits moderate heteroselectivity (Ps=0.74, 298 K). Thus, the choice of metal center is shown to be crucial in determining the level and mode of stereocontrol. The relative order of rates for the series of complexes is inversely related to metallic covalent radius: that is, La>Y>Lu. PMID:25044165

  14. High-index optical materials for 193nm immersion lithography

    NASA Astrophysics Data System (ADS)

    Burnett, John H.; Kaplan, Simon G.; Shirley, Eric L.; Horowitz, Deane; Clauss, Wilfried; Grenville, Andrew; Van Peski, Chris

    2006-03-01

    We report on our comprehensive survey of high-index UV optical materials that may enable extension of immersion lithography beyond a numerical aperture of 1.45. Band edge, refractive index, and intrinsic birefringence (IBR) at 193 nm determine basic viability. Our measurements of these properties have reduced the list of potential candidates to: ceramic spinel, lutetium aluminum garnet, and a class of germanium garnets. We discuss our measurements of the intrinsic properties of these materials and assess the present status of their material quality relative to requirements. Ceramic spinel has no significant IBR, but transmission and scatter for the best samples remain at least two orders of magnitude from specifications. Improving these would require a major development effort. Presently available lutetium aluminum garnet has material quality much closer to the specifications. However, the IBR is about three times the required value. The germanium garnets offer the possibility of a lower IBR, but a suitable candidate material has yet to be established.

  15. Crystal growth and scintillation properties of LSO and LYSO crystals

    NASA Astrophysics Data System (ADS)

    Mao, Rihua; Wu, Chen; Dai, Ling'En; Lu, Sheng

    2013-04-01

    Lutetium oxyorthosilicate (LSO) and lutetium-yttrium oxyorthosilicate (LYSO) single crystals were grown by Czochralski method and samples with dimension of 17 mm in cubic were made. The optical and scintillation properties for these samples were performed. It was found that optical transmittance observed for both LSO and LYSO matches well with the theoretical limits. The light output (L.O.) measured by a PMT with bialkali cathode was found to be 4100 p.e./MeV with an energy resolution of 10.2% and a decay time of 42 ns. Light output non-proportionality was found in energy scale below 356 keV. The γ-ray induced afterglow in LYSO found much less than that of the LSO sample.

  16. Interfacial reactions in borsic/Ti-3Al-2-1/2V composite

    NASA Technical Reports Server (NTRS)

    Rao, V. B.; Houska, C. R.; Unnam, J.; Brewer, W. D.; Tenney, D. R.

    1979-01-01

    The paper provides a detailed X-ray characterization of a borsic/Ti-3Al-2-1/2V composite, and to correlate the relative intensities of the reaction products with the mechanical properties. Based on X-ray integrated intensity data two stages of interface reactions were identified: during the first stage there is a simultaneous interdiffusion of Si, C, and Ti atoms at the filament/matrix interface resulting in the formation of Ti5Si3, TiSi and small amounts of TiSi2 and TiC. The second stage is associated with considerable TiSi2 and boride formation. It appears that the alpha-phase of Ti is more reactive in forming silicides and borides than the beta-phase. The silicide intensities and the reaction zone thicknesses are shown to be directly related to the reduction of the ultimate tensile strength by thermal degradation, and the results indicate that silicide reaction products are as detrimental to strength as the borides.

  17. B Layers and Adhesion on Armco Iron Substrate

    NASA Astrophysics Data System (ADS)

    Elias-Espinosa, M.; Ortiz-Domínguez, M.; Keddam, M.; Flores-Rentería, M. A.; Damián-Mejía, O.; Zuno-Silva, J.; Hernández-Ávila, J.; Cardoso-Legorreta, E.; Arenas-Flores, A.

    2014-08-01

    In this work, a kinetic model was suggested to evaluate the boron diffusion coefficient in the Fe2B layers grown on the Armco iron substrate by the powder-pack boriding. This thermochemical treatment was carried out in the temperature range of 1123-1273 K for treatment times ranging from 2 to 8 h. The boron diffusion coefficient in the Fe2B layers was estimated by solving the mass balance equation at the (Fe2B/substrate) interface with an inclusion of boride incubation time. To validate the present model, the simulated value of Fe2B layer thickness was compared with the experimental value obtained at 1253 K for a treatment time of 5 h. The morphology of Fe2B layers was observed by SEM and optical microscopy. Metallographic studies showed that the boride layer has a saw-tooth morphology in all the samples. The layer thickness measurements were done with the help of MSQ PLUS software. The Fe2B phase was identified by x-ray diffraction method. Finally, the adherence of Fe2B layers on the Armco iron substrate was qualitatively evaluated by using the Daimler-Benz Rockwell-C indentation technique. In addition, the estimated value of boron activation energy was compared to the literature data.

  18. Effects of Erosion Angle on Erosion Properties of Fe-B Alloy in Flowing Liquid Zinc

    NASA Astrophysics Data System (ADS)

    Liu, Guangzhu; Xing, Jiandong; Ma, Shengqiang; He, Yaling; Fu, Hanguang; Gao, Yuan; Wang, Yong; Wang, Yiran

    2015-05-01

    The effect of erosion angle on erosion behavior of the as-cast Fe-B alloy in flowing liquid zinc was investigated. The results show that the erosion rate of Fe-B alloy decreases linearly with increasing erosion angle. The erosion resistance of Fe-B alloy is better than that of 316L stainless steel, which is attributed to the favorable barrier effect of net-like Fe2B that resists erosion by flowing liquid zinc. Meanwhile, the ductile matrix can provide support in preventing borides from spalling and borides cause barrier effect on flowing liquid zinc during liquid zinc erosion, which shows a synergistic erosion-corrosion behavior between the matrix and borides. Moreover, an increase in erosion angle can cause a decrease in the removal effect of the flowing liquid zinc scouring component on the erosion compounds. Therefore, the quantity of erosion compounds increases at the erosion interface, weakening the mass transfer process and decreasing the erosion rate of the Fe-B alloy.

  19. Fusion welding of a modern borated stainless steel

    SciTech Connect

    Robino, C.V.; Cieslak, M.J.

    1997-01-01

    Experiments designed to assess the fabrication and service weldability of 304B4A borated stainless steel were conducted. Welding procedures and parameters for manual gas tungsten arc (GTA) welding, autogenous electron beam (EB) welding and filler-added EB welding were developed and found to be similar to those for austenitic stainless steels. Following the procedure development, four test welds were produced and evaluated by microstructural analysis and Charpy impact testing. Further samples were used for determination of the postweld heat treatment (PWHT) response of the welds. The fusion zone structure of welds in this alloy consists of primary austenite dendrites with an interdendritic eutectic-like austenite/boride constituent. Welds also show an appreciable partially molten zone that consists of the austenite/boride eutectic surrounding unmelted austenite islands. The microstructure of the EB welds was substantially finer than that of the GTA welds, and boride coarsening was not observed in the solid state heat-affected zone (HAZ) of either weld type. The impact toughness of as-welded samples was found to be relatively poor, averaging less than 10 J for both GTA and EB welds. For fusion zone notched GTA and EB samples and centerline notched EB samples, fracture generally occurred along the boundary between the partially molten and solid-state regions of the HAZ. The results of the PWHT study were very encouraging, with typical values of the impact energy for HAZ notched samples approaching 40 J, or twice the minimum code-acceptable value.

  20. Theoretical study of phase stability and elastic properties of T 0.75Y0.75B14 (T  =  Sc, Ti, V, Y, Zr, Nb, Si)

    NASA Astrophysics Data System (ADS)

    Hunold, Oliver; Music, Denis; Schneider, Jochen M.

    2016-03-01

    In this study the phase stability, elastic properties, and plastic behaviour of icosahedral transition metal borides T 0.75Y0.75B14 (T  =  Sc, Ti, V, Y, Zr, Nb, Si) have been investigated using density functional theory. Phase stability critically depends on the charge transferred by T and Y to the B icosahedra. For the metal sublattice occupancy investigated here, the minimum energy of formation is identified at an effective B icosahedra charge of  -1.8  ±  0.1. This charge corridor encompasses the highest phase stability among all the reported icosahedral transition metal boride systems so far. This data provides guidance for future experimental efforts: from a wear-resistance point of view, Sc0.75Y0.75B14, Ti0.75Y0.75B14, and Zr0.75Y0.75B14 exhibit a rather unique and attractive combination of large Young’s modulus values ranging from 488 to 514 GPa with the highest phase stability for icosahedral transition metals borides reported so far.

  1. Thin film synthesis of superconducting chemical compounds. Final report 1 January 1981-30 December 1983

    SciTech Connect

    Sienko, M.J.; Hoffmann, R.; Newman, J.A.; Burlitch, J.M.

    1984-05-31

    The objective of this research was to define the chemical factors that affect onset of superconductivity in ternary compounds: to determine how small changes in stoichiometry and microstructure influence critical temperature, how the number and placing of magnetic ions act to quench superconductivity, and how the crystal structure can be modified to enhance superconductivity. The approach was to synthesize, from ultrapure starting elements, ternary borides, silicides, sulfides and selenides of the second and third row transition elements, to characterize the new compounds for x-ray structure, electric and magnetic behavior, and then compare them with doped materials. Four kinds of compounds were investigated: rare earth diosmium disilicides, rare earth osmium-iridium borides, layered structure transition metal dichalcogenides, and Chevrel type molybdenum ternaries. Both the rare earth osmium-iridium borides and rare earth diosmium disilicides were synthesized by arc melting. The crystal structures were refined and magnetic susceptibility studies revealed conventional Hund's rule behavior in the disilicides while the (Pr, Nd) (Os, Ir) 4B4 compounds are characterized by Van Vleck paramagnetism of closely spaced multiplets. Only LaOs/sub 2/Si/sub 2/ and LuOs/sub 2/Si/sub 2/ compounds are superconducting with Tc's in the 2-4K range. In the layered compounds, lithium intercalated ZrS/sub 2/, ZrSe/sub 2/, NbS/sub 2/, and NbSe/sub 2/ were studied.

  2. Ce-doped single crystal and ceramic garnets for γ ray detection

    SciTech Connect

    Hull, G; Roberts, J; Kuntz, J; Fisher, S; Sanner, R; Tillotson, T; Drobshoff, A; Payne, S; Cherepy, N

    2007-07-30

    Ceramic and single crystal Lutetium Aluminum Garnet scintillators exhibit energy resolution with bialkali photomultiplier tube detection as good as 8.6% at 662 keV. Ceramic fabrication allows production of garnets that cannot easily be grown as single crystals, such as Gadolinium Aluminum Garnet and Terbium Aluminum Garnet. Measured scintillation light yields of Cerium-doped ceramic garnets indicate prospects for high energy resolution.

  3. Low valency in lanthanides: A theoretical study of NdF and LuF

    SciTech Connect

    Schoendorff, George; Wilson, Angela K.

    2014-06-14

    The ground and low-lying excited state potential energy curves of neodymium monofluoride were calculated using multireference (CASSCF) and single reference (EOM-CR-CCSD(T)) methods. Optimized bond lengths were obtained and accurate bond dissociation energies were computed. The EOM-CR-CCSD(T) method was used to determine the bond dissociation energy of lutetium monofluoride, and it is shown that core correlation is required to produce bond dissociation energies in agreement with experiment.

  4. Method for preparing high specific activity 177Lu

    SciTech Connect

    Mirzadeh, Saed; Du, Miting; Beets, Arnold L.; Knapp, Jr., Furn F.

    2004-04-06

    A method of separating lutetium from a solution containing Lu and Yb, particularly reactor-produced .sup.177 Lu and .sup.177 Yb, includes the steps of: providing a chromatographic separation apparatus containing LN resin; loading the apparatus with a solution containing Lu and Yb; and eluting the apparatus to chromatographically separate the Lu and the Yb in order to produce high-specific-activity .sup.177 Yb.

  5. Lattice dynamics of LuPO{sub 4}

    SciTech Connect

    Nipko, J.C. |; Loong, C.-K.; Loewenhaupt, M.; Reichardt, W.; Braden, M.; Boatner, L.A.

    1996-06-01

    Lutetium orthophosphate is an important nonmagnetic host material for rare-earth-activated luminescence applications. We have measured the LuPO{sub 4} phonon density of states and dispersion curves along the [{xi}00],[{xi}{xi}0], and [00{xi}] symmetry directions by neutron spectroscopy using polycrystalline and single-crystal samples. A quantitative analysis of the neutron results was carried out using a lattice-dynamical shell model.

  6. Atomic properties of Lu+

    NASA Astrophysics Data System (ADS)

    Paez, Eduardo; Arnold, K. J.; Hajiyev, Elnur; Porsev, S. G.; Dzuba, V. A.; Safronova, U. I.; Safronova, M. S.; Barrett, M. D.

    2016-04-01

    Singly ionized lutetium has recently been suggested as a potential clock candidate. Here we report a joint experimental and theoretical investigation of Lu+. Measurements relevant to practical clock operation are made and compared to atomic structure calculations. Calculations of scalar and tensor polarizabilities for clock states over a range of wavelengths are also given. These results will be useful for future work with this clock candidate.

  7. Resonance ionization mass spectrometry for isotopic abundance measurements

    NASA Technical Reports Server (NTRS)

    Miller, C. M.

    1986-01-01

    Resonance ionization mass spectrometry (RIMS) is a relatively new laser-based technique for the determination of isotopic abundances. The resonance ionization process depends upon the stepwise absorption of photons from the laser, promoting atoms of the element of interest through progressively higher electronic states until an ion is formed. Sensitivity arises from the efficiency of the resonant absorption process when coupled with the power available from commercial laser sources. Selectivity derives naturally from the distinct electronic structure of different elements. This isobaric discrimination has provided the major impetus for development of the technique. Resonance ionization mass spectrometry was used for analysis of the isotopic abundances of the rare earth lutetium. Isobaric interferences from ytterbium severely effect the ability to measure small amounts of the neutron-deficient Lu isotopes by conventional mass spectrometric techniques. Resonance ionization for lutetium is performed using a continuous-wave laser operating at 452 nm, through a sequential two-photon process, with one photon exciting the intermediate resonance and the second photon causing ionization. Ion yields for microgram-sized quantities of lutetium lie between 10(6) and 10(7) ions per second, at overall ionization efficiencies approaching 10(-4). Discrimination factors against ytterbium greater than 10(6) have been measured. Resonance ionization for technetium is also being explored, again in response to an isobaric interference, molybdenum. Because of the relatively high ionization potential for Tc, three-photon, two-color RIMS processes are being developed.

  8. Crystalline rare-earth activated oxyorthosilicate phosphor

    DOEpatents

    McClellan, Kenneth J.; Cooke, D. Wayne

    2004-02-10

    Crystalline, transparent, rare-earth activated lutetium oxyorthosilicate phosphor. The phosphor consists essentially of lutetium yttrium oxyorthosilicate activated with a rare-earth metal dopant M and having the general formula Lu(.sub.2-x-z)Y.sub.x M.sub.z SiO.sub.5, wherein 0.00.ltoreq.x.ltoreq.1.95, wherein 0.001.ltoreq.z.ltoreq.0.02, and wherein M is selected from Sm, Tb, Tm, Eu, Yb, and Pr. The phosphor also consists essentially of lutetium gadolinium oxyorthosilicate activated with a rare-earth metal dopant M and having the general formula Lu(.sub.2-x-z)Gd.sub.x M.sub.z SiO.sub.5, wherein 0.00.ltoreq.x.ltoreq.1.95, wherein 0.001.ltoreq.z.ltoreq.0.02, and wherein M is selected from Sm, Tb, Tm, Eu, Yb, and Pr. The phosphor also consists essentially of gadolinium yttrium oxyorthosilicate activated with a rare-earth metal dopant M and having the general formula Gd(.sub.2-x-z)Y.sub.x M.sub.z SiO.sub.5, wherein 0.00.ltoreq.x.ltoreq.1.95, wherein 0.001.ltoreq.z.ltoreq.0.02, and wherein M is selected from Sm, Tb, Tm, Eu, Yb, and Pr. The phosphor may be optically coupled to a photodetector to provide a radiation detector.

  9. Raman and structural characterization of LuAlO{sub 3}

    SciTech Connect

    Casu, Alberto; Ricci, Pier Carlo

    2011-11-15

    The structural and vibrational properties of lutetium orthoaluminate perovskite (LuAlO{sub 3}) were investigated by means of Raman spectroscopy and EXAFS measurements. The analysis of Raman spectra taken in four different polarized configurations along the principal axes at 20 K and room temperature conditions permits to assign the principal vibrational modes in LuAP single crystals and to confirm the belonging to the D{sub 2h}{sup 16} space group. EXAFS measurements were performed at room temperature in order to obtain local structural informations on the first and next nearest neighbors around lutetium absorptions sites. Unit cell parameters and bond lengths were determined by the analysis of the EXAFS spectroscopy at the L{sub 3} absorption edge of lutetium. The informations thus gathered on this compound can offer a useful addition in the framework of a full structural characterization of LuAlO{sub 3}. - Graphical abstract: Raman active mode in LuAP crystal. Highlights: > Structural characterization of LuAlO{sub 3} is obtained by Raman and EXAFS spectroscopies. > Vibrational modes, temperature-dependent variations studied by Raman spectroscopy. > Cell parameters and local characterization obtained by EXAFS spectroscopy.

  10. Etude des mecanismes de formation des microstructures lors du brasage isotherme de superalliages a base de nickel

    NASA Astrophysics Data System (ADS)

    Ruiz-Vargas, Jose

    This thesis reports theoretical and experimental investigations carried out to understand the mechanisms of microstructure formation during isothermal brazing, produced by brazing Inconel 625 and MC2 nickel-based superalloys with filler metal BNi-2. Firstly, studies were made on pure Ni to interpret microstructure's formation with simplified alloy chemistry. Microstructure formation have been studied when varying time at constant temperature (isothermal kinetics), but also when varying temperature for constant hold time (isochronal kinetics). The chemical composition and crystallography of the present phases have been identified, with the following results : (i) the fraction of dissolved base metal has been found proportional to the initial thickness of the brazing alloy, so that the composition of the liquid remains homogeneous with a precise initial equilibrium composition during the whole brazing process, (ii) the melting of the joint occurs in two steps : at lower temperature, it involves only partially melting, and boron diffusion in pure Ni leads to the precipitation of fine Ni3B borides at the interface ; in a second stage, at higher temperature, melting is complete and thermodynamic equilibrium requires significant dissolution of nickel, which also involves the dissolution of part of borides already formed. Secondly, nickel plating technique was used on Inconel 625 nickel-based superalloy. A thin layer of Ni with varying thickness, has been electrodeposited to observe the gradual dissolution of Inconel and microstructural features formation due to the presence of superalloy alloying elements. It has been observed that the nickel coating does not prevent precipitation in the base metal as boron diffuse rapidly through the coating width. In the intermediate nickel plating width, fragile precipitates of nickel borides have been observed, because the contribution of Inconel alloying elements to the melt was very limited. In absence of nickel plating on the

  11. Magnetic and Thermoelectric Properties of Boron-Rich Solids

    NASA Astrophysics Data System (ADS)

    Mori, Takao

    Boron forms various compounds with metal atoms occupying voids in the boron framework. As a synthesis method it has been found that the addition of small amounts of third elements like carbon, nitrogen, and silicon can result in the formation of novel and varied rare earth boron cluster structures. A wide variation of 1D, 2D, and 3D magnetic behavior with unexpectedly strong magnetic interactions has been discovered in rare earth boron icosahedra compounds which are magnetically dilute, f-electron insulators. As an intriguing phenomenon, the B12 icosahedra cluster, which is a building block of the structure, has been indicated to function as a novel mediator of magnetic interaction. These phenomena are borides. Attractive high temperature thermoelectric properties are also emerging in borides. Attractive high temperature thermoelectric properties are also emerging in this group of compounds, which is striking due to the great potential of utilizing waste heat. Recent developments on the long awaited n-type counterpart to boron carbide, the homologous series of RE-B-C(N) compounds, REB17CN, REB22C2N, and REB28.5C4, will be presented together with those of p-type REB44Si2. General new ways to improve the thermoelectric properties are also discussed. For example, seeding with highly electrically conductive metallic borides like REB4 and REB6 is found to be a way to significantly increase the thermoelectric figure of merit. Electric resistivity significantly decreases while Seebeck coefficients and thermal conductivity are not sizably affected.

  12. Liquid Phase Sintering of Boron-Containing Powder Metallurgy Steel with Chromium and Carbon

    NASA Astrophysics Data System (ADS)

    Wu, Ming-Wei; Fan, Yu-Chi; Huang, Her-Yueh; Cai, Wen-Zhang

    2015-11-01

    Liquid phase sintering is an effective method to improve the densification of powder metallurgy materials. Boron is an excellent alloying element for liquid phase sintering of Fe-based materials. However, the roles of chromium and carbon, and particularly that of the former, on liquid phase sintering are still undetermined. This study demonstrated the effects of chromium and carbon on the microstructure, elemental distribution, boride structure, liquid formation, and densification of Fe-B-Cr and Fe-B-Cr-C steels during liquid phase sintering. The results showed that steels with 0.5 wt pct C densify faster than those without 0.5 wt pct C. Moreover, although only one liquid phase forms in Fe-B-Cr steel, adding 0.5 wt pct C reduces the formation temperature of the liquid phase by about 50 K (°C) and facilitates the formation of an additional liquid, resulting in better densification at 1473 K (1200 °C). In both Fe-B-Cr and Fe-B-Cr-C steels, increasing the chromium content from 1.5 to 3 wt pct raises the temperature of liquid formation by about 10 K (°C). Thermodynamic simulations and experimental results demonstrated that carbon atoms dissolved in austenite facilitate the eutectic reaction and reduce the formation temperature of the liquid phase. In contrast, both chromium and molybdenum atoms dissolved in austenite delay the eutectic reaction. Furthermore, the 3Cr-0.5Mo additive in the Fe-0.4B steel does not change the typical boride structure of M2B. With the addition of 0.5 wt pct C, the crystal structure is completely transformed from M2B boride to M3(B,C) boro-carbide.

  13. Reactive multilayer synthesis of hard ceramic foils and films

    DOEpatents

    Makowiecki, D.M.; Holt, J.B.

    1996-02-13

    A method is disclosed for synthesizing hard ceramic materials such as carbides, borides and aluminides, particularly in the form of coatings provided on another material so as to improve the wear and abrasion performance of machine tools, for example. The method involves the sputter deposition of alternating layers of reactive metals with layers of carbon, boron, or aluminum and the subsequent reaction of the multilayered structure to produce a dense crystalline ceramic. The material can be coated on a substrate or formed as a foil which can be coiled as a tape for later use.

  14. Mechanism of ZrB2 Formation in Molten Al-V-Zr Alloy During Boron Treatment

    NASA Astrophysics Data System (ADS)

    Khaliq, Abdul; Rhamdhani, Muhammad Akbar; Brooks, Geoffrey A.; Grandfield, John

    2016-02-01

    Smelter-grade aluminum cannot be used for electrical conductor applications without the removal of transition metal impurities including zirconium (Zr) and vanadium (V). These impurities are removed by treating molten aluminum with boron bearing substances in the casthouse. Such procedures are called boron treatment. Transition metal impurities form their borides and settle at bottom of the furnace. Industrially, Al-B (AlB2/AlB12) master alloys are used for this process. Literature review showed that ZrB2 are more stable compared to VB2 and AlB2 in the temperatures ranging from 948 K to 1173 K (675 °C to 900 °C). As a result, ZrB2 will form preferentially in molten aluminum during boron treatment process. In this study, a systematic investigation on formation of the ZrB2 and VB2 borides in Al-V-Zr-B alloys was carried out at 1023 K (750 °C). Experiments showed that the mechanism of ZrB2 and VB2 borides formation in molten aluminum is complex. It involves the possible phenomenon of chemical reactions, mass transfer in liquid phase, diffusion through borides layers, and the dissolution of Al3Zr, AlB2/AlB12 in the molten aluminum. Scanning electron microscopy, Energy-dispersive X-ray, and electron backscattered diffraction analyses revealed the preferential formation of ZrB2 in the Al-Zr-V-B alloys at 1023 K (750 °C). Moreover, ICP-AES analysis showed the higher rate of Zr removal compared to V from Al-Zr-V-B alloys. Overall it was suggested that the kinetics of Zr removal was controlled by the mass transfer of Zr through liquid phase. The calculated mass transfer coefficient ( k m) for Zr was 1.15 × 10-3 m/s which is within the range of those values reported in the literature.

  15. Containerless processing of amorphous ceramics

    NASA Technical Reports Server (NTRS)

    Weber, J. K. Richard; Krishnan, Shankar; Schiffman, Robert A.; Nordine, Paul C.

    1990-01-01

    The absence of gravity allows containerless processing of materials which could not otherwise be processed. High melting point, hard materials such as borides, nitrides, and refractory metals are usually brittle in their crystalline form. The absence of dislocations in amorphous materials frequently endows them with flexibility and toughness. Systematic studies of the properties of many amorphous materials have not been carried out. The requirements for their production is that they can be processed in a controlled way without container interaction. Containerless processing in microgravity could permit the control necessary to produce amorphous forms of hard materials.

  16. Method for Synthesizing Extremeley High Temperature Melting Materials

    SciTech Connect

    Saboungi, Marie-Louise and Glorieux, Benoit

    2005-11-22

    The invention relates to a method of synthesizing high-temperature melting materials. More specifically the invention relates to a containerless method of synthesizing very high temperature melting materials such as borides, carbides and transition-metal, lanthanide and actinide oxides, using an Aerodynamic Levitator and a laser. The object of the invention is to provide a method for synthesizing extremely high-temperature melting materials that are otherwise difficult to produce, without the use of containers, allowing the manipulation of the phase (amorphous/crystalline/metastable) and permitting changes of the environment such as different gaseous compositions.

  17. Reactive multilayer synthesis of hard ceramic foils and films

    DOEpatents

    Makowiecki, Daniel M.; Holt, Joseph B.

    1996-01-01

    A method for synthesizing hard ceramic materials such as carbides, borides nd aluminides, particularly in the form of coatings provided on another material so as to improve the wear and abrasion performance of machine tools, for example. The method involves the sputter deposition of alternating layers of reactive metals with layers of carbon, boron, or aluminum and the subsequent reaction of the multilayered structure to produce a dense crystalline ceramic. The material can be coated on a substrate or formed as a foil which can be coild as a tape for later use.

  18. High temperature solar energy absorbing surfaces

    DOEpatents

    Schreyer, J.M.; Schmitt, C.R.; Abbatiello, L.A.

    A solar collector having an improved coating is provided. The coating is a plasma-sprayed coating comprising a material having a melting point above 500/sup 0/C at which it is stable and selected from the group of boron carbide, boron nitride, metals and metal oxides, nitrides, carbides, borides, and silicates. The coatings preferably have a porosity of about 15 to 25% and a thickness of less than 200 micrometers. The coatings can be provided by plasma-spraying particles having a mean diameter of about 10 to 200 micrometers.

  19. Numerical and experimental study of electron-beam coatings with modifying particles FeB and FeTi

    NASA Astrophysics Data System (ADS)

    Kryukova, Olga; Kolesnikova, Kseniya; Gal'chenko, Nina

    2016-07-01

    An experimental study of wear-resistant composite coatings based on titanium borides synthesized in the process of electron-beam welding of components thermo-reacting powders are composed of boron-containing mixture. A model of the process of electron beam coating with modifying particles of boron and titanium based on physical-chemical transformations is supposed. The dissolution process is described on the basis of formal kinetic approach. The result of numerical solution is the phase and chemical composition of the coating under nonequilibrium conditions, which is one of the important characteristics of the coating forming during electron beam processing. Qualitative agreement numerical calculations with experimental data was shown.

  20. Corrosion of Ceramic Materials

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth J.; Jacobson, Nathan S.

    1999-01-01

    Non-oxide ceramics are promising materials for a range of high temperature applications. Selected current and future applications are listed. In all such applications, the ceramics are exposed to high temperature gases. Therefore it is critical to understand the response of these materials to their environment. The variables to be considered here include both the type of ceramic and the environment to which it is exposed. Non-oxide ceramics include borides, nitrides, and carbides. Most high temperature corrosion environments contain oxygen and hence the emphasis of this chapter will be on oxidation processes.

  1. Foreword

    NASA Astrophysics Data System (ADS)

    Manghnani, Murli H.

    2015-09-01

    The 18th International Symposium on Boron, Borides and Related Materials was held in Hawaii Prince Hotel Waikiki, Honolulu, Hawaii, USA on August 31 to September 5, 2014 (ISBB 2014). A booklet of the Program and Abstracts prepared for the Symposium served as an important record of the scientific papers presented as oral paper (68) and as posters (53). The wide range of contributions in various areas of inter-disciplinary research in boron-related materials, and the discussions during the sessions, demonstrated impressive advancements and offer many future opportunities for individual as well as collaborative endeavors globally.

  2. Method For Synthesizing Extremely High-Temperature Melting Materials

    SciTech Connect

    Saboungi, Marie-Louise; Glorieux, Benoit

    2005-11-22

    The invention relates to a method of synthesizing high-temperature melting materials. More specifically the invention relates to a containerless method of synthesizing very high temperature melting materials such as borides, carbides and transition-metal, lanthanide and actinide oxides, using an Aerodynamic Levitator and a laser. The object of the invention is to provide a method for synthesizing extremely high-temperature melting materials that are otherwise difficult to produce, without the use of containers, allowing the manipulation of the phase (amorphous/crystalline/metastable) and permitting changes of the environment such as different gaseous compositions.

  3. Heat-resistance of composite electrochemical coatings based on nickel

    SciTech Connect

    Pokmurskii, V.I.; Dalisov, V.B.; Guslienko, Y.A.; Mardarevich, R.S.

    1986-02-01

    The authors study the features of oxidation and determine the temperature limits in the application of carbon steels with composite electrochemical coatings based on the Ni-B system. Coatings based on the Ni-B system deposited on carbon steels can operate for a long time at temperatures up to 750 degrees C. Above this temperature, they begin to decompose and oxidize strongly owing to the instability of nickel borides. A reliable functioning of a composite coating of the composition is possible in the absence of unreacted boron in it.

  4. Thermodynamic analysis of compatibility of several reinforcement materials with FeAl alloys

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1988-01-01

    Chemical compatibility of several reinforcement materials with FeAl alloys within the concentration range 40 to 50 at pct Al have been analyzed from thermodynamic considerations at 1173 and 1273 K. The reinforcement materials considered in this study include carbides, borides, oxides, nitrides, and silicides. Although several chemically compatible reinforcement materials are identified, the coefficients of thermal expansion for none of these materials match closely with that of FeAl alloys and this might pose serious problems in the design of composite systems based on FeAl alloys.

  5. Workshop on First Wall Coating

    NASA Astrophysics Data System (ADS)

    Kamada, K.; Fukutomi, M.

    1982-03-01

    Impurity control and first wall design in the JT 60 long pulse Tokamak is discussed. The present state of coating technology in Japan is reviewed with emphasis on fabrication methods and the characterization of thin coated films available by plasma spraying and chemical and physical vapor deposition. Surface preparation, radiation damage, internal stress, crystal structure and bonding are considered as well as the application of silicon carbide, titanium nitride, titanium carbide, titanium boride, and chromium nitride coatings by magnetron sputtering, long plating, electron beam evaporation, and gas absorption and reactive r.f. sputtering.

  6. Thermodynamic analysis of compatibility of several reinforcement materials with beta phase NiAl alloys

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1988-01-01

    Chemical compatibility of several reinforcement materials with beta phase NiAl alloys within the concentration range 40 to 50 at. percent Al have been analyzed from thermodynamic considerations at 1373 and 1573 K. The reinforcement materials considered in this study include carbides, borides, oxides, nitrides, beryllides, and silicides. Thermodynamic data for NiAl alloys have been reviewed and activity of Ni and Al in the beta phase have been derived at 1373 and 1573 K. Criteria for chemical compatibility between the reinforcement material and the matrix have been defined and several chemically compatible reinforcement materials have been defined.

  7. Mercury switch with non-wettable electrodes

    SciTech Connect

    Karnowsky, M.M.; Yost, F.G.

    1987-03-24

    This patent describes a mercury switch having spaced conductive electrodes with contacts thereon which are bridged by a mercury pool when the switch is closed and free of the mercury pool when the switch is open. The improvement described here comprises: contacts on the conductive electrodes formed of a material selected from the group consisting of metallic borides, nitrides and silicides, with the proviso that the silicides do not include the silicides of Cr, Mo and W; whereby mercury wetting of the contacts is precluded, thereby avoiding undesired bridging of the contacts in the open position of the switch.

  8. Passivating overcoat bilayer for multilayer reflective coatings for extreme ultraviolet lithography

    DOEpatents

    Montcalm, Claude; Stearns, Daniel G.; Vernon, Stephen P.

    1999-01-01

    A passivating overcoat bilayer is used for multilayer reflective coatings for extreme ultraviolet (EUV) or soft x-ray applications to prevent oxidation and corrosion of the multilayer coating, thereby improving the EUV optical performance. The overcoat bilayer comprises a layer of silicon or beryllium underneath at least one top layer of an elemental or a compound material that resists oxidation and corrosion. Materials for the top layer include carbon, palladium, carbides, borides, nitrides, and oxides. The thicknesses of the two layers that make up the overcoat bilayer are optimized to produce the highest reflectance at the wavelength range of operation. Protective overcoat systems comprising three or more layers are also possible.

  9. Concentration of trace elements in water samples by reductive precipitation

    SciTech Connect

    Skogerboe, R.K.; Hanagan, W.A.; Taylor, H.E.

    1985-12-01

    The use of borohydride reduction as a means of preconcentrating elements by precipitation as the element or as a boride has been explored. It has been shown that the optimized procedure reproducibly effects the precipitation of all 18 elements studied; only four of these exhibited recoveries less than 90%. The general ease of use, the demonstrated accuracy and precision, the high preconcentration factors available, the self-cleansing properties of the primary reagent, the granular character of the precipitate are all factors to recommend this approach. 25 references, 1 figure, 4 tables.

  10. The Microstructure Degradation of the IN 713C Nickel-Based Superalloy After the Stress Rupture Tests

    NASA Astrophysics Data System (ADS)

    Matysiak, Hubert; Zagorska, Malgorzata; Balkowiec, Alicja; Adamczyk-Cieslak, Boguslawa; Cygan, Rafal; Cwajna, Jan; Nawrocki, Jacek; Kurzydłowski, Krzysztof J.

    2014-09-01

    The aim of the work was to examine the degradation phenomena taking place in the microstructure of the as-cast IN 713C superalloy after stress rupture tests, performed at T = 980 °C under a tensile stress of 150 MPa. A directional growth of γ' phase (rafting) and decomposition of the NbC primary carbides accompanied by the precipitation of M23C6 secondary carbides rich in chromium and of γ' phase were observed. It was also indicated that the decomposition of the NbC primary carbides may be accompanied by the precipitation of M3B2 borides rich in Mo.

  11. Thermodynamic analysis of chemical compatibility of ceramic reinforcement materials with niobium aluminides

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1990-01-01

    Chemical compatibility of several reinforcement materials with three niobium aluminides, Nb3Al, Nb2Al, and NbAl3, were examined from thermodynamic considerations. The reinforcement materials considered in this study include carbides, borides, nitrides, oxides, silicides, and Engel-Brewer compounds. Thermodynamics of the Nb-Al system were reviewed and activities of Nb and Al were derived at desired calculation temperatures. Criteria for chemical compatibility between the reinforcement material and Nb-Al compounds have been defined and several chemically compatible reinforcement materials have been identified.

  12. Thermodynamic analysis of chemical compatibility of several reinforcement materials with niobium aluminides

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1989-01-01

    Chemical compatibility of several reinforcement materials with three niobium aluminides, Nb3Al, Nb2Al, and NbAl3, were examined from thermodynamic considerations. The reinforcement materials considered in this study include carbides, borides, nitrides, oxides, silicides, and Engel-Brewer compounds. Thermodynamics of the Nb-Al system were reviewed and activities of Nb and Al were derived at desired calculation temperatures. Criteria for chemical compatibility between the reinforcement material and Nb-Al compounds have been defined and several chemically compatible reinforcement materials have been identified.

  13. Modeling the mechanical behavior of ceramic and heterophase structures manufactured using selective laser sintering and spark plasma sintering

    NASA Astrophysics Data System (ADS)

    Skripnyak, Vladimir A.; Skripnyak, Evgeniya G.; Skripnyak, Vladimir V.; Vaganova, Irina K.

    A model for predicting mechanical properties of ultra-high temperature ceramics and composites manufactured by selective laser sintering (SLS) and spark plasma sintering (SPS) under shock loading is presented. The model takes into account the porous structure, the specific volume and average sizes of phases, and the temperature of sintering. Residual stresses in ceramic composites reinforced with particles of refractory borides, carbides and nitrides after SLS or SPS were calculated. It is shown that the spall strength of diboride-zirconium matrix composites can be increased by the decreasing of porosity and the introduction of inclusions of specially selected refractory strengthening phases.

  14. Thermodynamic analysis of chemical compatibility of several compounds with Fe-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1993-01-01

    Chemical compatibility between Fe-19.8Cr-4.8Al (weight percent), which is the base composition for the commercial superalloy MA956, and several carbides, borides, nitrides, oxides, and silicides was analyzed from thermodynamic considerations. The effect of addition of minor alloying elements, such as Ti, Y, and Y2O3, to the Fe-Cr-Al alloy on chemical compatibility between the alloy and various compounds was also analyzed. Several chemically compatible compounds that can be potential reinforcement materials and/or interface coating materials for Fe-Cr-Al based composites were identified.

  15. Assessment of the State of the Art of Ultra High Temperature Ceramics

    NASA Technical Reports Server (NTRS)

    Johnson, Sylvia; Gasch, Matt; Stackpoole, Mairead

    2009-01-01

    Ultra High Temperature Ceramics (UHTCs) are a family of materials that includes the borides, carbides and nitrides of hafnium-, zirconium- and titanium-based systems. UHTCs are famous for possessing some of the highest melting points of known materials. In addition, they are very hard, have good wear resistance, mechanical strength, and relatively high thermal conductivities (compared to other ceramic materials). Because of these attributes, UHTCs are ideal for thermal protection systems, especially those that require chemical and structural stability at extremely high operating temperatures. UHTCs have the potential to revolutionize the aerospace industry by enabling the development of sharp hypersonic vehicles or atmospheric entry probes capable of the most extreme entry conditions.

  16. In-situ Formation of Reinforcement Phases in Ultra High Temperature Ceramic Composites

    NASA Technical Reports Server (NTRS)

    Stackpoole, Margaret M (Inventor); Gasch, Matthew J (Inventor); Olson, Michael W (Inventor); Hamby, Ian W. (Inventor); Johnson, Sylvia M (Inventor)

    2013-01-01

    A tough ultra-high temperature ceramic (UHTC) composite comprises grains of UHTC matrix material, such as HfB.sub.2, ZrB.sub.2 or other metal boride, carbide, nitride, etc., surrounded by a uniform distribution of acicular high aspect ratio reinforcement ceramic rods or whiskers, such as of SiC, is formed from uniformly mixing a powder of the UHTC material and a pre-ceramic polymer selected to form the desired reinforcement species, then thermally consolidating the mixture by hot pressing. The acicular reinforcement rods may make up from 5 to 30 vol % of the resulting microstructure.

  17. Alumina-based ceramic composite

    DOEpatents

    Alexander, K.B.; Tiegs, T.N.; Becher, P.F.; Waters, S.B.

    1996-07-23

    An improved ceramic composite comprising oxide ceramic particulates, nonoxide ceramic particulates selected from the group consisting of carbides, borides, nitrides of silicon and transition metals and mixtures thereof, and a ductile binder selected from the group consisting of metallic, intermetallic alloys and mixtures thereof is described. The ceramic composite is made by blending powders of the ceramic particulates and the ductile to form a mixture and consolidating the mixture of under conditions of temperature and pressure sufficient to produce a densified ceramic composite. 5 figs.

  18. Extending the compositional limit of combustion-synthesized B{sub 4}C-TiB{sub 2} composites by field activation

    SciTech Connect

    Xue, H.; Munir, Z.A.

    1996-06-01

    Composites of B{sub 4}C-TiB{sub 2} with molar ratios B{sub 4}C/TiB{sub 2} of up to 8 were synthesized by field activated combustion. The combustion wave velocity depended on this ratio and increased approximately linearly with the applied field. The effect of the field was analyzed and its contribution to the combustion temperature was calculated. X-ray and microscopic analyses showed the synthesis to be a two-step process. Titanium boride forms at or near the leading edge of the combustion zone and B{sub 4}C forms at or near the trailing edge.

  19. Lightweight porous plastic plaque. [nickel cadmium batteries

    NASA Technical Reports Server (NTRS)

    Reid, M.

    1978-01-01

    The porosity and platability of various materials were investigated to determine a suitable substrate for nickel-plated electrodes. Immersion, ultrasonics, and flow-through plating techniques were tried using nonproprietary formulations, and proprietary phosphide and boride baths. Modifications to the selected material include variations in formulation and treatment, carbon loading to increase conductivity, and the incorporation of a grid. Problems to be solved relate to determining conductivities and porosities as a function of amount of nickel plated on the plastics; loading; charge and discharge curves of electrodes at different current densities; cell performance; and long-term degradation of electrodes.

  20. Incoherent x-ray emission of titanium diboride at the boron site

    SciTech Connect

    Ederer, D.L.; Winarski, R.; Ek, J. van

    1997-04-01

    This group has made a study of a large number of transition metal diborides and hexaborides. As an example they would like to consider one of them. This class of compounds are of technical interest because they are quite hard, metallic, and chemically stable, and have high melting points. In addition to the technical importance of the borides, the group is interested in compounds of this type because of the very strong 1s {r_arrow} p* resonance that has been observed and associated with the boron atom.

  1. Materials for high-temperature hydrogen fluorine environments. Final report, June 1976-December 1978

    SciTech Connect

    Holcombe, C.E. Jr.; Kovach, L.

    1981-03-01

    A determination has been made of the stability of 35 materials under high-temperature, fluorine rich, hydrogen fluoride torch testing. Refractory materials tested included 4 borides, 3 carbides, 3 nitrides, 12 oxides, 1 oxynitride, 1 sulfide, 10 metals, and carbon (10 types). Three materials distinctly performed better than nickel: lanthanum hexaboride, calcium hexaboride, and lanthanum silicon oxynitride. Of these, lanthanum hexaboride is the best candidate tested since it has an estimated upper use temperature > 1726 K, which is above the melting point and more than 300 K above the upper use temperature of nickel.

  2. Method of making a light weight battery plaque

    NASA Technical Reports Server (NTRS)

    Reid, M. A.; Post, R. E.; Soltis, D. G. (Inventor)

    1984-01-01

    A nickel plaque which may be coated with a suitable metal or compound to make an electrode for a fuel cell or battery is fabricated by directing nickel sensitizer, catalyst and plating solutions through a porous plastic substrate in the order named and at prescribed temperatures and flow rates. A boride compound dissolved in the plating solution decreases the electrical resistance of the plaque. Certain substrates may require treatment in an alkali solution to dissolve filler materials thereby increasing porosity to a required 65%.

  3. Reactive multilayer synthesis of hard ceramic foils and films

    SciTech Connect

    Makowiecki, D.M.; Holt, J.B.

    1993-12-31

    Disclosed is method for synthesizing hard ceramic materials such as carbides, borides and aluminides, particularly in the form of coatings provided on another material so as to improve the wear and abrasion performance of machine tools, for example. Method involves the sputter deposition of alternating layers of reactive metals with layers of carbon, boron, or aluminum and the subsequent reaction of the multilayered structure to produce a dense crystalline ceramic. The material can be coated on a substrate or formed as a foil which can be coiled as a tape for later use.

  4. Collisional radiative model for heavy atoms in hot non-local-thermodynamical-equilibrium plasmas

    NASA Astrophysics Data System (ADS)

    Bar-Shalom, A.; Oreg, J.; Klapisch, M.

    1997-07-01

    A collisional radiative model for calculating non-local-thermodynamical-equilibrium (non-LTE) spectra of heavy atoms in hot plasmas has been developed, taking into account the numerous excited and autoionizing states. This model uses superconfigurations as effective levels with an iterative procedure which converges to the detailed configuration spectrum. The non-LTE opacities and emissivities may serve as a reliable benchmark for simpler on-line models in hydrodynamic code simulations. The model is tested against detailed configuration calculations of selenium and is applied to non-LTE optically thin plasma of lutetium.

  5. Scanning electron and cathodoluminescence imaging of thin film Lu{sub 2}SiO{sub 5}:Ce scintillating materials

    SciTech Connect

    Rack, P. D.; Peak, J. D.; Melcher, C. L.; Fitz-Gerald, J. M.

    2007-12-10

    Cerium doped lutetium orthosilicate thin films were sputter deposited onto rough and smooth alumina substrates to compare their extrinsic photoluminescence efficiency. To understand the photoluminescence results, scanning electron and cathodoluminescence imaging were performed. The plane view and cross-section images revealed that dark cathodoluminescence regions were correlated with topology in both films, though the mechanisms for the degraded luminescence were different. For the rough films, substrate topology causes localized shadowing of the sputtered species which creates compositional inhomogeneities. The smooth films have protrusions caused by thermally induced stress and the reduced cathodoluminescence intensity is attributed to electron-hole surface recombination.

  6. Detection of rare earth elements in Powder River Basin sub-bituminous coal ash using laser-induced breakdown spectroscopy (LIBS)

    SciTech Connect

    Tran, Phuoc

    2015-10-01

    We reported our preliminary results on the use of laser-induced breakdown spectroscopy to analyze the rare earth elements contained in ash samples from Powder River Basin sub-bituminous coal (PRB-coal). We have identified many elements in the lanthanide series (cerium, europium, holmium, lanthanum, lutetium, praseodymium, promethium, samarium, terbium, ytterbium) and some elements in the actinide series (actinium, thorium, uranium, plutonium, berkelium, californium) in the ash samples. In addition, various metals were also seen to present in the ash samples

  7. Development of Scintillators in Nuclear Medicine.

    PubMed

    Khoshakhlagh, Mohammad; Islamian, Jalil Pirayesh; Abedi, Seyed Mohammad; Mahmoudian, Babak

    2015-01-01

    High-quality image is necessary for accurate diagnosis in nuclear medicine. There are many factors in creating a good image and detector is the most important one. In recent years, several detectors are studied to get a better picture. The aim of this paper is comparison of some type of these detectors such as thallium activated sodium iodide bismuth germinate cesium activated yttrium aluminum garnet (YAG: Ce) YAP: Ce "lutetium aluminum garnet activated by cerium" CRY018 "CRY019" lanthanum bromide and cadmium zinc telluride. We studied different properties of these crystals including density, energy resolution and decay times that are more important factors affecting the image quality. PMID:26420984

  8. Lu-hf total-rock isochron for the eucrite meteorites

    USGS Publications Warehouse

    Patchett, P.J.; Tatsumoto, M.

    1980-01-01

    The isotope 176Lu (2.6% of natural lutetium) decays by ??- to 176Hf, with a long half life. We present here the first Lu-Hf isochron. The eucrite meteorites, a suite of planetary igneous rocks of known age, 4,550 Myr, define a 10-point total-rock isochron with a slope of 0.0934 ?? 40, leading to a value of 3.53 ?? 0.14 ??1010yr for the ??--decay half life of 176Lu. The isochron intercept of 0.27973 ?? 12 gives the initial 176Hf/177Hf for the inner Solar System at the time of accretion. ?? 1980 Nature Publishing Group.

  9. Metal DiCarbides as Intermediate Species in thermal Ion Formation Mechanisms

    SciTech Connect

    Matthew G. Watrous; James E. Delmore

    2009-09-01

    The lanthanide elements (lanthanum to lutetium) adsorbed onto resin beads have been studied as thermal ionization sources. Temperatures at which these ion sources gave maximum intensities were measured for each of these elements. The temperature trends track the trends in the dissociation energies of the corresponding metal dicarbide compounds. The metal dicarbide functions as a carrier to take the lanthanide element to higher temperatures than otherwise attainable. This results in the release of the atomic species at a higher temperature where the ionization probability is significantly increased. This breaking of molecular bonds releasing the atoms at these elevated temperatures is hypothesized as the reason for high ionization efficiencies.

  10. Suppression of superconductivity in LuxZr1 -xB12: Evidence of static magnetic moments induced by nonmagnetic impurities

    NASA Astrophysics Data System (ADS)

    Sluchanko, N. E.; Azarevich, A. N.; Anisimov, M. A.; Bogach, A. V.; Gavrilkin, S. Yu.; Gilmanov, M. I.; Glushkov, V. V.; Demishev, S. V.; Khoroshilov, A. L.; Dukhnenko, A. V.; Mitsen, K. V.; Shitsevalova, N. Yu.; Filippov, V. B.; Voronov, V. V.; Flachbart, K.

    2016-02-01

    Based on low-temperature resistivity, heat capacity, and magnetization investigations, we show that the unusually strong suppression of superconductivity in LuxZr1 -xB12 (x <8 % ) BCS-type superconductors is caused by the emergence of static spin polarization in the vicinity of nonmagnetic lutetium impurities. The analysis of the obtained results points to a formation of static magnetic moments with μeff≈6 μB per Lu3 + ion (1S0 ground state, 4 f14 configuration) incorporated in the superconducting ZrB12 matrix. The size of these spin-polarized nanodomains was estimated to be about 5 Å.

  11. Scintillator Evaluation for High-Energy X-Ray Diagnostics

    SciTech Connect

    S. S. Lutz; S. A. Baker

    2001-09-01

    This report presents results derived from a digital radiography study performed using x-rays from a 2.3 MeV, rod-pinch diode. Detailed is a parameter study of cerium-doped lutetium ortho-silicate (LSO) scintillator thickness, as it relates to system resolution and detection quantum efficiency (DQE). Additionally, the detection statistics of LSO were compared with that of CsI(Tl). As a result of this study we found the LSO scintillator with a thickness of 3 mm to yield the highest system DQE over the range of spatial frequencies from 0.75 to 2.5 mm{sup -1}.

  12. Lu.sub.1-xI.sub.3:Ce.sub.x-a scintillator for gamma-ray spectroscopy and time-of-flight pet

    DOEpatents

    Shah, Kanai S.

    2008-02-12

    The present invention includes very fast scintillator materials including lutetium iodide doped with Cerium (Lu.sub.1-xI.sub.3:Ce.sub.x; LuI.sub.3:Ce). The LuI.sub.3 scintillator material has surprisingly good characteristics including high light output, high gamma-ray stopping efficiency, fast response, low cost, good proportionality, and minimal afterglow that the material is useful for gamma-ray spectroscopy, medical imaging, nuclear and high energy physics research, diffraction, non-destructive testing, nuclear treaty verification and safeguards, and geological exploration.

  13. The properties of electrochromic film electrodes of lanthanide diphthalocyanines in ethylene glycol

    SciTech Connect

    Collins, G.C.S.; Schiffrin, D.J.

    1985-08-01

    The electrochromic properties of film electrodes of lutetium, erbium, gadolinium, and ytterbium diphthalocyanines in contact with ethylene glycol solutions have been studied. The stability of the electrochromic film under electrochemical cycling in this medium is at least three orders of magnitude better than that in neutral aqueous solutions. The stability of the electrochromic is improved if the film is written galvanostatically from the yellow-tan to the green state. A simplified model for the galvanostatic transition is proposed, and some of the problems of this family of electrochromic materials are discussed.

  14. Production of glass microspheres comprising 90Y and (177)Lu for treating of hepatic tumors with SPECT imaging capabilities.

    PubMed

    Poorbaygi, Hosein; Reza Aghamiri, Seyed Mahmoud; Sheibani, Shahab; Kamali-Asl, Alireza; Mohagheghpoor, Elham

    2011-10-01

    Our objective was to determine if glass microspheres impregnated with two radionuclides, (90)Y as source of therapeutic beta emissions and (177)Lu as source of diagnostic gamma emissions can be useful for SPECT imaging during or after application of the (90)Y microspheres for treating of hepatic tumors. The glass-based microspheres labeled with (89)Y and lutetium (YAS (Lu)) or (89)Y and ytterbium (YAS (Yb)) were prepared by the sol-gel process where sol droplets directly were formed to gel microspheres. Results of the neutron activation indicate that such a combination of glass, microspheres allow bio-distribution studies by SPECT imaging with high resolution. PMID:21723135

  15. Efficient 2-μm laser oscillation of 5% Tm{sup 3+} : KLu(WO{sub 4}){sub 2} disks and 5% Tm{sup 3+} : KLu(WO{sub 4}){sub 2}/KLu(WO{sub 4}){sub 2} composite structures

    SciTech Connect

    Vatnik, S M; Vedin, I A; Kurbatov, P F; Pavlyuk, A A

    2014-11-30

    The spectral and lasing characteristics of active disk elements made of double potassium – lutetium tungstates 5% Tm : KLuW and 5% Tm : KLuW/KLuW composite structures are comparatively studied. Laser power of about 5 W in the cw regime at a wavelength of 1.85 μm was achieved in a composite sample with the active layer thickness of 250 μm. Under quasi-cw pumping, the slope efficiency of all the studied samples exceeded 50%. It is experimentally shown that the internal stresses in the composite structures strongly affect the spectral characteristics of the laser radiation. (lasers)

  16. Using dynamic radiography to determine the volume of an imploding cylinder

    NASA Astrophysics Data System (ADS)

    Lewis, Wilfred; Baker, Stuart A.; Ekdahl, Carl A.; Kurapatkin, Yu.; Oona, Hank; Rodriguez, P.; Schaefer, Tim; Turley, D.; Vesser, L.; Volkov, A.

    1999-10-01

    Experiments have been conducted in Sarov, Russia, with a dynamic radiographic system designed to establish the volume of an imploding 14-mm-diameter tungsten cylinder. Images were formed using a 65-MeV gamma source, lutetium oxyorthosilicate doped with cerium (LSO:Ce) radiation-to- light converter, and a fiber optic imaging bundle. Three radiographs were recorded in the course of approximately 2 microseconds using an electronic streak camera with intensified CCD readout. Significant improvements in system performance were achieved over lens coupling of components by the introduction of coherent fiber optics.

  17. Study of the time response of a LuAG(Pr) crystal for fast timing applications

    NASA Astrophysics Data System (ADS)

    Fraile, L. M.; Mach, H.; Picado, E.; Vedia, V.; Udías, J. M.

    2013-06-01

    The recently developed praseodymium-doped lutetium aluminum garnet, LuAG(Pr), holds a strong potential for fast timing applications. In this study we report on the time response of LuAG(Pr) at 22Na and 60Co photon energies. The measurements were performed using a small crystal cube of 1 cm3 coupled to a Hamamatsu R5320 photomultiplier tube. The full width at half maximum (FWHM) time resolution is found to be 147±2 ps at 60Co energies, and 238±2 ps at 22Na.

  18. MIRD Pamphlet No. 26: Joint EANM/MIRD Guidelines for Quantitative 177Lu SPECT Applied for Dosimetry of Radiopharmaceutical Therapy.

    PubMed

    Ljungberg, Michael; Celler, Anna; Konijnenberg, Mark W; Eckerman, Keith F; Dewaraja, Yuni K; Sjögreen-Gleisner, Katarina; Bolch, Wesley E; Brill, A Bertrand; Fahey, Frederic; Fisher, Darrell R; Hobbs, Robert; Howell, Roger W; Meredith, Ruby F; Sgouros, George; Zanzonico, Pat; Bacher, Klaus; Chiesa, Carlo; Flux, Glenn; Lassmann, Michael; Strigari, Lidia; Walrand, Stephan

    2016-01-01

    The accuracy of absorbed dose calculations in personalized internal radionuclide therapy is directly related to the accuracy of the activity (or activity concentration) estimates obtained at each of the imaging time points. MIRD Pamphlet no. 23 presented a general overview of methods that are required for quantitative SPECT imaging. The present document is next in a series of isotope-specific guidelines and recommendations that follow the general information that was provided in MIRD 23. This paper focuses on (177)Lu (lutetium) and its application in radiopharmaceutical therapy. PMID:26471692

  19. [Radionuclide therapy for cancer--what's new?].

    PubMed

    Hanna, Mäenpää; Mikko, Tenhunen

    2012-01-01

    Radionuclide therapy is radiation therapy, the effect of which is based on radiation damage in cancer cells. The most common radionuclide therapy for cancer is radioiodine therapy for thyroid cancer. Two new forms of treatment have recently been initiated in Finland: 177lutetium octreotate therapy for neuroendocrine tumors, pheochromocytoma and paraganglioma as well as radioembolization (selective internal radiation therapy, SIRT) with 90yttrium-coated resin beads against liver metastases. Still in experimental use, 223radium chloride is a drug prolonging survival in prostate cancer that has metastasized to bone. The treatments require special knowledge and collaboration between several units. PMID:23210283

  20. Synthesis and features of the structure and luminescence of monodisperse SiO2/(Lu1 - x Eu x )2O3 ( x = 0.07) core-shell heteroparticles

    NASA Astrophysics Data System (ADS)

    Ermolaeva, Yu. V.; Masalov, V. M.; Gruzintsev, A. N.; Yakimov, E. E.; Zver'kova, I. I.; Barthou, C.; Tolmachev, A. V.; Emel'Chenko, G. A.

    2010-08-01

    Monodisperse SiO2/Lu1.86Eu0.14O3 core-shell heteroparticles have been obtained using a method developed previously for the synthesis of spherical colloidal particles of silicon dioxide with a size spread of 2-2.5%, followed by the coprecipitation of europium-doped lutetium oxide nanocoating on these spheres. The structure of heteroparticles was studied and their photo- and cathodoluminescence spectra were analyzed. The luminescence decay time in heteroparticles is almost twice that in Lu1.86Eu0.14O3 phosphor powder prepared and treated under the same thermal conditions.

  1. Ultra High Temperature Ceramics' Processing Routes and Microstructures Compared

    NASA Technical Reports Server (NTRS)

    Gusman, Michael; Stackpoole, Mairead; Johnson, Sylvia; Gasch, Matt; Lau, Kai-Hung; Sanjurjo, Angel

    2009-01-01

    Ultra High Temperature Ceramics (UHTCs), such as HfB2 and ZrB2 composites containing SiC, are known to have good thermal shock resistance and high thermal conductivity at elevated temperatures. These UHTCs have been proposed for a number of structural applications in hypersonic vehicles, nozzles, and sharp leading edges. NASA Ames is working on controlling UHTC properties (especially, mechanical properties, thermal conductivity, and oxidation resistance) through processing, composition, and microstructure. In addition to using traditional methods of combining additives to boride powders, we are preparing UHTCs using coat ing powders to produce both borides and additives. These coatings and additions to the powders are used to manipulate and control grain-boundary composition and second- and third-phase variations within the UHTCs. Controlling the composition of high temperature oxidation by-products is also an important consideration. The powders are consolidated by hot-pressing or field-assisted sintering (FAS). Comparisons of microstructures and hardness data will be presented.

  2. Microstructure and elevated temperature wear behavior of induction melted Fe-based composite coating

    NASA Astrophysics Data System (ADS)

    Hu, Ge; Meng, Huimin; Liu, Junyou

    2014-10-01

    Fe-based composite coating prepared onto the component of guide wheel using ultrasonic frequency inductive cladding (UFIC) technique has been investigated in terms of microstructure, phase constitutions, microhardness and elevated temperature wear behavior by scanning electron microscopy (SEM), energy-dispersive spectrometer (EDS), X-ray diffraction (XRD), Vickers microhardness tester and ball-on-disc wear tester. The results indicated that the primary phase in the coating contained austenite γ-Fe, eutectic γ-Fe/(Cr,Fe)2B, boride (Cr,Fe)2B and precipitation enriched in Mo. The average microhardness of the coating was 760 ± 10 HV0.2, which was three times higher than that of the substrate. With increasing temperature, the friction coefficients of the coating and high-chromium cast iron decreased gradually while the wear rates increased during dry sliding wear condition. The relative wear resistance of the coating was 1.63 times higher than that of the high-chromium cast iron at 500 °C, which was ascribed to the hard borides with high thermal stability uniformly embedded in the coating and the formation of dense transfer layer formed onto the worn surface. The high temperature wear mechanism of the coating was dominated by mild abrasive wear. The study revealed that Fe-based composite coating had excellent high temperature wear resistance under dry sliding wear condition.

  3. Effect of Chromium on Microstructure and Properties of High Boron White Cast Iron

    NASA Astrophysics Data System (ADS)

    Liu, Zhongli; Chen, Xiang; Li, Yanxiang; Hu, Kaihua

    2008-03-01

    In this article, the effect of chromium on microstructure and properties of high boron white cast iron was studied. The results indicate that the microstructure of high boron white cast iron with different chromium content comprises a dendritic matrix and interdendritic eutectics, and the eutectic compound has a M2B-type chemical formula that does not change with the difference of chromium content. The increase of chromium not only increases the microhardness of boride, but also improves the morphology of boride, which is changed from continuous network to less continuous distribution. Moreover, with the chromium increase, martensite appears in the matrix under the as-cast condition, the appearance of which depends on the increase of chromium in the matrix and the uneven distribution of carbon in the matrix caused by chromium addition. After quenching in air, the matrixes of alloys all change to martensite. However, some secondary particles are found in the central area of the dendrite grains of alloys with higher chromium, and their existence is due to the difference of boron solubility in the matrix with different chromium content. In addition, the hardenability, hardness, and impact toughness are all improved with the increase in chromium.

  4. High-pressure densified solid solutions of alkaline earth hexaborides (Ca/Sr, Ca/Ba, Sr/Ba) and their high-temperature thermoelectric properties

    SciTech Connect

    Gürsoy, M.; Takeda, M.; Albert, B.

    2015-01-15

    Solid solutions of alkaline earth hexaborides were synthesized and densified by spark plasma sintering at 100 MPa. The high-temperature thermoelectric properties (Seebeck coefficients, electrical and thermal diffusivities, heat capacities) were measured between room temperature and 1073 K. CaB{sub 6}, SrB{sub 6}, BaB{sub 6} and the ternary hexaborides Ca{sub x}Sr{sub 1−x}B{sub 6}, Ca{sub x}Ba{sub 1−x}B{sub 6}, Sr{sub x}Ba{sub 1−x}B{sub 6} (x = 0.25, 0.5, 0.75) are n-type conducting compounds over the whole compositional and thermal ranges. The values of the figure of merit ZT for CaB{sub 6} (ca. 0.3 at 1073 K) were found to be significantly increased compared to earlier investigations which is attributed to the densification process. - Highlights: • Solid solutions of alkaline earth hexaborides were synthesized. • High-temperature thermoelectric properties of mixed calcium borides are excellent. • Spark plasma source densification results in high ZT values. • Borides are rare-earth free and refractory materials.

  5. Scoping corrosion tests on candidate waste package basket materials for the Yucca Mountain Project

    SciTech Connect

    Van Konynenburg, R.A.; Curits, P.C.; Summers, T.S.E.

    1998-03-01

    A scoping corrosion test was performed on candidate waste package basket materials. The corrosion medium was a pH-buffered solution of chemical species expected to be produced by radiolysis. The test was conducted at 90{degrees}C for 96 hours. Samples included aluminum-, copper-, stainless steel-, and zirconium-based metallic materials and several ceramics, incorporating neutron-absorbing elements. Sample weight losses and solution chemical changes were measured. Both corrosion of the host materials and dissolution of the neutron- absorbing elements were studied. The ceramics and the zirconium-based materials underwent only minor corrosion. the stainless steel-based materials performed well except for a welded sample. The aluminum- and copper-based materials exhibited the highest corrosion rates. Boron dissolution depends on it chemical form. Boron oxide and many metal borides dissolve readily in acidic solutions while high- chromium borides and boron carbide, though thermodynamically unstable, exhibit little dissolution in short times. the results of solution chemical analyses were consistent with this. Gadolinium did not dissolve significantly from monazite, and hafnium showed little dissolution from a variety of host materials, in keeping with its low solubility.

  6. Scoping corrosion tests on candidate waste package basket materials for the Yucca Mountain project

    SciTech Connect

    Konynenburg, R.A. van; Curtis, P.G.; Summers, T.S.E.

    1998-03-01

    A scoping corrosion test was performed on candidate waste package basket materials. The corrosion medium was a pH-buffered solution of chemical species expected to be produced by radiolysis. The test was conducted at 90 C for 96 hours. Samples included aluminum-, copper-, stainless steel- and zirconium-based metallic materials and several ceramics, incorporating neutron-absorbing elements. Sample weight losses and solution chemical changes were measured. Both corrosion of the host materials and dissolution of the neutron-absorbing elements were studied. The ceramics and the zirconium-based materials underwent only minor corrosion. The stainless steel-based materials performed well except for a welded sample. The aluminum- and copper-based materials exhibited the highest corrosion rates. Boron dissolution depends on its chemical form. Boron oxide and many metal borides dissolve readily in acidic solutions while high-chromium borides and boron carbide, though thermodynamically unstable, exhibit little dissolution in short times. The results of solution chemical analyses were consistent with this. Gadolinium did not dissolve significantly from monazite, and hafnium showed little dissolution from a variety of host materials, in keeping with its low solubility.

  7. New stable Re-B phases for ultra-hard materials

    SciTech Connect

    Zhao, Xin; Nguyen, Manh Cuong; Wang, Cai-Zhuang; Ho, Kai-Ming

    2014-11-12

    As a distinct class of ultra-hard materials, transition metal borides are found to have superior mechanical properties that challenge the traditional materials. In this work, we explored new stable structures for rhenium borides with different stoichiometries using genetic algorithm in combination with first-principles calculations. Based on theoretical calculations, ReB in a P-3m1 structure is found to be stable against decomposition reactions below 10 GPa and ReB3 in a P-6m2 structure is stable above 22 GPa. Two new phases of Re(2)B are predicted to be thermodynamically stable at pressures higher than 55 GPa and 80 GPa respectively. We also show that a C2/m structure discovered for ReB(4) has energy lower than that of the R-3m structure reported earlier (Wang et al 2013 J. Alloys Compd. 573 20). Elastic and vibrational properties from first-principles calculations indicate that the low-energy structures obtained in our search are mechanically and dynamically stable and are promising targets as new ultra-hard materials.

  8. Structural and Thermal Study of Nanocrystalline Fe-Al-B Alloy Prepared by Mechanical Alloying

    NASA Astrophysics Data System (ADS)

    Gharsallah, Hana Ibn; Sekri, Abderrahmen; Azabou, Myriam; Escoda, Luiza; Suñol, Joan Josep; Khitouni, Mohamed

    2015-08-01

    Nanostructured iron-aluminum alloy of Fe-25 at. pct Al composition doped with 0.2 at. pct B was prepared by mechanical alloying. The phase transformations and structural changes occurring in the studied material during mechanical alloying and during subsequent heating were investigated by SEM, XRD, and DSC techniques. The patterns so obtained were analyzed using the Rietveld program. The alloyed powders were disordered Fe(Al) solid solutions and Fe2B boride phase. The Fe2B boride phase is formed after 4 hours of milling. The crystallite size reduction to the nanometer scale (5 to 8 nm) is accompanied by an increase in lattice strains. The powder milled for 40 hours was annealed at temperatures of 523 K, 823 K, 883 K, and 973 K (250 °C, 550 °C, 610 °C, and 700 °C) for 2 hours. Low temperatures annealing are responsible for the relaxation of the disordered structure, while high temperatures annealing enabled supersaturated Fe(Al) solid solutions to precipitate out fines Fe3Al, Fe2Al5, and Fe4Al13 intermetallics and, also the recrystallization and the grain growth phenomena.

  9. Strong magnetic coupling in a magnetically dilute f-electron insulator: A dysprosium boron-cluster compound

    NASA Astrophysics Data System (ADS)

    Mori, T.; Sahara, R.; Kawazoe, Y.; Yubuta, K.; Shishido, T.; Grin, Y.

    2013-05-01

    Unexpectedly strong magnetic coupling is observed in boride insulators containing the B12 icosahedra as a structural unit. We have successfully synthesized Dy0.74B22C2N, which takes the RB22C2N-type crystal structure. The Dy phase was previously thought to not be possible to form. Spin glass-like behavior was observed with a broad peak in the zero field cooled (ZFC) magnetic susceptibility at T ˜ 44 K, while a large divergence for ZFC and field cooled (FC) curves is observed. The Curie-Weiss constant is determined to be θ =-43.9 K, and this system is indicated to have the strongest magnetic coupling ever observed for any rare earth boride insulator. Electronic structure and chemical bonding calculations were also made. Conventional mechanisms for f-electron magnetism cannot explain the strong coupling observed, which further indicates that the B12 icosahedra is functioning as a novel mediator of magnetic interaction.

  10. Transition Metal Diborides as Electrode Material for MHD Direct Power Extraction: High-temperature Oxidation of ZrB2-HfB2 Solid Solution with LaB6 Addition

    NASA Astrophysics Data System (ADS)

    Sitler, Steven; Hill, Cody; Raja, Krishnan S.; Charit, Indrajit

    2016-04-01

    Transition metal borides are being considered for use as potential electrode coating materials in magnetohydrodynamic direct power extraction plants from coal-fired plasma. These electrode materials will be exposed to aggressive service conditions at high temperatures. Therefore, high-temperature oxidation resistance is an important property. Consolidated samples containing an equimolar solid solution of ZrB2-HfB2 with and without the addition of 1.8 mol pct LaB6 were prepared by ball milling of commercial boride material followed by spark plasma sintering. These samples were oxidized at 1773 K (1500 °C) in two different conditions: (1) as-sintered and (2) anodized (10 V in 0.1 M KOH electrolyte). Oxidation studies were carried out in 0.3 × 105 and 0.1 Pa oxygen partial pressures. The anodic oxide layers showed hafnium enrichment on the surface of the samples, whereas the high-temperature oxides showed zirconium enrichment. The anodized samples without LaB6 addition showed about 2.5 times higher oxidation resistance in high-oxygen partial pressures than the as-sintered samples. Addition of LaB6 improved the oxidation resistance in the as-sintered condition by about 30 pct in the high-oxygen partial pressure tests.

  11. High-performance nanoscale composite coatings for boiler applications

    NASA Astrophysics Data System (ADS)

    Branagan, D. J.; Breitsameter, M.; Meacham, B. E.; Belashchenko, V.

    2005-06-01

    In this article, we will show how unconventional nanoscale composite coatings can be formed using conventional wire-arc thermal spray systems. The as-sprayed SHS7170 wire-arc coatings are found to develop an amorphous matrix structure containing starburst-shaped boride and carbide crystallites with sizes ranging from 60 to 140 nm. After heating to temperatures above the peak crystalline temperature (566 °C), a solid/state transformation occurs that results in the formation of an intimate three-phase matrix structure consisting of the same complex boride and carbide phases, along with α-iron interdispersed on a structural scale from 60 to 110 nm. The nanocomposite microstructure contains clean grain boundaries, which are found to be extremely stable and resist coarsening throughout the range of temperatures found in boilers. Additionally, the properties of the coating are presented including the bond strength, hardness, bend resistance, and impact resistance. The sprayability, forgiveness, and repairability of the SHS7170 wire-arc coatings are explained in detail, with an emphasis on field applicability in boiler environments. The performance of the SHS7170 coatings in boiler environments is measured via elevated temperature-erosion experiments conducted at 300, 450, and 600 °C using bed ash from an operating circulating fluidized-bed combustor boiler, and the results are compared with those for existing boiler coatings.

  12. Ceramic fibers from SI-B-C polymer precursors

    SciTech Connect

    Riccitiello, S.R. ); Hsu, M.S.; Chen, T.S. )

    1993-04-01

    Non-oxide ceramics such as silicon carbide (SiC), silicon nitride (Si[sub 3]N[sub 4]), and silicon borides (SiB[sub 4], SiB[sub 6]) have thermal stability, oxidation resistance, hardness, and varied electrical properties. All these materials can be prepared in a fiber form from a suitable polymer precursor. Silicon carbide fiber (Nicalon), for example, has been successfully produced by the polymer-pyrolysis route, and is presently available from Nippon Carbon. More recently, other fibers have been made available, such as the silicon nitride fiber from Dow Corning Co. and Tyranno fiber from Textron Specialty Materials. The above mentioned fibers, when tested over a temperature range from 25[degrees]C to 1400[degrees]C, experience degradation at elevated temperatures. Past work in ceramic materials has shown that the strength of ceramics containing both carbides and borides is sustained at elevated temperatures, with minimum oxidation. The work presented here describes the formation of ceramic fibers containing both elements, boron and silicon, prepared via the polymer precursor route previously reported by the authors, and discusses the fiber mechanical properties that are retained over the temperature range studied. 18 refs., 6 figs., 1 tab.

  13. Investigation of cobalt interference on lead hydride generation with tetrahydroborate(III) in the presence of hexacyanoferrate(III)

    NASA Astrophysics Data System (ADS)

    Zheng, Lin; Lin, Li; Zhu, Lihui; Jiang, Mindi

    2009-03-01

    The interference of Co(II) on plumbane generation with tetrahydroborate in the presence of hexacyanoferrate(III) was studied with a new mechanism proposed to explain the interference. The products that were obtained, following reactions of a CoCl 2 solution with tetrahydroborate(III), which interfere with plumbane generation, were precipitated and investigated by inductively-coupled plasma-atomic emission spectrometry and -mass spectrometry (ICP-OES and ICP-MS). Batch experiments of the potentiometer analysis and pH determination were performed to investigate a mechanism of Co(II) interference on plumbane generation, the role of hexacyanoferrate(III) on plumbane generation, and the function of the masking agent on Co(II) interference. The preferentially formed nanoscale catalytic and magnetic cobalt borides in the redox system cause a potential for a strong reducing condition and induces the precipitation of Fe(III) and Pb(II) in the solution, which is counter to plumbane generation. Potassium thiocyanate/oxalic acid/1,10-phenanthroline, as the combined masking agent and working with hexacyanoferrate(III), decreases the amount of borides in the precipitates and acts as a kind of buffer of the redox potential, which maintains the conditions for plumbane generation. This hydride generation method has been applied to the direct determination of trace Pb in cobalt oxide standard reference materials with a detection limit of 0.3 µg L - 1 .

  14. Layered titanium diboride: towards exfoliation and electrochemical applications.

    PubMed

    Lim, Chee Shan; Sofer, Zdeněk; Mazánek, Vlastimil; Pumera, Martin

    2015-08-01

    Layered transition metal diborides (TMDB), amongst other refractory metal borides, are commonly employed for material fabrication such as wear- and corrosion-resistant coatings due to their impressive chemical stability and thermal conductivity. In spite of the wide scope of studies carried out on TMDB in the physical field, investigations on its electrochemistry remain limited. Since the physical properties play a vital role in any material's electrochemical behaviour, we explore the viability of the most popular form of titanium boride, layered TiB2, as catalysts for electrochemical energy reactions, including hydrogen evolution and oxygen reduction. Three types of TiB2 were compared in this work - TiB2 separately modified with sodium naphtalenide and butyllithium in an attempt to exfoliate TiB2 and unmodified TiB2. The electrocatalytic activity displayed by all three TiB2 materials provides a wider range of opportunities for the application of TiB2 in material studies. PMID:26137856

  15. Removal of Vanadium from Molten Aluminum-Part I. Analysis of VB2 Formation

    NASA Astrophysics Data System (ADS)

    Khaliq, Abdul; Rhamdhani, Muhammad Akbar; Brooks, Geoffrey A.; Grandfield, John F.

    2014-04-01

    Aluminum has been used as an alternative to copper for electrical conductor applications. However, the presence of certain impurities in aluminum, such as V, Ti, Zr, Cr, and Fe, has detrimental effect on its electrical conductivity. These impurities can be removed by the addition of an Al-B master alloy containing AlB2 or AlB12 phase, known as boron treatment. The detailed mechanism of borides formation, however, is not well understood. In the current study, a systematic investigation of vanadium diborides (VB2) formation in the Al-V-B alloys was carried out. The study comprised thermodynamic assessment and experimental investigation on the Al-V-B system under typical industrial processing conditions. It was predicted from thermodynamic analysis that VB2 are stable borides of V and do not dissolve readily in the temperatures ranging from 948 K to 1173 K (675 °C to 900 °C). The experimental investigation showed that the mechanism of VB2 formation and V removal in an Al-V-B system is complex as it involves a number of steps such as chemical reaction, mass transfers in bulk liquid and inside the VB2 ring, and diffusions of B and V through the VB2 layer. Comparative analysis of thermodynamic and experimental results showed that the aluminum alloys were far from equilibrium and that the overall process was limited by the kinetics of B diffusion through the VB2 ring.

  16. METAL-MATRIX COMPOSITES AND THERMAL SPRAY COATINGS FOR EARTH MOVING MACHINES

    SciTech Connect

    Li Liu; Trent Weaver; F.W. Zok; C.G. Levi; Matthew T. Kiser

    2002-04-01

    In the fifth quarter, tooling for the steel MMC effort was redesigned based on the findings from the pressure casting trials of the previous quarter. While awaiting the arrival of that tooling, gravity casting trials were performed to assess modified performing technology and new hard particle systems. Steel-boride composite systems demonstrated good wetting and infiltration behavior, and fully infiltrated steel-boride composites were obtained under certain conditions. However, preform floating and particle dissolution are challenges which must be overcome. Ceramic oxide composites successfully pressure cast in a hot isostatic press at UC Santa Barbara were characterized and subject to fracture toughness testing. Resulting differences in fracture toughness are believed to be due to differences in matrix hardness, potentially imparted through reaction of the molten steel with the particles. Some evidence of bonding between the steel and oxide particles was noted on fracture surfaces. Arc lamp processing trials at Oak Ridge National Laboratory demonstrated that thermal spray coatings were successfully designed to facilitate fusion. All coatings investigated developed some degree of metallurgical bond after lamp fusion and for most coatings lamp fusion also further increased coating hardness. An overview of the progress during the 1st quarter of this project is given below. Research details are provided in the limited rights appendix to this report.

  17. Microstructural evolution during transient liquid phase bonding of Inconel 738LC using AMS 4777 filler alloy

    SciTech Connect

    Jalilvand, V.; Omidvar, H.; Shakeri, H.R.; Rahimipour, M.R.

    2013-01-15

    IN-738LC nickel-based superalloy was joined by transient liquid phase diffusion bonding using AMS 4777 filler alloy. The bonding process was carried out at 1050 Degree-Sign C under vacuum atmosphere for various hold times. Microstructures of the joints were studied by optical and scanning electron microscopy. Continuous centerline eutectic phases, characterized as nickel-rich boride, chromium-rich boride and nickel-rich silicide were observed at the bonds with incomplete isothermal solidification. In addition to the centerline eutectic products, precipitation of boron-rich particles was observed in the diffusion affected zone. The results showed that, as the bonding time was increased to 75 min, the width of the eutectic zone was completely removed and the joint was isothermally solidified. Homogenization of isothermally solidified joints at 1120 Degree-Sign C for 300 min resulted in the elimination of intermetallic phases formed at the diffusion affected zone and the formation of significant {gamma} Prime precipitates in the joint region. - Highlights: Black-Right-Pointing-Pointer TLP bonding of IN-738LC superalloy was performed using AMS 4777 filler alloy. Black-Right-Pointing-Pointer Insufficient diffusion time resulted in the formation of eutectic product. Black-Right-Pointing-Pointer Precipitation of B-rich particles was observed within the DAZ. Black-Right-Pointing-Pointer The extent of isothermal solidification increased with increasing holding time. Black-Right-Pointing-Pointer Homogenizing of joints resulted in the dissolution of DAZ intermetallics.

  18. Microwave method for synthesis of micro- and nanostructures with controllable composition during gyrotron discharge

    NASA Astrophysics Data System (ADS)

    Batanov, German M.; Borzosekov, Valentin D.; Golberg, Dmitri; Iskhakova, Ludmila D.; Kolik, Leonid V.; Konchekov, Evgeny M.; Kharchev, Nikolai K.; Letunov, Alexander A.; Malakhov, Dmitry V.; Milovich, Filipp O.; Obraztsova, Ekaterina A.; Petrov, Alexander E.; Ryabikina, Irina G.; Sarksian, Karen A.; Stepakhin, Vladimir D.; Skvortsova, Nina N.

    2016-01-01

    We introduce an approach toward the synthesis of micro- and nanostructures under nonequilibrium microwave discharges within metal-dielectric powder mixtures induced by powerful microwave gyrotron radiation. A new plasma-chemical reactor capable of sustaining a discharge regime with an afterglow phase of an order of magnitude longer than the gyrotron pulse duration was constructed for these experiments. In the nonequilibrium conditions of such a discharge, plasma-induced exothermic chemical reactions leading to the synthesis of various compounds were initiated. The synthesized structures were deposited on the reactor walls and on the impurity particles within the reactor. This method was tested under gyrotron-initiated discharges within various metal-dielectric powder mixtures of titanium-boron, molybdenum-boron, titanium-silicon-boron, molybdenum-boron nitride, molybdenum-tungsten-boron nitride, and so on. Depending on the powder mixture composition, reactor atmosphere, and other parameters, micro- and nanosized particles of boron nitride, titanium diboride, molybdenum boride, titanium boride, molybdenum, and molybdenum oxide, were synthesized, detected, and analyzed.

  19. Stability, elastic properties and fracture toughness of Al0.75X0.75B14 (X=Sc, Ti, V, Cr, Y, Zr, Nb, Mo) investigated using ab initio calculations.

    PubMed

    Emmerlich, Jens; Thieme, Niklas; to Baben, Moritz; Music, Denis; Schneider, Jochen M

    2013-08-21

    The effect of the transition metal valence electron concentration on the energy of formation, effective charge of B icosahedra, elastic properties, surface energy and fracture toughness was calculated using density functional theory for icosahedral transition metal borides of AlXB14 (X=Sc, Ti, V, Cr, Y, Zr, Nb, Mo). Consistent with previous work on AlYB14 (Kölpin et al 2009 J. Phys.: Condens. Matter 21 355006) it is shown that phase stability is generally dependent on the effective charge of the icosahedral transition metal borides. Also, ionization potential and electronegativity are identified as parameters affecting the effective charge of B icosahedra suitable for use in predicting the phase stability. Al0.75Y0.75B14, Al0.75Sc0.75B14 and Al0.75Zr0.75B14 have been identified as promising phases for application as protective coatings as they exhibit high phase stability and stiffness combined with a comparatively high fracture toughness. PMID:23877961

  20. Microstructural Characterization and Properties Evaluation of Ni-Based Hardfaced Coating on AISI 304 Stainless Steel by High Velocity Oxyfuel Coating Technique

    NASA Astrophysics Data System (ADS)

    Sharma, Prashant; Majumdar, Jyotsna Dutta

    2013-01-01

    The present study concerns a detailed investigation of microstructural evolution of nickel based hardfaced coating on AISI 304 stainless steel by high velocity oxy-fuel (HVOF) deposition technique. The work has also been extended to study the effect of coating on microhardness, wear resistance and corrosion resistance of the surface. Deposition has been conducted on sand blasted AISI 304 stainless steel by HVOF spraying technique using nickel (Ni)-based alloy [Ni: 68.4 wt pct, chromium (Cr): 17 wt pct, boron (B): 3.9 wt pct, silicon (Si): 4.9 wt pct and iron (Fe): 5.8 wt pct] of particle size 45 to 60 μm as precursor powder. Under the optimum process parameters, deposition leads to development of nano-borides (of chromium, Cr2B and nickel, Ni3B) dispersion in metastable and partly amorphous gamma nickel (γ-Ni) matrix. The microhardness of the coating was significantly enhanced to 935 VHN as compared to 215 VHN of as-received substrate due to dispersion of nano-borides in grain refined and partly amorphous nickel matrix. Wear resistance property under fretting wear condition against WC indenter was improved in as-deposited layer (wear rate of 4.65 × 10-7 mm3/mm) as compared to as-received substrate (wear rate of 20.81 × 10-7 mm3/mm). The corrosion resistance property in a 3.56 wt pct NaCl solution was also improved.

  1. Transition Metal Diborides as Electrode Material for MHD Direct Power Extraction: High-temperature Oxidation of ZrB2-HfB2 Solid Solution with LaB6 Addition

    NASA Astrophysics Data System (ADS)

    Sitler, Steven; Hill, Cody; Raja, Krishnan S.; Charit, Indrajit

    2016-06-01

    Transition metal borides are being considered for use as potential electrode coating materials in magnetohydrodynamic direct power extraction plants from coal-fired plasma. These electrode materials will be exposed to aggressive service conditions at high temperatures. Therefore, high-temperature oxidation resistance is an important property. Consolidated samples containing an equimolar solid solution of ZrB2-HfB2 with and without the addition of 1.8 mol pct LaB6 were prepared by ball milling of commercial boride material followed by spark plasma sintering. These samples were oxidized at 1773 K (1500 °C) in two different conditions: (1) as-sintered and (2) anodized (10 V in 0.1 M KOH electrolyte). Oxidation studies were carried out in 0.3 × 105 and 0.1 Pa oxygen partial pressures. The anodic oxide layers showed hafnium enrichment on the surface of the samples, whereas the high-temperature oxides showed zirconium enrichment. The anodized samples without LaB6 addition showed about 2.5 times higher oxidation resistance in high-oxygen partial pressures than the as-sintered samples. Addition of LaB6 improved the oxidation resistance in the as-sintered condition by about 30 pct in the high-oxygen partial pressure tests.

  2. The physical and mechanical metallurgy of advanced O+BCC titanium alloys

    NASA Astrophysics Data System (ADS)

    Cowen, Christopher John

    This thesis comprises a systematic study of the microstructural evolution, phase transformation behavior, elevated-temperature creep behavior, room-temperature and elevated-temperature tensile behavior, and room-temperature fatigue behavior of advanced titanium-aluminum-niobium (Ti-Al-Nb) alloys with and without boron additions. The specific alloys studied were: Ti-5A1-45Nb (at%), Ti-15Al-33Nb (at%), Ti-15Al-33Nb-0.5B (at%), Ti-15Al-33Nb-5B (at%), Ti-21Al-29Nb (at%), Ti-22Al-26Nb (at%), and Ti-22Al-26Nb-5B (at%). The only alloy composition that had been previously studied before this thesis work began was Ti-22Al-26Nb (at%). Publication in peer-reviewed material science journals of the work performed in this thesis has made data available in the scientific literature that was previously non-existent. The knowledge gap for Ti-Al-Nb phase equilibria over the compositional range of Ti-23Al-27Nb (at%) to Ti-12Al-38Nb (at%) that existed before this work began was successfully filled. The addition of 5 at% boron to the Ti-15Al-33Nb alloy produced 5-9 volume percent boride phase needles within the microstructure. The chemical composition of the boride phase measured by electron microprobe was determined to be approximately B 2TiNb. The lattice parameters of the boride phase were simulated through density functional theory calculations by collaborators at the Air Force Research Laboratory based on the measured composition. Using the simulated lattice parameters, electron backscatter diffraction kikuchi patterns and selected area electron diffraction patterns obtained from the boride phase were successfully indexed according to the space group and site occupancies of the B27 orthorhombic crystal structure. This suggests that half the Ti (c) Wyckoff positions are occupied by Ti atoms and the other half are occupied by Nb atoms in the boride phase lattice. Creep deformation behavior is the main focus of this thesis and in particular understanding the dominant creep

  3. Applications of phosphorescent materials for in-vivo imaging of brain structure and function

    NASA Astrophysics Data System (ADS)

    Boverman, Gregory; Shi, Xiaolei; Cotero, Victoria E.; Filkins, Robert J.; Srivastava, Alok M.; Lorraine, Peter W.; Neculaes, Vasile B.; Ishaque, A. N.

    2016-03-01

    A number of approaches have been developed for in-vivo imaging of neural function at the time scale of action potentials and at the spatial resolution of individual neurons. Remarkable results have been obtained with optogenetics, although the need for genetic modification is an important limitation of these approaches. Similarly, voltage and ion-sensitive dyes allow for optical imaging of action potentials but toxicity remains a problem. Additionally, optical techniques are often only able to be used up to a limited depth. Our preliminary work has shown that nanoparticles of common phosphorescent materials, believed to be generally non-toxic, specifically lutetium oxide and strontium aluminate, can be utilized for cellular imaging, for tomographic imaging, and that the particles can be designed to adhere to neurons. Additionally, lutetium oxide has been shown to be highly X-ray luminescent, potentially allowing for imaging deep within the brain, if the particles can be targeted properly. In ex vivo experiments, we have shown that the phosphorescence of strontium aluminate particles is significantly affected by electric fields similar in strength to those found in the vicinity of the cellular membrane of a neuron. This phenomenon is consistent with early published reports in the electroluminescence literature, namely the Gudden-Pohl effect. We will show results of the ex vivo imaging and dynamic electrical stimulation experiments. We will also show some preliminary ex vivo cell culture results, and will describe plans for future research, focusing on potential in both cell cultures and in vivo for animal models.

  4. Tuning a Lanthanide Complex To Be Responsive to the Environment in Solution.

    PubMed

    Golkowski, Ryan T; Settineri, Nicholas S; Zhao, Xikang; McMillin, David R

    2015-12-01

    The f-f emissions of lanthanide-ion complexes have predictable emission energies and many practical applications, but the emitting states are generally impervious to the surroundings. This investigation explores ligand- and metal-centered emission processes for a series of mixed-ligand complexes of composition M(X-T)(NO3)3, where the metal ion is europium, gadolinium, terbium, or lutetium, and X-T denotes the tridentate ligand 2,2':6',2″-terpyridine (H-T), 4'-phenyl-2,2':6',2″-terpyridine (Ph-T), or 4'-pyrrolidin-N-yl-2,2':6',2″-terpyridine (pyrr-T). The presence of the pyrrolidinyl substituent imparts intraligand charge-transfer (ILCT) character to the ligand-based excited states and reduces the energy gap between the singlet and the triplet excited states. An enhanced rate of intersystem crossing results in a lutetium complex with a relatively small fluorescence quantum yield (0.15%) and a gadolinium complex with an impressive phosphorescence yield of 9.6% in deaerated solution. The Tb(pyrr-T)(NO3)3 system is unique because the relatively low-energy triplet ILCT state equilibrates with the emissive f-f state. The result is a truly remarkable f-f emission signal that is sensitive to the polarity of the local environment as well as the presence of dioxygen. PMID:26571330

  5. Monte Carlo simulation of simultaneous radiation detection in the hybrid tomography system ClearPET-XPAD3/CT

    NASA Astrophysics Data System (ADS)

    Dávila, H. Olaya; Sevilla, A. C.; Castro, H. F.; Martínez, S. A.

    2016-07-01

    Using the Geant4 based simulation framework SciFW1, a detailed simulation was performed for a detector array in the hybrid tomography prototype for small animals called ClearPET / XPAD, which was built in the Centre de Physique des Particules de Marseille. The detector system consists of an array of phoswich scintillation detectors: LSO (Lutetium Oxy-ortosilicate doped with cerium Lu2SiO5:Ce) and LuYAP (Lutetium Ortoaluminate of Yttrium doped with cerium Lu0.7Y0.3AlO3:Ce) for Positron Emission Tomography (PET) and hybrid pixel detector XPAD for Computed Tomography (CT). Simultaneous acquisition of deposited energy and the corresponding time - position for each recorded event were analyzed, independently, for both detectors. interference between detection modules for PET and CT. Information about amount of radiation reaching each phoswich crystal and XPAD detector using a phantom in order to study the effectiveness by radiation attenuation and influence the positioning of the radioactive source 22Na was obtained. The simulation proposed will improve distribution of detectors rings and interference values will be taken into account in the new versions of detectors.

  6. The Characterization of Scintillator Performance at Temperatures up to 400 Degrees Centigrade

    SciTech Connect

    Boatner, Lynn A; Neal, John S; Kolopus, James A; Ramey, Joanne Oxendine; Akkurt, Hatice

    2013-01-01

    The logging and characterization of geothermal wells requires improved scintillator systems that are capable of operation at temperatures significantly above those commonly encountered in the logging of most conventional oil and gas wells (e.g., temperatures nominally in the range of up to 150oC.) Unfortunately, most of the existing data on the performance of scintillators for radiation detection at elevated temperatures is fragmentary, uncorrelated, and generally limited to relatively low temperatures in most cases to temperatures well below 200oC. We have designed a system for characterizing scintillator performance at temperatures extending up to 400oC under inert atmospheric conditions, and this system is applied here to the determination of scintillator performance at elevated temperatures for a wide range of scintillators including, among others: bismuth germanate, cadmium tungstate, cesium iodide, cesium iodide (Tl), cesium iodide (Na), sodium iodide, sodium iodide (Tl), lutetium oxy-orthosilicate (Ce), zinc tungstate, yttrium aluminum perovskite (Ce), yttrium aluminum garnet (Ce), lutetium aluminum perovskite (Ce), and barium fluoride, strontium iodide(Eu). The results of these high-temperature scintillator performance tests are described in detail here. Comparisons of the relative elevated-temperature properties of the various scintillator materials have resulted in the identification of promising scintillator candidates for high-temperature use in geothermal and fossil-fuel well environments.

  7. One-dimensional simulation of lanthanide isotachophoresis using COMSOL.

    PubMed

    Dixon, Derek R; Clark, Sue B; Ivory, Cornelius F

    2012-03-01

    Electrokinetic separations can be used to quickly separate rare earth metals to determine their forensic signature. In this work, we simulate the concentration and separation of trivalent lanthanide cations by isotachophoresis. A one-dimensional simulation is developed using COMSOL v4.0a, a commercial finite element simulator, to represent the isotachophoretic separation of three lanthanides: lanthanum, terbium, and lutetium. The binding ligand chosen for complexation with the lanthanides is α-hydroxyisobutyric acid (HIBA) and the buffer system includes acetate, which also complexes with the lanthanides. The complexes formed between the three lanthanides, HIBA, and acetate are all considered in the simulation. We observe that the presence of only lanthanide:HIBA complexes in a buffer system with 10 mM HIBA causes the slowest lanthanide peak (lutetium) to split from the other analytes. The addition of lanthanide:acetate complexes into the simulation of the same buffer system eliminates this splitting. Decreasing the concentration of HIBA in the buffer to 7 mM causes the analyte stack to migrate faster through the capillary. PMID:22522543

  8. Optimization of irradiation conditions for {sup 177}Lu production at the LVR-15 research reactor

    SciTech Connect

    Lahodova, Z.; Viererbl, L.; Klupak, V.; Srank, J.

    2012-07-01

    The use of lutetium in medicine has been increasing over the last few years. The {sup 177}Lu radionuclide is commercially available for research and test purposes as a diagnostic and radiotherapy agent in the treatment of several malignant tumours. The yield of {sup 177}Lu from the {sup 176}Lu(n,{gamma}){sup 177}Lu nuclear reaction depends significantly on the thermal neutron fluence rate. The capture cross-sections of both reaction {sup 176}Lu(n,{gamma}){sup 177}Lu and reaction {sup 177}Lu(n,{gamma}){sup 178}Lu are very high. Therefore a burn-up of target and product nuclides should be taken into account when calculating {sup 177}Lu activity. The maximum irradiation time, when the activity of the {sup 177}Lu radionuclide begins to decline, was found for different fluence rates. Two vertical irradiation channels at the LVR-15 nuclear research reactor were compared in order to choose the channel with better irradiation conditions, such as a higher thermal neutron fluence rate in the irradiation volume. In this experiment, lutetium was irradiated in a titanium capsule. The influence of the Ti capsule on the neutron spectrum was monitored using activation detectors. The choice of detectors was based on requirements for irradiation time and accurate determination of thermal neutrons. The following activation detectors were selected for measurement of the neutron spectrum: Ti, Fe, Ni, Co, Ag and W. (authors)

  9. Novel electro-optical coupling technique for magnetic resonance-compatible positron emission tomography detectors.

    PubMed

    Olcott, Peter D; Peng, Hao; Levin, Craig S

    2009-01-01

    A new magnetic resonance imaging (MRI)-compatible positron emission tomography (PET) detector design is being developed that uses electro-optical coupling to bring the amplitude and arrival time information of high-speed PET detector scintillation pulses out of an MRI system. The electro-optical coupling technology consists of a magnetically insensitive photodetector output signal connected to a nonmagnetic vertical cavity surface emitting laser (VCSEL) diode that is coupled to a multimode optical fiber. This scheme essentially acts as an optical wire with no influence on the MRI system. To test the feasibility of this approach, a lutetium-yttrium oxyorthosilicate crystal coupled to a single pixel of a solid-state photomultiplier array was placed in coincidence with a lutetium oxyorthosilicate crystal coupled to a fast photomultiplier tube with both the new nonmagnetic VCSEL coupling and the standard coaxial cable signal transmission scheme. No significant change was observed in 511 keV photopeak energy resolution and coincidence time resolution. This electro-optical coupling technology enables an MRI-compatible PET block detector to have a reduced electromagnetic footprint compared with the signal transmission schemes deployed in the current MRI/PET designs. PMID:19397853

  10. Evaluation of light transmission in blood with the photoangioplasty agent (ANTRIN) photosensitizer

    NASA Astrophysics Data System (ADS)

    Miles, Dale R.

    1998-07-01

    ANTRINTM photosensitizer, a lutetium texaphyrin-containing drug, is currently being evaluated in the clinic as a phototherapeutic agent for the treatment of peripheral vascular disease using photodynamic therapy, a procedure which has been designated as photoangioplasty. In order to better understand light delivery/timing, disease indication, and the features necessary in the design of light delivery devices, studies were carried out to measure the effect of hematocrit and photosensitizer concentration on the transmission of 732 nm light in rabbit blood and plasma. In blood, light transmission decreased exponentially with increasing hematocrit. An increase of 10 in the hematocrit (e.g., 35 to 45) resulted in a 40% decrease in the amount of transmitted light. In plasma, high concentrations of AntrinTM were observed 3 and 5 hours post administration (31.8 plus or minus 9.3 (mu) M and 14.3 plus or minus 8.3 (mu) M, respectively) compared to 24 hours after administration of the sensitizer (2.5 plus or minus 1.4 (mu) M). Increased plasma sensitizer levels correlated with decreased light transmission through plasma due to absorption of light by lutetium texaphyrin. An increase in the delivered light fluence would therefore be expected upon irradiation 24 hours versus 3 or 5 hours post administration of AntrinTM. However, other factors, such as drug uptake by plaque, would need to be considered in order to optimize the time interval between injection and irradiation.

  11. Synergistic electrocatalytic effect of nanostructured mixed films formed by functionalised gold nanoparticles and bisphthalocyanines.

    PubMed

    Medina-Plaza, C; Furini, L N; Constantino, C J L; de Saja, J A; Rodri Guez-Mendez, M L

    2014-12-01

    A synergistic electrocatalytic effect was observed in sensors where two electrocatalytic materials (functionalized gold nanoparticles and lutetium bisphthalocyanine) were co-deposited using the Langmuir-Blodgett technique. Films were prepared using a novel method where water soluble functionalised gold nanoparticles [(11-mercaptoundecyl)tetra(ethylene glycol)] (SAuNPs) were inserted in floating films of lutetium bisphthalocyanine (LuPc2) and dimethyldioctadecylammonium bromide (DODAB) as the amphiphilic matrix. The formation of stable and homogeneous mixed films was confirmed by π-A isotherms, BAM, UV-vis and Raman spectroscopy, as well as by SEM and TEM microscopy. The synergistic effect towards hydroquinone of the electrodes modified with LuPc2:DODAB/SAuNP was characterised by an increase in the intensity of the redox peaks and a reduction of the overpotential. This synergistic electrocatalytic effect arose from the interaction between the SAuNPs and the phthalocyanines that occur in the Langmuir-Blodgett films and from the high surface area provided by the nanostructured films. The sensitivity increased with the amount of LuPc2 and SAuNPs inserted in the films and limits of detection in the range of 10(-7)molL(-1) were attained. PMID:25440670

  12. A study on laser weldability improvement of newly developed Haynes 282 superalloy

    NASA Astrophysics Data System (ADS)

    Osoba, Lawrence Opeyemi

    Haynes alloy 282 is a new gamma prime (gamma') precipitation strengthened nickel-base superalloy developed for high temperature applications in land-based and aero turbine engines. Joining is a crucial process both during the manufacturing of new components and repair of service-damaged turbine parts. Unfortunately, the new superalloy cracks during laser beam welding (LBW), which is an attractive technique for joining superalloys components due to its low heat input characteristic that preclude the geometrical distortion of welded components. This research is therefore initiated with the goal of studying and developing an effective approach for preventing or minimizing cracking during LBW of the new superalloy Haynes 282. Careful and detailed electron microscopy and spectroscopy study reveal, for the first time, the formation of sub-micron grain boundary M5B3 particles, in the material. Microstructural study of welded specimens coupled with Gleeble thermo-mechanical physical simulations shows that the primary cause of weld heat affected zone (HAZ) cracking in the alloy is the sub-solidus liquation reaction of intergranular M5B3 borides in the material. Further weldability study showed that the HAZ liquation cracking problem worsens with reduction in welding heat input, which is normally necessary to produce the desired weld geometry with minimum distortion. In order to minimize the HAZ cracking during low heat input laser welding, microstructural modification of the alloy by heat treatment at 1080--1100°C has been developed. The pre-weld heat treatment minimizes cracking in the alloy by reducing the volume fraction of the newly identified M5B3 borides, while also minimizing non-equilibrium grain boundary segregation of boron liberated during dissociation of the boride particles. Further improvement in resistance to cracking was produced by subjecting the material to thermo-mechanically induced grain refinement coupled with a pre-weld heat treatment at 1080

  13. Nb{sub 2}OsB{sub 2}, with a new twofold superstructure of the U{sub 3}Si{sub 2} type: Synthesis, crystal chemistry and chemical bonding

    SciTech Connect

    Mbarki, Mohammed; Touzani, Rachid St.; Fokwa, Boniface P.T.

    2013-07-15

    The new ternary metal-rich boride, Nb{sub 2}OsB{sub 2}, was synthesized by arc-melting the elements in a water-cooled copper crucible under an argon atmosphere. The compound was characterized from single-crystal X-ray data and EDX measurements. It crystallizes as a new superstructure (space group P4/mnc, no. 128) of the tetragonal U{sub 3}Si{sub 2}-structure type with lattice parameters a=5.922(1) Å and c=6.879(2) Å. All of the B atoms are involved in B{sub 2} dumbbells with B–B distances of 1.89(4) Å. Structure relaxation using VASP (Vienna ab intio Simulation Package) has confirmed the space group and the lattice parameters. According to electronic structure calculations (TB–LMTO–ASA), the homoatomic B–B interactions are optimized and very strong, but relatively strong heteroatomic Os–B, Nb–B and Nb–Os bonds are also found: These interactions, which together build a three-dimensional network, are mainly responsible for the structural stability of this new phase. The density of state at the Fermi level predicts metallic behavior, as expected, from this metal-rich boride. - Graphical abstract: Nb{sub 2}OsB{sub 2} is, to the best of our knowledge, the first fully characterized phase in the ternary Nb–Os–B system. It crystallizes (space group P4/mnc, 128) with a new twofold superstructure of the U{sub 3}Si{sub 2} structure type (space group P4/mbm, 127), and is therefore the first boride in this structure family crystallizing with a superstructure of the U{sub 3}Si{sub 2} structure type. We show that the distortions leading to this superstructure occurs mainly in the Nb-layer, which tries to accommodate the large osmium atoms. The consequence of this puckering is the building osmium dumbbells instead of chains along [001]. - Highlights: • First compound in the Nb–Os–B system. • New twofold superstructure of U{sub 3}Si{sub 2} structure type. • Puckering of Nb-layer responsible for superstructure occurrence. • Chemical bonding studied

  14. The electronic structure of hard materials

    NASA Astrophysics Data System (ADS)

    Winarski, Robert Paul

    This research dissertation involves an experimental as well as a theoretical examination of the electronic structure of hard materials. The materials that are presented in this dissertation cover a wide class of materials, consisting of transition metal borides, irradiated polymer films, theoretically predicted superhard semiconductors, doped intermetallic alloys, and transition metal carbides. The borides are traditionally used in high temperature, hard coating applications, such as rocket nozzle linings, extreme wear surfaces, and corrosion coatings. Measurements of the borides appear to show that the bonding in these hard materials is primarily between the boron atoms in these systems. Also of note are the remarkably short interatomic distances between the boron atoms and between the boron and metal atoms in these materials. Irradiated polymer films are being developed for electronic applications, in the hopes that circuits can be developed that can benefit from the high thermal stability, dielectric properties, and mechanical properties provided by these materials. C3N4 is a theoretically predicted superhard material, and some of the first soft x-ray emission measurements of well-characterized samples of this compound are discussed in this work. Intermetallic alloys, in particular Ni3Al, are rather hard, but brittle metallic alloys. It has been found that the addition of boron atoms, in rather low concentrations, can increase the ductility of these alloys, allowing them to be utilized in a wider variety of applications. Measurements of this system have examined a question regarding the positioning of the boron atoms in the structures of this alloy. Finally, the transition metal carbides are used extensively as coatings in industrial applications such as cutting and grinding tools, and polishing compounds. Measurements of these materials suggest that the high degree of covalency between the metal and carbon atoms is primarily responsible for the hardness of

  15. Ab initio Computations of the Electronic, Mechanical, and Thermal Properties of Ultra High Temperature Ceramics (UHTC) ZrB2 and HfB2

    NASA Technical Reports Server (NTRS)

    Lawson, John W.; Bauschlicher, Charles W.; Daw, Murray

    2011-01-01

    Refractory materials such as metallic borides, often considered as ultra high temperature ceramics (UHTC), are characterized by high melting point, high hardness, and good chemical inertness. These materials have many applications which require high temperature materials that can operate with no or limited oxidation. Ab initio, first principles methods are the most accurate modeling approaches available and represent a parameter free description of the material based on the quantum mechanical equations. Using these methods, many of the intrinsic properties of these material can be obtained. We performed ab initio calculations based on density functional theory for the UHTC materials ZrB2 and HfB2. Computational results are presented for structural information (lattice constants, bond lengths, etc), electronic structure (bonding motifs, densities of states, band structure, etc), thermal quantities (phonon spectra, phonon densities of states, specific heat), as well as information about point defects such as vacancy and antisite formation energies.

  16. NASA research on refractory compounds.

    NASA Technical Reports Server (NTRS)

    Gangler, J. J.

    1971-01-01

    The behavior and properties of the refractory carbides, nitrides, and borides are being investigated by NASA as part of its research aimed at developing superior heat resistant materials for aerospace applications. Fundamental studies on the electronic and defect structures of the carbides indicate that there is promise for improving the strength and ductility of these materials. Studies of the zirconium-carbon-oxygen system show that zirconium oxycarbides of different compositions and lattice parameters can be formed between 1500 and 1900 C and are stable below 1500 C. More applied studies show that hot working generally improves the microstructure and therefore the strength of TiC and NbC. Sintering studies on UN indicate that very high densities can be achieved. Hot pressing of cermets of HfN and HfC produces good mechanical properties for high temperature bearing applications.

  17. Formation of Minor Phases in a Nickel-Based Disk Superalloy

    NASA Technical Reports Server (NTRS)

    Gabb, T. P.; Garg, A.; Miller, D. R.; Sudbrack, C. K.; Hull, D. R.; Johnson, D.; Rogers, R. B.; Gayda, J.; Semiatin, S. L.

    2012-01-01

    The minor phases of powder metallurgy disk superalloy LSHR were studied. Samples were consistently heat treated at three different temperatures for long times to approximate equilibrium. Additional heat treatments were also performed for shorter times, to then assess non-equilibrium conditions. Minor phases including MC carbides, M23C6 carbides, M3B2 borides, and sigma were identified. Their transformation temperatures, lattice parameters, compositions, average sizes and total area fractions were determined, and compared to estimates of an existing phase prediction software package. Parameters measured at equilibrium sometimes agreed reasonably well with software model estimates, with potential for further improvements. Results for shorter times representing non-equilibrium indicated significant potential for further extension of the software to such conditions, which are more commonly observed during heat treatments and service at high temperatures for disk applications.

  18. Grain boundary segregation of boron in Inconel 718

    SciTech Connect

    Chen, W.; Chaturvedi, M.C.; Richards, N.L.

    1998-07-01

    The segregation behavior of boron at grain boundaries in two INCONEL 718+ based alloys with different B concentrations was studied. The alloys, one containing 11 ppm of B and the other 43 ppm, were homogenized at 1,200 C for 2 hours followed by water quenching and air cooling. A strong segregation of boron at grain boundaries was observed using secondary ion mass spectrometry after the heat treatment in both the alloys. The segregation was found mainly to be of nonequilibrium type. The homogenized samples were also annealed at 1050 C for various lengths of time. During annealing, boride particles were observed to first form at grain boundaries and then to dissolve on continued annealing at 1050 C. The mechanisms of segregation and desegregation of B are discussed.

  19. Grain boundary segregation of boron in INCONEL 718

    NASA Astrophysics Data System (ADS)

    Chen, W.; Chaturvedi, M. C.; Richards, N. L.; McMahon, G.

    1998-07-01

    The segregation behavior of boron at grain boundaries in two INCONEL 718+ based alloys with different B concentrations was studied. The alloys, one containing 11 ppm of B and the other 43 ppm, were homogenized at 1200 °C for 2 hours followed by water quenching and air cooling. A strong segregation of boron at grain boundaries was observed using secondary ion mass spectrometry after the heat treatment in both the alloys. The segregation was found mainly to be of nonequilibrium type. The homogenized samples were also annealed at 1050 °C for various lengths of time. During annealing, boride particles were observed to first form at grain boundaries and then to dissolve on continued annealing at 1050 °C. The mechanisms of segregation and desegregation of B are discussed.

  20. Materials for high-temperature thermoelectric conversion

    NASA Technical Reports Server (NTRS)

    Feigelson, R. S.; Elwell, D.

    1983-01-01

    High boron materials of high efficiency for thermoelectric power generation and capable of prolonged operation at temperatures over 1200 C are discussed. Background theoretical studies indicated that the low carrier mobility of materials with beta boron and related structures is probably associated with the high density of traps. Experimental work was mainly concerned with silicon borides in view of promising data from European laboratories. A systematic study using structure determination and lattice constant measurements failed to confirm the existence of an SiBn phase. Only SiB6 and a solid solution of silicon in beta boron with a maximum solid solubility of 5.5-6 at % at 1650 C were found.

  1. Energy conversion device and method of reducing friction therein

    DOEpatents

    Solovyeva, Lyudmila Mikhaylovna; Jansson, Kyle S; Elmoursi, Alaa AbdelAzim; Zhu, Dong; Milner, Robert; Daughterty, Early Eugene; Higdon, Clifton Baxter; Elagamy, Kamel Abdel-Khalik; Hicks, Aaron Michael

    2013-10-08

    A device configured for converting energy includes a first surface, a second surface configured for moving with respect to the first surface during operation of the device, and a coating disposed on at least one of the first surface and the second surface. The coating includes a first layer of a ceramic alloy represented by the general formula AlMgB.sub.14--X, wherein X is present in an amount of from 0 to 70 parts by weight based on 100 parts by weight of the ceramic alloy and is a doping agent selected from the group of Group IV elements and borides and nitrides thereof, and a second layer disposed on the first layer and including carbon in a gradient concentration. The coating has a hardness of from 10 to 20 GPa and a coefficient of friction of less than or equal to 0.12.

  2. Techniques for increasing boron fiber fracture strain

    NASA Technical Reports Server (NTRS)

    Dicarlo, J. A.

    1977-01-01

    Improvement in the strain-to-failure of CVD boron fibers is shown possible by contracting the tungsten boride core region and its inherent flaws. The results of three methods are presented in which etching and thermal processing techniques were employed to achieve core flaw contraction by internal stresses available in the boron sheath. After commercially and treatment induced surface flaws were removed from 203 micrometers (8 mil) fibers, the core flaw was observed to be essentially the only source of fiber fracture. Thus, fiber strain-to-failure was found to improve by an amount equal to the treatment induced contraction on the core flaw. Commercial feasibility considerations suggest as the most cost effective technique that method in which as-produced fibers are given a rapid heat treatment above 700 C. Preliminary results concerning the contraction kinetics and fracture behavior observed are presented and discussed both for high vacuum and argon gas heat treatment environments.

  3. Diffusion Boronizing of H11 Hot Work Tool Steel

    NASA Astrophysics Data System (ADS)

    Jurči, Peter; Hudáková, Mária

    2011-10-01

    The H11 hot work tool steel was boronized at various processing parameters, austenitized, quenched, and tempered to a core hardness of 47-48 HRC. Microstructure, phase constitution, and microhardness of boronized layers were investigated. Effect of boronized region on the bulk properties was determined by the Charpy impact test. Structure of boronized regions is formed by the compound layers and diffusion inter-layer. The compound layers consisted of only (Fe,Cr)2B phase, but in the case of longer processing time, they contained also of the (Fe,Cr)B-phase. The inter-layer contained enhanced portion of carbides, formed due to carbon diffusion from the boride compounds toward the substrate. Microhardness of boronized layers exceeded considerably 2000 HV 0.1. However, boronizing led to a substantial lowering of the Charpy impact toughness of the material.

  4. Peculiarities of the formation of multicomponent AlN-TiB2-TiSi2 composite ceramics coatings during heat treatment

    NASA Astrophysics Data System (ADS)

    Pogrebnyak, A. D.; Kravchenko, Yu. A.; Dem'yanenko, A. A.; Sobol', O. V.; Beresnev, V. M.; Pshik, A. V.

    2015-06-01

    Results of studies of the morphology, elemental and phase compositions of coatings prepared by pulsed magnetron sputtering of the AlN-TiB2-TiSi2 composite ceramic target have been reported. The used technology allows us to prepare a protective amorphous-like layer with ordering areas with sizes up to 1 nm. The heat treatment of samples at 900 and 1300°C leads to the depletion of the coating surface of boride phases and the formation of α-Al2O3- and β]-TiO2-based protective films on the surface. The growth of crystallites of the nanostructured coating to 11-25 nm is observed. The annealing at 1300°C allows us to obtain the thermally stable crystalline state of substance, the nanohardness of which is 11 GPa.

  5. Oxidation-induced contraction and strengthening of boron fibers

    NASA Technical Reports Server (NTRS)

    Dicarlo, J. A.; Wagner, T. C.

    1981-01-01

    An investigation was conducted to measure and understand the physical and mechanical effects that occur in boron fibers during and after thermal treatment in a controlled oxygen argon gaseous mixture. Of principal concern was the optimization of this treatment as a secondary processing method for significantly improving fiber tensile strength. Strengthening was accomplished by an oxidation induced axial contraction of the fiber and a resulting axial compression of strength limiting flaws within the fiber's tungsten boride core. Various physical observations were used to develop mechanistic models for oxidation, contraction, and flow formation. Processing guidelines are discussed for possibly exceeding the 5.5 GN/sq m strength limit and also for achieving fiber strengthening during application of boron containing diffusion barrier coatings.

  6. Anisotropic elastic and vibrational properties of Ru2B3 and Os2B3: a first-principles investigation

    NASA Astrophysics Data System (ADS)

    Ozisik, Haci; Deligoz, Engin; Surucu, Gokhan; Bogaz Ozisik, Havva

    2016-07-01

    The structural, mechanical and lattice dynamical properties of Ru2B3 and Os2B3 have been investigated by using a first-principles method based on the density functional theory within the generalized gradient approximation. The single crystal elastic constants are numerically estimated using strain–stress approach. The polycrystalline aggregate elastic parameters are calculated from the single elastic constants via the Voigt–Reuss–Hill approximations. Subsequently, the ductility and brittleness are characterized with the estimation from Pugh’s rule (B/G) and Cauchy pressure. Additionally, the Debye temperature is calculated from the average elastic wave velocity obtained from bulk and shear moduli. The calculated parameters are consistent with the previous experimental and theoretical data. These borides are both mechanically and dynamically stable in the considered structure.

  7. Silicon sensors with pyramidal structures for neutron imaging

    NASA Astrophysics Data System (ADS)

    Kok, A.; Kohout, Z.; Hansen, T.-E.; Petersson, S.; Pospisil, S.; Rokne, J.; Slavicek, T.; Soligard, S.; Thungstrom, G.; Vykydal, Z.

    2014-04-01

    Neutron detection is a valuable tool in nuclear science research, homeland security, quality assurance in nuclear plants and medical applications. Recent developments and near future instrumentations in neutron imaging have a need for sensors with high spatial resolution, dynamic range, sensitivity and background discrimination. Silicon based neutron detectors can potentially fulfil these requirements. In this work, pad and pixel detectors with pyramidal micro-structures have been successfully fabricated that should have an improved detection efficiency when compared to conventional planar devices. Titanium di-boride (TiB2) and lithium fluoride (LiF) were deposited as the neutron converters. Excellent electrical performances were measured on both simple pad and pixel detectors. A selection of pad detectors was examined by alpha spectroscopy. Measurement with thermal neutrons from a 241Am-Be source shows an improvement in relative efficiency of up to 38% when compared to conventional planar devices.

  8. Review of Thermal Spray Coating Applications in the Steel Industry: Part 2—Zinc Pot Hardware in the Continuous Galvanizing Line

    NASA Astrophysics Data System (ADS)

    Matthews, S.; James, B.

    2010-12-01

    This two-part article series reviews the application of thermal spray coating technology in the production of steel and steel sheet products. Part 2 of this article series is dedicated to coating solutions in the continuous galvanizing line. The corrosion mechanisms of Fe- and Co-based bulk materials are briefly reviewed as a basis for the development of thermal spray coating solutions. WC-Co thermal spray coatings are commonly applied to low Al-content galvanizing hardware due to their superior corrosion resistance compared to Fe and Co alloys. The effect of phase degradation, carbon content, and WC grain size are discussed. At high Al concentrations, the properties of WC-Co coatings degrade significantly, leading to the application of oxide-based coatings and corrosion-resistant boride containing coatings. The latest results of testing are summarized, highlighting the critical coating parameters.

  9. The effect of anti-phase domain size on the ductility of a rapidly solidified Ni3Al-Cr alloy

    NASA Technical Reports Server (NTRS)

    Carro, G.; Bertero, G. A.; Wittig, J. E.; Flanagan, W. F.

    1989-01-01

    Tensile tests on splat-quenched Ni3Al-Cr alloys showed a sharp decrease in ductility with long-time annealing. The growth of the initially very-fine-size anti-phase domains showed a tenuous correlation with ductility up to a critical size, where ductility was lost. The grain size was relatively unaffected by these annealing treatments, but the grain-boundary curvature decreased, implying less toughness. An important observation was that, for the longest annealing time, a chromium-rich precipitate formed, which the data indicate could be a boride. Miniaturized tensile tests were performed on samples which were all obtained from the same splat-quenched foil, and the various domain sizes were controlled by subsequent annealing treatments.

  10. Microstructural observations in rapidly-solidified and heat-treated Ni3Al-Cr alloys

    NASA Technical Reports Server (NTRS)

    Carro, G.; Flanagan, W. F.

    1992-01-01

    The microstructural development following heat treatments of several rapidly-solidified Ni3Al-Cr and Ni3Al-Cr-B alloys is presented. Depending on composition, the as-solidified samples were either 100 percent gamma-prime phase - in the form of fine antiphase domains (APD) - or a mixture of gamma-prime (APDs) and beta phases. Upon annealing, the as-solidified microstructures transform to either APD-free gamma-prime or mixtures of gamma and gamma-prime phases. For those compositions where the quenched microstructures were 100 percent gamma-prime it was observed that APD coarsening followed conventional grain-growth kinetics, but when gamma phase precipitated on the APD boundaries the rate constant changed abruptly while the time exponent remained unaffected. It was also found that alloys containing critical amounts of chromium and boron are susceptible to precipitation of the boride Cr5B3.

  11. The use of moments of momentum to account for crystal habits

    NASA Technical Reports Server (NTRS)

    Barber, P. G.

    1985-01-01

    A three-step theory of crystal growth is proposed which involves first an association of molecules or ions in solution to form an impinging growth unit, then second the orientation of this unit prior to its impact on the surface of a crystal, and finally the attachment of this unit to the crystal face. From this theory the habit of a crystal is dependent upon the moments of momentum of the impinging growth unit. The results of sample calculations are presented or sodium chloride, succinic acid, sucrose, and chromium boride. The faces predicted by this proposed theory are compared with those predicted by other, energy-based calculations and with those experimentally observed. The proposed theory suggests alternative strategies for crystallization and habit modification which may be of technological importance. Listings of the two computer programs that were used are provided.

  12. Two phase titanium aluminide alloy

    DOEpatents

    Deevi, Seetharama C.; Liu, C. T.

    2001-01-01

    A two-phase titanic aluminide alloy having a lamellar microstructure with little intercolony structures. The alloy can include fine particles such as boride particles at colony boundaries and/or grain boundary equiaxed structures. The alloy can include alloying additions such as .ltoreq.10 at % W, Nb and/or Mo. The alloy can be free of Cr, V, Mn, Cu and/or Ni and can include, in atomic %, 45 to 55% Ti, 40 to 50% Al, 1 to 5% Nb, 0.3 to 2% W, up to 1% Mo and 0.1 to 0.3% B. In weight %, the alloy can include 57 to 60% Ti, 30 to 32% Al, 4 to 9% Nb, up to 2% Mo, 2 to 8% W and 0.02 to 0.08% B.

  13. Thermodynamic stability and unusual strength of ultra-incompressible rhenium nitrides

    SciTech Connect

    Zhang, R. F.; Lin, Zhijun; Mao, Ho-kwang; Zhao, Yusheng

    2011-02-11

    We report on a comprehensive study of thermodynamic and mechanical properties as well as a bond-deformation mechanism on ultra-incompressible Re{sub 2} N and Re{sub 3} N. The introduction of nitrogen into the rhenium lattice leads to thermodynamic instability in Re{sub 2} N at ambient conditions and enhanced incompressibility and strength for both rhenium nitrides. Rhenium nitrides, however, show substantially lower ideal shear strength than hard ReB{sub 2} and superhard c -BN, suggesting that they cannot be intrinsically superhard. An intriguing soft “ionic bond mediated plastic deformation” mechanism is revealed to underline the physical origin of their unusual mechanical strength. These results suggest a need to reformulate the design concept of intrinsically superhard transition-metal nitrides, borides, and carbides.

  14. NiCrSiB Coatings Deposited by Plasma Transferred Arc on Different Steel Substrates

    NASA Astrophysics Data System (ADS)

    Reinaldo, P. R.; D'Oliveira, A. S. C. M.

    2013-02-01

    Colmonoy 6 (NiCrSiB) is a Ni-based alloy recognized for its superior mechanical properties, attributed to the presence of a dispersion of hard carbides and borides, which is strongly dependent on processing technique. This work gathered microstructure data from the literature and analyzed Colmonoy 6 coatings deposited by plasma transferred arc hardfacing. The aim of the study was to determine the influence of PTA deposition parameters and substrate chemical composition on NiCrSiB coating characteristics. Coatings were characterized in terms of their hardness, dilution, and microstructure, as well as mass loss during abrasive sliding wear tests. The results showed that coating performance is strongly dependent on the chemical composition of the substrate. Carbon steel substrate yielded coatings with greater wear resistance. Processing parameters also alter the performance of coatings, and the lower current and lower travel speed result in reduced mass loss.

  15. Borosiliciding of Fe Ni alloys and evaluation of their resistance to abrasive wear

    NASA Astrophysics Data System (ADS)

    Sambogna, G.; Palombarini, G.; Carbucicchio, M.; Ciprian, R.

    2008-11-01

    X-ray diffraction analysis, Mössbauer measurements and metallographic observations were performed on borosilicide coatings grown at 850°C on Armco iron and the Fe64Ni36 binary alloy using a KBF4-activated powder mixture of B4C and Si3N4. The phase composition of the coatings was determined, a result allowing to show that the thermochemical treatment gives rise to iron boriding and iron siliciding reactions of different strength, depending on the treated material. The presence of Ni in the base metal allows iron-free nickel silicides to form as important components of the coating. The resistance of borosilicide coatings to abrasive wear is evaluated and discussed.

  16. Materials for high-temperature thermoelectric conversion

    SciTech Connect

    Feigelson, R.S.; Elwell, D.

    1983-04-01

    High boron materials of high efficiency for thermoelectric power generation and capable of prolonged operation at temperatures over 1200 C are discussed. Background theoretical studies indicated that the low carrier mobility of materials with beta boron and related structures is probably associated with the high density of traps. Experimental work was mainly concerned with silicon borides in view of promising data from European laboratories. A systematic study using structure determination and lattice constant measurements failed to confirm the existence of an SiB/sub n/ phase. Only SiB/sub 6/ and a solid solution of silicon in beta boron with a maximum solid solubility of 5.5-6 at % at 1650 C were found.

  17. Mo5PB2: a new superconductor in the Cr5B3 structure type with Tc = 9.2 K

    NASA Astrophysics Data System (ADS)

    McGuire, Michael; Parker, David

    Superconductivity has been reported recently in several ternary silicide-borides adopting the tetragonal Cr5B3 structure type, including Nb5Si3-xBx, Mo5SiB2, and W5SiB2, with critical temperatures ranging from 5.8-7.8 K. Here we report superconductivity with Tc exceeding 9 K in the phosphorus-containing analogue Mo5PB2. We have synthesized polycrystalline samples of the compound, made measurements of electrical resistivity, magnetic susceptibility, and heat capacity, and performed first principles electronic structure calculations. The highest Tc values occur in slightly phosphorus rich samples, with composition near Mo5P1.1B1.9. Together with the measured properties, the calculations suggest the superconductivity in these materials may be multi-band. Research sponsored by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

  18. Superconductivity between standard types: Multiband versus single-band materials

    NASA Astrophysics Data System (ADS)

    Vagov, A.; Shanenko, A. A.; Milošević, M. V.; Axt, V. M.; Vinokur, V. M.; Aguiar, J. Albino; Peeters, F. M.

    2016-05-01

    In the nearest vicinity of the critical temperature, types I and II of conventional single-band superconductors interchange at the Ginzburg-Landau parameter κ =1 /√{2 } . At lower temperatures this point unfolds into a narrow but finite interval of κ 's, shaping an intertype (transitional) domain in the (κ ,T ) plane. In the present work, based on the extended Ginzburg-Landau formalism, we show that the same picture of the two standard types with the transitional domain in between applies also to multiband superconductors. However, the intertype domain notably widens in the presence of multiple bands and can become extremely large when the system has a significant disparity between the band parameters. It is concluded that many multiband superconductors, such as recently discovered borides and iron-based materials, can belong to the intertype regime.

  19. The crystallization, magnetic and magnetocaloric properties in Fe 76.5-xNb xSi 15.5B 7Au 1 ribbons

    NASA Astrophysics Data System (ADS)

    Hoa, N. Q.; Gam, D. T. H.; Chau, N.; The, N. D.; Yu, S.-C.

    2007-03-01

    Fe 76.5-xNb xSi 15.5B 7Au 1 ribbons ( x=0.0, 1.5, 3.0, 4.5) have been fabricated by rapid quenching technique. The DSC measurements indicated that both first exothermal peak Tp1 (of α-Fe(Si) phase) and second peak Tp2 (of boride phase) as well as crystallization activation energy increase with increasing Nb content substituted, whereas saturation magnetization of samples decreases with x, due to ferromagnetic dilution. Besides, Curie temperature of amorphous phase decreases with x, i.e. Nb stabilizes amorphous structure of ribbons. The investigation of magnetic entropy change of studied samples showed that it may lead to magnetocaloric effect around respective Curie temperature of amorphous phase.

  20. Structural stability of W2B5 under high pressure

    NASA Astrophysics Data System (ADS)

    Kumar, N. R. Sanjay; Shekar, N. V. Chandra; Sahu, P. Ch.

    2015-05-01

    High-pressure structural stability studies have been carried out on tungsten boride W2B5 up to maximum pressure of 36 GPa using a Mao-Bell diamond-anvil cell at beamline BR-12 of the ELETTRA synchrotron facility (λ = 0.68881 Å). The hexagonal phase (S.G:P63/mmc) of W2B5 is stable up to the maximum pressure studied. The bulk modulus is estimated to be ~347 GPa using the Birch-Murnaghan equation of state. The variation of lattice parameters and bond lengths B-B and W-B have been studied and the c-axis is seen to be marginally more compressible than the a-axis.

  1. Molecular and polymeric ceramic precursors. Progress report, December 1, 1990--November 30, 1993

    SciTech Connect

    Sneddon, L.G.

    1993-05-01

    The development of new methods for the production of complex materials is one of the most important problems in modern solid state chemistry and materials science. This project is attempting to apply the synthetic principles which have evolved in inorganic and organometallic chemistry to the production of technologically important non-oxide ceramics, such as boron nitride, boron carbide and metal borides. Our recent work has now resulted in the production of new polymer systems, including poly(B-vinylborazine), polyvinylpentaborane and polyborazylene, that have proven to be high yield precursors to boron-based ceramic materials. Current work s now directed toward the synthesis of new types of molecular and polymeric boron-containing species and an exploration of the solid state properties of the ceramics that have been produced in these studies.

  2. The first spectroscopic observation of germanium carbide

    NASA Astrophysics Data System (ADS)

    Ruiz, Jose I.

    Electronic spectroscopy was used to obtain gas phase spectrum of the germanium carbide molecule in emission from a corona excited supersonic expansion source. The (2) 3pi -- X 3pi electronic transition was observed around the 21250 cm-1 region. In this system, vibrational bands and the rotational lines of the O = 0, 1, and 2 components were obtained and analyzed. The equilibrium transition energy is found at 21120.3 cm-1 and the fundamental vibrational frequency for the lowest energy ground state O = 2 component is 795.3 cm -1. This is the first spectroscopic observation of germanium carbide. An unsuccessful attempt to obtain the first electronic emission spectrum of aluminum boride is also described.

  3. High temperature, bonded titanium diboride sputter target

    SciTech Connect

    Hale, G.J.; Gates, W.G.

    1981-10-01

    A high-temperature bonding technique has been employed in the development of an improved sputter deposition target for hard, crack-prone materials such as titanium diboride (TiB/sub 2/). Titanium diboride was bonded to a thin metal backing plate, both materials having a similar linear coefficient of thermal expansion (LCTE) using a high-temperature braze alloy. The thin metal backing plate helps stabilize the movement of the target material during the sputter deposition operation. The bonded sputter target has a useable life of 50 to 75 times that of a unbonded target. This bonding technique may be used on a variety of hard, brittle, crack-prone, sputterable materials (including metal oxides, carbides borides, and nitrides). US Patent 4,209,375 has been issued as a result of this endeavor.

  4. Refractory semiconductors for high temperature thermoelectric energy conversion

    NASA Technical Reports Server (NTRS)

    Wood, Charles

    1987-01-01

    Thermoelectric energy conversion utilizing nuclear heat sources has been employed for several decades to generate power for deep space probes. In the past, lead telluride and, more recently, silicon-germanium alloys have been the prime choices as thermoelectric materials for this application. Currently, a number of refractory semiconductors are under investigation at the Jet Propulsion Laboratory in order to produce power sources of higher conversion efficiency and, thus, lower mass per unit of power output. Included among these materials are improved Si-Ge alloys, rare earth compounds and boron-rich borides. The criteria used to select thermoelectric materials, in general, and the above materials, in particular, will be discussed. The current state of the art and the accomplishments to date in thermoelectric materials research will be reviewed.

  5. On the controversial formation of silver diboride: Processing of Ag + 2B powders by spark plasma sintering

    NASA Astrophysics Data System (ADS)

    Musa, Clara; Orrù, Roberto; Licheri, Roberta; Cao, Giacomo

    2009-11-01

    Following recent theoretical studies based on electronic structure calculations conducted on Ag- and Au-borides which estimated their superconducting behaviour at elevated transition temperatures, the preparation of AgB 2 was attempted in this work by reactive Spark Plasma Sintering (SPS) from Ag and B elemental powders. It was found that, independently from the processing conditions adopted, the formation of a new phase, which corresponds to a small peak on the XRD pattern at 2 θ equal to about 28°, cannot be attributed to AgB 2. In fact, it was shown that the new phase detected on sintered pellets is most likely boric acid which is formed only if the sample is left in contact with air. If SPSed samples were stored under inert (Ar) atmosphere, no additional phases other than unreacted elements were observed.

  6. Effects of cobalt on the microstructure of Udimet 700. M.S. Thesis Final Report

    NASA Technical Reports Server (NTRS)

    Engel, M. A.

    1982-01-01

    Cobalt, a critical and "strategic" alloying element in many superalloys, was systematically substituted by nickel in experimental alloys Udimet 700 containing 0.1, 4.3, 8.6, 12.8 and the standard 17.0 wt.% cobalt. Electrolytic and chemical extraction techniques, X-ray diffraction, scanning electron and optical microscopy were used for the microstructural studies. The total weight fraction of gamma' was not significantly affected by the cobalt content, although a difference in the size and quantities of the primary and secondary gamma' phases was apparent. The lattice parameters of the gamma' were found to increase with increasing cobalt content while the lattice mismatch between the gamma matrix and gamma' phases decreased. Other significant effects of cobalt on the weight fraction, distribution and formation of the carbide and boride phases as well as the relative stability of the experimental alloys during long-time aging are also discussed.

  7. Direct synthesis of calcium borohydride

    DOEpatents

    Ronnebro, Ewa Carin Ellinor; Majzoub, Eric H.

    2009-10-27

    A method is disclosed for directly preparing an alkaline earth metal borohydride, i.e. Ca(BH.sub.4).sub.2, from the alkaline earth metal hydride and the alkaline earth metal boride. The borohydride thus prepared is doped with a small portion of a metal chloride catalyst compound, such as RuCl.sub.3, TiCl.sub.3, or a mixture of TiCl.sub.3 and palladium metal. The process provides for mechanically mixing the dry reagents under an inert atmosphere followed by charging the mixed materials with high pressure hydrogen at about 70 MPa while heating the mixture to about 400.degree. C. The method is relatively simple and inexpensive and provides reversible hydride compounds which are free of the usual contamination introduced by prior art wet chemical methods.

  8. Single-Crystalline B12As2 on m-plane (1100) 15R-SiC

    SciTech Connect

    Chen,H.; Wang, G.; Dudley, M.; Xu, Z.; Edgar, J.; Batten, T.; Kuball, M.; Zhang, L.; Zhu, Y.

    2008-01-01

    Single crystal, heteroepitaxial growth of icosahedral B12As2 (IBA, a boride semiconductor) on m-plane 15R-SiC is demonstrated. Previous studies of IBA on other substrates, i.e., (111)Si and (0001)6H-SiC, produced polycrystalline and twinned epilayers. In contrast, single-crystalline and untwinned IBA was achieved on m-plane 15R-SiC. Synchrotron white beam x-ray topography, Raman spectroscopy, and high resolution transmission electron microscopy confirm the high quality of the films. High quality growth is shown to be mediated by ordered nucleation of IBA on (474) substrate facets. This work demonstrates that m-plane 15R-SiC is a good substrate choice to grow high-quality untwinned IBA epilayers for future device applications.

  9. Microstructures of rapidly solidified powder and extruded rod of Ni{sub 3}Ge

    SciTech Connect

    Fang, J.; Schulson, E.M.

    1996-07-01

    Rapidly solidified powders and extruded rods of Ni{sub 3}Ge with and without 0.06 at. % boron were characterized using optical microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The powders were generally spherical and exhibited both dendritic and lamellar structures. The increase in lattice parameter per atom fraction of boron, {var_epsilon}, was estimated to be 0.33. Extrusion of the powders produced fine grains of about 2 {micro}m in diameter. The extruded materials were partially recrystallized and showed a minor preference for [111] orientation. Annealing at 950 C resulted in a fully recrystallized structure and a nearly random orientation. The addition of 0.06 at. % boron had no observable effect on the morphology, microstructure, and texture. Precipitates of borides were observed in the annealed boron-doped alloy, suggesting that the solubility of boron in Ni{sup 3}Ge may be below about 0.06 at. %.

  10. Magnetic structure of TbNi{sub 2}B{sub 2}C

    SciTech Connect

    Dervenagas, P.; Zarestky, J.; Stassis, C.; Goldman, A.I.; Canfield, P.C.; Cho, B.K.

    1996-04-01

    Neutron-diffraction techniques have been used to study the magnetic structure of TbNi{sub 2}B{sub 2}C. The measurements, performed on single crystals of this compound, show that below approximately 15 K the moments order in an almost longitudinal spin wave with wave vector along {ital a}{sup {asterisk}}. The magnitude of the wave vector is close to that obtained in the Ho, Er, and Gd compounds. This observation provides additional evidence that there are common Fermi-surface nesting features along {ital a}{sup {asterisk}} in the rare-earth nickel boride carbides which cause the magnetic ordering of the rare-earth moments via the Ruderman-Kittel-Kasuya-Yosida mechanism. Below approximately 8 K, the experimental results indicate the development of a small ferromagnetic component. {copyright} {ital 1996 The American Physical Society.}

  11. The friction and wear properties of sputtered hard refractory compounds

    NASA Technical Reports Server (NTRS)

    Brainard, W. A.

    1978-01-01

    Several refractory silicide, boride, and carbide coatings were examined. The coatings were applied to type 440C steel surfaces by radio-frequency sputtering. The friction and wear properties of the coatings were found to be related to stoichiometry and impurity content of the bulk coating as well as the degree of interfacial adherence between coating and substrate. Bulk coating stoichiometry could to a large extent be controlled by the application of a negative bias voltage during deposition. Adherence was promoted by the formation of an oxidized layer at the interface. Deliberate preoxidizing of the 440C produced enhanced adherence for many compounds which are related to the formation of a mixed oxide transition region.

  12. A functionally graded multilayer approach to the synthesis of boron containing ceramic thin films

    NASA Astrophysics Data System (ADS)

    Tavsanoglu, T.; Jeandin, M.; Addemir, O.; Yucel, O.

    2012-11-01

    Despite their excellent properties, adhesion problems are common for B4C and BCN thin films on different substrates when the film thickness exceeds about 500 nm. Three functionally graded multilayer designs; surface boronizing of the steel substrate before deposition (Boride underlayer/B4C), Ti/TiC/B4C and Ti/TiN/BCN structures were discussed in this study, to alleviate the adhesion problems. Cross-sectional FE-SEM examinations and elemental depth profiling by SIMS revealed the graded structure of the films. The elemental film composition measured by EPMA and the mechanical properties determined by nanoindentation demonstrated the graded chemical composition and the transition of the hardness and Young's modulus values between different layers respectively. The results demonstrated the possibility of growing well adherent boron containing ceramic coatings with thicknesses in the μm range by means of different graded underlayer designs.

  13. Photoemission study of ternary to penternary Fe-based metallic glasses: Chemical analysis of surface and bulk

    NASA Astrophysics Data System (ADS)

    Büttner, M.; Wang, H.-J.; Dongare, A. M.; Shiflet, G. J.; Reinke, P.; Oelhafen, P.; Mun, B. S.; Gu, X. J.; Poon, S. J.

    2007-08-01

    Bulk metallic glasses consisting of Fe, Mo, Cr, C, B, and Er have been investigated by x-ray photoelectron spectroscopy, aimed to elucidate the local atomic structure of the amorphous phase. In order to examine the electronic properties of this class of material, photon energy dependent measurements in combination with argon-ion irradiation were employed to identify and separate surface and bulk contributions to the spectra. The core levels suggest the presence of a carbon-rich surface layer with oxidized boron and metals, and metal carbides and borides in the bulk. Exposure to molecular oxygen and annealing experiments probe the chemical reactivity of the material. Formation of boron oxides at comparably low temperatures (300°C) might have consequences for the stability of the amorphous phase. We observe variations in binding energy of the Fe 3p core level with respect to the alloy composition, which indicate changes in the chemical state of iron.

  14. Insights into the ultrahigh glass-forming ability of the Fe-Co-Cr-Mo-C-B-Y alloy system from the electronic-structure perspective

    NASA Astrophysics Data System (ADS)

    Lu, Y. Z.; Huang, Y. J.; Wang, G.; Shen, J.

    2012-08-01

    The effect of cobalt on the glass-forming ability (GFA) of Fe-Co-Cr-Mo-C-B-Y bulk metallic glasses has been investigated by using ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy. The alloy containing 7% Co (Co7 alloy) exhibits the highest binding energy and the minimum electronic density of states at the Fermi energy in the valence band spectrum and possesses the largest carbide and metal boride peak intensity in the C 1s and B 1s core-level spectrum. The origin of the ultrahigh GFA for the Co7 alloy has been discussed in terms of the unique electronic structures, which are closely related to the densest atomic packing, the smallest atomic clusters, the minimum electronic density of states at the Fermi energy, and the most numerous transition-metal-carbon and transition-metal-boron bonds.

  15. Longitudinal residual stresses in boron fibers

    NASA Technical Reports Server (NTRS)

    Behrendt, D. R.

    1976-01-01

    A method of measuring the longitudinal residual stress distribution in boron fibers is presented. The residual stresses in commercial CVD boron on tungsten fibers of 102, 142, and 203 microns (4, 5.6, and 8 mil) diameters were determined. Results for the three sizes show a compressive stress at the surface 800 to -1400 MN/sq m 120 to -200 ksi), changing monotonically to a region of tensile stress within the boron. At approximately 25 percent of the original radius, the stress reaches a maximum tensile 600 to 1000 MN/sq m(90 to 150 ksi) and then decreases to compressive near the tungsten boride core. The core itself is under a compressive stress of approximately -1300 MN/sq m (-190 ksi). The effects of surface removal on core residual stress and core-initiated fracture are discussed.

  16. How to estimate hardness of crystals on a pocket calculator

    SciTech Connect

    Simunek, Antonin

    2007-05-01

    A generalization of the semiempirical microscopic model of hardness is presented and applied to currently studied borides, carbides, and nitrides of heavy transition metals. The hardness of OsB, OsC, OsN, PtN, RuC, RuB{sub 2}, ReB{sub 2}, OsB{sub 2}, IrN{sub 2}, PtN{sub 2}, and OsN{sub 2} crystals in various structural phases is predicted. It is found that none of the transition metal crystals is superhard, i.e., with hardness greater than 40 GPa. The presented method provides materials researchers with a practical tool in the search for new hard materials.

  17. New method for synthesis of metal carbides, nitrides and carbonitrides

    SciTech Connect

    Koc, R.; Folmer, J.S.; Kodambaka, S.K.

    1997-04-01

    The purpose of this work is to develop a novel synthesis method using a carbothermic reduction reaction of carbon coated precursors for producing high purity, submicron, non-agglomerated powders of metal carbide, metal nitride and metal boride systems. The authors also want to demonstrate the advantages of the process and provide information on the applicability of the process for synthesizing related advanced ceramic powders (e.g. SiC, WC, TiN, TiB{sub 2}, Si{sub 3}N{sub 4}). During the FY96 of the project, steps are taken to investigate the reaction mechanisms and phase evolution during the formation of TiC from carbon coated titania precursors and to produce submicron TiC powders with desired stoichiometries. Depending on the carbon content in the coated titania precursor, TiC powder was produced with different stoichiometries (different amount of oxygen and free carbon).

  18. Characterization and Computational Modeling of Minor Phases in Alloy LSHR

    NASA Technical Reports Server (NTRS)

    Jou, Herng-Jeng; Olson, Gregory; Gabb, Timothy; Garg, Anita; Miller, Derek

    2012-01-01

    The minor phases of powder metallurgy disk superalloy LSHR were studied. Samples were consistently heat treated at three different temperatures for long times to approach equilibrium. Additional heat treatments were also performed for shorter times, to assess minor phase kinetics in non-equilibrium conditions. Minor phases including MC carbides, M23C6 carbides, M3B2 borides, and sigma were identified. Their average sizes and total area fractions were determined. CALPHAD thermodynamics databases and PrecipiCalc(TradeMark), a computational precipitation modeling tool, were employed with Ni-base thermodynamics and diffusion databases to model and simulate the phase microstructural evolution observed in the experiments with an objective to identify the model limitations and the directions of model enhancement.

  19. Some properties of an advanced boron fiber. [high strength, splittable fibers

    NASA Technical Reports Server (NTRS)

    Behrendt, D. R.

    1979-01-01

    An advanced coreless boron fiber exhibits tensile strengths which are more than twice that of the normal CVD B/W fibers. The coreless fiber is made by the chemical removal of the tungsten boride core exposed by splitting the as-grown fiber. The easily splittable fiber is made by the chemical vapor deposition of boron on a larger than usual tungsten substrate. It is expected that the ease of splitting is related to residual stresses in these fibers. Measurements of the axial residual stresses in both the normal and the splittable fibers are presented and the results compared. Differences in these stresses are discussed in connection with the ease of splitting in the splittable fibers.

  20. The microstructure and properties of rapidly solidified, dispersion-strengthened NiAl

    NASA Technical Reports Server (NTRS)

    Jha, S. C.; Ray, R.

    1990-01-01

    An advanced rapid solidification technology for processing reactive and refractory alloys, utilized to produce large quantities of melt-spun filaments of NiAl, is presented. The melt-spun filaments are pulverized to fine particle sizes, and subsequently consolidated by hot extrusion or hot isostatic pressing. Rapid solidification process gives rise to very fine-grained microstructures. However, exposure to elevated temperature during hot consolidation leads to grain growth. Alloying agents such as borides, carbides, and tungsten can pin the grain boundaries and retard the grain growth. Various alloy compositions are investigated. The eventual goal is to utilize the hot-extruded and forged stock to grow single-crystal NiAl blades for advanced gas-turbine engine applications. Single-crystal NiAl, containing a uniform dispersion of carbide strengthening precipitates, is expected to lead to highly creep-resistant turbine blades, and is of considerable interest to the aerospace propulsion industry.

  1. Low-temperature deposition of TaB and TaB 2 by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Motojima, Seiji; Kito, Kazuhito; Sugiyama, Kohzo

    1982-02-01

    Tantalum borides were deposited on a copper substrate from a gas phase TaCl 5-BCl 3-H 2-Ar in the temperature range of 540-800°C. TaB 2 (single-phase) was deposited at a source gas flow ratio (BCl 3/TaCl 5) of six and a temperature above 600°C. On the other hand, TaB (single-phase) was deposited at BCl 3/TaCl 5 = 2-4 and 600-700°C. The microhardness of TaB and TaB 2 were 3250 and 3150 kg/mm 2, respectively. The TaB layer was stable to oxidation below 700° C and to acid corrosion.

  2. A metastable hard magnetic phase in the crystallization process of the Fe75Si11B10Nb3Sn1 alloy

    NASA Astrophysics Data System (ADS)

    Cremaschi, V.; Arcondo, B.; Vázquez, M.; Sirkin, H.

    1999-11-01

    A very interesting characteristic of FeSiB based amorphous alloys is its soft magnetic behavior. Most of these alloys remains soft along the crystallization process up to the nucleation of the iron borides. Examples of this are the widely studied Finemet and the FeSiBSn. In this work the crystallization of Fe76Si11B10Nb3 and Fe75Si11B10Nb3Sn1 is studied by means of X-ray diffraction, Mössbauer spectroscopy and coercive magnetic field measurements after one hour isothermal annealing at different temperatures. In the crystallization process of the latter alloy a hard magnetic phase appeared when the samples were annealed above 773 K. The soft magnetic behavior was recovered after annealing at 873 K. The hyperfine parameters as well as the X-ray diffraction patterns are reported.

  3. Three-dimensional nanometer scale analyses of precipitate structures and local compositions in titanium aluminide engineering alloys

    NASA Astrophysics Data System (ADS)

    Gerstl, Stephan S. A.

    Titanium aluminide (TiAl) alloys are among the fastest developing class of materials for use in high temperature structural applications. Their low density and high strength make them excellent candidates for both engine and airframe applications. Creep properties of TiAl alloys, however, have been a limiting factor in applying the material to a larger commercial market. In this research, nanometer scale compositional and structural analyses of several TiAl alloys, ranging from model Ti-Al-C ternary alloys to putative commercial alloys with 10 components are investigated utilizing three dimensional atom probe (3DAP) and transmission electron microscopies. Nanometer sized borides, silicides, and carbide precipitates are involved in strengthening TiAl alloys, however, chemical partitioning measurements reveal oxygen concentrations up to 14 at. % within the precipitate phases, resulting in the realization of oxycarbide formation contributing to the precipitation strengthening of TiAl alloys. The local compositions of lamellar microstructures and a variety of precipitates in the TiAl system, including boride, silicide, binary carbides, and intermetallic carbides are investigated. Chemical partitioning of the microalloying elements between the alpha2/gamma lamellar phases, and the precipitate/gamma-matrix phases are determined. Both W and Hf have been shown to exhibit a near interfacial excess of 0.26 and 0.35 atoms nm-2 respectively within ca. 7 nm of lamellar interfaces in a complex TiAl alloy. In the case of needle-shaped perovskite Ti3AlC carbide precipitates, periodic domain boundaries are observed 5.3+/-0.8 nm apart along their growth axis parallel to the TiAl[001] crystallographic direction with concomitant composition variations after 24 hrs. at 800°C.

  4. Microstructural study of transient liquid phase bonded DD98 and K465 superalloys at high temperature

    SciTech Connect

    Liu Jide Jin Tao; Zhao Nairen; Wang Zhihui; Sun Xiaofeng; Guan Hengrong; Hu Zhuangqi

    2011-05-15

    Microstructure of a transient liquid phase (TLP) bonded joint between single crystal DD98 and polycrystalline K465 superalloys was investigated by scanning electron microscopy, transmission electron microscopy and X-ray diffraction techniques. After bonding at 1190 deg. C for 2 h, many phases formed in the centerline of the bonding zone due to an incompletely solidified liquid interlayer. There are script-like, tree-like and blocky compounds besides solid solution {gamma} phase in this region. The script-like phase is CrB boride that is rich in Cr, the tree-like compound rich in Ni is M{sub 23}B{sub 6} with FCC structure, and the blocky phase enriched in Ti, Ta, and Nb, is MC carbide that resulted from the interdiffusion of C atoms between dissimilar base metals. After TLP bonding, many blocky and fine M{sub 6}C particles rich in Cr and W appeared in the diffusion zone of the K465 side. A number of blocky and platelet M{sub 3}B{sub 2} borides rich in W, Cr and Mo precipitated in the diffusion zone of the DD98 side. - Research Highlights: {yields} DD98 and K465 alloy was TLP bonded. {yields} The microstructure changes of different parts were studied. {yields} CrB, M{sub 23}B{sub 6} and MC formed in the bonding zone. {yields} M{sub 6}C appeared in diffusion zone of K465 side and M{sub 3}B{sub 2} existed in diffusion zone of DD98 side.

  5. First-row transition-metal-diborane and -borylene complexes.

    PubMed

    Sharmila, Dudekula; Mondal, Bijan; Ramalakshmi, Rongala; Kundu, Sangita; Varghese, Babu; Ghosh, Sundargopal

    2015-03-23

    A combined experimental and quantum chemical study of Group 7 borane, trimetallic triply bridged borylene and boride complexes has been undertaken. Treatment of [{Cp*CoCl}2 ] (Cp*=1,2,3,4,5-pentamethylcyclopentadienyl) with LiBH4 ⋅thf at -78 °C, followed by room-temperature reaction with three equivalents of [Mn2 (CO)10 ] yielded a manganese hexahydridodiborate compound [{(OC)4 Mn}(η(6) -B2 H6 ){Mn(CO)3 }2 (μ-H)] (1) and a triply bridged borylene complex [(μ3 -BH)(Cp*Co)2 (μ-CO)(μ-H)2 MnH(CO)3 ] (2). In a similar fashion, [Re2 (CO)10 ] generated [(μ3 -BH)(Cp*Co)2 (μ-CO)(μ-H)2 ReH(CO)3 ] (3) and [(μ3 -BH)(Cp*Co)2 (μ-CO)2 (μ-H)Co(CO)3 ] (4) in modest yields. In contrast, [Ru3 (CO)12 ] under similar reaction conditions yielded a heterometallic semi-interstitial boride cluster [(Cp*Co)(μ-H)3 Ru3 (CO)9 B] (5). The solid-state X-ray structure of compound 1 shows a significantly shorter boron-boron bond length. The detailed spectroscopic data of 1 and the unusual structural and bonding features have been described. All the complexes have been characterized by using (1) H, (11) B, (13) C NMR spectroscopy, mass spectrometry, and X-ray diffraction analysis. The DFT computations were used to shed light on the bonding and electronic structures of these new compounds. The study reveals a dominant B-H-Mn, a weak B-B-Mn interaction, and an enhanced B-B bonding in 1. PMID:25689833

  6. Review of the Development and Testing of a New Family of Boron and Gadolinium-Bearing Dual Thermal Neutron Absorbing Alloys - 13026

    SciTech Connect

    Schmidt, M.L.; Del Corso, G.J.; Klankowski, K.A.; Lherbier, L.W.; Novotnak, D.J.

    2013-07-01

    The development of a new class of Fe-based thermal neutron absorbing alloys (patent pending) containing both natural boron (B) and gadolinium (Gd) is reviewed. Testing has shown that Ar and N inert gas atomized powder metallurgy (PM) variants offer superior processability coupled with improved mechanical properties that exhibit reduced anisotropy and reduced corrosion rates compared to conventional cast/wrought processed material. PM processing results in a microstructure containing a uniform distribution of second phase borides and gadolinides, and the morphology of the gadolinides prevents the formation low melting point Gd-bearing phases at solidifying austenite boundaries. The new T316-based materials containing both B and Gd exhibit superior corrosion resistance compared to straight B-bearing T304 materials. By keeping the B content < 1 weight percent (%) and using Gd to attain an equivalent B (B{sub Eq}) content higher than that achievable through the use of B only, the new materials exhibit superior ductility, toughness and bendability as a result of significantly reduced area fraction of Cr-rich M{sub 2}B borides. Limiting the total area fraction of second phase particles to < 22% insures a product with superior bendability. By restricting B to < 1% and using Gd up to 2.5%, B{sub Eq} levels approaching 12% can be attained that provide a cost effective improvement in thermal neutron absorption capability compared to using B-10 enriched boron. The new materials can be easily bent during fabrication compared to existing metal matrix composite materials while offering similar thermal neutron absorption capability. Production lots containing B{sub Eq} levels of 4.0 and 7.5% (Micro-Melt{sup R} DuoSorb{sup TM} 316NU-40 and 75, respectively) are in the process of being fabricated for customer trial material. (authors)

  7. Improved Resistance to Laser Weld Heat-Affected Zone Microfissuring in a Newly Developed Superalloy HAYNES 282

    NASA Astrophysics Data System (ADS)

    Osoba, L. O.; Ding, R. G.; Ojo, O. A.

    2012-11-01

    Gleeble thermomechanical simulation and microstrucutural analyses of laser beam weldability of a newly developed precipitation-hardened nickel-base HAYNES alloy 282 were performed to better understand the fundamental cause of heat-affected zone (HAZ) cracking and how to prevent the cracking problem in the material. Submicron size intergranular M5B3 particles are identified for the first time in the present work by transmission electron microscopy, and were found to be the primary cause of HAZ grain boundary liquation cracking in the alloy. Complete dissolution of the liquating M5B3 particles by preweld heat treatment exacerbated rather than reduced susceptibility to cracking, which could be attributed to nonequilibrium intergranular segregation of boron atoms, liberated by the complete dissolution of the boride particles, during cooling from heat treatment temperature. Consequently, to reduce the HAZ cracking, a preweld heat treatment that reduces the volume fraction of the M5B3 particles while minimizing nonequilibrium grain boundary boron segregation is necessary, and this is possible by heat treating the alloy at 1353 K to 1373 K (1080 °C to 1100 °C). Further improvement in cracking resistance to produce crack-free welds is achieved by subjecting the alloy to thermomechanically induced grain refinement coupled with the preweld heat treatment at 1353 K (1080 °C). A Gleeble hot ductility test showed that formation of the crack-free welds is unexplainable by mere reduction in grain size without considering the effect of grain refinement on intergranular liquid produced by subsolidus liquation of the M5B3 borides.

  8. Characterization of segregation in nickel and titanium aluminides

    SciTech Connect

    Miller, M.K.; Larson, D.J.; Russell, K.F.

    1997-03-01

    Atom probe field ion microscopy has been used to characterize the distributions of microalloying additions in the microstructure of a variety of nickel and titanium aluminides. In Ni{sub 3}Al, boron additions were found to segregate to dislocations, low angle boundaries, stacking faults, antiphase boundaries, and grain boundaries. The boron and aluminum levels at grain boundaries were found to vary both from boundary to boundary and also along an individual boundary segment. In some cases, a boron-enriched film up to {approximately}3 nm thick was observed. In aluminum-enriched Ni{sub 3}Al, ultrafine clusters containing up to approximately 10 boron atoms were detected in the matrix. In contrast, the majority of the boron additions in NiAl was determined to be in the form of ultrafine MB{sub 2}-type precipitates. These precipitates offset the benefits of the boron segregation to the high angle grain boundaries. In molybdenum-doped NiAl, atom probe analyses indicated extremely low solubilities of the molybdenum and other trace impurities in the matrix and significant enrichments of molybdenum, nitrogen and silicon, boron, and iron at the grain boundaries. In boron-doped two phase {alpha}{sub 2} + {gamma} TiAl containing chromium, niobium, and tungsten, the boron level was found to be significantly depleted from the bulk level in both the {alpha}{sub 2} and {gamma} phases and a variety of coarse borides including TiB, TiB{sub 2} and a finer chromium-enriched (Ti, Cr){sub 2}B precipitate was observed. The tungsten and chromium were determined to partition preferentially to the {alpha}{sub 2} phase and also to segregated to the {alpha}{sub 2}-{gamma} and {gamma}-{gamma} interfaces. These results indicate that a significant proportion of the microalloying elements are consumed by the boride precipitates.

  9. {tau} phase formation in a TiC + TiB{sub 2} composite bonded with a nickel based binder alloy

    SciTech Connect

    Ogwu, A.A.; Davies, T.J.

    1999-05-21

    Densification and ductility has been achieved in a TiC + TiB{sub 2} cermet prepared by pressureless sintering using a nickel based binder with an additive, based on their proposed empirical model. In the context of bonding in the binary, Holleck et al have suggested that the structures of TiC and TiB{sub 2} allows coherence to be established between their most densely packed lattice planes. This favorable interfacial match in the TiC + TiB{sub 2} composite is assumed to encourage a high mobility of atoms across the interface, leading to densification during sintering. The fracture toughness of a TiC + TiB{sub 2} composite would also be expected to improve when good interfacial coherence exists between TiC and TiB{sub 2}. In the case of their preferred nickel-based binder, one of the reasons for selecting the additive is to prevent the formation o deleterious grain boundary phases like the {tau} phase which often forms in Ni-TiB{sub 2} systems, with the expectation that if new phases do form they would be soluble in a TiC + TiB{sub 2} matrix. Previous attempts to find suitable sintering additives for TiB{sub 2} revealed that Fe, Co and Ni binders reacted with the TiB{sub 2} at the sintering temperatures forming secondary borides of the type M{sub 2}B. The formation of these undesirable (secondary) borides has been identified to be linked to either the presence of contaminants like oxygen, carbon and nitrogen which react with Ti, leaving behind free boron for reaction with the selected metallic binder, or, a direct reaction between the metal binder and TiB{sub 2}.

  10. Investigations of the Deterioration of 22 Refractory Materials in a Mach Number 2 Jet at a Stagnation Temperature of 3,800 F

    NASA Technical Reports Server (NTRS)

    Lewis, B. W.

    1961-01-01

    A limited investigation of the deterioration characteristics of 22 refractory materials was conducted by exposing them to a stagnation temperature of 3,800 F in a Mach number 2 ceramic-heated jet at the Langley Research Center. The materials tested were six materials whose major constituent was silicon carbide, five cermets whose major constituent was titanium carbide, six materials whose major constituents were metal borides, four cermets containing alumina, and one silicon nitride model. Tests consisted of obtaining weight change and appearance changes for 1/2-inch-diameter hemispherical-nose cylindrical models exposed to the air jet for 30 seconds at a time for a total of four runs or 2 minutes exposure. Curves of weight changes plotted against the number of 30-second tests in the jet were obtained. Estimates of average surface temperature near the stagnation point of the model were obtained by use of a special temperature-measuring camera. The models were examined before and after the completion of the tests for possible changes in microstructure; no significant changes were found. The data obtained were analyzed with the view that the oxidation characteristics of the materials were the main factor in deterioration of the materials under the conditions of the tests. It was concluded that only those materials which changed in weight the least could be recommended for further extensive application-oriented evaluations. The following materials fell in this category: silicon carbide - silicon, chromium - 28-percent alumina cermet, titanium boride - 5-percent boron carbide. The remainder of the materials tested had oxidation characteristics which appeared to be too severely limiting of their general applications to flight vehicles.

  11. Asymptotically-Equal-To 10 eV ionization shift in Ir K{alpha}{sub 2} from a near-coincident Lu K-edge

    SciTech Connect

    Pereira, N. R.; Weber, B. V.; Phipps, D.; Schumer, J. W.; Seely, J. F.; Carroll, J. J.; VanHoy, J. R.; Slabkowska, K.; Polasik, M.

    2012-10-15

    Close to an x-ray filter's K-edge the transmission depends strongly on the photon energy. For a few atom pairs, the K-edge of one is only a few tens of eV higher than a K-line energy of another, so that a small change in the line's energy becomes a measurable change in intensity behind such a matching filter. Lutetium's K-edge is Asymptotically-Equal-To 27 eV above iridium's K{alpha}{sub 2} line, Asymptotically-Equal-To 63.287 keV for cold Ir. A Lu filter reduces this line's intensity by Asymptotically-Equal-To 10 % when it is emitted by a plasma, indicating an ionization shift {Delta}E Asymptotically-Equal-To 10{+-}1 eV.

  12. Fabrication and characterization of spark plasma sintered Ce:LuAG ceramic for scintillation application

    NASA Astrophysics Data System (ADS)

    Kumar, S. Arun; Senthilselvan, J.

    2016-05-01

    Rare earth Cerium doped Lutetium Aluminum Garnet (Ce:LuAG) ceramics are widely used as phosphor material in medical imaging and high-energy physics. Due to its technological importance, an attempt has been made to fabricate Ce:LuAG ceramics by using spark plasma sintering (SPS) technique. XRD patterns of SPS sintered Ce:LuAG ceramics reveals a mixed LuAG and CeO2 (antisite defect) phases. The microstructures of SPS sintered Ce:LuAG ceramics shows limited densification, inappropriate compaction of particles and existence of residual pores, voids between the grain boundaries affects the transparency of Ce:LuAG ceramics. Relative density and hardness of post sintered Ce:LuAG ceramic is also determined. The effect of Ce3+ doping concentration and sintering temperature on optical luminescence behavior of Ce:LuAG ceramic is presented.

  13. High resolution gamma ray tomography scanner for flow measurement and non-destructive testing applications

    SciTech Connect

    Hampel, U.; Bieberle, A.; Hoppe, D.; Kronenberg, J.; Schleicher, E.; Suehnel, T.; Zimmermann, F.; Zippe, C.

    2007-10-15

    We report on the development of a high resolution gamma ray tomography scanner that is operated with a Cs-137 isotopic source at 662 keV gamma photon energy and achieves a spatial image resolution of 0.2 line pairs/mm at 10% modulation transfer function for noncollimated detectors. It is primarily intended for the scientific study of flow regimes and phase fraction distributions in fuel element assemblies, chemical reactors, pipelines, and hydrodynamic machines. Furthermore, it is applicable to nondestructive testing of larger radiologically dense objects. The radiation detector is based on advanced avalanche photodiode technology in conjunction with lutetium yttrium orthosilicate scintillation crystals. The detector arc comprises 320 single detector elements which are operated in pulse counting mode. For measurements at fixed vessels or plant components, we built a computed tomography scanner gantry that comprises rotational and translational stages, power supply via slip rings, and data communication to the measurement personal computer via wireless local area network.

  14. A Younger Age for ALH84001 and Its Geochemical Link to Shergottite Sources in Mars

    NASA Astrophysics Data System (ADS)

    Lapen, T. J.; Righter, M.; Brandon, A. D.; Debaille, V.; Beard, B. L.; Shafer, J. T.; Peslier, A. H.

    2010-04-01

    Martian meteorite ALH84001 (ALH) is the oldest known igneous rock from Mars and has been used to constrain its early history. Lutetium-hafnium (Lu-Hf) isotope data for ALH indicate an igneous age of 4.091 ± 0.030 billion years, nearly coeval with an interval of heavy bombardment and cessation of the martian core dynamo and magnetic field. The calculated Lu/Hf and Sm/Nd (samarium/neodymium) ratios of the ALH parental magma source indicate that it must have undergone extensive igneous processing associated with the crystallization of a deep magma ocean. This same mantle source region also produced the shergottite magmas (dated 150 to 570 million years ago), possibly indicating uniform igneous processes in Mars for nearly 4 billion years.

  15. A younger age for ALH84001 and its geochemical link to shergottite sources in Mars.

    PubMed

    Lapen, T J; Righter, M; Brandon, A D; Debaille, V; Beard, B L; Shafer, J T; Peslier, A H

    2010-04-16

    Martian meteorite ALH84001 (ALH) is the oldest known igneous rock from Mars and has been used to constrain its early history. Lutetium-hafnium (Lu-Hf) isotope data for ALH indicate an igneous age of 4.091 +/- 0.030 billion years, nearly coeval with an interval of heavy bombardment and cessation of the martian core dynamo and magnetic field. The calculated Lu/Hf and Sm/Nd (samarium/neodymium) ratios of the ALH parental magma source indicate that it must have undergone extensive igneous processing associated with the crystallization of a deep magma ocean. This same mantle source region also produced the shergottite magmas (dated 150 to 570 million years ago), possibly indicating uniform igneous processes in Mars for nearly 4 billion years. PMID:20395507

  16. Application of scintillating properties of liquid xenon and silicon photomultiplier technology to medical imaging

    NASA Astrophysics Data System (ADS)

    Gomez-Cadenas, J. J.; Benlloch-Rodriguez, J. M.; Ferrario, Paola

    2016-04-01

    We describe a new positron emission time-of-flight apparatus using liquid xenon. The detector is based in a liquid xenon scintillating cell. The cell shape and dimensions can be optimized depending on the intended application. In its simplest form, the liquid xenon scintillating cell is a box in which two faces are covered by silicon photomultipliers and the others by a reflecting material such as Teflon. It is a compact, homogenous and highly efficient detector which shares many of the desirable properties of monolithic crystals, with the added advantage of high yield and fast scintillation offered by liquid xenon. Our initial studies suggest that good energy and spatial resolution comparable with that achieved by lutetium oxyorthosilicate crystals can be obtained with a detector based in liquid xenon scintillating cells. In addition, the system can potentially achieve an excellent coincidence resolving time of better than 100 ps.

  17. Biokinetic data and models for occupational intake of lanthanoids

    SciTech Connect

    Leggett, Richard Wayne; Ansoborlo, Eric; Bailey, Michael; Gregoratto, Demetrio; Pacquet, Francois; Taylor, David

    2014-05-12

    The lanthanoid (or lanthanide) chemical elements comprise fifteen elements with atomic numbers 57 (lanthanum) through 71 (lutetium). This paper reviews data related to the biological behavior of these elements in the human body and proposes biokinetic models for application to occupational intake of radio-lanthanoids. Generic (element-independent) absorption rates from the respiratory and alimentary tracts to blood are proposed. The proposed systemic models are largely generic but include some element-specific parameter values to reflect regular changes with ionic radius in certain aspects of the behavior of the lanthanoids. This work was performed within the internal dosimetry task group (INDOS) of Committee 2 of the International Commission on Radiological Protection (ICRP).

  18. Biokinetic data and models for occupational intake of lanthanoids

    DOE PAGESBeta

    Leggett, Richard Wayne; Ansoborlo, Eric; Bailey, Michael; Gregoratto, Demetrio; Pacquet, Francois; Taylor, David

    2014-05-12

    The lanthanoid (or lanthanide) chemical elements comprise fifteen elements with atomic numbers 57 (lanthanum) through 71 (lutetium). This paper reviews data related to the biological behavior of these elements in the human body and proposes biokinetic models for application to occupational intake of radio-lanthanoids. Generic (element-independent) absorption rates from the respiratory and alimentary tracts to blood are proposed. The proposed systemic models are largely generic but include some element-specific parameter values to reflect regular changes with ionic radius in certain aspects of the behavior of the lanthanoids. This work was performed within the internal dosimetry task group (INDOS) of Committeemore » 2 of the International Commission on Radiological Protection (ICRP).« less

  19. THE ATOMIC WEIGHTS COMMISSION AND ISOTOPIC ABUNDANCE RATIO DETERMINATIONS.

    SciTech Connect

    HOLDEN, N.E.

    2005-08-07

    Following Thomson's discovery of stable isotopes in non-radioactive chemical elements, the derivation of atomic weight values from mass spectrometric measurements of isotopic abundance ratios moved very slowly. Forty years later, only 3 1/2 % of the recommended values were based on mass spectrometric measurements and only 38% in the first half century. It might be noted that two chemical elements (tellurium and mercury) are still based on chemical measurements, where the atomic weight value calculated from the relative isotopic abundance measurement either agrees with the value from the chemical measurement or the atomic weight value calculated from the relative isotopic abundance measurement falls within the uncertainty of the chemical measurement of the atomic weight. Of the 19 chemical elements, whose atomic weight is based on non-corrected relative isotopic abundance measurements, five of these are two isotope systems (indium, iridium, lanthanum, lutetium and tantalum) and one is a three-isotope system (oxygen).

  20. Development of Scintillators in Nuclear Medicine

    PubMed Central

    Khoshakhlagh, Mohammad; Islamian, Jalil Pirayesh; Abedi, Seyed Mohammad; Mahmoudian, Babak

    2015-01-01

    High-quality image is necessary for accurate diagnosis in nuclear medicine. There are many factors in creating a good image and detector is the most important one. In recent years, several detectors are studied to get a better picture. The aim of this paper is comparison of some type of these detectors such as thallium activated sodium iodide bismuth germinate cesium activated yttrium aluminum garnet (YAG: Ce) YAP: Ce “lutetium aluminum garnet activated by cerium” CRY018 “CRY019” lanthanum bromide and cadmium zinc telluride. We studied different properties of these crystals including density, energy resolution and decay times that are more important factors affecting the image quality. PMID:26420984