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Sample records for algan cladding layer

  1. Strain-compensated AlGaN /GaN/InGaN cladding layers in homoepitaxial nitride devices

    NASA Astrophysics Data System (ADS)

    Czernecki, R.; Krukowski, S.; Targowski, G.; Prystawko, P.; Sarzynski, M.; Krysko, M.; Kamler, G.; Grzegory, I.; Leszczynski, M.; Porowski, S.

    2007-12-01

    One of the most important problems in III-nitride violet laser diode technology is the lattice mismatch between the AlGaN cladding layers and the rest of the epitaxial structure. For efficiently working devices, it is necessary to have both a high Al content and thick claddings. This leads, however, to severe sample bowing and even cracking of the upper layer. In this work, we propose a cladding structure of strain-compensated AlGaN /GaN/InGaN superlattice grown by metal-organic vapor phase epitaxy on bulk GaN substrates. Various thicknesses and compositions of the layers were employed. We measured the radius of bowing, lattice mismatches, aluminum and indium contents, and densities of threading dislocations. The proposed cladding structures suppress bowing and cracking, which are the two parasitic effects commonly experienced in laser diodes with bulk AlGaN claddings. The suppression of cracking and bowing is shown to occur due to modified strain energy distribution of the superlattices structure.

  2. Determination of gain in AlGaN cladding free nitride laser diodes

    SciTech Connect

    Muziol, G.; Turski, H.; Wolny, P.

    2013-08-05

    The optical gain spectra of InGaN-based multiple-quantum-well (MQW) laser diodes (LDs) grown by plasma-assisted molecular beam epitaxy are compared for different emission wavelengths. Two AlGaN cladding free LDs with similar epitaxial structures but with different In compositions in MQW were grown to study the dependence of material gain on lasing wavelength. As the emission wavelength increased from 432 to 458 nm, the differential modal gain decreased from 5.7 to 4.7 cm/kA, and the optical losses increased from 40 to 46 cm{sup −1} resulting in an increase in threshold current density. This dependence is attributed to lower optical mode confinement of LD emitting at longer wavelength. We found a strong decrease of confinement factor with increasing wavelength.

  3. Analysis of HVPE grown AlGaN layers on honeycomb patterned sapphire

    NASA Astrophysics Data System (ADS)

    Fleischmann, Simon; Mogilatenko, Anna; Hagedorn, Sylvia; Richter, Eberhard; Goran, Daniel; Schäfer, Peter; Zeimer, Ute; Weyers, Markus; Tränkle, Günther

    2015-03-01

    Thick AlxGa1-xN layers were grown by hydride vapor phase epitaxy on hexagonally patterned sapphire substrates. Non-c-planar growth is found inside the etched honeycombs which in part hinders coalescence of the c-plane AlGaN layer growing on top of the ridges. From X-ray diffraction, electron backscatter diffraction and scanning electron microscopy, the orientations of the parasitic crystallites were identified as {11-22} and {1-103} AlGaN growing on m-plane sapphire sidewalls as well as c-plane oriented AlGaN growing on n-plane sidewall facets which are located in the corners of the combs. According to the geometry of parasitic crystallites, it is further observed, that the semipolar growth occurring on sapphire m-plane sidewalls does not hinder the coalescence of c-plane AlGaN growing on top of the ridges, whereas fast propagation of parasitic crystallites nucleating on n-plane sidewall facets leads to delayed layer coalescence.

  4. Strain and defects in Si-doped (Al)GaN epitaxial layers

    NASA Astrophysics Data System (ADS)

    Forghani, Kamran; Schade, Lukas; Schwarz, Ulrich T.; Lipski, Frank; Klein, Oliver; Kaiser, Ute; Scholz, Ferdinand

    2012-11-01

    Si is the most common dopant in (Al)GaN based devices acting as a donor. It has been observed that Si induces tensile strain in (Al)GaN films, which leads to an increasing tendency for cracking of such films with the increase of Si content and/or the increase of Al content. Based on x-ray investigations, the Si-doped films have a larger in-plane lattice constant than their undoped buffer layers, indicating involvement of a mechanism other than the change of lattice constants expected from an alloying effect. In this work, we present a model about Si dislocation interaction while debating other proposed models in the literature. According to our model, Si atoms are attracted to the strain dipole of edge-type dislocations in (Al)GaN films. It is expected that Si is more incorporated on that side of the dislocation, which is under compression leading to the formation of off-balanced dipoles with reduced compressive component. In response to such off-balanced dipoles—appearing as tensile dominant strain dipoles—the dislocation lines climb in order to accommodate the excess tensile strain. However, this dislocation climb mechanism is hindered by forces exerted by vacancies created due to the climb process. Accordingly, we have observed a lower strain level in our Si doped layers when they contain fewer dislocations. These findings were further supported by x-ray diffraction, transmission electron microscopy, and micro-photoluminescence investigations.

  5. Low temperature p-type doping of (Al)GaN layers using ammonia molecular beam epitaxy for InGaN laser diodes

    SciTech Connect

    Malinverni, M. Lamy, J.-M.; Martin, D.; Grandjean, N.; Feltin, E.; Dorsaz, J.; Castiglia, A.; Rossetti, M.; Duelk, M.; Vélez, C.

    2014-12-15

    We demonstrate state-of-the-art p-type (Al)GaN layers deposited at low temperature (740 °C) by ammonia molecular beam epitaxy (NH{sub 3}-MBE) to be used as top cladding of laser diodes (LDs) with the aim of further reducing the thermal budget on the InGaN quantum well active region. Typical p-type GaN resistivities and contact resistances are 0.4 Ω cm and 5 × 10{sup −4} Ω cm{sup 2}, respectively. As a test bed, we fabricated a hybrid laser structure emitting at 400 nm combining n-type AlGaN cladding and InGaN active region grown by metal-organic vapor phase epitaxy, with the p-doped waveguide and cladding layers grown by NH{sub 3}-MBE. Single-mode ridge-waveguide LD exhibits a threshold voltage as low as 4.3 V for an 800 × 2 μm{sup 2} ridge dimension and a threshold current density of ∼5 kA cm{sup −2} in continuous wave operation. The series resistance of the device is 6 Ω and the resistivity is 1.5 Ω cm, confirming thereby the excellent electrical properties of p-type Al{sub 0.06}Ga{sub 0.94}N:Mg despite the low growth temperature.

  6. Anisotropic optical properties of semipolar AlGaN layers grown on m-plane sapphire

    NASA Astrophysics Data System (ADS)

    Feneberg, Martin; Winkler, Michael; Klamser, Juliane; Stellmach, Joachim; Frentrup, Martin; Ploch, Simon; Mehnke, Frank; Wernicke, Tim; Kneissl, Michael; Goldhahn, Rüdiger

    2015-05-01

    The valence band order of AlxGa 1 -x N is investigated experimentally by analyzing the anisotropic dielectric functions of semipolar (11 2 ¯ 2 ) AlGaN thin films grown on m-plane Al2O3. Point-by-point fitted dielectric functions are obtained by spectroscopic ellipsometry and corresponding inter-band transition energies are extracted. The known strain situation of the sample layers is used to correct for the small strain-induced energy shifts within k . p perturbation theory. It also is used to identify transitions related to the three valence bands. Transitions with E ⊥ c from the Γ9 valence band verify an inter-band bowing parameter of b =0.9 eV . The transitions with E || c allow determining the crystal field splitting energy which can be described by a linear interpolation between the values for GaN and AlN satisfactorily.

  7. Impedance analysis of nano thickness layered AlGaN acoustic sensor deposited by thermionic vacuum arc

    NASA Astrophysics Data System (ADS)

    Özen, Soner; Bilgiç, Eyüp; Gülmez, Gülay; Şenay, Volkan; Pat, Suat; Korkmaz, Şadan; Mohammadigharehbagh, Reza

    2016-03-01

    In this study, AlGaN acoustic sensor was deposited on aluminum metal substrate by thermionic vacuum arc (TVA) method for the first time. Gallium materials are used in many applications for optoelectronic device and semiconductor technology. Thermionic vacuum arc is the deposition technology for the variously materials and applications field. The thickness of the acoustic sensor is in deposited as nano layer. Impedance analyses were realized. Also, TVA production parameters and some properties of the deposited layers were investigated. TVA is a fast deposition technology for the gallium compounds and doped gallium compounds. Obtained results show that AlGaN materials are very promising materials. Moreover, these acoustic sensors have been produced by TVA technology.

  8. Low absorption loss p-AlGaN superlattice cladding layer for current-injection deep ultraviolet laser diodes

    NASA Astrophysics Data System (ADS)

    Martens, M.; Kuhn, C.; Ziffer, E.; Simoneit, T.; Kueller, V.; Knauer, A.; Rass, J.; Wernicke, T.; Einfeldt, S.; Weyers, M.; Kneissl, M.

    2016-04-01

    Current injection into AlGaN-based laser diode structures with high aluminum mole fractions for deep ultraviolet emission is investigated. The electrical characteristics of laser diode structures with different p-AlGaN short period superlattice (SPSL) cladding layers with various aluminum mole fractions are compared. The heterostructures contain all elements that are needed for a current-injection laser diode including cladding and waveguide layers as well as an AlGaN quantum well active region emitting near 270 nm. We found that with increasing aluminum content in the p-AlGaN cladding, the diode turn-on voltage increases, while the series resistance slightly decreases. By introducing an SPSL instead of bulk layers, the operating voltage is significantly reduced. A gain guided broad area laser diode structure with transparent p-Al0.70Ga0.30N waveguide layers and a transparent p-cladding with an average aluminum content of 81% was designed for strong confinement of the transverse optical mode and low optical losses. Using an optimized SPSL, this diode could sustain current densities of more than 4.5 kA/cm2.

  9. Composition dependent valence band order in c-oriented wurtzite AlGaN layers

    SciTech Connect

    Neuschl, B. Helbing, J.; Knab, M.; Lauer, H.; Madel, M.; Thonke, K.; Feneberg, M.

    2014-09-21

    The valence band order of polar wurtzite aluminum gallium nitride (AlGaN) layers is analyzed for a dense series of samples, grown heteroepitaxially on sapphire substrates, covering the complete composition range. The excitonic transition energies, found by temperature dependent photoluminescence (PL) spectroscopy, were corrected to the unstrained state using input from X-ray diffraction. k∙p theory yields a critical relative aluminum concentration x{sub c}=(0.09±0.05) for the crossing of the uppermost two valence bands for strain free material, shifting to higher values for compressively strained samples, as supported by polarization dependent PL. The analysis of the strain dependent valence band crossing reconciles the findings of other research groups, where sample strain was neglected. We found a bowing for the energy band gap to the valence band with Γ₉ symmetry of b{sub Γ₉}=0.85eV, and propose a possible bowing for the crystal field energy of b{sub cf}=-0.12eV. A comparison of the light extraction efficiency perpendicular and parallel to the c axis of Al{sub x}Ga{sub 1-x}N/Al{sub y}Ga{sub 1-y}N quantum well structures is discussed for different compositions.

  10. The influence of growth conditions on the surface morphology and development of mechanical stresses in Al(Ga)N layers during metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Lundin, W. V.; Zavarin, E. E.; Brunkov, P. N.; Yagovkina, M. A.; Troshkov, S. I.; Sakharov, A. V.; Nikolaev, A. E.; Tsatsulnikov, A. F.

    2016-04-01

    We have studied the influence of technological parameters on the surface morphology and development of mechanical stresses in Al(Ga)N layers during their growth by metalorganic vapor phase epitaxy (MOVPE) on sapphire substrates. Minimization of tensile stresses under conditions of a retained atomically smooth surface can be achieved by using a combination of factors including (i) nitridation of substrate in ammonia flow, (ii) formation of two-layer AlN-Al(Ga)N structures by introducing a small amount (several percent) of Ga after growth of a thin AlN layer, and (iii) reduction of ammonia flow during growth of an Al(Ga)N layer.

  11. Improved efficiency of near-ultraviolet LEDs using a novel p-type AlGaN hole injection layer

    NASA Astrophysics Data System (ADS)

    Xu, Mingsheng; Zhou, Quanbin; Zhang, Heng; Wang, Hong; Zhang, Xichun

    2016-06-01

    We investigate a novel near-ultraviolet light-emitting diode (NUV-LED) with a p-type AlGaN (pAlGaN) hole injection layer to replace the conventional p-type GaN layer. The optical properties are studied numerically with simulations. Our calculated results indicate that a pAlGaN layer can significantly improve both light output power and internal quantum efficiency of a NUV-LED. The light power of NUV-LED with constant and gradually increasing Al content of the pAlGaN layer increases by 215% and 266% compared to a conventional LED. We also find that the elimination of the interface barrier and suppression of the polarization field are the key factors that lead to the improved NUV-LED performance.

  12. Effects of Si-doping on structural, electrical, and optical properties of polar and non-polar AlGaN epi-layers

    NASA Astrophysics Data System (ADS)

    Yang, Hongquan; Zhang, Xiong; Wang, Shuchang; Wang, Yi; Luan, Huakai; Dai, Qian; Wu, Zili; Zhao, Jianguo; Cui, Yiping

    2016-08-01

    The polar (0001)-oriented c-plane and non-polar (11 2 bar 0) -oriented a-plane wurtzite AlGaN epi-layers were successfully grown on polar (0001)-oriented c-plane and semi-polar (1 1 bar 02) -oriented r-plane sapphire substrates, respectively with various Si-doping levels in a low pressure metal organic chemical vapor deposition (MOCVD) system. The morphological, structural, electrical, and optical properties of the polar and non-polar AlGaN epi-layers were studied with scanning electron microscopy (SEM), X-ray diffraction (XRD), Hall effect, and Raman spectroscopy. The characterization results show that Si dopants incorporated into the polar and non-polar AlGaN films induced a relaxation of compressive residual strain and a generation of biaxial tensile strain on the surface in consequence of the dislocation climbing. In particular, it was found that the Si-induced compressive strain relaxation in the non-polar AlGaN samples can be promoted by the structural anisotropy as compared with the polar counterparts. The gradually increased relaxation of compressive residual strain in both polar and non-polar AlGaN samples with increasing Si-doping level was attributed to the Si-induced enhancement in the opportunity for the dislocations to interact and annihilate. This implies that the crystal quality for both polar and non-polar AlGaN epi-layers can be remarkably improved by Si-doping.

  13. Wafer-scale crack-free AlGaN on GaN through two-step selective-area growth for optically pumped stimulated emission

    NASA Astrophysics Data System (ADS)

    Ko, Young-Ho; Bae, Sung-Bum; Kim, Sung-Bock; Kim, Dong Churl; Leem, Young Ahn; Cho, Yong-Hoon; Nam, Eun-Soo

    2016-07-01

    Crack-free AlGaN template has been successfully grown over entire 2-in. wafer by using 2-step selective-area growth (SAG). The GaN truncated structure was obtained by vertical growth mode with low growth temperature. AlGaN of second step was grown under lateral growth mode. Low pressure enhanced the relative ratio of lateral to vertical growth rate as well as absolute overall growth rate. High V/III ratio was favorable for lateral growth mode. Crack-free planar AlGaN was obtained under low pressure of 30 Torr and high V/III ratio of 4400. The AlGaN was crack-free over entire 2-in. wafer and had quite uniform Al-mole fraction. The dislocation density of the AlGaN with 20% Al-composition was as low as ~7.6×108 /cm2, measured by cathodoluminescence. GaN/AlGaN multi-quantum well (MQW) with cladding and waveguide layers were grown on the crack-free AlGaN template with low dislocation density. It was confirmed that the MQW on the AlGaN template emitted the stimulated emission at 355.5 nm through optical pumping experiment. The AlGaN obtained by 2-step SAG would provide high crystal quality for highly-efficient optoelectronic devices as well as the ultraviolet laser diode.

  14. In situ atomic layer deposition half cycle study of Al2O3 growth on AlGaN

    NASA Astrophysics Data System (ADS)

    Brennan, Barry; Qin, Xiaoye; Dong, Hong; Kim, Jiyoung; Wallace, Robert M.

    2012-11-01

    The atomic layer deposition (ALD) of Al2O3 on the native oxide and hydrofluoric acid treated Al0.25Ga0.75 N surface was studied using in situ X-ray photoelectron spectroscopy (XPS), after each individual "half cycle" of the ALD process. Initially, Al2O3, Ga2O3, and N-O states were detected on both surfaces at differing concentrations. During the course of the deposition process, the N-O bonds are seen to decrease to within XPS detection limits, as well as a small decrease in the Ga2O3 concentration. The Al2O3 growth rate initially is seen to be very low, indication of low reactivity between the trimethyl-aluminum molecule and the AlGaN surface.

  15. Preparation of Plasma Cladding Gradient Wear-Resistant Layer and Study on Its Impact Fatigue Properties

    NASA Astrophysics Data System (ADS)

    Zhang, Dekun; Liu, Yuan; Yin, Yan

    2016-02-01

    Plasma cladding technology is used to prepare plasma cladding gradient wear-resistant specimens, and the performance of these specimens is analyzed and compared with those of single cladding specimens. The results indicate that plasma cladding gradient wear-resistant layers implement the gradient changes in microstructure and hardness from the surface of the outer cladding layer to the fusion line and that the outer and inner cladding layers are well combined, the inner cladding layer can improve rapid decreases in hardness of single wear-resistant samples from the cladding layer to the matrix, changes in hardness from the outer to inner cladding layer are buffered, and the inner cladding layer performs important functions in the transition between the outer cladding layer and substrate. The highest hardness of the outer layer, which reaches 735 HV0.1, is approximately 3.9 times that of the matrix. The impact fatigue resistance performance of the plasma gradient cladding specimens is superior to that of single cladding specimens, and fatigue cracks begin to form only after 1 × 105 cyclical impacts.

  16. Effect of surface pretreatment on interfacial chemical bonding states of atomic layer deposited ZrO{sub 2} on AlGaN

    SciTech Connect

    Ye, Gang; Arulkumaran, Subramaniam; Ng, Geok Ing; Li, Yang; Ang, Kian Siong; Wang, Hong; Liu, Zhi Hong

    2015-09-15

    Atomic layer deposition (ALD) of ZrO{sub 2} on native oxide covered (untreated) and buffered oxide etchant (BOE) treated AlGaN surface was analyzed by utilizing x-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy. Evidenced by Ga–O and Al–O chemical bonds by XPS, parasitic oxidation during deposition is largely enhanced on BOE treated AlGaN surface. Due to the high reactivity of Al atoms, more prominent oxidation of Al atoms is observed, which leads to thicker interfacial layer formed on BOE treated surface. The results suggest that native oxide on AlGaN surface may serve as a protecting layer to inhibit the surface from further parasitic oxidation during ALD. The findings provide important process guidelines for the use of ALD ZrO{sub 2} and its pre-ALD surface treatments for high-k AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors and other related device applications.

  17. New Al0.25Ga0.75N/GaN high electron mobility transistor with partial etched AlGaN layer

    NASA Astrophysics Data System (ADS)

    Yuan, Song; Duan, Baoxing; Yuan, Xiaoning; Cao, Zhen; Guo, Haijun; Yang, Yintang

    2016-05-01

    In this letter, a new Al0.25Ga0.75N/GaN high electron mobility transistor (HEMT) with the AlGaN layer is partial etched is reported for the first time. The two-dimensional electron gas (2DEG) density in the HEMTs is changed by partially etching the AlGaN layer. A new electric field peak is introduced along the interface between the AlGaN layer and the GaN buffer by the electric field modulation effect. The high electric field near the gate in the proposed Al0.25Ga0.75N/GaN HEMT is effectively decreased, which makes the surface electric field more uniform. Compared with the conventional structure, the breakdown voltage can be improved by 58% for the proposed Al0.25Ga0.75N/GaN HEMT and the current collapse can be reduced resulting from the more uniform surface electric field.

  18. Improved mobility of AlGaN channel heterojunction material using an AlGaN/GaN composite buffer layer

    NASA Astrophysics Data System (ADS)

    Wen, Hui-Juan; Zhang, Jin-Cheng; Lu, Xiao-Li; Wang, Zhi-Zhe; Ha, Wei; Ge, Sha-Sha; Cao, Rong-Tao; Hao, Yue

    2014-03-01

    The quality of an AlGaN channel heterojunction on a sapphire substrate is massively improved by using an AlGaN/GaN composite buffer layer. We demonstrate an Al0.4Ga0.5N/Al0.18Ga0.82N heterojunction with a state-of-the-art mobility of 815 cm2/(V·s) and a sheet resistance of 890 Ω/□ under room temperature. The crystalline quality and the electrical properties of the AlGaN heterojunction material are analyzed by atomic force microscopy, high-resolution X-ray diffraction, and van der Pauw Hall and capacitance—voltage (C—V) measurements. The results indicate that the improved electrical properties should derive from the reduced surface roughness and low dislocation density.

  19. Impact of post-deposition annealing on interfacial chemical bonding states between AlGaN and ZrO{sub 2} grown by atomic layer deposition

    SciTech Connect

    Ye, Gang; Arulkumaran, Subramaniam; Ng, Geok Ing; Li, Yang; Ang, Kian Siong; Wang, Hong; Liu, Zhi Hong

    2015-03-02

    The effect of post-deposition annealing on chemical bonding states at interface between Al{sub 0.5}Ga{sub 0.5}N and ZrO{sub 2} grown by atomic layer deposition (ALD) is studied by angle-resolved x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. It has been found that both of Al-O/Al 2p and Ga-O/Ga 3d area ratio decrease at annealing temperatures lower than 500 °C, which could be attributed to “clean up” effect of ALD-ZrO{sub 2} on AlGaN. Compared to Ga spectra, a much larger decrease in Al-O/Al 2p ratio at a smaller take-off angle θ is observed, which indicates higher effectiveness of the passivation of Al-O bond than Ga-O bond through “clean up” effect near the interface. However, degradation of ZrO{sub 2}/AlGaN interface quality due to re-oxidation at higher annealing temperature (>500 °C) is also found. The XPS spectra clearly reveal that Al atoms at ZrO{sub 2}/AlGaN interface are easier to get oxidized as compared with Ga atoms.

  20. Four- and five-layer silicon-clad dielectric waveguides

    NASA Technical Reports Server (NTRS)

    Mcwright, G.; Batchman, T. E.

    1981-01-01

    Computer modeling studies conducted on four-layer silicon-clad dielectric waveguides indicate that the attenuation (alpha) and mode index (beta/K) behave as exponentially damped sinusoids as the silicon thickness is increased. The observed effect can be explained quite simply as a periodic coupling between the guided modes of the lossless structure and the lossy modes supported by the high-refractive index silicon. The attenuation and mode index are significantly altered by conductivity changes in the silicon; an amplitude modulator and an intensity modulator were proposed using these results. Predicted high attenuations in the device may be reduced significantly with a silicon dioxide buffer layer between the semiconductor and the polystyrene guide. Experimental confirmation of the predicted characteristics is still necessary. A number of thin-silicon film waveguides have been RF sputtered but attenuation measurements to verify the damped oscillatory behavior are forthcoming. Conductivity variations of the silicon should demonstrate the modulation capabilities.

  1. Quantitative study for surface properties of AlGaN epi-layers by ARXPS

    NASA Astrophysics Data System (ADS)

    Yang, Hongquan; Zhang, Xiong; Wang, Shuchang; Zhu, Min; Cui, Yiping

    2015-11-01

    The surface chemical properties of AlxGa1-xN (x=0.35, 0.47, 0.60) epi-layers grown on c-plane sapphire substrates by metal-organic chemical vapor deposition (MOCVD) were quantitatively characterized by angle-resolved X-ray photoelectron spectroscopy (ARXPS). The results suggested that the Ga Auger peak for the AlxGa1-xN epi-layers was greatly suppressed with increasing Al composition since the amount of N-Ga bonds were dramatically decreased. Moreover, more Al-O bonds were found near the surfaces of the AlxGa1-xN epi-layers with relatively high Al composition due to the large chemical affinity of aluminum to oxygen. In addition, the Al composition in the AlxGa1-xN epi-layers was showed to be non-uniform because Al atom has higher oxidizability and lower mobility than Ga atom, especially for the AlxGa1-xN epi-layers with relatively high Al composition. Our work should be very helpful to further investigation of the surface properties for making Al-containing III-nitrides optoelectronic devices.

  2. Improved characteristics of ultraviolet AlGaN multiple-quantum-well laser diodes with step-graded quantum barriers close to waveguide layers

    NASA Astrophysics Data System (ADS)

    Cai, Xuefen; Li, Shuping; Kang, Junyong

    2016-09-01

    Ultraviolet AlGaN multiple-quantum-well laser diodes (LDs) with step-graded quantum barriers (QBs) instead of conventional first and last QBs close to waveguide layers are proposed. The characteristics of this type of laser diodes are numerically investigated by using the software PICS3D and it is found that the performances of these LDs are greatly improved. The results indicates that the structure with step-graded QBs exhibits higher output light power, slope efficiency and emission intensity, as well as lower series resistance and threshold current density under the identical condition, compared with conventional LD structure.

  3. Two coexisting mechanisms of dislocation reduction in an AlGaN layer grown using a thin GaN interlayer

    SciTech Connect

    Bai, J.; Wang, T.; Parbrook, P. J.; Wang, Q.; Lee, K. B.; Cullis, A. G.

    2007-09-24

    A significant dislocation reduction is achieved in an AlGaN layer grown on an AlN buffer by introducing a thin GaN interlayer. The mechanisms for the dislocation reduction are explored by transmission electron microscopy, energy-dispersive x-ray spectroscopy, atomic force microscopy, and micro-Raman spectroscopy. The GaN interlayer grown on the AlN takes the form of platelets. The mechanisms of dislocation reduction in the platelet area and the area between the platelets are different. In the GaN platelets, due to the large misfit strain, the threading dislocations (TDs) in the AlN layer migrate into the interface and annihilate with each other. However, the GaN between the platelets is highly strained so that a higher density of TDs from AlN is incorporated into the upper layer. The coalescing of the platelets induced by the AlGaN growth makes the TDs in the areas between the platelets assemble and annihilate, resulting in additional dislocation reduction.

  4. Digitally Alloyed Modulated Precursor Flow Epitaxial Growth of Ternary AlGaN with Binary AlN and GaN Sub-Layers and Observation of Compositional Inhomogeneity

    NASA Astrophysics Data System (ADS)

    Kim, Hee Jin; Choi, Suk; Yoo, Dongwon; Ryou, Jae-Hyun; Hawkridge, Michael E.; Liliental-Weber, Zuzanna; Dupuis, Russell D.

    2010-05-01

    We report the growth of ternary aluminum gallium nitride (AlGaN) layers on AlN/sapphire template/substrates by digitally alloyed modulated precursor flow epitaxial growth (DA-MPEG), which combined an MPEG AlN sub-layer with a conventional metalorganic chemical vapor deposition (MOCVD)-grown GaN sub-layer. The overall composition in DA-MPEG Al x Ga1- x N was controlled by adjustment of the growth time (i.e., the thickness) of the GaN sub-layer. As the GaN sub-layer growth time increased, the Al composition in AlGaN decreased to 50%, but the surface morphology of the AlGaN layer became rough, and a three-dimensional structure with islands appeared for the DA-MPEG AlGaN with relatively thick GaN sub-layers, possibly resulting from the Ga adatom surface migration behavior and/or the strain built up from lattice mismatch between AlN and GaN sub-layers with increasing GaN sub-layer growth time. Through strain analysis by high-resolution x-ray diffraction, reciprocal space mapping, and scanning transmission electron microscopy, it was found that there was compositional inhomogeneity in the DA-MPEG AlGaN with AlN and GaN binary sub-layers for the case of the layer with relatively thick GaN sub-layers.

  5. Formation of Hard Surfacing Layers of WC-Co with Electron Beam Cladding Method

    NASA Astrophysics Data System (ADS)

    Abe, Nobuyuki; Morimoto, Junji

    Hard surfacing layers of WC-Co/Ni-base self-fluxing alloy were successfully formed on a steel substrate using an electron beam cladding method. The WC particles were densely and homogenously dispersed within the Ni-base self-fluxing alloy without porosity. The effect of the electron beam conditions on layer formation was investigated, and the cladding layer properties were examined by hardness tests, abrasive wear tests and immersion corrosion tests. It was found that the cladding layers showed higher hardness and abrasion resistance with increasing WC-Co mixing ratio, however, corrosion resistance decreased with WC-Co mixing ratio. A coating layer having high abrasive and corrosion resistance simultaneously was achieved by multiple cladding of high WC-Co mixing ratio layers after low WC-Co mixing ratio layers.

  6. Inhomogeneous distribution of defect-related emission in Si-doped AlGaN epitaxial layers with different Al content and Si concentration

    SciTech Connect

    Kurai, Satoshi Ushijima, Fumitaka; Yamada, Yoichi; Miyake, Hideto; Hiramatsu, Kazumasa

    2014-02-07

    The spatial distribution of luminescence in Si-doped AlGaN epitaxial layers that differ in Al content and Si concentration has been studied by cathodoluminescence (CL) mapping in combination with scanning electron microscopy. The density of surface hillocks increased with decreasing Al content and with increasing Si concentration. The mechanisms giving rise to those hillocks are likely different. The hillocks induced surface roughening, and the compositional fluctuation and local donor-acceptor-pair (DAP) emission at hillock edges in AlGaN epitaxial layers were enhanced irrespective of the origin of the hillocks. The intensity of local DAP emission was related to Si concentration, as well as to hillock density. CL observation revealed that DAP emission areas were present inside the samples and were likely related to dislocations concentrated at hillock edges. Possible candidates for acceptors in the observed DAP emission that are closely related in terms of both Si concentration and hillock edges with large deformations are a V{sub III}-Si{sub III} complex and Si{sub N}, which are unfavorable in ordinary III-nitrides.

  7. Polymeric waveguide electro-optic beam-steering device with DNA biopolymer conductive cladding layers

    NASA Astrophysics Data System (ADS)

    Aga, Roberto S.; Ouchen, Fahima; Lesko, Alyssa; Telek, Brian A.; Fehrman Cory, Emily M.; Bartsch, Carrie M.; Lombardi, Jack; Grote, James; Heckman, Emily M.

    2012-11-01

    A polymer electro-optic (EO) waveguide beam-steering device with deoxyribonucleic acid (DNA) biopolymer conductive cladding layers and a core layer of the commercially available EO polymer SEO100 is demonstrated with 100% relative poling efficiency. This demonstration device exhibits a deflection efficiency of 99 mrad/kV with a corresponding in-device EO coefficient r33 of 124 pm/V at 1550 nm. When the DNA biopolymer bottom cladding layer is replaced by the commonly used cladding polymer UV15, the deflection efficiency and in-device r33 drop to 34 mrad/kV and 43 pm/V, respectively.

  8. Persistent photoconductivity in AlGaN/GaN heterojunction channels caused by the ionization of deep levels in the AlGaN barrier layer

    SciTech Connect

    Murayama, H.; Akiyama, Y.; Niwa, R.; Sakashita, H.; Sakaki, H.; Kachi, T.; Sugimoto, M.

    2013-12-04

    Time-dependent responses of drain current (I{sub d}) in an AlGaN/GaN HEMT under UV (3.3 eV) and red (2.0 eV) light illumination have been studied at 300 K and 250 K. UV illumination enhances I{sub d} by about 10 %, indicating that the density of two-dimensional electrons is raised by about 10{sup 12} cm{sup −2}. When UV light is turned off at 300 K, a part of increased I{sub d} decays quickly but the other part of increment is persistent, showing a slow decay. At 250 K, the majority of increment remains persistent. It is found that such a persistent increase of I{sub d} at 250 K can be partially erased by the illumination of red light. These photo-responses are explained by a simple band-bending model in which deep levels in the AlGaN barrier get positively charged by the UV light, resulting in a parabolic band bending in the AlGaN layer, while some potion of those deep levels are neutralized by the red light.

  9. Transparent conducting oxide clad limited area epitaxy semipolar III-nitride laser diodes

    NASA Astrophysics Data System (ADS)

    Myzaferi, A.; Reading, A. H.; Cohen, D. A.; Farrell, R. M.; Nakamura, S.; Speck, J. S.; DenBaars, S. P.

    2016-08-01

    The bottom cladding design of semipolar III-nitride laser diodes is limited by stress relaxation via misfit dislocations that form via the glide of pre-existing threading dislocations (TDs), whereas the top cladding is limited by the growth time and temperature of the p-type layers. These design limitations have individually been addressed by using limited area epitaxy (LAE) to block TD glide in n-type AlGaN bottom cladding layers and by using transparent conducting oxide (TCO) top cladding layers to reduce the growth time and temperature of the p-type layers. In addition, a TCO-based top cladding should have significantly lower resistivity than a conventional p-type (Al)GaN top cladding. In this work, LAE and indium-tin-oxide cladding layers are used simultaneously in a ( 20 2 ¯ 1 ) III-nitride laser structure. Lasing was achieved at 446 nm with a threshold current density of 8.5 kA/cm2 and a threshold voltage of 8.4 V.

  10. Microscopic potential fluctuations in Si-doped AlGaN epitaxial layers with various AlN molar fractions and Si concentrations

    NASA Astrophysics Data System (ADS)

    Kurai, Satoshi; Miyake, Hideto; Hiramatsu, Kazumasa; Yamada, Yoichi

    2016-01-01

    Nanoscopic potential fluctuations of Si-doped AlGaN epitaxial layers with the AlN molar fraction varying from 0.42 to 0.95 and Si-doped Al0.61Ga0.39N epitaxial layers with Si concentrations of 3.0-37 × 1017 cm-3 were investigated by cathodoluminescence (CL) imaging combined with scanning electron microscopy. The spot CL linewidths of AlGaN epitaxial layers broadened as the AlN molar fraction was increased to 0.7, and then narrowed at higher AlN molar fractions. The experimental linewidths were compared with the theoretical prediction from the alloy broadening model. The trends displayed by our spot CL linewidths were consistent with calculated results at AlN molar fractions of less than about 0.60, but the spot CL linewidths were markedly broader than the calculated linewidths at higher AlN molar fractions. The dependence of the difference between the spot CL linewidth and calculated line broadening on AlN molar fraction was found to be similar to the dependence of reported S values, indicating that the vacancy clusters acted as the origin of additional line broadening at high AlN molar fractions. The spot CL linewidths of Al0.61Ga0.39N epitaxial layers with the same Al concentration and different Si concentrations were nearly constant in the entire Si concentration range tested. From the comparison of reported S values, the increase of VAl did not contribute to the linewidth broadening, unlike the case of the VAl clusters.

  11. Microstructure and properties of pure iron/copper composite cladding layers on carbon steel

    NASA Astrophysics Data System (ADS)

    Wan, Long; Huang, Yong-xian; Lü, Shi-xiong; Huang, Ti-fang; Lü, Zong-liang

    2016-08-01

    In the present study, pure iron/copper composite metal cladding was deposited onto carbon steel by tungsten inert gas welding. The study focused on interfacial morphological, microstructural, and mechanical analyses of the composite cladding layers. Iron liquid-solid-phase zones were formed at copper/steel and iron interfaces because of the melting of the steel substrate and iron. Iron concentrated in the copper cladding layer was observed to exhibit belt, globule, and dendrite morphologies. The appearance of iron-rich globules indicated the occurrence of liquid phase separation (LPS) prior to solidification, and iron-rich dendrites crystallized without the occurrence of LPS. The maximum microhardness of the iron/steel interface was lower than that of the copper/steel interface because of the diffusion of elemental carbon. All samples fractured in the cladding layers. Because of a relatively lower strength of the copper layer, a short plateau region appeared when shear movement was from copper to iron.

  12. On the importance of AlGaN electron blocking layer design for GaN-based light-emitting diodes

    SciTech Connect

    Sheng Xia, Chang Simon Li, Z. M.; Sheng, Yang

    2013-12-02

    There has been confusion regarding the usefulness of AlGaN electron blocking layer (EBL) in GaN-based light-emitting diodes (LEDs) with some published experimental data indicating that the LEDs without EBL performed better than those with it. InGaN/GaN LEDs have been investigated numerically to analyze its actual effect in these devices. Simulation results show that hole blocking effect of EBL mainly determines the effectiveness of using it which is more sensitive to its Al composition, band offset ratio, and polarization charges. It is found that the choice of Al composition is critical for EBL to improve the optical performance of GaN-based LEDs.

  13. Experimental Study on Surface Characteristics of Laser Cladding Layer Regulated by High-Frequency Microforging

    NASA Astrophysics Data System (ADS)

    Fan, Xiang Fang; Zhou, Ju; Qiu, Chang Jun; He, Bin; Ye, Jiang; Yuan, Bo; Pi, Zhengqing

    2011-03-01

    High-frequency microforging technology is used to produce micrometer-scale plastic deformation on the surface of material out of the vibration impact of a forging punch, and the cumulative effect of its various frequencies on micrometer-scale plastic deformation can cause changes of surface microstructure and mechanical properties. This study used (1) a self-made machine to treat NiCrBSi alloy, (2) a mechanical comparator and optical microscopy (OM) to study the geometric characteristics of plastic deformation, (3) OM and scanning electric microscopy (SEM) to observe influence on surface microstructure and cracking behavior of the laser cladding layer under microforging, (4) x-ray diffractometer (XRD) to measure the surface residual stress of laser cladding layer before and after forging, and (5) microhardness tester and wearing experimental machine to study changes of microhardness, friction coefficient, and wear characteristics of laser cladding layer after microforging. The results have shown that high-frequency microforging could produce plastic deformation about 150 μm deep on the surface of NiCrBSi alloy clad by laser. Regular dendrite and eutectic crystallization microstructure, which is a peculiar characteristic of the laser cladding layer, was broken into pieces and formed residual compression residual stress on the surface. Resistance to cracking of laser cladding layer improved greatly, microhardness and wearability increased, and the friction coefficient did not under go a noticeable change.

  14. Effect of AlGaN/GaN strained layer superlattice period on InGaN MQW laser diodes[Multiple Quantum Wells

    SciTech Connect

    Hansen, M.; Abare, A.C.; Kozodoy, P.; Katona, T.M.; Craven, M.D.; Speck, J.S.; Mishra, U.K.; Coldren, L.A.; DenBaars, S.P.

    2000-07-01

    AlGaN/GaN strained layer superlattices have been employed in the cladding layers of InGaN multi-quantum well laser diodes grown by metalorganic chemical vapor deposition (MOCVD). Superlattices have been investigated for strain relief of the cladding layer, as well as an enhanced hole concentration, which is more than ten times the value obtained for bulk AlGaN films. Laser diodes with strained layer superlattices as cladding layers were shown to have superior structural and electrical properties compared to laser diodes with bulk AlGaN cladding layers. As the period of the strained layer superlattices is decreased, the threshold voltage, as well as the threshold current density, is decreased. The resistance to vertical conduction through p-type superlattices with increasing superlattice period is not offset by the increase in hole concentration for increasing superlattice spacing, resulting in higher voltages.

  15. Microstructure and Tribological Properties of In Situ Synthesized TiN Reinforced Ni/Ti Alloy Clad Layer Prepared by Plasma Cladding Technique

    NASA Astrophysics Data System (ADS)

    Jin, Guo; Li, Yang; Cui, Huawei; Cui, Xiufang; Cai, Zhaobing

    2016-06-01

    A Ni/Ti composite coating enhanced by an in situ synthesized TiN phase was fabricated on FV520B steel by plasma cladding technology. The in situ formation of the TiN phase was confirmed by XRD, SEM, and TEM. The cladding layer consisted of three regions on going from the top to the bottom, namely, columnar grain regions, columnar dendritic regions, and fine grain regions. The cladding layer was composed of Ni3Ti, TiN, (Fe, Ni), and Ti phases. The dendritic and columnar regions were mainly composed of the Ni3Ti and (Fe, Ni) phases. The Ti phase was observed at the branches of dendrite crystals and columnar grains. The volume fraction of the TiN phase in the cladding layer was about 3.2%. The maximum micro-hardness value of the in situ formed coating (760 HV0.2) was higher than that of the pure coating (537 HV0.2). The cladding layer had a small amount of scratch and wear debris when a load of 20 N was used. As the test load increased, the wear debris in the cladding layer also increased and the massive furrows were not observed.

  16. Microstructure and Tribological Properties of In Situ Synthesized TiN Reinforced Ni/Ti Alloy Clad Layer Prepared by Plasma Cladding Technique

    NASA Astrophysics Data System (ADS)

    Jin, Guo; Li, Yang; Cui, Huawei; Cui, Xiufang; Cai, Zhaobing

    2016-04-01

    A Ni/Ti composite coating enhanced by an in situ synthesized TiN phase was fabricated on FV520B steel by plasma cladding technology. The in situ formation of the TiN phase was confirmed by XRD, SEM, and TEM. The cladding layer consisted of three regions on going from the top to the bottom, namely, columnar grain regions, columnar dendritic regions, and fine grain regions. The cladding layer was composed of Ni3Ti, TiN, (Fe, Ni), and Ti phases. The dendritic and columnar regions were mainly composed of the Ni3Ti and (Fe, Ni) phases. The Ti phase was observed at the branches of dendrite crystals and columnar grains. The volume fraction of the TiN phase in the cladding layer was about 3.2%. The maximum micro-hardness value of the in situ formed coating (760 HV0.2) was higher than that of the pure coating (537 HV0.2). The cladding layer had a small amount of scratch and wear debris when a load of 20 N was used. As the test load increased, the wear debris in the cladding layer also increased and the massive furrows were not observed.

  17. Effect of rare earth oxide on the properties of laser cladding layer and machining vibration suppressing in side milling

    NASA Astrophysics Data System (ADS)

    Zhao, Yanhua; Sun, Jie; Li, Jianfeng

    2014-12-01

    Laser cladding, which can increase the hardness and wear resistance of the used components, is widely used in remanufacture and sustainable manufacturing field. Generally, laser cladding layer should to be machined to meet the function as well as the assembly requirements. Milling is an effective mean for precision machining. However, there exist great differences of physical and mechanical performances between laser cladding layer and substrate material, including microstructure, hardness, wear resistance, etc. This produces some new milling problems for laser cladding layer, such as machining vibration which may lead to low productivity and worse surface integrity. Thus, it is necessary to develop a novel laser cladding powder which can improve the surface hardness and wear resistance, while reducing the machining vibration in milling. Laser cladding layer was prepared by FeCr alloy and La2O3 mixed powder. The effect of La2O3 on the coating properties was investigated. Signal analysis methods of the time and frequency domain were used to evaluate the effect of the La2O3 on machining vibration in the side milling laser cladding layer. The key findings of this study are: (a) with the La2O3 content increasing, the grain size decreases dramatically and the microstructure of laser cladding layer are refine; (b) the hardness and wear resistance of the coatings with La2O3 are improved significantly; and (c) the machining vibrations of laser cladding layer with La2O3 are obviously reduced and the chatter is effectively avoided occurring.

  18. Growth of high quality and uniformity AlGaN/GaN heterostructures on Si substrates using a single AlGaN layer with low Al composition.

    PubMed

    Cheng, Jianpeng; Yang, Xuelin; Sang, Ling; Guo, Lei; Zhang, Jie; Wang, Jiaming; He, Chenguang; Zhang, Lisheng; Wang, Maojun; Xu, Fujun; Tang, Ning; Qin, Zhixin; Wang, Xinqiang; Shen, Bo

    2016-01-01

    By employing a single AlGaN layer with low Al composition, high quality and uniformity AlGaN/GaN heterostructures have been successfully grown on Si substrates by metal-organic chemical vapor deposition (MOCVD). The heterostructures exhibit a high electron mobility of 2150 cm(2)/Vs with an electron density of 9.3 × 10(12) cm(-2). The sheet resistance is 313 ± 4 Ω/◻ with ±1.3% variation. The high uniformity is attributed to the reduced wafer bow resulting from the balance of the compressive stress induced and consumed during the growth, and the thermal tensile stress induced during the cooling down process. By a combination of theoretical calculations and in situ wafer curvature measurements, we find that the compressive stress consumed by the dislocation relaxation (~1.2 GPa) is comparable to the value of the thermal tensile stress (~1.4 GPa) and we should pay more attention to it during growth of GaN on Si substrates. Our results demonstrate a promising approach to simplifying the growth processes of GaN-on-Si to reduce the wafer bow and lower the cost while maintaining high material quality. PMID:26960730

  19. Growth of high quality and uniformity AlGaN/GaN heterostructures on Si substrates using a single AlGaN layer with low Al composition

    NASA Astrophysics Data System (ADS)

    Cheng, Jianpeng; Yang, Xuelin; Sang, Ling; Guo, Lei; Zhang, Jie; Wang, Jiaming; He, Chenguang; Zhang, Lisheng; Wang, Maojun; Xu, Fujun; Tang, Ning; Qin, Zhixin; Wang, Xinqiang; Shen, Bo

    2016-03-01

    By employing a single AlGaN layer with low Al composition, high quality and uniformity AlGaN/GaN heterostructures have been successfully grown on Si substrates by metal-organic chemical vapor deposition (MOCVD). The heterostructures exhibit a high electron mobility of 2150 cm2/Vs with an electron density of 9.3 × 1012 cm‑2. The sheet resistance is 313 ± 4 Ω/◻ with ±1.3% variation. The high uniformity is attributed to the reduced wafer bow resulting from the balance of the compressive stress induced and consumed during the growth, and the thermal tensile stress induced during the cooling down process. By a combination of theoretical calculations and in situ wafer curvature measurements, we find that the compressive stress consumed by the dislocation relaxation (~1.2 GPa) is comparable to the value of the thermal tensile stress (~1.4 GPa) and we should pay more attention to it during growth of GaN on Si substrates. Our results demonstrate a promising approach to simplifying the growth processes of GaN-on-Si to reduce the wafer bow and lower the cost while maintaining high material quality.

  20. Growth of high quality and uniformity AlGaN/GaN heterostructures on Si substrates using a single AlGaN layer with low Al composition

    PubMed Central

    Cheng, Jianpeng; Yang, Xuelin; Sang, Ling; Guo, Lei; Zhang, Jie; Wang, Jiaming; He, Chenguang; Zhang, Lisheng; Wang, Maojun; Xu, Fujun; Tang, Ning; Qin, Zhixin; Wang, Xinqiang; Shen, Bo

    2016-01-01

    By employing a single AlGaN layer with low Al composition, high quality and uniformity AlGaN/GaN heterostructures have been successfully grown on Si substrates by metal-organic chemical vapor deposition (MOCVD). The heterostructures exhibit a high electron mobility of 2150 cm2/Vs with an electron density of 9.3 × 1012 cm−2. The sheet resistance is 313 ± 4 Ω/◻ with ±1.3% variation. The high uniformity is attributed to the reduced wafer bow resulting from the balance of the compressive stress induced and consumed during the growth, and the thermal tensile stress induced during the cooling down process. By a combination of theoretical calculations and in situ wafer curvature measurements, we find that the compressive stress consumed by the dislocation relaxation (~1.2 GPa) is comparable to the value of the thermal tensile stress (~1.4 GPa) and we should pay more attention to it during growth of GaN on Si substrates. Our results demonstrate a promising approach to simplifying the growth processes of GaN-on-Si to reduce the wafer bow and lower the cost while maintaining high material quality. PMID:26960730

  1. Laser Cladding of Ni-WC Layers with Graded WC Content

    NASA Astrophysics Data System (ADS)

    Amado, J. M.; Montero, J.; Tobar, M. J.; Yáñez, A.

    Coating techniques using powder as added material can be adapted for the manufacture of composition gradients if a mixing unit is included in the powder feed system. As for the laser cladding technology, FGM can be obtained if mixing parameters are changed along the process. This work deals with the development of NiCrBSi layers with WC graded composition. The purpose is to obtain longitudinal compositional gradients within distances of millimeters along a laser scan. To accomplish this task, the capabilities and time delays in the feeding system are identified and analyzed. Preliminar tests on single cladding beads show results in reasonable agreement with expectations.

  2. Microstructure and mechanical properties of hot wire laser clad layers for repairing precipitation hardening martensitic stainless steel

    NASA Astrophysics Data System (ADS)

    Wen, Peng; Cai, Zhipeng; Feng, Zhenhua; Wang, Gang

    2015-12-01

    Precipitation hardening martensitic stainless steel (PH-MSS) is widely used as load-bearing parts because of its excellent overall properties. It is economical and flexible to repair the failure parts instead of changing new ones. However, it is difficult to keep properties of repaired part as good as those of the substrate. With preheating wire by resistance heat, hot wire laser cladding owns both merits of low heat input and high deposition efficiency, thus is regarded as an advantaged repairing technology for damaged parts of high value. Multi-pass layers were cladded on the surface of FV520B by hot wire laser cladding. The microstructure and mechanical properties were compared and analyzed for the substrate and the clad layer. For the as-cladded layer, microstructure was found non-uniform and divided into quenched and tempered regions. Tensile strength was almost equivalent to that of the substrate, while ductility and impact toughness deteriorated much. With using laser scanning layer by layer during laser cladding, microstructure of the clad layers was tempered to fine martensite uniformly. The ductility and toughness of the clad layer were improved to be equivalent to those of the substrate, while the tensile strength was a little lower than that of the substrate. By adding TiC nanoparticles as well as laser scanning, the precipitation strengthening effect was improved and the structure was refined in the clad layer. The strength, ductility and toughness were all improved further. Finally, high quality clad layers were obtained with equivalent or even superior mechanical properties to the substrate, offering a valuable technique to repair PH-MSS.

  3. FEM simulation on rotating piercing process of double-layer clad sheet with Coulomb friction

    NASA Astrophysics Data System (ADS)

    Tzou, Gow-Yi; Hwang, Yeong-Maw; Teng, Hsiang-Yu

    2013-12-01

    This study proposes a new piercing technology with rotating punch on the double-layer clad sheet; it carries out an FEM simulation on rotating piercing process using DEFORM-3D commercial software. Frictions among the punch, the blank holder, the dies and the double-layer clad sheet material are assumed as Coulomb friction, but can be different. The surface of the inner diameter, the effective stress, the effective strain, velocity field, damage, burr and the shearing force can be determined form the FEM simulation. In this study, effects of various piercing conditions such as the clearance, the punch nose angle, the frictional factor, the rotating angular velocity, the shearing force, and burr on shearing characteristics are explored effectively to realize the feasibility of FEM model.

  4. Solid-Particle Erosion Behaviour of WC/Ni Composite Clad layers with Different Contents of WC Particles

    NASA Astrophysics Data System (ADS)

    Paul, C. P.; Mishra, S. K.; Tiwari, P.; Kukreja, L. M.

    2013-09-01

    We investigated the solid particle erosion behaviour of WC-reinforced Ni-matrix based laser clad layers to improve the performance of engineering components for potential power plant applications. WC-reinforced Ni-matrix based laser clad layers having various compositions of WC (5, 10 and 15wt%) were deposited on austenitic stainless steel substrates. The laser clad layers were characterised using optical and scanning electron microscopy, microhardness testing and air-jet erosion testing. In solid particle erosion studies using the air-jet erosion tester, the set of testing parameters, including air-erodent compositions, erodent particle velocities and impact angles, was selected by using the Taguchi technique. The morphologies of the worn surfaces were used to predict the wear mechanisms. The results of a microstructural examination of the cross-sections of laser clad revealed a good metallurgical bond between the WC-reinforced Ni matrix and the austenitic stainless steel substrate. Dissociation/partial melting/full melting of WC particles was not observed in the laser clad layers. The microhardness value in the laser cladding zone was between 900-2400 VHN, while it was 230-270 VHN on the substrate. The results of erosion wear studies of the WC-Ni laser clad surface revealed that the erosion behaviour of the WC-Ni laser clad is primarily governed by erodent jet velocity followed by impact angle. The erosion does not much depend on the Ni-concentration in the MMC or the erodent feed rate. The wear signature at the erosion wear surface indicated that the erosion was primarily governed by a ductile erosion mechanism followed by the removal of WC particles from the matrix. The erosion resistance of the Ni-clad layer with WC was found to be at least four times higher than that without WC particles. The quantified contribution of various erosion parameters is useful for function-based design of components with extended service life.

  5. Crack Free Tungsten Carbide Reinforced Ni(Cr) Layers obtained by Laser Cladding

    NASA Astrophysics Data System (ADS)

    Amado, J. M.; Tobar, M. J.; Yáñez, A.; Amigó, V.; Candel, J. J.

    The development of hardfacing coatings has become technologically significant in many industries A common approach is the production of metal matrix composites (MMC) layers. In this work NiCr-WC MMC hardfacing layers are deposited on C25 steel by means of laser cladding. Spheroidal fused tungsten carbides is used as reinforcement phase. Three different NiCr alloys with different Cr content were tested. Optimum conditions to obtain dense, uniform carbide distribution and hardness close to nominal values were defined. The effect of Cr content respect to the microstructure, susceptibility for cracking and the wear rate of the resulting coating will also be discussed.

  6. Thermal conductivity tensors of the cladding and active layers of interband cascade lasers

    NASA Astrophysics Data System (ADS)

    Zhou, Chuanle; Cui, Boya; Vurgaftman, I.; Canedy, C. L.; Kim, C. S.; Kim, M.; Bewley, W. W.; Merritt, C. D.; Abell, J.; Meyer, J. R.; Grayson, M.

    2014-12-01

    The cross-plane and in-plane thermal conductivities of the W-active stages and InAs/AlSb superlattice optical cladding layer of an interband cascade laser (ICL) were characterized for temperatures ranging from 15 K to 324 K. The in-plane thermal conductivity of the active layer is somewhat larger than the cross-plane value at temperatures above about 30 K, while the thermal conductivity tensor becomes nearly isotropic at the lowest temperatures studied. These results will improve ICL performance simulations and guide the optimization of thermal management.

  7. Towards AlN optical cladding layers for thermal management in hybrid lasers

    NASA Astrophysics Data System (ADS)

    Mathews, Ian; Lei, Shenghui; Nolan, Kevin; Levaufre, Guillaume; Shen, Alexandre; Duan, Guang-Hua; Corbett, Brian; Enright, Ryan

    2015-06-01

    Aluminium Nitride (AlN) is proposed as a dual function optical cladding and thermal spreading layer for hybrid ridge lasers, replacing current benzocyclobutene (BCB) encapsulation. A high thermal conductivity material placed in intimate contact with the Multi-Quantum Well active region of the laser allows rapid heat removal at source but places a number of constraints on material selection. AlN is considered the most suitable due to its high thermal conductivity when deposited at low deposition temperatures, similar co-efficient of thermal expansion to InP, its suitable refractive index and its dielectric nature. We have previously simulated the possible reduction in the thermal resistance of a hybrid ridge laser by replacing the BCB cladding material with a material of higher thermal conductivity of up to 319 W/mK. Towards this goal, we demonstrate AlN thin-films deposited by reactive DC magnetron sputtering on InP.

  8. Residual stress and crack initiation in laser clad composite layer with Co-based alloy and WC + NiCr

    NASA Astrophysics Data System (ADS)

    Lee, Changmin; Park, Hyungkwon; Yoo, Jaehong; Lee, Changhee; Woo, WanChuck; Park, Sunhong

    2015-08-01

    Although laser cladding process has been widely used to improve the wear and corrosion resistance, there are unwanted cracking issues during and/or after laser cladding. This study investigates the tendency of Co-based WC + NiCr composite layers to cracking during the laser cladding process. Residual stress distributions of the specimen are measured using neutron diffraction and elucidate the correlation between the residual stress and the cracking in three types of cylindrical specimens; (i) no cladding substrate only, (ii) cladding with 100% stellite#6, and (iii) cladding with 55% stellite#6 and 45% technolase40s. The microstructure of the clad layer was composed of Co-based dendrite and brittle eutectic phases at the dendritic boundaries. And WC particles were distributed on the matrix forming intermediate composition region by partial melting of the surface of particles. The overlaid specimen exhibited tensile residual stress, which was accumulated through the beads due to contraction of the coating layer generated by rapid solidification, while the non-clad specimen showed compressive. Also, the specimen overlaid with 55 wt% stellite#6 and 45 wt% technolase40s showed a tensile stress higher than the specimen overlaid with 100% stellite#6 possibly, due to the difference between thermal expansion coefficients of the matrix and WC particles. Such tensile stresses can be potential driving force to provide an easy crack path ways for large brittle fractures combined with the crack initiation sites such as the fractured WC particles, pores and solidification cracks. WC particles directly caused clad cracks by particle fracture under the tensile stress. The pores and solidification cracks also affected as initiation sites and provided an easy crack path ways for large brittle fractures.

  9. Multi-layered dielectric cladding plasmonic microdisk resonator filter and coupler

    SciTech Connect

    Han Cheng, Bo; Lan, Yung-Chiang

    2013-02-15

    This work develops the plasmonic microdisk filter/coupler, whose effectiveness is evaluated by finite-difference time-domain simulation and theoretical analyses. Multi-layer dielectric cladding is used to prevent the scattering of surface plasmons (SPs) from a silver microdisk. This method allows devices that efficiently perform filter/coupler functions to be developed. The resonant conditions and the effective refractive index of bounded SP modes on the microdisk are determined herein. The waveguide-to-microdisk distance barely influences the resonant wavelength but it is inversely related to the bandwidth. These findings are consistent with predictions made using the typical ring resonator model.

  10. Performance improvement of GaN-based near-UV LEDs with InGaN/AlGaN superlattices strain relief layer and AlGaN barrier

    NASA Astrophysics Data System (ADS)

    Jia, Chuanyu; Yu, Tongjun; Feng, Xiaohui; Wang, Kun; Zhang, Guoyi

    2016-09-01

    The carrier confinement effect and piezoelectric field-induced quantum-confined stark effect of different GaN-based near-UV LED samples from 395 nm to 410 nm emission peak wavelength were investigated theoretically and experimentally. It is found that near-UV LEDs with InGaN/AlGaN multiple quantum wells (MQWs) active region have higher output power than those with InGaN/GaN MQWs for better carrier confinement effect. However, as emission peak wavelength is longer than 406 nm, the output power of the near-UV LEDs with AlGaN barrier is lower than that of the LEDs with GaN barrier due to more serious spatial separation of electrons and holes induced by the increase of piezoelectric field. The N-doped InGaN/AlGaN superlattices (SLs) were adopted as a strain relief layer (SRL) between n-GaN and MQWs in order to suppress the polarization field. It is demonstrated the output power of near-UV LEDs is increased obviously by using SLs SRL and AlGaN barrier for the discussed emission wavelength range. Besides, the forward voltage of near-UV LEDs with InGaN/AlGaN SLs SRL is lower than that of near-UV LEDs without SRL.

  11. Stress analysis and probabilistic assessment of multi-layer SiC-based accident tolerant nuclear fuel cladding

    NASA Astrophysics Data System (ADS)

    Stone, J. G.; Schleicher, R.; Deck, C. P.; Jacobsen, G. M.; Khalifa, H. E.; Back, C. A.

    2015-11-01

    Silicon carbide (SiC) fiber, SiC matrix composites (SiC/SiC) are being considered as a cladding material for light water reactors in order to improve safety performance. Engineered, multi-layer cladding designs consisting of both monolithic SiC (mSiC) and SiC/SiC have been examined as promising concepts to meet both strength and impermeability requirements. A new model has been developed to calculate stresses and failure probabilities for multi-layer cladding consisting of SiC-based materials in reactor operating conditions. The results show that stresses in SiC-based cladding are dominated by temperature-dependent irradiation-induced swelling, with the largest stresses occurring during the cold shutdown conditions. Failure probabilities are driven by the resulting tensile stresses at the cladding inner wall, while the outer wall is subject to compressive stresses. This indicates that the inner SiC/SiC, outer mSiC concept has the lowest failure probability, as the pseudo-plastic deformation of the composite reduces tensile loading and the compressed monolith provides a reliable, impermeable barrier to fission product release.

  12. Polarization engineering of back-illuminated separate absorption and multiplication AlGaN avalanche photodiodes

    NASA Astrophysics Data System (ADS)

    Yang, Guofeng; Wang, Fuxue

    2016-08-01

    The back-illuminated separate absorption and multiplication AlGaN avalanche photodiodes (APDs) with a p-type graded AlGaN layer have been designed to investigate the polarization engineering on the performance of the devices. The calculated results show that the APD with p-graded AlGaN layer exhibits lower avalanche breakdown voltage and increased maximum multiplication gain compared to the structure with conventional p-type AlGaN layer. The improved performance of the designed APD is numerically explained by the polarization-assisted enhancement of the ionization electric field in the multiplication region and polarization doping effect caused by the p-type graded layer.

  13. Monitoring and Controlling of Strain During MOCVD of AlGaN for UV Optoelectronics

    SciTech Connect

    Han, J.; Crawford, M.H.; Shul, R.J.; Hearne, S.J.; Chason, E.; Figiel, J.J.; Banas, M.

    1999-01-14

    The grown-in tensile strain, due to a lattice mismatch between AlGaN and GaN, is responsible for the observed cracking that seriously limits the feasibility of nitride-based ultraviolet (UV) emitters. We report in-situ monitoring of strain/stress during MOCVD of AlGaN based on a wafer-curvature measurement technique. The strain/stress measurement confirms the presence of tensile strain during growth of AlGaN pseudomorphically on a thick GaN layer. Further growth leads to the onset of stress relief through crack generation. We find that the growth of AlGaN directly on low-temperature (LT) GaN or AlN buffer layers results in a reduced and possibly controllable strain.

  14. Modeling of high composition AlGaN channel high electron mobility transistors with large threshold voltage

    SciTech Connect

    Bajaj, Sanyam Hung, Ting-Hsiang; Akyol, Fatih; Nath, Digbijoy; Rajan, Siddharth

    2014-12-29

    We report on the potential of high electron mobility transistors (HEMTs) consisting of high composition AlGaN channel and barrier layers for power switching applications. Detailed two-dimensional (2D) simulations show that threshold voltages in excess of 3 V can be achieved through the use of AlGaN channel layers. We also calculate the 2D electron gas mobility in AlGaN channel HEMTs and evaluate their power figures of merit as a function of device operating temperature and Al mole fraction in the channel. Our models show that power switching transistors with AlGaN channels would have comparable on-resistance to GaN-channel based transistors for the same operation voltage. The modeling in this paper shows the potential of high composition AlGaN as a channel material for future high threshold enhancement mode transistors.

  15. Microstructure and Wear Behavior of Laser Clad Multi-layered Fe-based Amorphous Coatings on Steel Substrates

    NASA Astrophysics Data System (ADS)

    Paul, Tanaji; Alavi, S. Habib; Biswas, Sourabh; Harimkar, Sandip P.

    2015-12-01

    Single and multi-layered (with two and three layers) coatings of Fe48Cr15Mo14Y2C15B6 amorphous alloy were applied to AISI 1018 steel substrates via laser cladding. XRD analysis indicated partial retention of the amorphous phase along with the formation of oxide and carbide phases. Cross-sectional SEM micrographs revealed relatively sound coatings laser clad with single layer of amorphous alloy; however, cracks and voids were observed in the two and three layered amorphous coatings. The specimens with single and two layered amorphous coatings exhibited surface hardness of about 650 VHN while the hardness of the specimens with three layered amorphous coatings (~1100 VHN) nearly equaled the hardness of previously reported sintered amorphous alloys of similar compositions. The ball-on-disc wear analysis demonstrated a reverse trend wherein the single and two layered amorphous coatings exhibited lower weight loss during the wear test cycle due to superior surface soundness while the three layered amorphous coatings showed aggravated wear due to internal voids and cracks.

  16. Model analysis of separate-confinement heterojunction lasers with inhomogeneous cladding layers

    SciTech Connect

    Streifer, W.; Burnham, R.D.; Scifres, D.R.

    1983-05-01

    Separate-confinement heterostructure lasers with thin active regions are analyzed. For four different interior-cladding-region refractive-index spatial variations, i.e., step, triangular, parabolic, and inverted parabolic, wave-guide modes are calculated and thresholds are compared. Based on optical considerations alone, the step-index profile has the lowest threshold; however, for optimum cladding thicknesses the differences are not great.

  17. Annealing induced interfacial layers in niobium-clad stainless steel developed as a bipolar plate material for polymer electrolyte membrane fuel cell stacks

    SciTech Connect

    Hong, Sung Tae; Weil, K. Scott; Choi, Jung-Pyung; Bae, In-Tae; Pan, Jwo

    2010-05-01

    Niobium (Nb)-clad 304L stainless steel (SS) manufactured by cold rolling is currently under consideration for use as a bipolar plate material in polymer electrolyte membrane fuel cell (PEMFC) stacks. To make the fabrication of bipolar plates using the Nb-clad SS feasible, annealing may be necessary for the Nb-clad SS to reduce the springback induced by cold rolling. However, the annealing can develop an interfacial layer between the Nb cladding and the SS core and the interfacial layer plays a key role in the failure of the Nb-clad SS as reported earlier [JPS our work]. In this investigation, the Nb-clad SS specimens in as-rolled condition were annealed at different combinations of temperature and time. Based on the results of scanning electron microscope (SEM) analysis, an annealing process map for the Nb-clad SS was obtained. The results of SEM analysis and Transmission Electron Microscope (TEM) analysis also suggest that different interfacial layers occurred based on the given annealing conditions.

  18. A Multi-Layered Ceramic Composite for Impermeable Fuel Cladding for COmmercial Wate Reactors

    SciTech Connect

    Feinroth, Herbert

    2008-03-03

    A triplex nuclear fuel cladding is developed to further improve the passive safety of commercial nuclear plants, to increase the burnup and durablity of nuclear fuel, to improve the power density and economics of nuclear power, and to reduce the amount of spent fuel requiring disposal or recycle.

  19. Electrical properties of n-type AlGaN with high Si concentration

    NASA Astrophysics Data System (ADS)

    Takeda, Kunihiro; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu

    2016-05-01

    The electrical properties of Si-doped AlGaN layers (AlN molar fractions: 0.03-0.06) with the donor concentrations (N D) from 8.8 × 1017 to 4.5 × 1020 cm-3 were investigated by variable-temperature Hall effect measurement using the van der Pauw method. A minimum resistivity of 3.6 × 10-4 Ω cm was obtained for Si-doped AlGaN with a smooth surface at room temperature. We found that the activation energy of the Si donor is affected by the Coulomb interaction in the AlGaN layer with N D values from 8.8 × 1017 to 2.5 × 1020 cm-3. In several AlGaN layers, the free-electron concentration did not vary with sample temperature, as expected in the case of degeneracy. The localization of GaN in the AlGaN layer was speculated as a cause of degeneracy of samples.

  20. InP photonic wire waveguide using InAlAs oxide cladding layer.

    PubMed

    Takenaka, Mitsuru; Nakano, Yoshiaki

    2007-06-25

    We proposed a novel InP based photonic wire waveguide with an InAlAs oxide cladding. The InGaAsP/InAlAs-oxide structure in the vertical direction provides an ultrahigh index contrast waveguide, and it allows a bend radius of a few mum with no vertical leakage loss. The InP photonic wire waveguide with a 500x300-nm rectangular channel core (refractive index n ~ 3.36) and an InAlAs oxide cladding (n ~ 2.4) was numerically analyzed using the three-dimensional time-domain beam propagation method (3D TD-BPM). We predicted that the U-bend waveguide with a 3-mum bend radius can be realized with the propagation loss of < 0.5 dB. PMID:19547173

  1. Investigation of the thickness effect to impedance analysis results AlGaN acoustic sensor

    NASA Astrophysics Data System (ADS)

    Özen, Soner; Bilgiç, Eyüp; Gülmez, Gülay; Şenay, Volkan; Pat, Suat; Korkmaz, Şadan; Mohammadigharehbagh, Reza

    2016-03-01

    In this study, AlGaN acoustic sensors were deposited on aluminum metal substrate by thermionic vacuum arc (TVA) method, for the first time. Impedance analyses of the fabricated acoustic sensors were investigated for the determining of effect of the nano layer thickness. Thickness values are very close to each others. Fabricated sensors have been fabricated from AlGaN deposited on aluminum substrates. Gallium materials are used in many applications for optoelectronic device and semiconductor technology. Thermionic vacuum arc is the deposition technology for the variously materials and applications field. TVA production parameters and some properties of the deposited layers were investigated. TVA is the fast deposition technology for the gallium compounds and doped gallium compounds. Obtained results that AlGaN layer are very promising material for an acoustic sensor but also TVA is proper fast technology for the production.

  2. Piezoelectric domains in the AlGaN hexagonal microrods: Effect of crystal orientations

    NASA Astrophysics Data System (ADS)

    Sivadasan, A. K.; Mangamma, G.; Bera, Santanu; Kamruddin, M.; Dhara, Sandip

    2016-05-01

    Presently, the piezoelectric materials are finding tremendous applications in the micro-mechanical actuators, sensors, and self-powered devices. In this context, the studies pertaining to piezoelectric properties of materials in the different size ranges are very important for the scientific community. The III-nitrides are exceptionally important, not only for optoelectronic but also for their piezoelectric applications. In the present study, we synthesized AlGaN via self-catalytic vapor-solid mechanism by atmospheric pressure chemical vapor deposition technique on AlN base layer over intrinsic Si(100) substrate. The growth process is substantiated using X-ray diffraction and X-ray photoelectron spectroscopy. The Raman and photoluminescence studies reveal the formation of AlGaN microrods in the wurtzite phase and ensure the high optical quality of the crystalline material. The single crystalline, direct wide band gap and hexagonally shaped AlGaN microrods are studied for understanding the behavior of the crystallites under the application of constant external electric field using the piezoresponse force microscopy. The present study is mainly focused on understanding the behavior of induced polarization for the determination of piezoelectric coefficient of AlGaN microrod along the c-axis and imaging of piezoelectric domains in the sample originating because of the angular inclination of AlGaN microrods with respect to its AlN base layers.

  3. Performance enhancement of AlGaN deep-ultraviolet light-emitting diodes with varied superlattice barrier electron blocking layer

    NASA Astrophysics Data System (ADS)

    Liu, Songqing; Ye, Chunya; Cai, Xuefen; Li, Shuping; Lin, Wei; Kang, Junyong

    2016-05-01

    The AlGaN-based deep-UV LEDs with specific design of varied superlattice barrier electron blocking layer (EBL) has been investigated numerically by APSYS software. The proposed structure exhibits significant improvement in the light output power, internal quantum efficiency, current-voltage curve and electroluminescence intensity. After analyzing the profiles of energy band diagrams, carriers concentration and radiative recombination rate, we find the main advantages of proposed structure are ascribed to higher barrier suppressing electron leakage and reduced barrier for hole injection. Thus, compared with reference sample, the proposed EBL design may be a good method for improving the whole performance of UV LEDs.

  4. Microstructure evolution and mechanical properties of multiple-layer laser cladding coating of 308L stainless steel

    NASA Astrophysics Data System (ADS)

    Li, Kaibin; Li, Dong; Liu, Dongyu; Pei, Guangyu; Sun, Lei

    2015-06-01

    Multiple-layer laser cladding of 308L stainless steel was obtained by a fiber laser using a way of wire feeding to repair the surface scrapped or erosive parts of 316L stainless steel. The microstructure of the coating was measured by a metallographic microscope, and phase composition was determined by X-ray diffraction. The results show that good metallurgical bonding can be obtained between the 308L stainless steel coating and 316L stainless steel substrate. The coating is mainly composed of columnar dendrites, and there are also a few planar crystals and cellular dendrites distributed in the bonding zone. Meanwhile, some equiaxed grains and steering dendrites are distributed in the apex of the coating. Grains incorporate in epitaxial columnar dendrite's growth between different layers and tracks. It has been proved using XRD that the coating basically consists of austenite and a small amount of δ ferrite. The coating solidifies in FA mode according to the Creq/Nieq ratio and metallurgical analysis results. The average content of δ ferrite is about 10.48% and morphologies of the ferrite are mostly vermicular, skeletal and lathy. Due to heat treatment and different cooling rate, the δ ferrite content generally increases as the number of laser cladding layers increases. The coating and the substrate have equivalent microhardness, and softening zone does not appear in the heat affected zone. The tensile strength and elongation of the coating are 548 MPa and 40%, about 86% and 74% of the substrate, respectively. Ductile fracture is proved by the emergence of obvious dimples in the fracture surface.

  5. A structural model for multi-layered ceramic cylinders and its application to silicon carbide cladding of light water reactor fuel

    NASA Astrophysics Data System (ADS)

    Lee, Youho; Kazimi, Mujid S.

    2015-03-01

    A thermo-mechanical model for stress distribution and Weibull statistical fracture of a multi-layered SiC cladding for LWR fuel is developed. The model is validated by comparing its results to those of the Finite Element Analysis (FEA) code ANSYS. In steady-state operation, the temperature sensitive swelling may lead to undesirable tensile stresses which is anticipated to challenge the structural integrity of the fission-gas retaining inner layer of CVD-SiC monolith in a triple layer design with the composite being the middle layer. The stress distribution is sensitive to potential differences in the swelling of the monolith from that of the composite layer. The sensitivity is discussed in this work. A double-layered SiC cladding that employs the inner SiCf /SiC composite layer, and the outer CVD-SiC layer has also been analyzed. This SiC cladding design significantly reduces failure probability as it appropriately allocates peak tensile stresses in the inner composite while significantly reducing tensile stress levels of the CVD-SiC monolith.

  6. Predominant growth of non-polar a-plane (Al,Ga)N on patterned c-plane sapphire by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Mogilatenko, A.; Hagedorn, S.; Richter, E.; Zeimer, U.; Goran, D.; Weyers, M.; Tränkle, G.

    2013-03-01

    We report for the first time on predominant growth of non-polar a-plane (Al,Ga)N layers on patterned c-plane AlN/sapphire templates with ridges oriented along the [11¯00]Al2O3 direction. The layers were grown by hydride vapor phase epitaxy. During the first stages of the growth (Al,Ga)N nucleates simultaneously on top of the ridges, inside the trenches and on the trench sidewalls. As a result, two different (Al,Ga)N orientations are formed with respect to the horizontal growth front: c-plane (Al,Ga)N on the c-plane ridges as well as inside the trenches and a-plane (Al,Ga)N on the trench sidewalls. The growth rate of a-plane (Al,Ga)N exceeds that of c-plane regions, which leads to the complete overgrowth of c-plane (Al,Ga)N by the a-plane oriented material.

  7. Multi-clad black display panel

    DOEpatents

    Veligdan, James T.; Biscardi, Cyrus; Brewster, Calvin

    2002-01-01

    A multi-clad black display panel, and a method of making a multi-clad black display panel, are disclosed, wherein a plurality of waveguides, each of which includes a light-transmissive core placed between an opposing pair of transparent cladding layers and a black layer disposed between transparent cladding layers, are stacked together and sawed at an angle to produce a wedge-shaped optical panel having an inlet face and an outlet face.

  8. Fiber-Type Random Laser Based on a Cylindrical Waveguide with a Disordered Cladding Layer.

    PubMed

    Zhang, Wei Li; Zheng, Meng Ya; Ma, Rui; Gong, Chao Yang; Yang, Zhao Ji; Peng, Gang Ding; Rao, Yun Jiang

    2016-01-01

    This letter reports a fiber-type random laser (RL) which is made from a capillary coated with a disordered layer at its internal surface and filled with a gain (laser dye) solution in the core region. This fiber-type optical structure, with the disordered layer providing randomly scattered light into the gain region and the cylindrical waveguide providing confinement of light, assists the formation of random lasing modes and enables a flexible and efficient way of making random lasers. We found that the RL is sensitive to laser dye concentration in the core region and there exists a fine exponential relationship between the lasing intensity and particle concentration in the gain solution. The proposed structure could be a fine platform of realizing random lasing and random lasing based sensing. PMID:27220636

  9. Fiber-Type Random Laser Based on a Cylindrical Waveguide with a Disordered Cladding Layer

    NASA Astrophysics Data System (ADS)

    Zhang, Wei Li; Zheng, Meng Ya; Ma, Rui; Gong, Chao Yang; Yang, Zhao Ji; Peng, Gang Ding; Rao, Yun Jiang

    2016-05-01

    This letter reports a fiber-type random laser (RL) which is made from a capillary coated with a disordered layer at its internal surface and filled with a gain (laser dye) solution in the core region. This fiber-type optical structure, with the disordered layer providing randomly scattered light into the gain region and the cylindrical waveguide providing confinement of light, assists the formation of random lasing modes and enables a flexible and efficient way of making random lasers. We found that the RL is sensitive to laser dye concentration in the core region and there exists a fine exponential relationship between the lasing intensity and particle concentration in the gain solution. The proposed structure could be a fine platform of realizing random lasing and random lasing based sensing.

  10. Fiber-Type Random Laser Based on a Cylindrical Waveguide with a Disordered Cladding Layer

    PubMed Central

    Zhang, Wei Li; Zheng, Meng Ya; Ma, Rui; Gong, Chao Yang; Yang, Zhao Ji; Peng, Gang Ding; Rao, Yun Jiang

    2016-01-01

    This letter reports a fiber-type random laser (RL) which is made from a capillary coated with a disordered layer at its internal surface and filled with a gain (laser dye) solution in the core region. This fiber-type optical structure, with the disordered layer providing randomly scattered light into the gain region and the cylindrical waveguide providing confinement of light, assists the formation of random lasing modes and enables a flexible and efficient way of making random lasers. We found that the RL is sensitive to laser dye concentration in the core region and there exists a fine exponential relationship between the lasing intensity and particle concentration in the gain solution. The proposed structure could be a fine platform of realizing random lasing and random lasing based sensing. PMID:27220636

  11. Advantages of the AlGaN spacer in InAlN high-electron-mobility transistors grown using metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Yamada, Atsushi; Ishiguro, Tetsuro; Kotani, Junji; Tomabechi, Shuichi; Nakamura, Norikazu; Watanabe, Keiji

    2016-05-01

    We demonstrate the advantages of an AlGaN spacer layer in an InAlN high-electron-mobility transistor (HEMT). We investigated the effects of the growth parameters of the spacer layer on electron mobility in InAlN HEMTs grown by metalorganic vapor phase epitaxy, focusing on the surface roughness of the spacer layer and sharpness of the interface with the GaN channel layer. The electron mobility degraded, as evidenced by the formation of a graded AlGaN layer at the top of the GaN channel layer and the surface roughness of the AlN spacer layer. We believe that the short migration length of aluminum atoms is responsible for the observed degradation. An AlGaN spacer layer was employed to suppress the formation of the graded AlGaN layer and improve surface morphology. A high electron mobility of 1550 cm2 V‑1 s‑1 and a low sheet resistance of 211 Ω/sq were achieved for an InAlN HEMT with an AlGaN spacer layer.

  12. The generation of misfit dislocations in facet-controlled growth of AlGaN /GaN films

    NASA Astrophysics Data System (ADS)

    Cherns, D.; Sahonta, S.-L.; Liu, R.; Ponce, F. A.; Amano, H.; Akasaki, I.

    2004-11-01

    The relaxation of tensile stresses in AlGaN layers grown on GaN /(0001)sapphire by facet-controlled epitaxial lateral overgrowth is reported. It is shown that a-type misfit dislocations are introduced at inclined {112¯2} AlGaN /GaN interfaces, with strong evidence for a half-loop nucleation and glide mechanism driven by shear stresses present on the (0001) slip plane. In addition to relieving misfit stresses, these dislocations introduce grain rotations of up to 10-2rad across the AlGaN /GaN boundaries, leading to tilt boundaries at the meeting front between laterally growing wings and between regions growing in the lateral and [0001] directions. The effects of these processes on the defect density in subsequent layers are examined.

  13. Radiation Hard AlGaN Detectors and Imager

    SciTech Connect

    2012-05-01

    Radiation hardness of AlGaN photodiodes was tested using a 65 MeV proton beam with a total proton fluence of 3x10{sup 12} protons/cm{sup 2}. AlGaN Deep UV Photodiode have extremely high radiation hardness. These new devices have mission critical applications in high energy density physics (HEDP) and space explorations. These new devices satisfy radiation hardness requirements by NIF. NSTec is developing next generation AlGaN optoelectronics and imagers.

  14. Influence of substrate miscut angle on surface morphology and luminescence properties of AlGaN

    SciTech Connect

    Kusch, Gunnar Edwards, Paul R.; Bruckbauer, Jochen; Martin, Robert W.; Li, Haoning; Parbrook, Peter J.; Sadler, Thomas C.

    2014-03-03

    The influence of substrate miscut on Al{sub 0.5}Ga{sub 0.5} N layers was investigated using cathodoluminescence (CL) hyperspectral imaging and secondary electron imaging in an environmental scanning electron microscope. The samples were also characterized using atomic force microscopy and high resolution X-ray diffraction. It was found that small changes in substrate miscut have a strong influence on the morphology and luminescence properties of the AlGaN layers. Two different types are resolved. For low miscut angle, a crack-free morphology consisting of randomly sized domains is observed, between which there are notable shifts in the AlGaN near band edge emission energy. For high miscut angle, a morphology with step bunches and compositional inhomogeneities along the step bunches, evidenced by an additional CL peak along the step bunches, are observed.

  15. Relaxation of compressively strained AlGaN by inclined threading dislocations.

    SciTech Connect

    Follstaedt, David Martin; Lee, Stephen Roger; Crawford, Mary Hagerott; Provencio, Paula Polyak; Allerman, Andrew Alan; Floro, Jerrold Anthony

    2005-06-01

    Transmission electron microscopy and x-ray diffraction were used to assess the microstructure and strain of Al{sub x}Ga{sub 1?x}N(x = 0.61-0.64) layers grown on AlN. The compressively-strained AlGaN is partially relaxed by inclined threading dislocations, similar to observations on Si-doped AlGaN by P. Cantu, F. Wu, P. Waltereit, S. Keller, A. E. Romanov, U. K. Mishra, S. P. DenBaars, and J. S. Speck [Appl. Phys. Lett. 83, 674 (2003) ]; however, in our material, the dislocations bend before the introduction of any Si. The bending may be initiated by the greater lattice mismatch or the lower dislocation density of our material, but the presence of Si is not necessarily required. The relaxation by inclined dislocations is quantitatively accounted for with the model of A. E. Romanov and J. S. Speck [Appl. Phys. Lett. 83, 2569 (2003)], and we demonstrate the predicted linear dependence of relaxation on layer thickness. Notably, such relaxation was not found in tensile strained AlGaN grown on GaN [J. A. Floro, D. M. Follstaedt, P. Provencio, S. J. Hearne, and S. R. Lee, J. Appl. Phys. 96, 7087 (2004)], even though the same mechanism appears applicable.

  16. Computational model for residual stresses in a clad plate and clad fracture specimens

    SciTech Connect

    Rybicki, E.F.; Stonesifer, R.B.

    1986-10-01

    This report contains the results from computed residual stresses for three stainless steel clad plate configurations. Each simulates a condition of interest to a study on the effect of surface cracks in the clad layer of reactor pressure vessels. The configurations analyzed were the as-received 118-mm thick clad plate, a 32-mm thick specimen with a full-thickness of cladding weld metal, and a 32-mm thick specimen with a half-thickness of clad layer. The most accurate predictions of the available experimental results were made using the properties of 19Cr-9Ni-Mo-W material. The analytical model assumes that the stresses at the initial condition of 538/sup 0/C for the stress relief anneal are zero. Plastic strains develop during cooling and all subsequent conditions such as machining or temperature changes cause the cladding residual stresses to decrease. In parting-out of specimens from the initial 118-mm thick clad plate, the resulting residual stresses in the clad layer depend upon the sequence of metal removal. If excess base metal is removed first and then somes cladding subsequently removed, the residual stresses in the clad layer are significantly reduced. On the other hand, partial removal of cladding first results in additional plastic deformation in the clad layer and the retention of residual stresses near the material yield strength at the completion of the machining operation.

  17. Engineering lattice matching, doping level, and optical properties of KY(WO4)2:Gd, Lu, Yb layers for a cladding-side-pumped channel waveguide laser

    NASA Astrophysics Data System (ADS)

    Aravazhi, Shanmugam; Geskus, Dimitri; van Dalfsen, Koop; Vázquez-Córdova, Sergio A.; Grivas, Christos; Griebner, Uwe; García-Blanco, Sonia M.; Pollnau, Markus

    2013-05-01

    Single-crystalline KY1- x-y-z GdxLuyYbz(WO4)2 layers are grown onto undoped KY(WO4)2 substrates by liquid-phase epitaxy. The purpose of co-doping the KY(WO4)2 layer with suitable fractions of Gd3+ and Lu3+ is to achieve lattice-matched layers that allow us to engineer a high refractive-index contrast between waveguiding layer and substrate for obtaining tight optical mode confinement and simultaneously accommodate a large range of Yb3+ doping concentrations by replacing Lu3+ ions of similar ionic radius for a variety of optical amplifier or laser applications. Crack-free layers, up to a maximum lattice mismatch of ~0.08 %, are grown with systematic variations of Y3+, Gd3+, Lu3+, and Yb3+ concentrations, their refractive indices are measured at several wavelengths, and Sellmeier dispersion curves are derived. The influence of co-doping on the spectroscopy of Yb3+ is investigated. As evidenced by the experimental results, the lattice constants, refractive indices, and transition cross-sections of Yb3+ in these co-doped layers can be approximated with good accuracy by weighted averages of data from the pure compounds. The obtained information is exploited to fabricate a twofold refractive-index-engineered sample consisting of a highly Yb3+-doped tapered channel waveguide embedded in a passive planar waveguide, and a cladding-side-pumped channel waveguide laser is demonstrated.

  18. Reactor vessel cladding separate effects studies

    SciTech Connect

    Corwin, W.R.

    1985-01-01

    The existence of a layer of tough weld overlay cladding on the interior of a light-water reactor pressure vessel could mitigate damage caused during certain overcooling transients. The potential benefit of the cladding is that it could keep a short surface flaw, which would otherwise become long, from growing either by impeding crack initiation or by arresting a running crack. Two aspects critical to cladding behavior will be reported: irradiation effects on cladding toughness and the response of mechanically loaded, flawed structures in the presence of cladding. 15 refs., 24 figs., 6 tabs.

  19. Radiation damage resistance of AlGaN detectors for applications in the extreme-ultraviolet spectral range

    SciTech Connect

    Barkusky, Frank; Peth, Christian; Bayer, Armin; Mann, Klaus; John, Joachim; Malinowski, Pawel E.

    2009-09-15

    We report on the fabrication of aluminum gallium nitride (AlGaN) Schottky-photodiode-based detectors. AlGaN layers were grown using metal-organic chemical vapor deposition (MOCVD) on Si(111) wafers. The diodes were characterized at a wavelength of 13.5 nm using a table-top extreme-ultraviolet (EUV) radiation source, consisting of a laser-produced xenon plasma and a Schwarzschild objective. The responsivity of the diodes was tested between EUV energies ranging from 320 nJ down to several picojoules. For low fluences, a linear responsivity of 7.14 mAs/J could be determined. Saturation starts at approximately 1 nJ, merging into a linear response of 0.113 mAs/J, which could be attributed to the photoeffect on the Au electrodes on top of the diode. Furthermore, degradation tests were performed up to an absolute dose of 3.3x10{sup 19} photons/cm{sup 2}. AlGaN photodiodes were compared to commercially available silicon-based photodetectors. For AlGaN diodes, responsivity does not change even for the highest EUV dose, whereas the response of the Si diode decreases linearly to {approx}93% after 2x10{sup 19} photons/cm{sup 2}.

  20. Laser Cladding

    NASA Astrophysics Data System (ADS)

    Lepski, Dietrich; Brückner, Frank

    Laser cladding is a modern technology whose uses include, for example, the creation of protective coatings to reduce wear and corrosion on engine parts and tools. The aircraft and automotive industries are examples of industries in which it is much used. This account considers the theory of a number of aspects of the process in detail. The first to be studied is the interaction of the laser beam directly with the powder that is being deposited; the effects of gravity, beam shadowing, and particle heating are investigated. This is followed by a discussion of the mechanisms by which the particles adhere to the surface of the work piece and are absorbed into it. In order to understand the process, a study of the melt pool and the associated temperature distribution is necessary; it is then possible to infer the final bead geometry. An inevitable consequence of a thermal process such as laser cladding is the induced thermal stress and resulting distortion of the work piece. The fundamentals are discussed, a numerical model presented and in addition a simple heuristic model is given. The use of induction-assisted laser cladding as a means of preventing the formation of cracks is discussed.

  1. Solar-blind AlGaN 256x256 p-i-n detectors and focal plane arrays

    NASA Astrophysics Data System (ADS)

    Reine, M. B.; Hairston, A.; Lamarre, P.; Wong, K. K.; Tobin, S. P.; Sood, A. K.; Cooke, C.; Pophristic, M.; Guo, S.; Peres, B.; Singh, R.; Eddy, C. R., Jr.; Chowdhury, U.; Wong, M. M.; Dupuis, R. D.; Li, T.; DenBaars, S. P.

    2006-02-01

    This paper reports the development of aluminum-gallium nitride (AlGaN or Al xGa 1-xN) photodiode technology for high-operability 256×256 hybrid Focal Plane Arrays (FPAs) for solar-blind ultraviolet (UV) detection in the 260-280 nm spectral region. These hybrid UV FPAs consist of a 256×256 back-illuminated AlGaN p-i-n photodiode array, operating at zero bias voltage, bump-mounted to a matching 256×256 silicon CMOS readout integrated circuit (ROIC) chip. The unit cell size is 30×30 μm2. The photodiode arrays were fabricated from multilayer AlGaN films grown by MOCVD on 2" dia. UV-transparent sapphire substrates. Improvements in AlGaN material growth and device design enabled high quantum efficiency and extremely low leakage current to be achieved in high-operability 256×256 p-i-n photodiode arrays with cuton and cutoff wavelengths of 260 and 280 nm, placing the response in the solar-blind wavelength region (less than about 280 nm) where solar radiation is heavily absorbed by the ozone layer. External quantum efficiencies (at V=0, 270 nm, no antireflection coating) as high as 58% were measured in backilluminated devices. A number of 256×256 FPAs, with the AlGaN arrays fabricated from films grown at three different facilities, achieved response operabilities as high as 99.8%, response nonuniformities (σ/μ) as low as 2.5%, and zero-bias resistance median values as high as 1×10 16 ohm, corresponding to R 0A products of 7×10 10 ohm-cm2. Noise Equivalent Irradiance (NEI) data were measured on these FPAs. Median NEI values at 1 Hz are 250-500 photons/pixel-s, with best-element values as low as 90 photons/pixel-s at 1 Hz.

  2. Improved performance in vertical GaN Schottky diode assisted by AlGaN tunneling barrier

    NASA Astrophysics Data System (ADS)

    Cao, Y.; Chu, R.; Li, R.; Chen, M.; Williams, A. J.

    2016-03-01

    In a vertical GaN Schottky barrier diode, the free electron concentration n in the 6-μm-thick drift layer was found to greatly impact the diode reverse leakage current, which increased from 2.1 × 10-7 A to 3.9 × 10-4 A as n increased from 7.5 × 1014 cm-3 to 6.3 × 1015 cm-3 at a reverse bias of 100 V. By capping the drift layer with an ultrathin 5-nm graded AlGaN layer, reverse leakage was reduced by more than three orders of magnitude with the same n in the drift layer. We attribute this to the increased Schottky barrier height with the AlGaN at the surface. Meanwhile, the polarization field within the graded AlGaN effectively shortened the depletion depth, which led to the formation of tunneling current at a relatively small forward bias. The turn-on voltage in the vertical Schottky diodes was reduced from 0.77 V to 0.67 V—an advantage in reducing conduction loss in power switching applications.

  3. Assembly of phosphonic acids on GaN and AlGaN

    NASA Astrophysics Data System (ADS)

    Simpkins, B. S.; Hong, S.; Stine, R.; Mäkinen, A. J.; Theodore, N. D.; Mastro, M. A.; Eddy, C. R., Jr.; Pehrsson, P. E.

    2010-01-01

    Self-assembled monolayers of octadecylphosphonic acid and 16-phosphonohexadecanoic acid (PHDA) were formed on the semiconductor substrates gallium nitride (GaN) and aluminium gallium nitride (AlGaN). The presence of the molecular layers was verified through x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. Structural information was acquired with infrared spectroscopy which verified the bonding orientation of the carboxyl-containing PHDA. The impact of the molecular layers on the channel conductivity and the surface electronic structure of an AlGaN/GaN heterostructure was measured. Our results indicate that pinning of the surface Fermi level prohibits modification of the channel conductivity by the layer. However, a surface dipole of ~0.8 eV is present and associated with both phosphonic acid layers. These results are of direct relevance to field-effect-based biochemical sensors and metal-semiconductor contact formation for this system and provide a fundamental basis for further applications of GaN and AlGaN technology in the fields of biosensing and microelectronics.

  4. Process development for cladding APT tungsten targets

    SciTech Connect

    Horner, M H; Barber, R; Dalder, E

    2000-11-27

    This report describes development of processes for cladding APT Target tungsten components with a thin layer (0.127-mm) of Alloy 718, Alloy 600 or 316L stainless steel alloy. The application requires that the cladding be thermally bonded to the tungsten in order to transfer heat generated in the tungsten volume to a surrounding coolant. High temperature diffusion bonding using the hot isostatic processing (HIP) technique was selected as the method for creating a metallurgical bond between pure tungsten tubes and rods and the cladding materials. Bonding studies using a uniaxially loaded vacuum hot press were conducted in preliminary experiments to determine acceptable time-temperature conditions for diffusion bonding. The results were successfully applied in cladding tungsten rods and tubes with these alloys. Temperatures 800-810 C were suitable for cladding tungsten with Alloy 600 and 316L stainless steel alloy, whereas tungsten was clad with Alloy 718 at 1020 C.

  5. On the increased efficiency in InGaN-based multiple quantum wells emitting at 530-590 nm with AlGaN interlayers

    NASA Astrophysics Data System (ADS)

    Koleske, D. D.; Fischer, A. J.; Bryant, B. N.; Kotula, P. G.; Wierer, J. J.

    2015-04-01

    InGaN/AlGaN/GaN-based multiple quantum wells (MQWs) with AlGaN interlayers (ILs) are investigated, specifically to examine the fundamental mechanisms behind their increased radiative efficiency at wavelengths of 530-590 nm. The AlzGa1-zN (z~0.38) IL is ~1-2 nm thick, and is grown after and at the same growth temperature as the ~3 nm thick InGaN quantum well (QW). This is followed by an increase in temperature for the growth of a ~10 nm thick GaN barrier layer. The insertion of the AlGaN IL within the MQW provides various benefits. First, the AlGaN IL allows for growth of the InxGa1-xN QW well below typical growth temperatures to achieve higher x (up to~0.25). Second, annealing the IL capped QW prior to the GaN barrier growth improves the AlGaN IL smoothness as determined by atomic force microscopy, improves the InGaN/AlGaN/GaN interface quality as determined from scanning transmission electron microscope images and x-ray diffraction, and increases the radiative efficiency by reducing non-radiative defects as determined by time-resolved photoluminescence measurements. Finally, the AlGaN IL increases the spontaneous and piezoelectric polarization induced electric fields acting on the InGaN QW, providing an additional red-shift to the emission wavelength as determined by Schrodinger-Poisson modeling and fitting to the experimental data. The relative impact of increased indium concentration and polarization fields on the radiative efficiency of MQWs with AlGaN ILs is explored along with implications to conventional longer wavelength emitters.

  6. Effect of V/III ratio on the growth of (11 2 bar 2) AlGaN by metalorganic vapour phase epitaxy

    NASA Astrophysics Data System (ADS)

    Dinh, Duc V.; Alam, S. N.; Parbrook, P. J.

    2016-02-01

    The effect of V/III ratio on the growth and properties of AlGaN layers grown on (112bar2) AlN templates grown on (101bar0) sapphire by metalorganic vapour phase epitaxy was studied. The surface morphology of the (112bar2) AlGaN layers and the (112bar2) AlN templates showed an undulation along [ 1 1 bar 00 ] AlGaN , AlN. The Al-content and thickness of the layers increased with decreasing V/III ratio due to a reduction in the parasitic reactions of the precursors. The Al-content of the (112bar2) layers was found to be in the range of 29.5-47.9%, which is lower than the composition of the simultaneously grown (0001) reference layers (30.4-58.0%). This was attributed to a higher density of cation (nitrogen) dangling bonds on the (112bar2) surface. Low temperature photoluminescence measurements of the (112bar2) layers showed an emission wavelength that shifts gradually from 273 nm to 306 nm with increasing V/III ratio. A decreased PL intensity of the layers with decreasing V/III ratio was attributed to an increase in cation vacancies. The Stokes-shift of the (112bar2) layers was estimated to be about 60-194 meV, and this shift increases with increasing Al-content (decreasing V/III ratio) correlated to an increased exciton localization.

  7. Onset of surface stimulated emission at 260 nm from AlGaN multiple quantum wells

    SciTech Connect

    Li, Xiaohang E-mail: dupuis@gatech.edu; Xie, Hongen; Ponce, Fernando A.; Ryou, Jae-Hyun; Detchprohm, Theeradetch; Dupuis, Russell D. E-mail: dupuis@gatech.edu

    2015-12-14

    We demonstrated onset of deep-ultraviolet (DUV) surface stimulated emission (SE) from c-plane AlGaN multiple-quantum well (MQW) heterostructures grown on a sapphire substrate by optical pumping at room temperature. The onset of SE became observable at a pumping power density of 630 kW/cm{sup 2}. Spectral deconvolution revealed superposition of a linearly amplified spontaneous emission peak at λ ∼ 257.0 nm with a full width at half maximum (FWHM) of ∼12 nm and a superlinearly amplified SE peak at λ ∼ 260 nm with a narrow FWHM of less than 2 nm. In particular, the wavelength of ∼260 nm is the shortest wavelength of surface SE from III-nitride MQW heterostructures to date. Atomic force microscopy and scanning transmission electron microscopy measurements were employed to investigate the material and structural quality of the AlGaN heterostructures, showing smooth surface and sharp layer interfaces. This study offers promising results for AlGaN heterostructures grown on sapphire substrates for the development of DUV vertical cavity surface emitting lasers (VCSELs)

  8. Nuclear fuel elements having a composite cladding

    DOEpatents

    Gordon, Gerald M.; Cowan, II, Robert L.; Davies, John H.

    1983-09-20

    An improved nuclear fuel element is disclosed for use in the core of nuclear reactors. The improved nuclear fuel element has a composite cladding of an outer portion forming a substrate having on the inside surface a metal layer selected from the group consisting of copper, nickel, iron and alloys of the foregoing with a gap between the composite cladding and the core of nuclear fuel. The nuclear fuel element comprises a container of the elongated composite cladding, a central core of a body of nuclear fuel material disposed in and partially filling the container and forming an internal cavity in the container, an enclosure integrally secured and sealed at each end of said container and a nuclear fuel material retaining means positioned in the cavity. The metal layer of the composite cladding prevents perforations or failures in the cladding substrate from stress corrosion cracking or from fuel pellet-cladding interaction or both. The substrate of the composite cladding is selected from conventional cladding materials and preferably is a zirconium alloy.

  9. Cladding Alloys for Fluoride Salt Compatibility

    SciTech Connect

    Muralidharan, Govindarajan; Wilson, Dane F; Walker, Larry R; Santella, Michael L; Holcomb, David Eugene

    2011-06-01

    This report provides an overview of several candidate technologies for cladding nickel-based corrosion protection layers onto high-temperature structural alloys. The report also provides a brief overview of the welding and weld performance issues associated with joining nickel-clad nickel-based alloys. From the available techniques, two cladding technologies were selected for initial evaluation. The first technique is a line-of-sight method that would be useful for cladding large structures such as vessel interiors or large piping. The line-of-sight method is a laser-based surface cladding technique in which a high-purity nickel powder mixed into a polymer binder is first sprayed onto the surface, baked, and then rapidly melted using a high-power laser. The second technique is a vapor phase technique based on the nickel-carbonyl process that is suitable for cladding inaccessible surfaces such as the interior surfaces of heat exchangers. An initial evaluation for performed on the quality of nickel claddings processed using the two selected cladding techniques.

  10. Solar-blind AlGaN 256×256 p-i-n detectors and focal plane arrays

    NASA Astrophysics Data System (ADS)

    Reine, M. B.; Hairston, A.; Lamarre, P.; Wong, K. K.; Tobin, S. P.; Sood, A. K.; Cooke, C.; Pophristic, M.; Guo, S.; Peres, B.; Singh, R.; Eddy, C. R. _Jr., Jr.; Chowdhury, U.; Wong, M. M.; Dupuis, R. D.; Li, T.; DenBaars, S. P.

    2006-02-01

    This paper reports the development of aluminum-gallium nitride (AlGaN or Al xGa 1-xN) photodiode technology for high-operability 256×256 hybrid Focal Plane Arrays (FPAs) for solar-blind ultraviolet (UV) detection in the 260-280 nm spectral region. These hybrid UV FPAs consist of a 256×256 back-illuminated AlGaN p-i-n photodiode array, operating at zero bias voltage, bump-mounted to a matching 256×256 silicon CMOS readout integrated circuit (ROIC) chip. The unit cell size is 30×30 μm2. The photodiode arrays were fabricated from multilayer AlGaN films grown by MOCVD on 2" dia. UV-transparent sapphire substrates. Improvements in AlGaN material growth and device design enabled high quantum efficiency and extremely low leakage current to be achieved in high-operability 256×256 p-i-n photodiode arrays with cuton and cutoff wavelengths of 260 and 280 nm, placing the response in the solar-blind wavelength region (less than about 280 nm) where solar radiation is heavily absorbed by the ozone layer. External quantum efficiencies (at V=0, 270 nm, no antireflection coating) as high as 58% were measured in back-illuminated devices. A number of 256×256 FPAs, with the AlGaN arrays fabricated from films grown at three different facilities, achieved response operabilities as high as 99.8%, response nonuniformities (σ/μ) as low as 2.5%, and zero-bias resistance median values as high as 1×10 16 ohm, corresponding to R0A products of 7×10 10 ohm-cm2. Noise Equivalent Irradiance (NEI) data were measured on these FPAs. Median NEI values at 1 Hz are 250-500 photons/pixel-s, with best-element values as low as 90 photons/pixel-s at 1 Hz.

  11. Electrical Properties of Recessed Algan/Gan Schottky Diodes Under off-State Stress

    NASA Astrophysics Data System (ADS)

    Florovič, Martin; Kováč, Jaroslav; Benko, Peter; Chvála, Aleš; Škriniarová, Jaroslava; Kordó, Peter

    2014-09-01

    Electrical properties of recessed and non-recessed AlGaN/GaN Schottky diodes under off-state stress were investigated. The samples were consecutively stressed by the stepped negative bias (-60 V). Before and after the stress I-V and C-V characteristics were evaluated to verify the device degradation process. Finally, the degradation mechanism and the influence of AlGaN recessed layer thickness on the electrical properties of the Schottky diodes were analysed. It was found that the short time stress influence on I-V characteristics was most negligible for the non-recessed sample. Shallow and deep recessed samples exhibited initial trap filling and reverse current decrease. Generally it was found that the stress voltage near 60 V caused recoverable device degradation

  12. Nuclear reactor fuel element with vanadium getter on cladding

    DOEpatents

    Johnson, Carl E.; Carroll, Kenneth G.

    1977-01-01

    A nuclear reactor fuel element is described which has an outer cladding, a central core of fissionable or mixed fissionable and fertile fuel material and a layer of vanadium as an oxygen getter on the inner surface of the cladding. The vanadium reacts with oxygen released by the fissionable material during irradiation of the core to prevent the oxygen from reacting with and corroding the cladding. Also described is a method for coating the inner surface of small diameter tubes of cladding with a layer of vanadium.

  13. GaInN light-emitting diodes using separate epitaxial growth for the p-type region to attain polarization-inverted electron-blocking layer, reduced electron leakage, and improved hole injection

    SciTech Connect

    Meyaard, David S. Lin, Guan-Bo; Ma, Ming; Fred Schubert, E.; Cho, Jaehee; Han, Sang-Heon; Kim, Min-Ho; Shim, HyunWook; Sun Kim, Young

    2013-11-11

    A GaInN light-emitting diode (LED) structure is analyzed that employs a separate epitaxial growth for the p-type region, i.e., the AlGaN electron-blocking layer (EBL) and p-type GaN cladding layer, followed by wafer or chip bonding. Such LED structure has a polarization-inverted EBL and allows for uncompromised epitaxial-growth optimization of the p-type region, i.e., without the need to consider degradation of the quantum-well active region during p-type region growth. Simulations show that such an LED structure reduces electron leakage, reduces the efficiency droop, improves hole injection, and has the potential to extend high efficiencies into the green spectral region.

  14. Hot Forging of a Cladded Component by Automated GMAW Process

    NASA Astrophysics Data System (ADS)

    Rafiq, Muhammad; Langlois, Laurent; Bigot, Régis

    2011-01-01

    Weld cladding is employed to improve the service life of engineering components by increasing corrosion and wear resistance and reducing the cost. The acceptable multi-bead cladding layer depends on single bead geometry. Hence, in first step, the relationship between input process parameters and the single bead geometry is studied and in second step a comprehensive study on multi bead clad layer deposition is carried out. This paper highlights an experimental study carried out to get single layer cladding deposited by automated Gas Metal Arc Welding (GMAW) process and to find the possibility of hot forming of the cladded work piece to get the final hot formed improved structure. GMAW is an arc welding process that uses an arc between a consumable electrode and the welding pool with an external shielding gas and the cladding is done by alongside deposition of weld beads. The experiments for single bead were conducted by varying the three main process parameters wire feed rate, arc voltage and welding speed while keeping other parameters like nozzle to work distance, shielding gas and its flow rate and torch angle constant. The effect of bead spacing and torch orientation on the cladding quality of single layer from the results of single bead deposition was studied. Effect of the dilution rate and nominal energy on the cladded layer hot bending quality was also performed at different temperatures.

  15. Electroslag Strip Cladding of Steam Generators With Alloy 690

    SciTech Connect

    Consonni, M.; Maggioni, F.; Brioschi, F.

    2006-07-01

    The present paper details the results of electroslag cladding and tube-to-tubesheet welding qualification tests conducted by Ansaldo-Camozzi ESC with Alloy 690 (Alloy 52 filler metal) on steel for nuclear power stations' steam generators shell, tubesheet and head; the possibility of submerged arc cladding on first layer was also considered. Test results, in terms of chemical analysis, mechanical properties and microstructure are reproducible and confidently applicable to production cladding and show that electroslag process can be used for Alloy 52 cladding with exceptionally stable and regular operation and high productivity. The application of submerged arc cladding process to the first layer leads to a higher base metal dilution, which should be avoided. Moreover, though the heat affected zone is deeper with electroslag cladding, in both cases no coarsened grain zone is found due to recrystallization effect of second cladding layer. Finally, the application of electroslag process to cladding of Alloy 52 with modified chemical composition, was proved to be highly beneficial as it strongly reduces hot cracking sensitivity, which is typical of submerged arc cladded Alloy 52, both during tube-to-tubesheet welding and first re-welding. (authors)

  16. Growth of AlGaN on silicon substrates: a novel way to make back-illuminated ultraviolet photodetectors

    NASA Astrophysics Data System (ADS)

    McClintock, Ryan; Razeghi, Manijeh

    2015-08-01

    AlGaN, with its tunable wide-bandgap is a good choice for the realization of ultraviolet photodetectors. AlGaN films tend to be grown on foreign substrates such as sapphire, which is the most common choice for back-illuminated devices. However, even ultraviolet opaque substrates like silicon holds promise because, silicon can be removed by chemical treatment to allow back-illumination,1 and it is a very low-cost substrate which is available in large diameters up to 300 mm. However, Implementation of silicon as the solar-blind PD substrates requires overcoming the lattice-mismatch (17%) with the AlxGa1-xN that leads to high density of dislocation and crack-initiating stress. In this talk, we report the growth of thick crack-free AlGaN films on (111) silicon substrates through the use of a substrate patterning and mask-less selective area regrowth. This technique is critical as it decouples the epilayers and the substrate and allows for crack-free growth; however, the masking also helps to reduce the dislocation density by inclining the growth direction and encouraging dislocations to annihilate. A back-illuminated p-i-n PD structure is subsequently grown on this high quality template layer. After processing and hybridizing the device we use a chemical process to selectively remove the silicon substrate. This removal has minimal effect on the device, but it removes the UV-opaque silicon and allows back-illumination of the photodetector. We report our latest results of back-illuminated solar-blind photodetectors growth on silicon.

  17. Dual Band Deep Ultraviolet AlGaN Photodetectors

    NASA Technical Reports Server (NTRS)

    Aslam, S.; Miko, L.; Stahle, C.; Franz, D.; Pugel, D.; Guan, B.; Zhang, J. P.; Gaska, R.

    2007-01-01

    We report on the design, fabrication and characterization of a back-illuminated voltage bias selectable dual-band AlGaN UV photodetector. The photodetector can separate UVA and W-B band radiation by bias switching a two terminal n-p-n homojunction structure that is fabricated in the same pixel. When a forward bias is applied between the top and bottom electrodes, the detector can sense UV-A and reject W-B band radiation. Alternatively, under reverse bias, the photodetector can sense UV-B and reject UV-A band radiation.

  18. Research on Microstructure and Property of Fe-VC Composite Material Made by Laser Cladding

    NASA Astrophysics Data System (ADS)

    Zhang, Wei

    The experiment of laser cladding on the surface of H13 steel was made. Vanadium carbide (VC) powder and Fe-base alloy powder were used as cladding material. The microstructure and property of laser cladding layer were studied. The research showed that laser cladding layer had better properties such as minute crystals, deeper layer, higher hardness and good metallurgical bonding with base metal. The average hardness of cladding zone was 900HV0.2. The average hardness of cladding layer increased five times than that of base material. H13 steel was widely used in the field of hot dies. Using laser cladding, the good wear layer would greatly increase the mold useful life.

  19. Enhancement of optical polarization degree of AlGaN quantum wells by using staggered structure.

    PubMed

    Wang, Weiying; Lu, Huimin; Fu, Lei; He, Chenguang; Wang, Mingxing; Tang, Ning; Xu, Fujun; Yu, Tongjun; Ge, Weikun; Shen, Bo

    2016-08-01

    Staggered AlGaN quantum wells (QWs) are designed to enhance the transverse-electric (TE) polarized optical emission in deep ultraviolet (DUV) light- emitting diodes (LED). The optical polarization properties of the conventional and staggered AlGaN QWs are investigated by a theoretical model based on the k·p method as well as polarized photoluminescence (PL) measurements. Based on an analysis of the valence subbands and momentum matrix elements, it is found that AlGaN QWs with step-function-like Al content in QWs offers much stronger TE polarized emission in comparison to that from conventional AlGaN QWs. Experimental results show that the degree of the PL polarization at room temperature can be enhanced from 20.8% of conventional AlGaN QWs to 40.2% of staggered AlGaN QWs grown by MOCVD, which is in good agreement with the theoretical simulation. It suggests that polarization band engineering via staggered AlGaN QWs can be well applied in high efficiency AlGaN-based DUV LEDs. PMID:27505782

  20. A metallurgical analysis of laser-clad H13

    SciTech Connect

    Koch, J.; Hetzner, D.; Mazumder, J.

    1996-12-31

    Rapid prototyping and rapid manufacturing processes are being employed to decrease the time required to develop new products. Laser cladding can be used to produce metal parts directly from CAD drawings. To apply this technology, multiple layers of metal clad are first deposited on a substrate. The clad is then tempered or annealed at periodic stages throughout the buildup process and also prior to machining. The component is then hardened and tempered by conventional heat treating procedures and ground or machined to final size. This investigation considers the response of the clad and base metal to this series of processing variables. H13, an air hardening die steel, was selected for the clads and the base metal. This alloy is commonly used for hot working dies. The response of the clad and substrate to the various heat treatments was evaluated.

  1. Roll Casting of Aluminum Alloy Clad Strip

    SciTech Connect

    Nakamura, R.; Tsuge, H.; Haga, T.; Watari, H.; Kumai, S.

    2011-01-17

    Casting of aluminum alloy three layers of clad strip was tried using the two sets of twin roll casters, and effects of the casting parameters on the cladding conditions were investigated. One twin roll caster was mounted on the other twin roll caster. Base strip was 8079 aluminum alloy and overlay strips were 6022 aluminum alloy. Effects of roll-load of upper and lower casters and melt temperature of the lower caster were investigated. When the roll-load of the upper and lower caster was large enough, the overlay strip could be solidified and be connected. The overlay strip could be connected when the melt of the overlay strip cast by the lower caster was low enough. Sound three layers of clad strip could be cast by proper conditions.

  2. An electrically injected AlGaN nanowire laser operating in the ultraviolet-C band

    SciTech Connect

    Zhao, S.; Liu, X.; Kang, J.; Mi, Z.; Woo, S. Y.; Botton, G. A.

    2015-07-27

    We have investigated the molecular beam epitaxial growth and characterization of nearly defect-free AlGaN nanowire heterostructures grown directly on Si substrate. By exploiting the Anderson localization of light, we have demonstrated electrically injected AlGaN nanowire lasers that can operate at 262.1 nm. The threshold current density is 200 A/cm{sup 2} at 77 K. The relatively low threshold current is attributed to the high Q-factor of the random cavity and the three-dimensional quantum confinement offered by the atomic-scale composition modulation in self-organized AlGaN nanowires.

  3. Efficient charge carrier injection into sub-250 nm AlGaN multiple quantum well light emitting diodes

    NASA Astrophysics Data System (ADS)

    Mehnke, Frank; Kuhn, Christian; Guttmann, Martin; Reich, Christoph; Kolbe, Tim; Kueller, Viola; Knauer, Arne; Lapeyrade, Mickael; Einfeldt, Sven; Rass, Jens; Wernicke, Tim; Weyers, Markus; Kneissl, Michael

    2014-08-01

    The design and Mg-doping profile of AlN/Al0.7Ga0.3N electron blocking heterostructures (EBH) for AlGaN multiple quantum well (MQW) light emitting diodes (LEDs) emitting below 250 nm was investigated. By inserting an AlN electron blocking layer (EBL) into the EBH, we were able to increase the quantum well emission power and significantly reduce long wavelength parasitic luminescence. Furthermore, electron leakage was suppressed by optimizing the thickness of the AlN EBL while still maintaining sufficient hole injection. Ultraviolet (UV)-C LEDs with very low parasitic luminescence (7% of total emission power) and external quantum efficiencies of 0.19% at 246 nm have been realized. This concept was applied to AlGaN MQW LEDs emitting between 235 nm and 263 nm with external quantum efficiencies ranging from 0.002% to 0.93%. After processing, we were able to demonstrate an UV-C LED emitting at 234 nm with 14.5 μW integrated optical output power and an external quantum efficiency of 0.012% at 18.2 A/cm2.

  4. Efficient charge carrier injection into sub-250 nm AlGaN multiple quantum well light emitting diodes

    SciTech Connect

    Mehnke, Frank Kuhn, Christian; Guttmann, Martin; Reich, Christoph; Kolbe, Tim; Rass, Jens; Wernicke, Tim; Kueller, Viola; Knauer, Arne; Lapeyrade, Mickael; Einfeldt, Sven; Weyers, Markus; Kneissl, Michael

    2014-08-04

    The design and Mg-doping profile of AlN/Al{sub 0.7}Ga{sub 0.3}N electron blocking heterostructures (EBH) for AlGaN multiple quantum well (MQW) light emitting diodes (LEDs) emitting below 250 nm was investigated. By inserting an AlN electron blocking layer (EBL) into the EBH, we were able to increase the quantum well emission power and significantly reduce long wavelength parasitic luminescence. Furthermore, electron leakage was suppressed by optimizing the thickness of the AlN EBL while still maintaining sufficient hole injection. Ultraviolet (UV)-C LEDs with very low parasitic luminescence (7% of total emission power) and external quantum efficiencies of 0.19% at 246 nm have been realized. This concept was applied to AlGaN MQW LEDs emitting between 235 nm and 263 nm with external quantum efficiencies ranging from 0.002% to 0.93%. After processing, we were able to demonstrate an UV-C LED emitting at 234 nm with 14.5 μW integrated optical output power and an external quantum efficiency of 0.012% at 18.2 A/cm{sup 2}.

  5. Microscopic Morphology and Microstructure of Ti-N and Ti-Ni Phase Between the Dilution Zone and the Clad Zone in Laser Remelting NiCrBSi/TiN Layer on Ti-6Al-4V Alloy Surface

    NASA Astrophysics Data System (ADS)

    Liu, Rongxiang; Guo, Lixin; Lei, Tingquan

    The microscopic morphology and microstructure of Ti-N and Ti-Ni phase between the dilution zone and the clad zone in laser remelting NiCrBSi/TiN layer on a Ti-6Al-4V alloy were characterized using TEM and SEM. The experimental results showed that during laser irradiation heating, TiN particles were partially dissolved into the melted Ni-base alloy, and the dissolved Ti and N atoms were precipitated in the form of TiN, TiN0.3. Ti exhibits height activity, it combines with Ni forming Ti2Ni, TiNi matrix intermetallic during laser remelting, faults exist in the Ti2Ni and TiNi phase, and crystal lattice of TiNi phase is superlattice. Lastly, the cause of the formation of the Ti-N and Ti-Ni phase is discussed.

  6. A comparison of the 60Co gamma radiation hardness, breakdown characteristics and the effect of SiN x capping on InAlN and AlGaN HEMTs for space applications

    NASA Astrophysics Data System (ADS)

    Smith, M. D.; O'Mahony, D.; Vitobello, F.; Muschitiello, M.; Costantino, A.; Barnes, A. R.; Parbrook, P. J.

    2016-02-01

    Electrical performance and stability of InAlN and AlGaN high electron mobility transistors (HEMTs) subjected 9.1 mrad of 60Co gamma radiation and off-state voltage step-stressing until breakdown are reported. Comparison with commercially available production-level AlGaN HEMT devices, which showed negligible drift in DC performance throughout all experiments, suggests degradation mechanisms must be managed and suppressed through development of advanced epitaxial and surface passivation techniques in order to fully exploit the robustness of the III-nitride material system. Of the research level devices without dielectric layer surface capping, InAlN HEMTs exhibited the greater stability compared with AlGaN under off-state bias stressing and gamma irradiation in terms of their DC characteristics, although AlGaN HEMTs had significantly higher breakdown voltages. The effect of plasma-enhanced chemical vapour deposition SiN x surface capping is explored, highlighting the sensitivity of InAlN HEMT performance to surface passivation techniques. InAlN-SiN x HEMTs suffered more from trap related degradation than AlGaN-SiN x devices in terms of radiation hardness and step-stress characteristics, attributed to an increased capturing of carriers in traps at the InAlN/SiN x interface.

  7. MOCVD growth of AlGaN UV LEDs

    SciTech Connect

    Han, J.; Crawford, M.H.

    1998-09-01

    Issues related to the MOCVD growth of AlGaN, specifically the gas-phase parasitic reactions among TMG, TMA, and NH{sub 3}, are studied using an in-situ optical reflectometer. It is observed that the presence of the well-known gas phase adduct (TMA: NH{sub 3}) could seriously hinder the incorporation behavior of TMGa. Relatively low reactor pressures (30--50 Torr) are employed to grow an AlGaN/GaN SCH QW p-n diode structure. The UV emission at 360 nm (FWHM {approximately} 10 nm) represents the first report of LED operation from an indium-free GaN QW diode.

  8. Initial Cladding Condition

    SciTech Connect

    E. Siegmann

    2000-08-22

    The purpose of this analysis is to describe the condition of commercial Zircaloy clad fuel as it is received at the Yucca Mountain Project (YMP) site. Most commercial nuclear fuel is encased in Zircaloy cladding. This analysis is developed to describe cladding degradation from the expected failure modes. This includes reactor operation impacts including incipient failures, potential degradation after reactor operation during spent fuel storage in pool and dry storage and impacts due to transportation. Degradation modes include cladding creep, and delayed hydride cracking during dry storage and transportation. Mechanical stresses from fuel handling and transportation vibrations are also included. This Analysis and Model Report (AMR) does not address any potential damage to assemblies that might occur at the YMP surface facilities. Ranges and uncertainties have been defined. This analysis will be the initial boundary condition for the analysis of cladding degradation inside the repository. In accordance with AP-2.13Q, ''Technical Product Development Planning'', a work plan (CRWMS M&O 2000c) was developed, issued, and utilized in the preparation of this document. There are constraints, caveats and limitations to this analysis. This cladding degradation analysis is based on commercial Pressurized Water Reactor (PWR) fuel with Zircaloy cladding but is applicable to Boiling Water Reactor (BWR) fuel. Reactor operating experience for both PWRs and BWRs is used to establish fuel reliability from reactor operation. It is limited to fuel exposed to normal operation and anticipated operational occurrences (i.e. events which are anticipated to occur within a reactor lifetime), and not to fuel that has been exposed to severe accidents. Fuel burnup projections have been limited to the current commercial reactor licensing environment with restrictions on fuel enrichment, oxide coating thickness and rod plenum pressures. The information provided in this analysis will be used in

  9. Explosive Welding and Cladding

    NASA Astrophysics Data System (ADS)

    Meuken, D.; Carton, E. P.

    2004-07-01

    Explosive welding or cladding is usually performed on relative thick plates by means of a large scale parallel plate set-up. At TNO-PML several of the explosive welding configurations that were developed mainly in the nineteen sixties and seventies are being investigated for their potential use in modern industrial applications. Configurations for explosive cladding of curved surfaces such as tubes and rods are also being examined. This can be used to make special bimetallic heat exchanger tubes, or for the protection of electrodes that are used in electrolysis. Explosive line and seam welding are important bonding techniques that allow the welding of both similar and dissimilar metal plates and sheets. Here, bonding occurs over a small overlapping fraction of the two surfaces. This requires only a small amount of explosive (e.g. 5 g/m for line welds in thin ductile sheets). Explosive foil cladding can be used as an alternative coating technique. Plates that are clad with a foil on one or both sides were fabricated in one process step. They can be further machined or deformed using conventional techniques, due to the ductility of the bond and clad material.

  10. Effect of Specific Energy Input on Microstructure and Mechanical Properties of Nickel-Base Intermetallic Alloy Deposited by Laser Cladding

    NASA Astrophysics Data System (ADS)

    Awasthi, Reena; Kumar, Santosh; Chandra, Kamlesh; Vishwanadh, B.; Kishore, R.; Viswanadham, C. S.; Srivastava, D.; Dey, G. K.

    2012-12-01

    This article describes the microstructural features and mechanical properties of nickel-base intermetallic alloy laser-clad layers on stainless steel-316 L substrate, with specific attention on the effect of laser-specific energy input (defined as the energy required per unit of the clad mass, kJ/g) on the microstructure and properties of the clad layer, keeping the other laser-cladding parameters same. Defect-free clad layers were observed, in which various solidified zones could be distinguished: planar crystallization near the substrate/clad interface, followed by cellular and dendritic morphology towards the surface of the clad layer. The clad layers were characterized by the presence of a hard molybdenum-rich hexagonal close-packed (hcp) intermetallic Laves phase dispersed in a relatively softer face-centered cubic (fcc) gamma solid solution or a fine lamellar eutectic phase mixture of an intermetallic Laves phase and gamma solid solution. The microstructure and properties of the clad layers showed a strong correlation with the laser-specific energy input. As the specific energy input increased, the dilution of the clad layer increased and the microstructure changed from a hypereutectic structure (with a compact dispersion of characteristic primary hard intermetallic Laves phase in eutectic phase mixture) to near eutectic or hypoeutectic structure (with reduced fraction of primary hard intermetallic Laves phase) with a corresponding decrease in the clad layer hardness.

  11. Compact cladding-pumped planar waveguide amplifier and fabrication method

    DOEpatents

    Bayramian, Andy J.; Beach, Raymond J.; Honea, Eric; Murray, James E.; Payne, Stephen A.

    2003-10-28

    A low-cost, high performance cladding-pumped planar waveguide amplifier and fabrication method, for deployment in metro and access networks. The waveguide amplifier has a compact monolithic slab architecture preferably formed by first sandwich bonding an erbium-doped core glass slab between two cladding glass slabs to form a multi-layer planar construction, and then slicing the construction into multiple unit constructions. Using lithographic techniques, a silver stripe is deposited and formed at a top or bottom surface of each unit construction and over a cross section of the bonds. By heating the unit construction in an oven and applying an electric field, the silver stripe is then ion diffused to increase the refractive indices of the core and cladding regions, with the diffusion region of the core forming a single mode waveguide, and the silver diffusion cladding region forming a second larger waveguide amenable to cladding pumping with broad area diodes.

  12. All AlGaN epitaxial structure solar-blind avalanche photodiodes with high efficiency and high gain

    NASA Astrophysics Data System (ADS)

    Wu, Hualong; Wu, Weicong; Zhang, Hongxian; Chen, Yingda; Wu, Zhisheng; Wang, Gang; Jiang, Hao

    2016-05-01

    Solar-blind avalanche photodiodes were fabricated with an all AlGaN-based epitaxial structure on sapphire by metal–organic chemical vapor deposition. The devices demonstrate a maximum responsivity of 114.1 mA/W at 278 nm and zero bias, corresponding to an external quantum efficiency (EQE) of 52.7%. The EQE improves to 64.8% under a bias of ‑10 V. Avalanche gain higher than 2 × 104 was obtained at a bias of ‑140 V. The high performance is attributed to the all AlGaN-based p–i–n structure comprised of undoped and Si-doped n-type Al0.4Ga0.6N on a high quality AlN layer and highly conductive p-type AlGaN grown with In-surfactant-assisted Mg-delta doping.

  13. Dependence of radiative and nonradiative recombination on carrier density and Al content in thick AlGaN epilayers

    NASA Astrophysics Data System (ADS)

    Podlipskas, Ž.; Aleksiejūnas, R.; Kadys, A.; Mickevičius, J.; Jurkevičius, J.; Tamulaitis, G.; Shur, M.; Shatalov, M.; Yang, J.; Gaska, R.

    2016-04-01

    Dynamics of radiative and nonradiative recombination of non-equilibrium carriers is investigated in thick AlGaN epitaxial layers with Al content ranging from 0.11 to 0.71. The internal quantum efficiency (IQE) in the epilayers was obtained using two approaches: either estimated from PL measurements or calculated using the recombination coefficients of a simple ABC model, retrieved by fitting the kinetics of light induced transient gratings (LITG). At photoexcited carrier densities below ~1019 cm-3, both approaches provided similar IQE values indicating that the simple ABC model is applicable to analyze carrier recombination at such carrier densities. The increase in IQE at higher carrier densities slowed down for the values extracted from PL considerably faster than for those obtained from LITG transients. This discrepancy is explained in terms of the mixed nature of the rate coefficient B caused by the onset of the density-activated nonradiative recombination at high carrier densities.

  14. Catalytic activity of enzymes immobilized on AlGaN /GaN solution gate field-effect transistors

    NASA Astrophysics Data System (ADS)

    Baur, B.; Howgate, J.; von Ribbeck, H.-G.; Gawlina, Y.; Bandalo, V.; Steinhoff, G.; Stutzmann, M.; Eickhoff, M.

    2006-10-01

    Enzyme-modified field-effect transistors (EnFETs) were prepared by immobilization of penicillinase on AlGaN /GaN solution gate field-effect transistors. The influence of the immobilization process on enzyme functionality was analyzed by comparing covalent immobilization and physisorption. Covalent immobilization by Schiff base formation on GaN surfaces modified with an aminopropyltriethoxysilane monolayer exhibits high reproducibility with respect to the enzyme/substrate affinity. Reductive amination of the Schiff base bonds to secondary amines significantly increases the stability of the enzyme layer. Electronic characterization of the EnFET response to penicillin G indicates that covalent immobilization leads to the formation of an enzyme (sub)monolayer.

  15. Measurement and simulation of top- and bottom-illuminated solar-blind AlGaN metal-semiconductor-metal photodetectors with high external quantum efficiencies

    SciTech Connect

    Brendel, Moritz Helbling, Markus; Knigge, Andrea; Brunner, Frank; Weyers, Markus

    2015-12-28

    A comprehensive study on top- and bottom-illuminated Al{sub 0.5}Ga{sub 0.5}N/AlN metal-semiconductor-metal (MSM) photodetectors having different AlGaN absorber layer thickness is presented. The measured external quantum efficiency (EQE) shows pronounced threshold and saturation behavior as a function of applied bias voltage up to 50 V reaching about 50% for 0.1 μm and 67% for 0.5 μm thick absorber layers under bottom illumination. All experimental findings are in very good accordance with two-dimensional drift-diffusion modeling results. By taking into account macroscopic polarization effects in the hexagonal metal-polar +c-plane AlGaN/AlN heterostructures, new insights into the general device functionality of AlGaN-based MSM photodetectors are obtained. The observed threshold/saturation behavior is caused by a bias-dependent extraction of photoexcited holes from the Al{sub 0.5}Ga{sub 0.5}N/AlN interface. While present under bottom illumination for any AlGaN layer thickness, under top illumination this mechanism influences the EQE-bias characteristics only for thin layers.

  16. Effect of Capping on Electrical and Optical Properties of GaN Layers Grown by HVPE

    NASA Astrophysics Data System (ADS)

    Reshchikov, M. A.; Usikov, A.; Helava, H.; Makarov, Yu.; Puzyk, M. V.; Papchenko, B. P.

    2016-04-01

    Gallium nitride, grown by hydride vapor phase epitaxy and capped with a thin AlGaN layer, was studied by photoluminescence (PL) methods. The concentration of free electrons in GaN was found from the time-resolved PL data, and the concentrations of point defects were estimated from the steady-state PL measurements. The intensity of PL from GaN decreases moderately after capping it with Si-doped AlGaN, and it decreases dramatically after capping with Mg-doped AlGaN. At the same time, the concentration of free electrons and the concentrations of main radiative defects in GaN are not affected by the AlGaN capping. We demonstrate that PL is a powerful tool for nondestructive characterization of semiconductor layers buried under overlying device structures.

  17. GaAs Solar Cells Grown by Hydride Vapor-Phase Epitaxy and the Development of GaInP Cladding Layers

    SciTech Connect

    Simon, John; Schulte, Kevin L.; Young, David L.; Haegel, Nancy M.; Ptak, Aaron J.

    2016-01-01

    The high cost of high-efficiency III-V photovoltaic devices currently limits them to niche markets. Hydride vapor-phase epitaxy (HVPE) growth of III-V materials recently reemerged as a low-cost, high-throughput alternative to conventional metal- organic vapor-phase epitaxy (MOVPE) growth of high-efficiency solar cells. Previously, we demonstrated unpassivated HVPEgrown GaAs p-n junctions with good quantum efficiency and high open-circuit voltage (Voc). In this work, we demonstrate the growth of GaInPby HVPE for use as a high-quality surface passivation layer to GaAs solar cells. Solar cells grown with GaInP window layers show significantly improved quantum efficiency compared with unpassivated cells, increasing the short-circuit current (JSC) of these low-cost devices. These results show the potential of low-cost HVPE for the growth of high-quality III-V devices.

  18. Preliminary Design Report for Modeling of Hydrogen Uptake in Fuel Rod Cladding During Severe Accidents

    SciTech Connect

    Siefken, Larry James

    1999-02-01

    Preliminary designs are described for models of hydrogen and oxygen uptake in fuel rod cladding during severe accidents. Calculation of the uptake involves the modeling of seven processes: (1) diffusion of oxygen from the bulk gas into the boundary layer at the external cladding surface, (2) diffusion from the boundary layer into the oxide layer, (3) diffusion from the inner surface of the oxide layer into the metallic part of the cladding, (4) uptake of hydrogen in the event that the clad-ding oxide layer is dissolved in a steam-starved region, (5) embrittlement of cladding due to hydrogen uptake, (6) cracking of cladding during quenching due to its embrittlement and (7) release of hydrogen from the cladding after cracking of the cladding. An integral diffusion method is described for calculating the diffusion processes in the cladding. Experimental results are presented that show a rapid uptake of hydrogen in the event of dissolution of the oxide layer and a rapid release of hydrogen in the event of cracking of the oxide layer. These experimental results are used as a basis for calculating the rate of hydrogen uptake and the rate of hydrogen release. The uptake of hydrogen is limited to the equilibrium solubility calculated by applying Sievert's law. The uptake of hydrogen is an exothermic reaction that accelerates the heatup of a fuel rod. An embrittlement criteria is described that accounts for hydrogen and oxygen concentration and the extent of oxidation. A design is described for implementing the models for hydrogen and oxygen uptake and cladding embrittlement into the programming framework of the SCDAP/RELAP5 code. A test matrix is described for assessing the impact of the proposed models on the calculated behavior of fuel rods in severe accident conditions. This report is a revision and reissue of the report entitled; "Preliminary Design Report for Modeling of Hydrogen Uptake in Fuel Rod Cladding During Severe Accidents."

  19. Innovations in laser cladding and direct metal deposition

    NASA Astrophysics Data System (ADS)

    Brückner, Frank; Nowotny, Steffen; Leyens, Christoph

    2012-03-01

    The present paper reviews recent progress in productivity, precision and quality of laser-based cladding and additive layer manufacturing. Recently, we have demonstrated the great benefits obtained from induction assisted laser cladding. This novel hybrid technology combines high deposition rates with excellent cladding properties. Laser-based direct metal deposition is a novel concept for the fabrication of components and repair as well as geometrical surface modifications. Newly developed nozzle design allows focused powder spots to generate wall thicknesses of about 30 μm. An in-depth understanding of the processes and the resulting materials properties is key for the development of technically viable and economically reasonable customized solutions.

  20. Characteristics of a long-period fiber grating with reduced cladding for refractive index sensing

    NASA Astrophysics Data System (ADS)

    Chen, Haiyun; Gu, Zhengtian

    2011-10-01

    The sensitivity to surrounding refractive index (SRI) of a long-period fiber grating (LPFG) can be effectively improved by decreasing the cladding radius. When the cladding is reduced, a three-layer model is necessary to evaluate the effective refractive index (ERI) of the core mode. A variation of SRI can induce a greater resonant wavelength shift when the core mode is coupled to a higher-order cladding mode. However, as the cladding is reduced further, the highest-order cladding mode would be cut off, i.e. the number of cladding modes that a given fiber structure can support would be less; thus, the higher-order cladding modes that can be used for higher sensitivity are limited. Hence, the implementation of high sensitivity for SRI sensing with cladding-reduced LPFGs is dependent on the proper combination of cladding radius and cladding mode order. Based on the vector coupled-mode theory, the transmission spectrum and sensitivity are numerically analyzed with respect to the cladding radius, which shows that the SRI sensitivity of the HE12 mode with cladding radius a 2 = 20 µm is 32 times as high as that with a 2 = 62.5 µm and the SRI resolution is available to the order of 10-7.

  1. Zircoloy Cladding Oxidation Simulation for LWR under LOCA Conditions

    2003-04-25

    PRECIP-2 simulates zircaloy cladding oxidation under LOCA conditions of LWR’s. The code calculates oxygen concentration distribution across the cladding wall by solving the diffusion equation with moving boundary conditions, taking into account the structure change of the beta— phase, i.e. alpha precipitation during the cooling period. The code also predicts total oxygen uptake, thicknesses of alpha, beta and oxide layers.

  2. EPRI fuel cladding integrity program

    SciTech Connect

    Yang, R.

    1997-01-01

    The objectives of the EPRI fuel program is to supplement the fuel vendor research to assure that utility economic and operational interests are met. To accomplish such objectives, EPRI has conducted research and development efforts to (1) reduce fuel failure rates and mitigate the impact of fuel failures on plant operation, (2) provide technology to extend burnup and reduce fuel cycle cost. The scope of R&D includes fuel and cladding. In this paper, only R&D related to cladding integrity will be covered. Specific areas aimed at improving fuel cladding integrity include: (1) Fuel Reliability Data Base; (2) Operational Guidance for Defective Fuel; (3) Impact of Water Chemistry on Cladding Integrity; (4) Cladding Corrosion Data and Model; (5) Cladding Mechanical Properties; and (6) Transient Fuel Cladding Response.

  3. Investigation of semiconductor clad optical waveguides

    NASA Technical Reports Server (NTRS)

    Batchman, T. E.; Carson, R. F.

    1985-01-01

    A variety of techniques have been proposed for fabricating integrated optical devices using semiconductors, lithium niobate, and glasses as waveguides and substrates. The use of glass waveguides and their interaction with thin semiconductor cladding layers was studied. Though the interactions of these multilayer waveguide structures have been analyzed here using glass, they may be applicable to other types of materials as well. The primary reason for using glass is that it provides a simple, inexpensive way to construct waveguides and devices.

  4. Cladding embrittlement during postulated loss-of-coolant accidents.

    SciTech Connect

    Billone, M.; Yan, Y.; Burtseva, T.; Daum, R.; Nuclear Engineering Division

    2008-07-31

    The effect of fuel burnup on the embrittlement of various cladding alloys was examined with laboratory tests conducted under conditions relevant to loss-of-coolant accidents (LOCAs). The cladding materials tested were Zircaloy-4, Zircaloy-2, ZIRLO, M5, and E110. Tests were performed with specimens sectioned from as-fabricated cladding, from prehydrided (surrogate for high-burnup) cladding, and from high-burnup fuel rods which had been irradiated in commercial reactors. The tests were designed to determine for each cladding material the ductile-to-brittle transition as a function of steam oxidation temperature, weight gain due to oxidation, hydrogen content, pre-transient cladding thickness, and pre-transient corrosion-layer thickness. For short, defueled cladding specimens oxidized at 1000-1200 C, ring compression tests were performed to determine post-quench ductility at {le} 135 C. The effect of breakaway oxidation on embrittlement was also examined for short specimens oxidized at 800-1000 C. Among other findings, embrittlement was found to be sensitive to fabrication processes--especially surface finish--but insensitive to alloy constituents for these dilute zirconium alloys used as cladding materials. It was also demonstrated that burnup effects on embrittlement are largely due to hydrogen that is absorbed in the cladding during normal operation. Some tests were also performed with longer, fueled-and-pressurized cladding segments subjected to LOCA-relevant heating and cooling rates. Recommendations are given for types of tests that would identify LOCA conditions under which embrittlement would occur.

  5. Zircaloy-2 lined zirconium barrier fuel cladding

    SciTech Connect

    Williams, C.D.; Marlowe, M.O.; Rand, R.A.; Armijo, J.S.; Adamson, R.B.; Wisner, S.B.

    1996-12-31

    The introduction of Zr-lined barrier fuel clad tubing by GE in the early 1980s to counter the pellet-clad interaction (PCI) failure mechanism in fuel for boiling water reactors provided a major improvement in fuel reliability and operational flexibility. While the frequency of fuel failures has been substantially reduced in the past decade, an increased tendency has been observed for failed fuel rods to exhibit post-failure degradation in the form of longer cracks that allow release of radioactive off-gas and contamination of the reactor coolant circuit with tramp fuel material. One factor involved in this degradation is hydriding of the cladding at a location remote from the initial perforation of the fuel rod. This local hydriding can lead to a secondary crack initiation in the cladding when stressed by the fuel expansion accompanying a power increase. A modification of Zr-lined barrier fuel clad tubing has been developed to retard post-failure local hydriding while retaining the proven PCI resistance of the high-purity sponge Zr barrier. By adding a thin inner layer of corrosion-resistant Zircaloy-2 bonded to the inner surface of the Zr-barrier tube, the resistance to internal corrosion and hydrogen generation in a perforated fuel cladding tube is made equivalent to that of an all-Zircaloy-2 tube. Tests show that the PCI mitigating capability of the Zr barrier. By adding a thin layer of corrosion-resistant Zircaloy-2 bonded to the inner surface of the Zr-barrier tube, the resistance to internal corrosion and hydrogen generation in a perforated fuel cladding tube is made equivalent to that of an all-Zircaloy-2 tube. Tests show that the PCI mitigating capability of the Zr barrier is not compromised by this inner Zircaloy-2 liner. Materials considerations and manufacturing technology used to integrate this optional inner liner with other Zr barrier tubing properties and performance requirements are discussed with a summary of testing experience.

  6. Prostate specific antigen detection using AlGaN /GaN high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Kang, B. S.; Wang, H. T.; Lele, T. P.; Tseng, Y.; Ren, F.; Pearton, S. J.; Johnson, J. W.; Rajagopal, P.; Roberts, J. C.; Piner, E. L.; Linthicum, K. J.

    2007-09-01

    Antibody-functionalized Au-gated AlGaN /GaN high electron mobility transistors (HEMTs) were used to detect prostate specific antigen (PSA). The PSA antibody was anchored to the gate area through the formation of carboxylate succinimdyl ester bonds with immobilized thioglycolic acid. The AlGaN /GaN HEMT drain-source current showed a rapid response of less than 5s when target PSA in a buffer at clinical concentrations was added to the antibody-immobilized surface. The authors could detect a wide range of concentrations from 10pg/mlto1μg/ml. The lowest detectable concentration was two orders of magnitude lower than the cutoff value of PSA measurements for clinical detection of prostate cancer. These results clearly demonstrate the promise of portable electronic biological sensors based on AlGaN /GaN HEMTs for PSA screening.

  7. Leakage mechanism in GaN and AlGaN Schottky interfaces

    NASA Astrophysics Data System (ADS)

    Hashizume, Tamotsu; Kotani, Junji; Hasegawa, Hideki

    2004-06-01

    Based on detailed temperature-dependent current-voltage (I-V-T) measurements the mechanism of leakage currents through GaN and AlGaN Schottky interfaces is discussed. The experiments were compared to calculations based on thin surface barrier model in which the effects of surface defects were taken into account. Our simulation method reproduced the experimental I-V-T characteristics of the GaN and AlGaN Schottky diodes, and gave excellent fitting results to the reported Schottky I-V curves in GaN for both forward and reverse biases at different temperatures. The present results indicate that the barrier thinning caused by unintentional surface-defect donors enhances the tunneling transport processes, leading to large leakage currents through GaN and AlGaN Schottky interfaces.

  8. An analysis of temperature dependent piezoelectric Franz-Keldysh effect in AlGaN

    NASA Astrophysics Data System (ADS)

    Hou, Y. T.; Teo, K. L.; Li, M. F.; Uchida, Kazuo; Tokunaga, Hiroki; Akutsu, Nakao; Matsumoto, Koh

    2000-02-01

    Strong Franz-Keldysh oscillations near the band gap of AlGaN are observed in the contactless electroreflectance (CER) studies of a GaN/InGaN/AlGaN multilayer structure. The line shape analysis of the CER spectra at different temperatures provides an accurate determination of the AlGaN band gap energies and the built-in electric fields. Using the existing data of the thermal expansion coefficients of GaN and sapphire, and the piezoelectric constants of AlGaN, the temperature dependence of the electric field is estimated and is in good agreement with the experimental results between 15 and 300 K. We attribute such electric field to the piezoelectric strain effect.

  9. A Probabilistic-Micro-mechanical Methodology for Assessing Zirconium Alloy Cladding Failure

    SciTech Connect

    Pan, Y.M.; Chan, K.S.; Riha, D.S.

    2007-07-01

    Cladding failure of fuel rods caused by hydride-induced embrittlement is a reliability concern for spent nuclear fuel after extended burnup. Uncertainties in the cladding temperature, cladding stress, oxide layer thickness, and the critical stress value for hydride reorientation preclude an assessment of the cladding failure risk. A set of micro-mechanical models for treating oxide cracking, blister cracking, delayed hydride cracking, and cladding fracture was developed and incorporated in a computer model. Results obtained from the preliminary model calculations indicate that at temperatures below a critical temperature of 318.5 deg. C [605.3 deg. F], the time to failure by delayed hydride cracking in Zr-2.5%Nb decreased with increasing cladding temperature. The overall goal of this project is to develop a probabilistic-micro-mechanical methodology for assessing the probability of hydride-induced failure in Zircaloy cladding and thereby establish performance criteria. (authors)

  10. Fuel pin cladding

    DOEpatents

    Vaidyanathan, Swaminathan; Adamson, Martyn G.

    1986-01-01

    An improved fuel pin cladding, particularly adapted for use in breeder reactors, consisting of composite tubing with austenitic steel on the outer portion of the thickness of the tube wall and with nickel and/or ferritic material on the inner portion of the thickness of the tube wall. The nickel forms a sacrificial barrier as it reacts with certain fission products thereby reducing fission product activity at the austenitic steel interface. The ferritic material forms a preventive barrier for the austenitic steel as it is immune to liquid metal embrittlement. The improved cladding permits the use of high density fuel which in turn leads to a better breeding ratio in breeder reactors, and will increase the threshold at which failure occurs during temperature transients.

  11. Fuel pin cladding

    DOEpatents

    Vaidyanathan, S.; Adamson, M.G.

    1983-12-16

    An improved fuel pin cladding, particularly adapted for use in breeder reactors, is described which consist of composite tubing with austenitic steel on the outer portion of the thickness of the tube wall and with nickel an/or ferritic material on the inner portion of the thickness of the tube wall. The nickel forms a sacrificial barrier as it reacts with certain fission products thereby reducing fission product activity at the austenitic steel interface. The ferritic material forms a preventive barrier for the austenitic steel as it is immune to liquid metal embrittlement. The improved cladding permits the use of high density fuel which in turn leads to a better breeding ratio in breeder reactors, and will increase the threshold at which failure occurs during temperature transients.

  12. Fuel pin cladding

    DOEpatents

    Vaidyanathan, S.; Adamson, M.G.

    1986-01-28

    Disclosed is an improved fuel pin cladding, particularly adapted for use in breeder reactors, consisting of composite tubing with austenitic steel on the outer portion of the thickness of the tube wall and with nickel and/or ferritic material on the inner portion of the thickness of the tube wall. The nickel forms a sacrificial barrier as it reacts with certain fission products thereby reducing fission product activity at the austenitic steel interface. The ferritic material forms a preventive barrier for the austenitic steel as it is immune to liquid metal embrittlement. The improved cladding permits the use of high density fuel which in turn leads to a better breeding ratio in breeder reactors, and will increase the threshold at which failure occurs during temperature transients. 2 figs.

  13. Charpy toughness and tensile properties of a neutron irradiated stainless steel submerged-arc weld cladding overlay

    SciTech Connect

    Corwin, W.R.; Berggren, R.G.; Nanstad, R.K.

    1984-01-01

    The possibility of stainless steel cladding increasing the resistance of an operating nuclear reactor pressure vessel to extension of surface flaws is highly dependent upon the irradiated properties of the cladding. Therefore, weld overlay cladding irradiated at temperatures and fluences relevant to power reactor operation was examined. The cladding was applied to a pressure vessel steel plate by the submerged-arc, single-wire, oscillating electrode method. Three layers of cladding were applied to provide a cladding thickness adequate for fabrication of test specimens. The first layer was type 309, and the upper two layers were type 308 stainless steel. There was considerable dilution of the type 309 in the first layer of cladding as a result of excessive melting of the base plate. Specimens for the irradiation study were taken from near the base plate/cladding interface and also from the upper layers of cladding. Charpy V-notch and tensile specimens were irradiated at 288/sup 0/C to neutron fluences of 2 x 10/sup 23/ n/m/sup 2/ (E > 1 MeV). When irradiated, both types 308 and 309 cladding showed a 5 to 40% increase in yield strength accompanied by a slight increase in ductility in the temperature range from 25 to 288/sup 0/C. All cladding exhibited ductile-to-brittle transition behavior during impact testing.

  14. AlGaN Channel Transistors for Power Management and Distribution

    NASA Technical Reports Server (NTRS)

    VanHove, James M.

    1996-01-01

    Contained within is the Final report of a Phase 1 SBIR program to develop AlGaN channel junction field effect transistors (JFET). The report summarizes our work to design, deposit, and fabricate JFETS using molecular beam epitaxy growth AlGaN. Nitride growth is described using a RF atomic nitrogen plasma source. Processing steps needed to fabricate the device such as ohmic source-drain contacts, reactive ion etching, gate formation, and air bride fabrication are documented. SEM photographs of fabricated power FETS are shown. Recommendations are made to continue the effort in a Phase 2 Program.

  15. Large-Format AlGaN PIN Photodiode Arrays for UV Images

    NASA Technical Reports Server (NTRS)

    Aslam, Shahid; Franz, David

    2010-01-01

    A large-format hybridized AlGaN photodiode array with an adjustable bandwidth features stray-light control, ultralow dark-current noise to reduce cooling requirements, and much higher radiation tolerance than previous technologies. This technology reduces the size, mass, power, and cost of future ultraviolet (UV) detection instruments by using lightweight, low-voltage AlGaN detectors in a hybrid detector/multiplexer configuration. The solar-blind feature eliminates the need for additional visible light rejection and reduces the sensitivity of the system to stray light that can contaminate observations.

  16. Formation quality optimization of laser hot wire cladding for repairing martensite precipitation hardening stainless steel

    NASA Astrophysics Data System (ADS)

    Wen, Peng; Feng, Zhenhua; Zheng, Shiqing

    2015-01-01

    Laser cladding is an advantaged repairing technology due to its low heat input and high flexibility. With preheating wire by resistance heat, laser hot wire cladding shows better process stability and higher deposition efficiency compared to laser cold wire/powder cladding. Multi-pass layer were cladded on the surface of martensite precipitation hardening stainless steel FV520B by fiber laser with ER410NiMo wire. Wire feed rate and preheat current were optimized to obtain stable wire transfer, which guaranteed good formation quality of single pass cladding. Response surface methodology (RSM) was used to optimize processing parameters and predict formation quality of multi-pass cladding. Laser power P, scanning speed Vs, wire feed rate Vf and overlap ratio η were selected as the input variables, while flatness ratio, dilution and incomplete fusion value as the responses. Optimal clad layer with flat surface, low dilution and no incomplete fusion was obtained by appropriately reducing Vf, and increasing P, Vs and η. No defect like pore or crack was found. The tensile strength and impact toughness of the clad layer is respectively 96% and 86% of those of the substrate. The clad layer showed nonuniform microstructure and was divided into quenched areas with coarse lath martensite and tempered areas with tempered martensite due to different thermal cycles in adjacent areas. The tempered areas showed similar hardness to the substrate.

  17. Preliminary design report for modeling of hydrogen uptake in fuel rod cladding during severe accidents

    SciTech Connect

    Siefken, L.J.

    1998-08-01

    Preliminary designs are described for models of the interaction of Zircaloy and hydrogen and the consequences of this interaction on the behavior of fuel rod cladding during severe accidents. The modeling of this interaction and its consequences involves the modeling of seven processes: (1) diffusion of oxygen from the bulk gas into the boundary layer at the external cladding surface, (2) diffusion from the boundary layer into the oxide layer at the cladding external surface, (3) diffusion from the inner surface of the oxide layer into the metallic part of the cladding, (4) uptake of hydrogen in the event that the cladding oxide layer is dissolved in a steam-starved region, (5) embrittlement of cladding due to hydrogen uptake, (6) cracking of cladding during quenching due to its embrittlement and (7) release of hydrogen from the cladding after cracking of the cladding. An integral diffusion method is described for calculating the diffusion processes in the cladding. Experimental and theoretical results are presented that show the uptake of hydrogen in the event of dissolution of the oxide layer occurs rapidly and that show the release of hydrogen in the event of cracking of the cladding occurs rapidly. These experimental results are used as a basis for calculating the rate of hydrogen uptake and the rate of hydrogen release. The uptake of hydrogen is limited to the equilibrium solubility calculated by applying Sievert`s law. The uptake of hydrogen is an exothermic reaction that accelerates the heatup of a fuel rod. An embrittlement criteria is described that accounts for hydrogen and oxygen concentration and the extent of oxidation. A design is described for implementing the models for Zr-H interaction into the programming framework of the SCDAP/RELAP5 code. A test matrix is described for assessing the impact of the Zr-H interaction models on the calculated behavior of fuel rods in severe accident conditions.

  18. Aluminum incorporation efficiencies in A- and C-plane AlGaN grown by MOVPE

    NASA Astrophysics Data System (ADS)

    Dong-Yue, Han; Hui-Jie, Li; Gui-Juan, Zhao; Hong-Yuan, Wei; Shao-Yan, Yang; Lian-Shan, Wang

    2016-04-01

    The aluminum incorporation efficiencies in nonpolar A-plane and polar C-plane AlGaN films grown by metalorganic vapour phase epitaxy (MOVPE) are investigated. It is found that the aluminum content in A-plane AlGaN film is obviously higher than that in the C-plane sample when the growth temperature is above 1070 °C. The high aluminum incorporation efficiency is beneficial to fabricating deep ultraviolet optoelectronic devices. Moreover, the influences of the gas inlet ratio, the V/III ratio, and the chamber pressure on the aluminum content are studied. The results are important for growing the AlGaN films, especially nonpolar AlGaN epilayers. Project supported by the National Natural Science Foundation of China (Grant Nos. 61504128, 61504129, 61274041, and 11275228), the National Basic Research Program of China (Grant No. 2012CB619305), the National High Technology Research and Development Program of China (Grant Nos. 2014AA032603, 2014AA032609, and 2015AA010801), and the Guangdong Provincial Scientific and Technologic Planning Program, China (Grant No. 2014B010119002).

  19. Effect of stress on the Al composition evolution in AlGaN grown using metal organic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    He, Chenguang; Qin, Zhixin; Xu, Fujun; Zhang, Lisheng; Wang, Jiaming; Hou, Mengjun; Zhang, Shan; Wang, Xinqiang; Ge, Weikun; Shen, Bo

    2016-05-01

    Two series of AlGaN samples with different stresses were designed to investigate the effect of stress on the Al composition. X-ray diffraction reciprocal space mapping (XRD RSM) demonstrated that the AlGaN epilayers with different stresses have large Al composition differences despite the same growth conditions. The largest Al composition difference reached up to 21.3%, which was also confirmed using secondary ion mass spectroscopy (SIMS). This result is attributed to a large stress discrepancy in the AlGaN epilayers. Finally, the dependences of the solid-phase Al composition on the gas-phase Al composition under different stresses were systematically analyzed.

  20. Aerogel-clad optical fiber

    DOEpatents

    Sprehn, Gregory A.; Hrubesh, Lawrence W.; Poco, John F.; Sandler, Pamela H.

    1997-01-01

    An optical fiber is surrounded by an aerogel cladding. For a low density aerogel, the index of refraction of the aerogel is close to that of air, which provides a high numerical aperture to the optical fiber. Due to the high numerical aperture, the aerogel clad optical fiber has improved light collection efficiency.

  1. Aerogel-clad optical fiber

    DOEpatents

    Sprehn, G.A.; Hrubesh, L.W.; Poco, J.F.; Sandler, P.H.

    1997-11-04

    An optical fiber is surrounded by an aerogel cladding. For a low density aerogel, the index of refraction of the aerogel is close to that of air, which provides a high numerical aperture to the optical fiber. Due to the high numerical aperture, the aerogel clad optical fiber has improved light collection efficiency. 4 figs.

  2. Oxidation resistant claddings for superalloys.

    NASA Technical Reports Server (NTRS)

    Gedwill, M. A.; Grisaffe, S. J.

    1971-01-01

    The oxidation protection afforded IN-100 and WI-52 superalloys by thin claddings of NiCrAlSi and FeCrAlY alloys was examined primarily at 1090 C. Comparisons were made with commercial aluminide coatings using cyclic furnace and high velocity burner rig tests. In furnace tests, NiCrAlSi on IN-100 and FeCrAlY on WI-52 performed as well or better than two aluminide coatings. Burner rig performance of the FeCrAlY cladding was better than that of the NiCrAlSi cladding on IN-100 and the aluminide coating on WI-52, but less than the aluminide coating on IN-100. An aluminized NiCrAlSi cladding performed better than any coating or cladding.

  3. Oxidation resistant claddings for superalloys.

    NASA Technical Reports Server (NTRS)

    Gedwill, M. A.; Grisaffe, S. J.

    1972-01-01

    The oxidation protection afforded IN-100 and WI-52 superalloys by thin claddings of NiCrAlSi and FeCrAlY alloys was examined primarily at 1090 C. Comparisons were made with commercial aluminide coatings, using cyclic furnace and high-velocity burner rig tests. In furnace tests, NiCrAlSi on IN-100 and FeCrAlY on WI-52 performed as well as or better than two aluminide coatings. Burner rig performance of the FeCrAlY cladding was better than that of the NiCrAlSi cladding on IN-100 and the aluminide coating on WI-52, but less than the aluminide coating on IN-100. An aluminized NiCrAlSi cladding performed better than any coating or cladding.

  4. LWR pellet-cladding interactions: Materials solutions to SCC

    NASA Astrophysics Data System (ADS)

    Edsinger, Kurt; Murty, K. Linga

    2001-07-01

    Zirconium alloys are commonly used as fuel-cladding tubes in water reactors because of their inherent resistance to a variety of environmental conditions. One of the major fuel-reliability issues of the 1970s and early 1980s was pellet cladding interaction (PCI). The mechanism of PCI is one of stress corrosion cracking (SCC) by a combination of aggressive fission products and cladding stress from pellet expansion. The severity of the problem, in particular in boiling water reactors, led to the development of barrier cladding by co-extrusion of Zircaloy-2 with an inner iodide zirconium that essentially eliminated the PCI-related failures. However, the substantially lower corrosion resistance of the zirconium layer led to clad breach and failures by other mechanisms. The difference in corrosion resistance could lead to some dramatic differences in post-failure fuel operations. This article briefly summarizes how PCI-SCC factors led to the development of PCI-resistant fuel cladding and concludes with a note on future research needs.

  5. Residual stresses in weld deposited clad pressure vessels and nozzles

    SciTech Connect

    Jones, D.P.; Mabe, W.R.; Shadley, J.R.; Rybicki, E.F.

    1998-04-01

    Results of through-thickness residual stress measurements are provided for a variety of samples of weld deposited 308/309L stainless steel and Alloy 600 cladding on low-alloy pressure vessel ferritic steels. Clad thicknesses between 5 and 9mm on samples that vary in thickness from 45 to 200mm were studied. The samples were taken from flat plates, from a spherical head of a pressure vessel, from a ring-segment of a nozzle bore, and from the transition radius between a nozzle and a pressure vessel shell. A layer removal method was used to measure the residual stresses. The effects of uncertainties in elastic constants (Young`s modulus and Poisson`s ratio) as well as experimental error are assessed. All measurements were done at room temperature. The results of this work indicate that curvature plays a significant role in cladding residual stress and that tensile residual stresses as high as the yield stress can be measured in the cladding material. Since the vessel from which the spherical and nozzle corner samples were taken was hydrotested, and the flat plate specimens were taken from specimens used in mechanical fatigue testing, these results suggest that rather high tensile residual stresses can be retained in the cladding material even after some mechanical loading associated with hydrotesting and that higher levels of hydrotest loading would be required to alter the cladding residual stresses.

  6. Characterization of SiC-SiC composites for accident tolerant fuel cladding

    NASA Astrophysics Data System (ADS)

    Deck, C. P.; Jacobsen, G. M.; Sheeder, J.; Gutierrez, O.; Zhang, J.; Stone, J.; Khalifa, H. E.; Back, C. A.

    2015-11-01

    Silicon carbide (SiC) is being investigated for accident tolerant fuel cladding applications due to its high temperature strength, exceptional stability under irradiation, and reduced oxidation compared to Zircaloy under accident conditions. An engineered cladding design combining monolithic SiC and SiC-SiC composite layers could offer a tough, hermetic structure to provide improved performance and safety, with a failure rate comparable to current Zircaloy cladding. Modeling and design efforts require a thorough understanding of the properties and structure of SiC-based cladding. Furthermore, both fabrication and characterization of long, thin-walled SiC-SiC tubes to meet application requirements are challenging. In this work, mechanical and thermal properties of unirradiated, as-fabricated SiC-based cladding structures were measured, and permeability and dimensional control were assessed. In order to account for the tubular geometry of the cladding designs, development and modification of several characterization methods were required.

  7. Technique for examining the fuel/cladding interface by TEM. [LMFBR

    SciTech Connect

    Yang, W.J.S.; Makenas, B.J.; Thomas, L.E.

    1983-05-01

    Fuel and fission-product interactions with the fuel-pin cladding is an area of concern and has been evaluated in the past principally by in-cell optical metallographic and electron-microprobe examinations. The applicability of three techniques for preparing specimens to reveal the microstructural details and local microchemistry of the fuel/cladding interface under conditions of high-resolution-scanning transmission-electron microscopy has been investigated. The specimen preparation techniques were designed to preserve the fuel/cladding interface and provide and maintain a specimen surface free from smearable alpha contamination. One of the techniques, Ni plating of a fuel cladding sample, preserved the entire cladding cross-section for examination. An Fe-oxide layer on the cladding inner surface was found in specimens prepared by this method. All three techniques of specimen preparation are described in some detail, along with their advantages and disadvantages.

  8. Clad Metals, Roll Bonding and their Applications for SOFC Interconnects

    SciTech Connect

    Chen, L.; Yang, Zhenguo; Jha, B.; Xia, Guanguang; Stevenson, Jeffry W.

    2005-12-01

    High temperature oxidation resistant alloys are currently considered as candidate materials for construction of interconnects in intermediate temperature SOFCs. Among these alloys however, different groups of alloys demonstrate different advantages and disadvantages for the interconnect applications, and few if any can completely satisfied the stringent requirements for the applications. To integrate the advantages and avoid the disadvantages of different groups of alloys, cladding has been proposed as the approach to fabricate metallic layered interconnect structures. To examine the feasibility of this approach, the austenitic Ni-base alloy Haynes 230 and the ferritic stainless steel AL453 were selected as examples and manufactured into a clad metal. It’s suitability as interconnect construction materials were investigated. This paper will give a brief overview of the cladding approach and discuss the viability of this technology to fabricate the metallic layered-structure interconnects.

  9. Clad metals by roll bonding for SOFC interconnects

    NASA Astrophysics Data System (ADS)

    Chen, L.; Jha, B.; Yang, Zhenguo; Xia, Guang-Guang; Stevenson, Jeffry W.; Singh, Prabhakar

    2006-08-01

    High-temperature oxidation-resistant alloys are currently considered as a candidate material for construction of interconnects in intermediate-temperature solid oxide fuel cells. Among these alloys, however, different groups of alloys demonstrate different advantages and disadvantages, and few, if any, can completely satisfy the stringent requirements for the application. To integrate the advantages and avoid the disadvantages of different groups of alloys, cladding has been proposed as one approach in fabricating metallic layered interconnect structures. To examine the feasibility of this approach, the austenitic Ni-base alloy Haynes 230 and the ferritic stainless steel AL 453 were selected as examples and manufactured into a clad metal. Its suitability as an interconnect construction material was investigated. This paper provides a brief overview of the cladding approach and discusses the viability of this technology to fabricate the metallic layered-structure interconnects.

  10. Effects of Bonding Conditions on Bondability Using Zn/Al/Zn Clad Solder

    NASA Astrophysics Data System (ADS)

    Yamaguchi, T.; Ikeda, O.; Oda, Y.; Hata, S.; Kuroki, K.; Kuroda, H.; Hirose, A.

    2015-12-01

    Three-layer Zn/Al/Zn clad solders have been developed for high-temperature die attachment. The clad structure is used to improve the wettability and bondability of Zn-Al eutectic solder by preventing Al oxidation. The effects of the bonding conditions on the bondability with Zn/Al/Zn clad solder were investigated. Bonding was achieved in the temperature range from 385°C to 420°C under N2 atmosphere with oxygen concentration below 100 ppm. However, the bonding strength of the joint formed under N2 + 4% H2 atmosphere was almost 0 MPa, and stripe defects and air gaps remained in the bond layer. To improve the bondability under N2 + 4% H2 and expand the application range, a five-layer Cu/Zn/Al/Zn/Cu clad solder was developed in an attempt to prevent the Zn layers from being oxidized by the outer Cu layers. Cross-sectional observation of the Cu/Zn/Al/Zn/Cu clad solder revealed that the surface was covered by a Cu layer, and that Cu5Zn8 layers grew between the Cu and Zn layers. This clad solder exhibited high shear strength of over 80 MPa when formed under N2 + 4% H2 atmosphere, and no stripe defects or air gaps were observed in the bond layer.

  11. Microstructure and Abrasive Wear Performance of Ni-Wc Composite Microwave Clad

    NASA Astrophysics Data System (ADS)

    Bansal, Amit; Zafar, Sunny; Sharma, Apurbba Kumar

    2015-10-01

    In the present work, Ni-WC powder was deposited on mild steel substrate to develop clads through microwave hybrid heating technique. The cladding trials were carried out in an industrial microwave applicator at 1.1 kW for 540 s. The Ni-WC composite clads were characterized for microstructure and abrasive wear performance through combination of x-ray diffraction, electron and optical microscopy, microhardness, and wear tests. Phase analysis of the Ni-WC clad indicated the presence of stable carbides such as WC, W2C, Ni2W4C, and Fe6W6C. The microstructure study of the clad layer revealed the presence of a uniformly distributed interlocked WC-based reinforcement embedded in the Ni-based matrix. The average Vicker's microhardness in the clad layer was observed to be 1028 ± 90 HV, which was approximately three times the microhardness of the substrate. Abrasive wear resistance of the microwave clads was superior to the MS substrate. Abrasion was the main wear mechanism in the Ni-WC clads and the substrate samples. However, the presence of WC-based reinforcement in the composite clads reduced microcutting, resulting in enhanced wear resistance.

  12. Radiographic Inspection of Fueled Clads

    SciTech Connect

    Timothy J. Roney; Karen M. Wendt

    2005-04-01

    Five general purpose heat source (GPHS) fueled clads were radiographically inspected at the Idaho National Laboratory (INL). The girth weld region of each clad had previously passed visual examination, ring gauge test, and leak test but showed “positive” indications on the ultrasonic (UT) test. Positive ultrasonic indications are allowable under certain weld conditions; radiographic inspection provides a secondary nonintrusive means of clad inspection and may confirm allowable anomalies from the UT inspection. All the positive UT indications were found to exhibit allowable weld shield fusion or mismatch conditions. No indication of void defects was found. One additional clad (FCO371) was deemed unacceptable for radiographic inspection due to an unknown black substance that obscured the angular origin on the weld so that the angular offset to the UT indication could not be found.

  13. Synthesis, morphology and optical properties of GaN and AlGaN semiconductor nanostructures

    SciTech Connect

    Kuppulingam, B. Singh, Shubra Baskar, K.

    2014-04-24

    Hexagonal Gallium Nitride (GaN) and Aluminum Gallium Nitride (AlGaN) nanoparticles were synthesized by sol-gel method using Ethylene Diamine Tetra Acetic acid (EDTA) complex route. Powder X-ray diffraction (PXRD) analysis confirms the hexagonal wurtzite structure of GaN and Al{sub 0.25}Ga{sub 0.75}N nanoparticles. Surface morphology and elemental analysis were carried out by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray spectroscopy (EDX). The room temperature Photoluminescence (PL) study shows the near band edge emission for GaN at 3.35 eV and at 3.59 eV for AlGaN nanoparticles. The Aluminum (Al) composition of 20% has been obtained from PL emission around 345 nm.

  14. Bias Selectable Dual Band AlGaN Ultra-violet Detectors

    NASA Technical Reports Server (NTRS)

    Yan, Feng; Miko, Laddawan; Franz, David; Guan, Bing; Stahle, Carl M.

    2007-01-01

    Bias selectable dual band AlGaN ultra-violet (UV) detectors, which can separate UV-A and UV-B using one detector in the same pixel by bias switching, have been designed, fabricated and characterized. A two-terminal n-p-n photo-transistor-like structure was used. When a forward bias is applied between the top electrode and the bottom electrode, the detectors can successfully detect W-A and reject UV-B. Under reverse bias, they can detect UV-B and reject UV-A. The proof of concept design shows that it is feasible to fabricate high performance dual-band UV detectors based on the current AlGaN material growth and fabrication technologies.

  15. Cladding material, tube including such cladding material and methods of forming the same

    DOEpatents

    Garnier, John E.; Griffith, George W.

    2016-03-01

    A multi-layered cladding material including a ceramic matrix composite and a metallic material, and a tube formed from the cladding material. The metallic material forms an inner liner of the tube and enables hermetic sealing of thereof. The metallic material at ends of the tube may be exposed and have an increased thickness enabling end cap welding. The metallic material may, optionally, be formed to infiltrate voids in the ceramic matrix composite, the ceramic matrix composite encapsulated by the metallic material. The ceramic matrix composite includes a fiber reinforcement and provides increased mechanical strength, stiffness, thermal shock resistance and high temperature load capacity to the metallic material of the inner liner. The tube may be used as a containment vessel for nuclear fuel used in a nuclear power plant or other reactor. Methods for forming the tube comprising the ceramic matrix composite and the metallic material are also disclosed.

  16. High growth rate of AlGaN for buffer structures for GaN on Si to increase throughput

    NASA Astrophysics Data System (ADS)

    Matsumoto, Koh; Ubukata, Akinori; Ikenaga, Kazutada; Naito, Kazuki; Yamamoto, Jun; Yano, Yoshiki; Tabuchi, Toshiya; Yamaguchi, Akira; Ban, Yuzaburo; Uchiyama, Kosuke

    2012-03-01

    Throughput requirement of the epitaxial process of GaN on Si is described. The impact of the growth rate of AlGaN for the buffer layer of GaN on Si is highlighted. In the attempt of growing GaN on Si, we have tested a production scale high flow speed MOVPE reactor (TAIYO NIPPON SANSO UR25k) for 6 inch X 7 wafers. Al0.58Ga0.42N was grown with the growth rate of 1.85μm/hr at 30 kPa. AlN was grown with the growth rate of 1.4μm/hr at 13kPa. AlN/GaN SLS (5nm/20nm) was also grown at the growth rate of 1.4μm/hr. An excellent uniformity of aluminum concentration of less than 0.5% was also obtained for Al0.58Ga0.42N. The challenge which we are facing to further increase of the throughput is summarized.

  17. High power cladding light strippers

    NASA Astrophysics Data System (ADS)

    Wetter, Alexandre; Faucher, Mathieu; Sévigny, Benoit

    2008-02-01

    The ability to strip cladding light from double clad fiber (DCF) fibers is required for many different reasons, one example is to strip unwanted cladding light in fiber lasers and amplifiers. When removing residual pump light for example, this light is characterized by a large numerical aperture distribution and can reach power levels into the hundreds of watts. By locally changing the numerical aperture (N.A.) of the light to be stripped, it is possible to achieve significant attenuation even for the low N.A. rays such as escaped core modes in the same device. In order to test the power-handling capability of this device, one hundred watts of pump and signal light is launched from a tapered fusedbundle (TFB) 6+1x1 combiner into a high power-cladding stripper. In this case, the fiber used in the cladding stripper and the output fiber of the TFB was a 20/400 0.06/0.46 N.A. double clad fiber. Attenuation of over 20dB in the cladding was measured without signal loss. By spreading out the heat load generated by the unwanted light that is stripped, the package remained safely below the maximum operating temperature internally and externally. This is achieved by uniformly stripping the energy along the length of the fiber within the stripper. Different adhesive and heat sinking techniques are used to achieve this uniform removal of the light. This suggests that these cladding strippers can be used to strip hundreds of watts of light in high power fiber lasers and amplifiers.

  18. Calculation of hydrogen and oxygen uptake in fuel rod cladding during severe accidents using the integral diffusion method -- Final Design Report

    SciTech Connect

    Siefken, L.J.

    1999-05-01

    Final designs are described for models of hydrogen and oxygen uptake in fuel rod cladding during severe accidents. Calculation of the uptake involves the modeling of seven processes: (1) diffusion of oxygen from the bulk gas into the boundary layer at the external cladding surface, (2) diffusion from the boundary layer into the oxide layer, (3) diffusion from the inner surface of the oxide layer into the metallic part of the cladding, (4) uptake of hydrogen in the event that the cladding oxide layer is dissolved in a steam-starved region, (5) embrittlement of cladding due to hydrogen uptake, (6) cracking of cladding during quenching due to its embrittlement and (7) release of hydrogen from the cladding after cracking of the cladding. An integral diffusion method is described for calculating the diffusion processes in the cladding. Experimental results are presented that show a rapid uptake of hydrogen in the event of dissolution of the oxide layer and a rapid release of hydrogen in the event of cracking of the oxide layer. These experimental results are used as a basis for calculating the rate of hydrogen uptake and the rate of hydrogen release. A description is given of the implementation of the models for hydrogen and oxygen uptake and cladding embrittlement into the programming framework of the SCDAP/RELAP5/MOD3.3 code.

  19. Calculation of Hydrogen and Oxygen Uptake in Fuel Rod Cladding During Severe Accidents Using the Integral Diffusion Method - Final Design Report

    SciTech Connect

    Siefken, Larry James

    1999-06-01

    Final designs are described for models of hydrogen and oxygen uptake in fuel rod cladding during severe accidents. Calculation of the uptake involves the modeling of seven processes: (1) diffusion of oxygen from the bulk gas into the boundary layer at the external cladding surface, (2) diffusion from the boundary layer into the oxide layer, (3) diffusion from the inner surface of the oxide layer into the metallic part of the cladding, (4) uptake of hydrogen in the event that the cladding oxide layer is dissolved in a steam-starved region, (5) embrittlement of cladding due to hydrogen uptake, (6) cracking of cladding during quenching due to its embrittlement and (7) release of hydrogen from the cladding after cracking of the cladding. An integral diffusion method is described for calculating the diffusion processes in the cladding. Experimental results are presented that show a rapid uptake of hydrogen in the event of dissolution of the oxide layer and a rapid release of hydrogen in the event of cracking of the oxide layer. These experimental results are used as a basis for calculating the rate of hydrogen uptake and the rate of hydrogen release. A description is given of the implementation of the models for hydrogen and oxygen uptake and cladding embrittlement into the programming framework of the SCDAP/RELAP5/MOD3.3 code.

  20. Growth of AlGaN epilayers related gas-phase reactions using TPIS-MOCVD

    NASA Astrophysics Data System (ADS)

    Kim, Sunwoon; Seo, Junho; Lee, Kyuhan; Lee, Haeseok; Park, Keunseop; Kim, Younghoon; Kim, Chang-Soo

    2002-11-01

    AlGaN epilayers on GaN/sapphire were successfully grown under various growth conditions using a thermally pre-cracked ion-supplied metalorganic chemical vapor deposition. The Al composition in the solid was affected by the gas-phase parasitic reaction between NH 3 and trimethylaluminum (TMAl). As the operating pressure decreased, the Al composition in the solid increased over the ideal incorporation efficiency. This is due to a scavenging effect and a site-blocking effect. As the TMAl flow rate increased with fixed flow rates of NH 3 and trimethylgallium (TMGa), the Al concentration in the solid increased but started to saturate. As the TMGa flow rate decreased, the solid Al composition increased linearly, which means different parasitic reactions between TMGa:NH 3 and TMAl:NH 3. In addition, we found that the separating plate that was inserted to the reactor in front of the heated susceptor to separate ammonia gas flow from MO source input played an important role in the AlGaN growth. Particularly, the separating plate was more attractive under high operating pressure. When it was inserted, a white crystalline solid formed by the adduct (TMAl:NH 3) of parasitic reaction in the gas phase disappeared. It also increased the Al concentration in the solid. SEM images of AlGaN epilayer's surface showed many small islands due to the lack of surface mobility of adatoms.

  1. Growth of AlGaN alloys exhibiting enhanced luminescence efficiency

    NASA Astrophysics Data System (ADS)

    Sampath, A. V.; Garrett, G. A.; Collins, C. J.; Sarney, W. L.; Readinger, E. D.; Newman, P. G.; Shen, H.; Wraback, M.

    2006-04-01

    Interest in developing ultraviolet emitters using the III-Nitride family of semiconductors has sparked considerable effort in fabricating AlGaN alloys that exhibit enhanced luminescence based on strong carrier localization, similar to their InGaN brethren. In this paper, we report on the growth of such alloys by plasma-assisted molecular beam epitaxy (PA-MBE) without the use of indium. This enhancement is attributed to the presence of nanoscale compositional inhomogeneities (NCIs) in these materials. The emission wavelength in these materials has been tuned between 275 nm and 340 nm by varying growth conditions. The effects of dislocations on double heterostructures (DHs) that employ an NCI AlGaN active region has been investigated, with an internal quantum efficiency as high as 32% obtained for the lowest dislocation density samples (3×1010 cm-2). Prototype DH-ultraviolet light emitting diodes (DH-UVLEDs) emitting at 324 nm were fabricated employing an NCI AlGaN alloy as the active region.

  2. High-efficiency blue LEDs with thin AlGaN interlayers in InGaN/GaN MQWs grown on Si (111) substrates

    NASA Astrophysics Data System (ADS)

    Kimura, Shigeya; Yoshida, Hisashi; Ito, Toshihide; Okada, Aoi; Uesugi, Kenjiro; Nunoue, Shinya

    2016-02-01

    We demonstrate high-efficiency blue light-emitting diodes (LEDs) with thin AlGaN interlayers in InGaN/GaN multiquantum wells (MQWs) grown on Si (111) substrates. The peak external quantum efficiency (EQE) ηEQE of 82% at room temperature and the hot/cold factor (HCF) of 94% have been obtained by using the functional thin AlGaN interlayers in the MQWs in addition to reducing threading dislocation densities (TDDs) in the blue LEDs. An HCF is defined as ηEQE(85°C)/ηEQE(25°C). The blue LED structures were grown by metal-organic chemical vapor deposition on Si (111) substrates. The MQWs applied as an active layer have 8- pairs of InGaN/AlyGa1-yN/GaN (0<=y<=1) heterostructures. Thinfilm LEDs were fabricated by removing the Si (111) substrates from the grown layers. It is observed by high-resolution transmission electron microscopy and three-dimensional atom probe analysis that the 1 nm-thick AlyGa1-yN interlayers, whose Al content is y=0.3 or less, are continuously formed. EQE and the HCFs of the LEDs with thin Al0.15Ga0.85N interlayers are enhanced compared with those of the samples without the interlayers in the low-current-density region. We consider that the enhancement is due to both the reduction of the nonradiative recombination centers and the increase of the radiative recombination rate mediated by the strain-induced hole carriers indicated by the simulation of the energy band diagram.

  3. Clad metals, roll bonding and their applications for SOFC interconnects

    NASA Astrophysics Data System (ADS)

    Chen, Lichun; Yang, Zhenguo; Jha, Bijendra; Xia, Guanguang; Stevenson, Jeffry W.

    Metallic interconnects have been becoming an increasingly interesting topic in the development in intermediate temperature solid oxide fuel cells (SOFC). High temperature oxidation resistant alloys are currently considered as candidate materials. Among these alloys however, different groups of alloys demonstrate different advantages and disadvantages, and few if any can completely satisfy the stringent requirements for the application. To integrate the advantages and avoid the disadvantages of different groups of alloys, clad metal has been proposed for SOFC interconnect applications and interconnect structures. This paper gives a brief overview of the cladding approach and its applications, and discuss the viability of this technology to fabricate the metallic layered-structure interconnects. To examine the feasibility of this approach, the austenitic Ni-base alloy Haynes 230 and the ferritic stainless steel AL 453 were selected as examples and manufactured into a clad metal. Its suitability as an interconnect construction material was investigated.

  4. Clad metals by roll bonding for SOFC interconnects

    SciTech Connect

    Chen, L.; Jha, B; Yang, Z Gary; Xia, Gordon; Stevenson, Jeffry W.; Singh, Prabhakar

    2006-08-01

    Metallic interconnects have been becoming an increasingly interesting topic in the development in intermediate temperature solid oxide fuel cells (SOFC). High temperature oxidation resistant alloys are currently considered as candidate materials. Among these alloys however, different groups of alloys demonstrate different advantages and disadvantages, and few if any can completely satisfy the stringent requirements for the application. To integrate the advantages and avoid the disadvantages of different groups of alloys, clad metal has been proposed for SOFC interconnect applications and interconnect structures. This paper gives a brief overview of the cladding approach and its applications, and discuss the viability of this technology to fabricate the metallic layered-structure interconnects. To examine the feasibility of this approach, the austenitic Ni-base alloy Haynes 230 and the ferritic stainless steel AL 453 were selected as examples and manufactured into a clad metal. Its suitability as an interconnect construction material was investigated.

  5. Cladding Alloys for Fluoride Salt Compatibility Final Report

    SciTech Connect

    Muralidharan, Govindarajan; Wilson, Dane F; Santella, Michael L; Holcomb, David Eugene

    2011-05-01

    This interim report provides an overview of several candidate technologies for cladding nickel-based corrosion protection layers onto high-temperature structural alloys. The report also provides a brief overview of the welding and weld performance issues associated with joining nickel-clad nickel-based alloys. From the available techniques, two cladding technologies were selected for initial evaluation. The first technique is a line-of-sight method that would be useful for coating large structures such as vessel interiors or large piping. The line-of-sight method is a laser-based surface cladding technique in which a high-purity nickel powder mixed into a polymer binder is first sprayed onto the surface, baked, and then rapidly melted using a high power laser. The second technique is a vapor phase technique based on the nickel-carbonyl process that is suitable for coating inaccessible surfaces such as the interior surfaces of heat exchangers. The final project report will feature an experimental evaluation of the performance of the two selected cladding techniques.

  6. Low-stress silicon cladding made by pulsed-ion-assisted evaporation

    NASA Astrophysics Data System (ADS)

    Sheikh, David A.

    2015-09-01

    A low-stress, polishable, silicon (Si) cladding process for lightweight mirrors is presented. The cladding process is based on the thermal evaporation of silicon in the presence of low-energy argon ions. The process utilizes an ion bombardment technique whereby the coating stress of a silicon film is manipulated periodically from compressive to tensile in order to achieve a low net stress for the complete layer. A Si cladding with little intrinsic stress is desirable to minimize bending that would otherwise distort the figure of very lightweight mirrors. The process has yielded silicon claddings up to 100-microns thick, with less than 85 MPa of compressive stress. This polishable Si cladding was specifically designed for silicon carbide mirror substrates, however, it is also suitable for graphite composite, beryllium, and aluminum mirror substrates, which may be difficult or impossible to polish to sufficient mirror quality without a specialized coating.

  7. Clad Degradation - FEPs Screening Arguments

    SciTech Connect

    E. Siegmann

    2004-03-17

    The purpose of this report is to document the screening of the cladding degradation features, events, and processes (FEPs) for commercial spent nuclear fuel (CSNF). This report also addresses the effect of some FEPs on both the cladding and the CSNF, DSNF, and HLW waste forms where it was considered appropriate to address the effects on both materials together. This report summarizes the work of others to screen clad degradation FEPs in a manner consistent with, and used in, the Total System Performance Assessment-License Application (TSPA-LA). This document was prepared according to ''Technical Work Plan for Waste Form Degradation Modeling, Testing, and Analyses in Support of LA'' (BSC 2004a [DIRS 167796]).

  8. Weld cladding of hard surfaces

    NASA Astrophysics Data System (ADS)

    Habrekke, T.

    1993-02-01

    A literature study about clad welding of hard surfaces on steel is performed. The purpose was to see what kind of methods are mainly used, and particular attention is paid to clad welding of rolls. The main impression from this study is that several methods are in use. Some of these must be considered as 'too exotic' for the aim of the program, such as laser build-up welding. However, clad welding of hard surfaces to rolls is widely used around the world, and there is no need for particularly advanced welding methods to perform the work. The welding consumables and the way the welding is carried out is of more important character. The report will give some comments to this, and hopefully will give a short review of the current technology in this field.

  9. DECONTAMINATION OF ZIRCALOY CLADDING HULLS FROM SPENT NUCLEAR FUEL

    SciTech Connect

    Rudisill, T.

    2010-09-29

    The feasibility of decontaminating spent fuel cladding hulls using hydrofluoric acid (HF) was investigated as part of the Global Energy Nuclear Partnership (GNEP) Separations Campaign. The concentrations of the fission product and transuranic (TRU) isotopes in the decontaminated hulls were compared to the limits for determining the low level waste (LLW) classification in the United States (US). The {sup 90}Sr and {sup 137}Cs concentrations met the disposal criteria for a Class C LLW; although, in a number of experiments the criteria for disposal as a Class B LLW were met. The TRU concentration in the hulls generally exceeded the Class C LLW limit by at least an order of magnitude. The concentration decreased sharply as the initial 30-40 {micro}m of the cladding hull surface were removed. At depths beyond this point, the TRU activity remained relatively constant, well above the Class C limit. Reprocessing of spent nuclear fuel generates a cladding waste which would likely require disposal as a Greater than Class C LLW in the US. If the cladding hulls could be treated to remove a majority of the actinide and fission product contamination, the hulls could potentially meet acceptance criteria for disposal as a LLW or allow recycle of the Zr metal. Discard of the hulls as a LLW would result in significant cost savings compared to disposal as a Greater than Class C waste which currently has no disposition path. During fuel irradiation and reprocessing, radioactive materials are produced and deposited in the Zircaloy cladding. Due to short depths of penetration, the majority of the fission products and actinide elements are located in the ZrO{sub 2} layer which forms on the surface of the cladding during fuel irradiation. Therefore, if the oxide layer is removed, the majority of the contamination should also be removed. It is very difficult, if not impossible to remove all of the activity from spent fuel cladding since traces of U and Th in the unirradiated Zircaloy

  10. Silicon cladding for mirror substrates

    NASA Astrophysics Data System (ADS)

    Duston, Christopher J.; Gunda, Nilesh; Schwartz, Jay R.; Robichaud, Joseph L.

    2009-08-01

    To reduce the finishing costs of silicon carbide mirror substrates, silicon claddings are applied allowing the surfaces to be more easily diamond turned and polished than the bare chemical vapor deposited (CVD) silicon carbide or bimodal reaction bonded SiC (RB-SiC). The benefits of using silicon as the optical face will be reviewed as will the process for applying plasma enhanced chemical vapor (PE-CVD) deposited amorphous silicon cladding on substrates. Using one mirror as an example, the successful finishing results will be shared.

  11. Vanadium diffusion coating on HT-9 cladding for mitigating the fuel cladding chemical interactions

    NASA Astrophysics Data System (ADS)

    Lo, Wei-Yang; Yang, Yong

    2014-08-01

    Fuel cladding chemical interaction (FCCI) has been identified as one of the crucial issues for developing Ferritic/Martensitic (F/M) stainless steel claddings for metallic fuels in a fast reactor. The anticipated elevated temperature and high neutron flux can significantly aggravate the FCCI, in terms of formation of inter-diffusion and lower melting point eutectic phases. To mitigate the FCCI, vanadium carbide coating as a diffusion barrier was deposited on the HT-9 substrate using a pack cementation diffusion coating (PCDC) method, and the processing temperature was optimized down to 730 °C. A solid metallurgical bonding between the coating layer and substrate was achieved, and the coating is free from through depth cracks. The microstructural characterizations using SEM and TEM show a nanostructured grain structure. EDS/WDS and XRD analysis confirm the phase of coating layer as V2C. Diffusion couple tests at 660 °C for 100 h demonstrate that V2C layer with a thickness of less than 5 μm can effectively eliminate the inter-diffusion between the lanthanide cerium and HT-9 steel.

  12. Optimizing electroslag cladding with finite element modeling

    SciTech Connect

    Li, M.V.; Atteridge, D.G.; Meekisho, L.

    1996-12-31

    Electroslag cladding of nickel alloys onto carbon steel propeller shafts was optimized in terms of interpass temperatures. A two dimensional finite element model was used in this study to analyze the heat transfer induced by multipass electroslag cladding. Changes of interpass temperatures during a cladding experiment with uniform initial temperature distribution on a section of shaft were first simulated. It was concluded that uniform initial temperature distribution would lead to interpass temperatures out of the optimal range if continuous cladding is expected. The difference in the cooling conditions among experimental and full size shafts and its impact on interpass temperatures during the cladding were discussed. Electroslag cladding onto a much longer shaft, virtually an semi infinite long shaft, was analyzed with specific reference to the practical applications of electroslag cladding. Optimal initial preheating temperature distribution was obtained for continuous cladding on full size shafts which would keep the interpass temperatures within the required range.

  13. Mechanism of stress-driven composition evolution during hetero-epitaxy in a ternary AlGaN system

    PubMed Central

    He, Chenguang; Qin, Zhixin; Xu, Fujun; Zhang, Lisheng; Wang, Jiaming; Hou, Mengjun; Zhang, Shan; Wang, Xinqiang; Ge, Weikun; Shen, Bo

    2016-01-01

    Two AlGaN samples with different strain were designed to investigate mechanism of stress-driven composition evolution. It is discovered that AlGaN grown on AlN or (AlN/GaN superlattices (SLs))/GaN both consist of two distinct regions with different compositions: transition region and uniform region, which is attributed to the compositional pulling effect. The formation of the transition region is due to the partial stress release caused by the generation of misfit dislocations near the hetero-interface. And the Al composition in the uniform region depends on the magnitude of residual strain. The difference in relaxation degree is 80.5% for the AlGaN epilayers grown on different underlayers, leading to a large Al composition difference of 22%. The evolutionary process of Al composition along [0001] direction was investigated in detail. PMID:27112969

  14. Laser diodes with 353 nm wavelength enabled by reduced-dislocation-density AlGaN templates

    SciTech Connect

    Crawford, Mary H.; Allerman, Andrew A.; Armstrong, Andrew M.; Smith, Michael L.; Cross, Karen C.

    2015-10-30

    We fabricated optically pumped and electrically injected ultraviolet (UV) lasers on reduced-threading-dislocation-density (reduced-TDD) AlGaN templates. The overgrowth of sub-micron-wide mesas in the Al0.32Ga0.68N templates enabled a tenfold reduction in TDD, to (2–3) × 108 cm–2. Optical pumping of AlGaN hetero-structures grown on the reduced-TDD templates yielded a low lasing threshold of 34 kW/cm2 at 346 nm. Room-temperature pulsed operation of laser diodes at 353 nm was demonstrated, with a threshold of 22.5 kA/cm2. Furthermore, reduced-TDD templates have been developed across the entire range of AlGaN compositions, presenting a promising approach for extending laser diodes into the deep UV.

  15. Mechanism of stress-driven composition evolution during hetero-epitaxy in a ternary AlGaN system.

    PubMed

    He, Chenguang; Qin, Zhixin; Xu, Fujun; Zhang, Lisheng; Wang, Jiaming; Hou, Mengjun; Zhang, Shan; Wang, Xinqiang; Ge, Weikun; Shen, Bo

    2016-01-01

    Two AlGaN samples with different strain were designed to investigate mechanism of stress-driven composition evolution. It is discovered that AlGaN grown on AlN or (AlN/GaN superlattices (SLs))/GaN both consist of two distinct regions with different compositions: transition region and uniform region, which is attributed to the compositional pulling effect. The formation of the transition region is due to the partial stress release caused by the generation of misfit dislocations near the hetero-interface. And the Al composition in the uniform region depends on the magnitude of residual strain. The difference in relaxation degree is 80.5% for the AlGaN epilayers grown on different underlayers, leading to a large Al composition difference of 22%. The evolutionary process of Al composition along [0001] direction was investigated in detail. PMID:27112969

  16. Mechanism of stress-driven composition evolution during hetero-epitaxy in a ternary AlGaN system

    NASA Astrophysics Data System (ADS)

    He, Chenguang; Qin, Zhixin; Xu, Fujun; Zhang, Lisheng; Wang, Jiaming; Hou, Mengjun; Zhang, Shan; Wang, Xinqiang; Ge, Weikun; Shen, Bo

    2016-04-01

    Two AlGaN samples with different strain were designed to investigate mechanism of stress-driven composition evolution. It is discovered that AlGaN grown on AlN or (AlN/GaN superlattices (SLs))/GaN both consist of two distinct regions with different compositions: transition region and uniform region, which is attributed to the compositional pulling effect. The formation of the transition region is due to the partial stress release caused by the generation of misfit dislocations near the hetero-interface. And the Al composition in the uniform region depends on the magnitude of residual strain. The difference in relaxation degree is 80.5% for the AlGaN epilayers grown on different underlayers, leading to a large Al composition difference of 22%. The evolutionary process of Al composition along [0001] direction was investigated in detail.

  17. Laser diodes with 353 nm wavelength enabled by reduced-dislocation-density AlGaN templates

    DOE PAGESBeta

    Crawford, Mary H.; Allerman, Andrew A.; Armstrong, Andrew M.; Smith, Michael L.; Cross, Karen C.

    2015-10-30

    We fabricated optically pumped and electrically injected ultraviolet (UV) lasers on reduced-threading-dislocation-density (reduced-TDD) AlGaN templates. The overgrowth of sub-micron-wide mesas in the Al0.32Ga0.68N templates enabled a tenfold reduction in TDD, to (2–3) × 108 cm–2. Optical pumping of AlGaN hetero-structures grown on the reduced-TDD templates yielded a low lasing threshold of 34 kW/cm2 at 346 nm. Room-temperature pulsed operation of laser diodes at 353 nm was demonstrated, with a threshold of 22.5 kA/cm2. Furthermore, reduced-TDD templates have been developed across the entire range of AlGaN compositions, presenting a promising approach for extending laser diodes into the deep UV.

  18. Persistent photoconductivity study in AlGaN superlattice

    NASA Astrophysics Data System (ADS)

    Wang, Li-wei; Xu, Jin-tong; Wang, Nili; Xu, Peng-xiao; Li, Xiangyang

    2014-11-01

    The transport properties of GaN and its alloys are attracting increasing interest due to the potential application of these materials for solar blind photodetectors and high mobility transistors. Because of the large band gap, the applications of AlxGa1-xN are extensive, such as for visible-blind ultraviolet detectors, laser diodes, and short-wave light emitting diodes (LEDs). However, the persistent photoconductivity (PPC) of GaN based photoconductive devices affects its applications. In order to study the origin of PPC, we designed solar blind ultraviolet photoconductive detector, which consists of n - Al0.65Ga0.35N top contact layer (100nm), n-Al0.42Ga0.58N/i-Al0.65Ga0.35N superlattice layers (200nm), i- Al0.65Ga0.35N layer (600nm), AlN buffer layer and double polished sapphire substrate. Moreover, there are photoconductive devices with different photosensitive areas. Investigations of electric-field effects and thermal effects on PPC in n-Al0.42Ga0.58N/i-Al0.65Ga0.35N superlattice are presented. We have observed that, by applying a high-voltage pulse, the course of PPC was effectively accelerated: With the same pulse width and different voltage, in the appropriate range, the higher of the voltage, the course of PPC was more effectively accelerated; with the same voltage and different pulse width, in the appropriate range, the wider of the pulse width, the course of PPC was more effectively accelerated. And PPC effect strongly depends on the temperature. The decay time of the PPC depend on the temperature and become longer with a decreasing temperature.

  19. Hydrogen permeation in FeCrAl alloys for LWR cladding application

    NASA Astrophysics Data System (ADS)

    Hu, Xunxiang; Terrani, Kurt A.; Wirth, Brian D.; Snead, Lance L.

    2015-06-01

    FeCrAl, an advanced oxidation-resistant iron-based alloy class, is a highly prevalent candidate as an accident-tolerant fuel cladding material. Compared with traditional zirconium alloy fuel cladding, increased tritium permeation through FeCrAl fuel cladding to the primary coolant is expected, raising potential safety concerns. In this study, the hydrogen permeability of several FeCrAl alloys was obtained using a static permeation test station, which was calibrated and validated using 304 stainless steel. The high hydrogen permeability of FeCrAl alloys leads to concerns with respect to potentially significant tritium release when used for fuel cladding in LWRs. The total tritium inventory inside the primary coolant of a light water reactor was quantified by applying a 1-dimensional steady state tritium diffusion model to demonstrate the dependence of tritium inventory on fuel cladding type. Furthermore, potential mitigation strategies for tritium release from FeCrAl fuel cladding were discussed and indicate the potential for application of an alumina layer on the inner clad surface to serve as a tritium barrier. More effort is required to develop a robust, economical mitigation strategy for tritium permeation in reactors using FeCrAl clad fuel assemblies.

  20. Hydrogen permeation in FeCrAl alloys for LWR cladding application

    DOE PAGESBeta

    Hu, Xunxiang; Terrani, Kurt A.; Wirth, Brian D.; Snead, Lance L.

    2015-03-19

    FeCrAl is an advanced oxidation-resistant iron-based alloy class, is a highly prevalent candidate as an accident-tolerant fuel cladding material. Compared with traditional zirconium alloy fuel cladding, increased tritium permeation through FeCrAl fuel cladding to the primary coolant is expected, raising potential safety concerns. In our study, the hydrogen permeability of several FeCrAl alloys was obtained using a static permeation test station, which was calibrated and validated using 304 stainless steel. The high hydrogen permeability of FeCrAl alloys leads to concerns with respect to potentially significant tritium release when used for fuel cladding in LWRs. Also, the total tritium inventory insidemore » the primary coolant of a light water reactor was quantified by applying a 1-dimensional steady state tritium diffusion model to demonstrate the dependence of tritium inventory on fuel cladding type. Furthermore, potential mitigation strategies for tritium release from FeCrAl fuel cladding were discussed and indicate the potential for application of an alumina layer on the inner clad surface to serve as a tritium barrier. More effort is required to develop a robust, economical mitigation strategy for tritium permeation in reactors using FeCrAl clad fuel assemblies.« less

  1. Hydrogen permeation in FeCrAl alloys for LWR cladding application

    SciTech Connect

    Hu, Xunxiang; Terrani, Kurt A.; Wirth, Brian D.; Snead, Lance L.

    2015-03-19

    FeCrAl is an advanced oxidation-resistant iron-based alloy class, is a highly prevalent candidate as an accident-tolerant fuel cladding material. Compared with traditional zirconium alloy fuel cladding, increased tritium permeation through FeCrAl fuel cladding to the primary coolant is expected, raising potential safety concerns. In our study, the hydrogen permeability of several FeCrAl alloys was obtained using a static permeation test station, which was calibrated and validated using 304 stainless steel. The high hydrogen permeability of FeCrAl alloys leads to concerns with respect to potentially significant tritium release when used for fuel cladding in LWRs. Also, the total tritium inventory inside the primary coolant of a light water reactor was quantified by applying a 1-dimensional steady state tritium diffusion model to demonstrate the dependence of tritium inventory on fuel cladding type. Furthermore, potential mitigation strategies for tritium release from FeCrAl fuel cladding were discussed and indicate the potential for application of an alumina layer on the inner clad surface to serve as a tritium barrier. More effort is required to develop a robust, economical mitigation strategy for tritium permeation in reactors using FeCrAl clad fuel assemblies.

  2. Cladding-mode obtained by core-offset structure and applied in fiber Bragg grating sensor

    NASA Astrophysics Data System (ADS)

    Zhang, Xinpu; Peng, Wei; Liu, Yun; Li, Hong; Jing, Zhenguo; Yu, Qi; Zhou, Xinlei; Yao, Wenjuan; Wang, Yanjie; Liang, Yuzhang

    2011-12-01

    Comparing to core-modes of optical fibers, some cladding-modes are more sensitive to the surroundings which are very valuable to sensing application; recently, a novel type of FBG sensor with core-offset structure attracts more and more interests. Normally, the forward core-mode is not only reflected and coupled to the backward core mode by the Fiber Bragg Grating in the step-type photosensitive single mode fiber, but also coupled to the backward cladding-modes and the radiation modes, eventually they will leak or be absorbed by the high refraction index coating layer. These backward cladding-modes can also be used for sensing analysis. In this paper, we propose and develop a core-offset structure to obtain the backward core-mode and backward cladding-modes by using the wavelength shift of the backward core-mode and the power of the backward cladding-modes in Fiber Bragg Grating sensor, and the power of the backward cladding-modes are independent from temperature variation. We develop a mode coupling sensor model between the forward core-mode and the backward cladding-modes, and demonstrate two coupling methods in the core-offset structure experimentally. The sensor is fabricated and demonstrated for refractive index monitoring. Some specific works are under investigation now, more analysis and fabrication will be done to improve this cladding-mode based sensor design for applicable sensing technology.

  3. An Innovative Ceramic Corrosion Protection System for Zircaloy Cladding

    SciTech Connect

    Ronald H. Baney, Dr. D. Butt, Dr. P. Demkowicz, Dr. G. Fuchs Department of Materials Science; James S. Tulenko, Department of Nuclear and Radiological Engineering; University of Florida.

    2003-02-19

    Light Water reactor (LWR) fuel performance is currently limited by thermal, chemical and mechanical constraints associated with the design, fabrication, and operation of the fuel in incore operation. Corrosion of the zirconium based (Zircaloy-4) alloy cladding of the fuel is a primary limiting factor. Recent success at the University of Florida in developing thin ceramic films with great adhesive properties for metal substrates offers an innovative breakthrough for eliminating a major weakness of the Zircaloy clad. ?The University of Florida proposes to coat the existing Zircaloy clad tubes with a ceramic coating for corrosion protection. An added bonus of this approach would be the implementation of a boron-containing burnable poison outer layer will also be demonstrated as part of the ceramic coating development. In this proposed effort, emphasis will be on the ceramic coating with only demonstration of feasibility on the burnable outer coating approach. This proposed program i s expected to give a step change (approximately a doubling) in clad lifetime before failure due to corrosion. In the development of ceramic coatings for Zircaloy-4 clad, silicon carbide and zirconium carbide coatings will first be applied to Zircaloy-4 coupons and cladding samples by thermal assisted chemical vapor deposition, plasma assisted chemical vapor deposition or by laser ablation deposition. All of these processes are in use at the University of Florida and have shown great potential. The questions of adhesion and thermal expansion mismatch of the ceramic coating to the Zircaloy substrate will be addressed. Several solutions to these conditions will be examined, if needed. These solutions include the use of a zirconium oxide compliant layer, employment of a laser roughened surface and the use of a gradient composition interlayer. These solutions have already been shown to be effective for other high modulus coatings on metal substrates. Mechanical properties and adhesion of the

  4. Fracture properties of a neutron-irradiated stainless steel submerged arc weld cladding overlay

    SciTech Connect

    Corwin, W.R.; Berggren, R.G.; Nanstad, R.K.

    1984-01-01

    The ability of stainless steel cladding to increase the resistance of an operating nuclear reactor pressure vessel to extension of surface flaws depends greatly on the properties of the irradiated cladding. Therefore, weld overlay cladding irradiated at temperatures and fluences relevant to power reactor operation was examined. The cladding was applied to a pressure vessel steel plate by the submerged arc, single-wire, oscillating-electrode method. Three layers of cladding provided a thickness adequate for fabrication of test specimens. The first layer was type 309, and the upper two layers were type 308 stainless steel. The type 309 was diluted considerably by excessive melting of the base plate. Specimens were taken from near the base plate-cladding interface and also from the upper layers. Charpy V-notch and tensile specimens were irradiated at 288/sup 0/C to a fluence of 2 x 10/sup 23/ neutrons/m/sup 2/ (>1 MeV). 10 refs., 16 figs., 4 tabs.

  5. ZIRCONIUM-CLADDING OF THORIUM

    DOEpatents

    Beaver, R.J.

    1961-11-21

    A method of cladding thorium with zirconium is described. The quality of the bond achieved between thorium and zirconium by hot-rolling is improved by inserting and melting a thorium-zirconium alloy foil between the two materials prior to rolling. (AEC)

  6. Effect of Temperature and Sheet Temper on Isothermal Solidification Kinetics in Clad Aluminum Brazing Sheet

    NASA Astrophysics Data System (ADS)

    Benoit, Michael J.; Whitney, Mark A.; Wells, Mary A.; Winkler, Sooky

    2016-07-01

    Isothermal solidification (IS) is a phenomenon observed in clad aluminum brazing sheets, wherein the amount of liquid clad metal is reduced by penetration of the liquid clad into the core. The objective of the current investigation is to quantify the rate of IS through the use of a previously derived parameter, the Interface Rate Constant (IRC). The effect of peak temperature and initial sheet temper on IS kinetics were investigated. The results demonstrated that IS is due to the diffusion of silicon (Si) from the liquid clad layer into the solid core. Reduced amounts of liquid clad at long liquid duration times, a roughened sheet surface, and differences in resolidified clad layer morphology between sheet tempers were observed. Increased IS kinetics were predicted at higher temperatures by an IRC model as well as by experimentally determined IRC values; however, the magnitudes of these values are not in good agreement due to deficiencies in the model when applied to alloys. IS kinetics were found to be higher for sheets in the fully annealed condition when compared with work-hardened sheets, due to the influence of core grain boundaries providing high diffusivity pathways for Si diffusion, resulting in more rapid liquid clad penetration.

  7. Effect of Temperature and Sheet Temper on Isothermal Solidification Kinetics in Clad Aluminum Brazing Sheet

    NASA Astrophysics Data System (ADS)

    Benoit, Michael J.; Whitney, Mark A.; Wells, Mary A.; Winkler, Sooky

    2016-09-01

    Isothermal solidification (IS) is a phenomenon observed in clad aluminum brazing sheets, wherein the amount of liquid clad metal is reduced by penetration of the liquid clad into the core. The objective of the current investigation is to quantify the rate of IS through the use of a previously derived parameter, the Interface Rate Constant (IRC). The effect of peak temperature and initial sheet temper on IS kinetics were investigated. The results demonstrated that IS is due to the diffusion of silicon (Si) from the liquid clad layer into the solid core. Reduced amounts of liquid clad at long liquid duration times, a roughened sheet surface, and differences in resolidified clad layer morphology between sheet tempers were observed. Increased IS kinetics were predicted at higher temperatures by an IRC model as well as by experimentally determined IRC values; however, the magnitudes of these values are not in good agreement due to deficiencies in the model when applied to alloys. IS kinetics were found to be higher for sheets in the fully annealed condition when compared with work-hardened sheets, due to the influence of core grain boundaries providing high diffusivity pathways for Si diffusion, resulting in more rapid liquid clad penetration.

  8. Microstructural examination of high temperature creep failure of Zircaloy-2 cladding in irradiated PHWR fuel pins

    NASA Astrophysics Data System (ADS)

    Mishra, Prerna; Sah, D. N.; Kumar, Sunil; Anantharaman, S.

    2012-10-01

    Cladding samples taken from the ballooned region of the irradiated Zircaloy-2 cladded PHWR fuel pins which failed during isothermal heating tests carried out at 800-900 °C were examined using optical and scanning electron microscopy. The examination of samples from the fuel pin tested at 900 °C showed an intergranular mode of failure in the cladding due to formation of cracks, cavities and zirconium hydride precipitates on the grain boundaries in the cladding material. A thin hard α-Zr(O) layer was observed on outer surface due to dissolution of the oxide layer formed during reactor operation. Grain boundary sliding was identified to be the main mode of creep deformation of Zircaloy-2 at 900 °C. Examination of the cladding tested at 800 °C showed absence of cracks or cavities in the deformed material and no localisation of hydrides was observed at the grain boundaries. The failure of the cladding occurred after necking followed by extensive wall thinning of the cladding tube.

  9. Extreme Radiation Hardness and Space Qualification of AlGaN Optoelectronic Devices

    SciTech Connect

    Sun, Ke-Xun; Balakrishnan, Kathik; Hultgren, Eric; Goebel, John; Bilenko, Yuri; Yang, Jinwei; Sun, Wenhong; Shatalov, Max; Hu, Xuhong; Gaska, Remis

    2010-09-21

    Unprecedented radiation hardness and environment robustness are required in the new generation of high energy density physics (HEDP) experiments and deep space exploration. National Ignition Facility (NIF) break-even shots will have a neutron yield of 1015 or higher. The Europa Jupiter System Mission (EJSM) mission instruments will be irradiated with a total fluence of 1012 protons/cm2 during the space journey. In addition, large temperature variations and mechanical shocks are expected in these applications under extreme conditions. Hefty radiation and thermal shields are required for Si and GaAs based electronics and optoelectronics devices. However, for direct illumination and imaging applications, shielding is not a viable option. It is an urgent task to search for new semiconductor technologies and to develop radiation hard and environmentally robust optoelectronic devices. We will report on our latest systematic experimental studies on radiation hardness and space qualifications of AlGaN optoelectronic devices: Deep UV Light Emitting Diodes (DUV LEDs) and solarblind UV Photodiodes (PDs). For custom designed AlGaN DUV LEDs with a central emission wavelength of 255 nm, we have demonstrated its extreme radiation hardness up to 2x1012 protons/cm2 with 63.9 MeV proton beams. We have demonstrated an operation lifetime of over 26,000 hours in a nitrogen rich environment, and 23,000 hours of operation in vacuum without significant power drop and spectral shift. The DUV LEDs with multiple packaging styles have passed stringent space qualifications with 14 g random vibrations, and 21 cycles of 100K temperature cycles. The driving voltage, current, emission spectra and optical power (V-I-P) operation characteristics exhibited no significant changes after the space environmental tests. The DUV LEDs will be used for photoelectric charge management in space flights. For custom designed AlGaN UV photodiodes with a central response wavelength of 255 nm, we have demonstrated

  10. Quantum chemical mechanism in parasitic reaction of AlGaN alloys formation

    NASA Astrophysics Data System (ADS)

    Makino, Osamu; Nakamura, Koichi; Tachibana, Akitomo; Tokunaga, Hiroki; Akutsu, Nakao; Matsumoto, Koh

    2000-06-01

    The mechanism of parasitic reactions among trimethylaluminum (TMA), trimethylgallium (TMG), and NH 3 in atmospheric pressure (AP) MOVPE for growth of AlGaN is theoretically studied using the quantum chemical method. The calculations show that metal-nitrogen chain growth reaction easily proceeds through the successive reactions of 'complex formation with NH 3' and 'CH 4 elimination by the bimolecular mechanism'. Additionally, a parasitic reaction in APMOVPE using other raw material is also investigated. The calculated result shows that small change of raw material raises activation energy of parasitic reaction, and, thus, the parasitic reaction is suppressed. This result suggests a way to improve APMOVPE by a suitable choice of substituent.

  11. Ray-optic analysis of the (bio)sensing ability of ring-cladding hollow waveguides

    NASA Astrophysics Data System (ADS)

    Zheltikov, A. M.

    2008-01-01

    Ray-optic analysis of transmission spectra and the leakage loss of ring-cladding hollow waveguides suggests that such waveguides offer an attractive platform for the creation of compact and efficient biochemical sensors and sensor arrays. The ring cladding in such waveguides serves as a built-in Fabry-Perot interferometer, allowing the detection of few-nanometer-thick molecular layers and ensuring a high sensitivity of transmission spectra of waveguide modes to small changes in the refractive index of an analyte filling the hollow core and air holes in the waveguide cladding.

  12. Process improvement in laser hot wire cladding for martensitic stainless steel based on the Taguchi method

    NASA Astrophysics Data System (ADS)

    Huang, Zilin; Wang, Gang; Wei, Shaopeng; Li, Changhong; Rong, Yiming

    2016-07-01

    Laser hot wire cladding, with the prominent features of low heat input, high energy efficiency, and high precision, is widely used for remanufacturing metal parts. The cladding process, however, needs to be improved by using a quantitative method. In this work, volumetric defect ratio was proposed as the criterion to describe the integrity of forming quality for cladding layers. Laser deposition experiments with FV520B, one of martensitic stainless steels, were designed by using the Taguchi method. Four process variables, namely, laser power (P), scanning speed (V s), wire feed rate (V f), and wire current (I), were optimized based on the analysis of signal-to-noise (S/N) ratio. Metallurgic observation of cladding layer was conducted to compare the forming quality and to validate the analysis method. A stable and continuous process with the optimum parameter combination produced uniform microstructure with minimal defects and cracks, which resulted in a good metallurgical bonding interface.

  13. Methods for improved growth of group III nitride buffer layers

    DOEpatents

    Melnik, Yurity; Chen, Lu; Kojiri, Hidehiro

    2014-07-15

    Methods are disclosed for growing high crystal quality group III-nitride epitaxial layers with advanced multiple buffer layer techniques. In an embodiment, a method includes forming group III-nitride buffer layers that contain aluminum on suitable substrate in a processing chamber of a hydride vapor phase epitaxy processing system. A hydrogen halide or halogen gas is flowing into the growth zone during deposition of buffer layers to suppress homogeneous particle formation. Some combinations of low temperature buffers that contain aluminum (e.g., AlN, AlGaN) and high temperature buffers that contain aluminum (e.g., AlN, AlGaN) may be used to improve crystal quality and morphology of subsequently grown group III-nitride epitaxial layers. The buffer may be deposited on the substrate, or on the surface of another buffer. The additional buffer layers may be added as interlayers in group III-nitride layers (e.g., GaN, AlGaN, AlN).

  14. Cobalt-Free Laser Cladding on AISI Type 316L Stainless Steel for Improved Cavitation and Slurry Erosion Wear Behavior

    NASA Astrophysics Data System (ADS)

    Paul, C. P.; Gandhi, B. K.; Bhargava, P.; Dwivedi, D. K.; Kukreja, L. M.

    2014-09-01

    Laser cladding of Colmonoy-5 (a nickel base alloy) and Metco-41C (an iron base alloy) on AISI type 316L stainless steel (SS316L) and their wear behaviors were investigated to establish Co-free clad layers for potential applications in nuclear industry. A 3.5 kW CO2 laser-based system was used to optimize the laser cladding on SS316L substrate. The observed optimum parameters were: laser power of 1.6 kW, scan speed of 0.6 m/min, and powder feed rate of 8 g/min with 60% overlapping. The microstructure studies revealed that the clad layers primarily comprise very fine columnar dendritic structures, while clad-substrate interface exhibited planar and non-epitaxial mode of solidification due to high cooling rates. The cavitation and slurry erosion behaviors of laser clad layers were also compared to that of Stellite-6 for potential direct replacement. The cavitation erosion resistance was improved by a factor of 1.6, 3.7, and 4.1, while the slurry erosion resistances at an impingement angle of 30° were 1.5, 4.8, and 1.8 times better for laser clad surfaces of Colmonoy-5, Metco-41C, and Stellite-6, respectively, as compared to that of bare SS316L substrate. The study demonstrated that Metco-41C is a better choice as Co-free clad material for potential nuclear applications.

  15. Cobalt-Free Laser Cladding on AISI Type 316L Stainless Steel for Improved Cavitation and Slurry Erosion Wear Behavior

    NASA Astrophysics Data System (ADS)

    Paul, C. P.; Gandhi, B. K.; Bhargava, P.; Dwivedi, D. K.; Kukreja, L. M.

    2014-12-01

    Laser cladding of Colmonoy-5 (a nickel base alloy) and Metco-41C (an iron base alloy) on AISI type 316L stainless steel (SS316L) and their wear behaviors were investigated to establish Co-free clad layers for potential applications in nuclear industry. A 3.5 kW CO2 laser-based system was used to optimize the laser cladding on SS316L substrate. The observed optimum parameters were: laser power of 1.6 kW, scan speed of 0.6 m/min, and powder feed rate of 8 g/min with 60% overlapping. The microstructure studies revealed that the clad layers primarily comprise very fine columnar dendritic structures, while clad-substrate interface exhibited planar and non-epitaxial mode of solidification due to high cooling rates. The cavitation and slurry erosion behaviors of laser clad layers were also compared to that of Stellite-6 for potential direct replacement. The cavitation erosion resistance was improved by a factor of 1.6, 3.7, and 4.1, while the slurry erosion resistances at an impingement angle of 30° were 1.5, 4.8, and 1.8 times better for laser clad surfaces of Colmonoy-5, Metco-41C, and Stellite-6, respectively, as compared to that of bare SS316L substrate. The study demonstrated that Metco-41C is a better choice as Co-free clad material for potential nuclear applications.

  16. Models for the Configuration and Integrity of Partially Oxidized Fuel Rod Cladding at High Temperatures

    SciTech Connect

    Siefken, L.J.

    1999-01-01

    Models were designed to resolve deficiencies in the SCDAP/RELAP5/MOD3.2 calculations of the configuration and integrity of hot, partially oxidized cladding. These models are expected to improve the calculations of several important aspects of fuel rod behavior. First, an improved mapping was established from a compilation of PIE results from severe fuel damage tests of the configuration of melted metallic cladding that is retained by an oxide layer. The improved mapping accounts for the relocation of melted cladding in the circumferential direction. Then, rules based on PIE results were established for calculating the effect of cladding that has relocated from above on the oxidation and integrity of the lower intact cladding upon which it solidifies. Next, three different methods were identified for calculating the extent of dissolution of the oxidic part of the cladding due to its contact with the metallic part. The extent of dissolution effects the stress and thus the integrity of the oxidic part of the cladding. Then, an empirical equation was presented for calculating the stress in the oxidic part of the cladding and evaluating its integrity based on this calculated stress. This empirical equation replaces the current criterion for loss of integrity which is based on temperature and extent of oxidation. Finally, a new rule based on theoretical and experimental results was established for identifying the regions of a fuel rod with oxidation of both the inside and outside surfaces of the cladding. The implementation of these models is expected to eliminate the tendency of the SCDAP/RELAP5 code to overpredict the extent of oxidation of the upper part of fuel rods and to underpredict the extent of oxidation of the lower part of fuel rods and the part with a high concentration of relocated material. This report is a revision and reissue of the report entitled, Improvements in Modeling of Cladding Oxidation and Meltdown.

  17. Direct Laser Cladding , Current Status and Future Scope of Application

    NASA Astrophysics Data System (ADS)

    Weisheit, A.; Gasser, A.; Backes, G.; Jambor, T.; Pirch, N.; Wissenbach, K.

    During the last decades Direct Laser Cladding has become an established technique in many industrial fields for applying wear and corrosion protection layers on metallic surfaces as well as for the repair of high value-added components. The most important application fields are die and tool making, turbine components for aero engines and power generation, machine components such as axes and gears, and oil drilling components. Continuous wave (CW) lasers with a power up to 18 kW are used on automated machines with three or more axes, enabling 3D cladding . The outstanding feature of DLC is the high precision which leads to a minimum heat input into the work piece and a very low distortion. Due to the high cooling rates a fine grained microstructure is achieved during solidification. A new development in laser cladding is micro cladding in a size range below 50 \\upmum especially for electronic and medical applications. Furthermore, additive manufacturing is coming again into focus as a clean and resource-efficient method to manufacture and modify functional prototypes as well as unique and small lot parts.

  18. Fundamental metallurgical aspects of axial splitting in zircaloy cladding

    SciTech Connect

    Chung, H. M.

    2000-04-03

    Fundamental metallurgical aspects of axial splitting in irradiated Zircaloy cladding have been investigated by microstructural characterization and analytical modeling, with emphasis on application of the results to understand high-burnup fuel failure under RIA situations. Optical microscopy, SEM, and TEM were conducted on BWR and PWR fuel cladding tubes that were irradiated to fluence levels of 3.3 x 10{sup 21} n cm{sup {minus}2} to 5.9 x 10{sup 21} n cm{sup {minus}2} (E > 1 MeV) and tested in hot cell at 292--325 C in Ar. The morphology, distribution, and habit planes of macroscopic and microscopic hydrides in as-irradiated and posttest cladding were determined by stereo-TEM. The type and magnitude of the residual stress produced in association with oxide-layer growth and dense hydride precipitation, and several synergistic factors that strongly influence axial-splitting behavior were analyzed. The results of the microstructural characterization and stress analyses were then correlated with axial-splitting behavior of high-burnup PWR cladding reported for simulated-RIA conditions. The effects of key test procedures and their implications for the interpretation of RIA test results are discussed.

  19. CBED study of grain misorientations in AlGaN epilayers.

    PubMed

    Sahonta, S-L; Cherns, D; Liu, R; Ponce, F A; Amano, H; Akasaki, I

    2005-04-01

    Large angle convergent beam electron diffraction (LACBED) has been used to examine AlGaN epilayers grown by facet-controlled epitaxial lateral overgrowth on GaN/(0001) sapphire substrates in prototype UV laser structures. The substrates, defined by masks with seed openings along a <10-10> stripe direction, had GaN seed columns with {11-22} surfaces. Studies were carried out on cross-sectional samples cut perpendicular to the stripe axis. An LACBED analysis of the orientation of (000 2) planes, and of the (11-20) planes parallel to the stripe axis, revealed that the AlGaN wings were both rotated by angles of 1-2 x 10(-2)radians about the 10-10 stripe axis with respect to the underlying GaN, and distorted due to misfit strains. It is shown that the results are consistent with the observed structure of the AlGaN/GaN and the wing/wing boundaries, and with a new model for the generation of a-type misfit dislocations at the AlGaN/GaN interface. PMID:15777597

  20. Microstructure and properties of Fe-based composite coating by laser cladding Fe-Ti-V-Cr-C-CeO2 powder

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Zou, Yong; Zou, Zengda; Wu, Dongting

    2015-01-01

    In situ TiC-VC reinforced Fe-based cladding layer was obtained on low carbon steel surface by laser cladding with Fe-Ti-V-Cr-C-CeO2 alloy powder. The microstructure, phases and properties of the cladding layer were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), transmission electron microscopy (TEM), potentio-dynamic polarization and electro-chemical impedance spectroscopy (EIS). Results showed Fe-Ti-V-Cr-C-CeO2 alloy powder formed a good cladding layer without defects such as cracks and pores. The phases of the cladding layer were α-Fe, γ-Fe, TiC, VC and TiVC2. The microstructures of the cladding layer matrix were lath martensite and retained austenite. The carbides were polygonal blocks with a size of 0.5-2 μm and distributed uniformly in the cladding layer. High resolution transmission electron microscopy showed the carbide was a complex matter composed of nano TiC, VC and TiVC2. The cladding layer with a hardness of 1030 HV0.2 possessed good wear and corrosion resistance, which was about 16.85 and 9.06 times than that of the substrate respectively.

  1. Simulation for spectral response of solar-blind AlGaN based p-i-n photodiodes

    NASA Astrophysics Data System (ADS)

    Xue, Shiwei; Xu, Jintong; Li, Xiangyang

    2015-04-01

    In this article, we introduced how to build a physical model of refer to the device structure and parameters. Simulations for solar-blind AlGaN based p-i-n photodiodes spectral characteristics were conducted in use of Silvaco TCAD, where device structure and parameters are comprehensively considered. In simulation, the effects of polarization, Urbach tail, mobility, saturated velocities and lifetime in AlGaN device was considered. Especially, we focused on how the concentration-dependent Shockley-Read-Hall (SRH) recombination model affects simulation results. By simulating, we analyzed the effects in spectral response caused by TAUN0 and TAUP0, and got the values of TAUN0 and TAUP0 which can bring a result coincides with test results. After that, we changed their values and made the simulation results especially the part under 255 nm performed better. In conclusion, the spectral response between 200 nm and 320 nm of solar-blind AlGaN based p-i-n photodiodes were simulated and compared with test results. We also found that TAUN0 and TAUP0 have a large impact on spectral response of AlGaN material.

  2. An extrinsic fmax > 100 GHz InAlN/GaN HEMT with AlGaN back barrier

    NASA Astrophysics Data System (ADS)

    Bo, Liu; Zhihong, Feng; Shaobo, Dun; Xiongwen, Zhang; Guodong, Gu; Yuangang, Wang; Peng, Xu; Zezhao, He; Shujun, Cai

    2013-04-01

    We report the DC and RF performance of InAlN/GaN high-electron mobility transistors with AlGaN back barrier grown on SiC substrates. These presented results confirm the high performance that is reachable by InAlN-based technology. The InAlN/GaN HEMT sample showed a high 2DEG mobility of 1550 cm2/(V·s) at a 2DEG density of 1.7 × 1013 cm-2. DC and RF measurements were performed on the unpassivated device with 0.2 μm “T“ gate. The maximum drain current density at VGS = 2 V is close to 1.05 A/mm in a reproducible way. The reduction in gate leakage current helps to increase the frequency performance of AlGaN back barrier devices. The power gain cut-off frequency of a transistor with an AlGaN back barrier is 105 GHz, which is much higher than that of the device without an AlGaN back barrier at the same gate length. These results indicate InAlN/GaN HEMT is a promising candidate for millimeter-wave application.

  3. CLAD DEGRADATION - FEPS SCREENING ARGUMENTS

    SciTech Connect

    R. Schreiner

    2004-10-21

    The purpose of this report is to evaluate and document the screening of the clad degradation features, events, and processes (FEPs) with respect to modeling used to support the Total System Performance Assessment-License Application (TSPA-LA). This report also addresses the effect of certain FEPs on both the cladding and the commercial spent nuclear fuel (CSNF), DOE-owned spent nuclear fuel (DSNF), and defense high-level waste (DHLW) waste forms, as appropriate to address the effects on multiple materials and both components (FEPs 2.1.09.09.0A, 2.1.09.11.0A, 2.1.11.05.0A, 2.1.12.02.0A, and 2.1.12.03.0A). These FEPs are expected to affect the repository performance during the postclosure regulatory period of 10,000 years after permanent closure. Table 1-1 provides the list of cladding FEPs, including their screening decisions (include or exclude). The primary purpose of this report is to identify and document the analysis, screening decision, and TSPA-LA disposition (for included FEPs) or screening argument (for excluded FEPs) for these FEPs related to clad degradation. In some cases, where a FEP covers multiple technical areas and is shared with other FEP reports, this report may provide only a partial technical basis for the screening of the FEP. The full technical basis for shared FEPs is addressed collectively by the sharing FEP reports. The screening decisions and associated TSPA-LA dispositions or screening arguments from all of the FEP reports are cataloged in a project-specific FEPs database.

  4. NUCLEAR REACTOR COMPENENT CLADDING MATERIAL

    DOEpatents

    Draley, J.E.; Ruther, W.E.

    1959-01-27

    Fuel elements and coolant tubes used in nuclear reactors of the heterogeneous, water-cooled type are described, wherein the coolant tubes extend through the moderator and are adapted to contain the fuel elements. The invention comprises forming the coolant tubes and the fuel element cladding material from an alloy of aluminum and nickel, or an alloy of aluminum, nickel, alloys are selected to prevent intergranular corrosion of these components by water at temperatures up to 35O deg C.

  5. Microstructure and phase evolution in laser clad chromium carbide-NiCrMoNb

    NASA Astrophysics Data System (ADS)

    Venkatesh, L.; Samajdar, I.; Tak, Manish; Doherty, Roger D.; Gundakaram, Ravi C.; Prasad, K. Satya; Joshi, S. V.

    2015-12-01

    Microstructural development in laser clad layers of Chromium carbide (CrxCy)-NiCrMoNb on SA 516 steel has been investigated. Although the starting powder contained both Cr3C2 and Cr7C3, the clad layers showed only the presence of Cr7C3. Microtexture measurements by electron back scattered diffraction (EBSD) revealed primary dendritic Cr7C3 with Ni rich FCC metallic phase being present in the interdendritic spaces. Further annealing of the laser clad layers and furnace melting of the starting powder confirmed that Cr7C3 is the primary as well as stable carbide phase in this multi component system. Increase in laser power and scanning speed progressively reduced carbide content in the laser clad layers. Increased scanning speed, which enhances the cooling rate, also led to reduction in the secondary arm spacing (λ2) of the Cr7C3 dendrites. The clad layer hardness increased with carbide content and with decreased dendrite arm spacing.

  6. Calculation of hydrogen and oxygen uptake in fuel rod cladding during severe accidents using the integral diffusion method -- Preliminary design report

    SciTech Connect

    Siefken, L.J.

    1999-02-01

    Preliminary designs are described for models of hydrogen and oxygen uptake in fuel rod cladding during severe accidents. Calculation of the uptake involves the modeling of seven processes: (1) diffusion of oxygen from the bulk gas into the boundary layer at the external cladding surface, (2) diffusion from the boundary layer into the oxide layer, (3) diffusion from the inner surface of the oxide layer into the metallic part of the cladding, (4) uptake of hydrogen in the event that the cladding oxide layer is dissolved in a steam-starved region, (5) embrittlement of cladding due to hydrogen uptake, (6) cracking of cladding during quenching due to its embrittlement and (7) release of hydrogen from the cladding after cracking of the cladding. An integral diffusion method is described for calculating the diffusion processes in the cladding. Experimental results are presented that show a rapid uptake of hydrogen in the event of dissolution of the oxide layer and a rapid release of hydrogen in the event of cracking of the oxide layer. These experimental results are used as a basis for calculating the rate of hydrogen uptake and the rate of hydrogen release. The uptake of hydrogen is limited to the equilibrium solubility calculated by applying Sievert's law. The uptake of hydrogen is an exothermic reaction that accelerates the heatup of a fuel rod. An embrittlement criteria is described that accounts for hydrogen and oxygen concentration and the extent of oxidation. A design is described for implementing the models for hydrogen and oxygen uptake and cladding embrittlement into the programming framework of the SCDAP/RELAP5 code. A test matrix is described for assessing the impact of the proposed models on the calculated behavior of fuel rods in severe accident conditions. This report is a revision and reissue of the report entitled; ``Preliminary Design Report for Modeling of Hydrogen Uptake in Fuel Rod Cladding During Severe Accidents.''

  7. Failure behavior of Zircaloy-4 cladding after oxidation and water quench

    NASA Astrophysics Data System (ADS)

    Kim, Jun Hwan; Lee, Myoung Ho; Choi, Byoung Kwon; Jeong, Yong Hwan

    2007-05-01

    Simulated LOCA (loss of coolant accident) tests and subsequent mechanical tests on Zircaloy-4 cladding were carried out to evaluate the failure behavior of the cladding. Zircaloy-4 claddings were oxidized in a steam environment from 900 to 1250 °C for a given time period followed by a flooding of cool water to simulate LOCA tests. After the simulated LOCA test, the ductility of the oxidized cladding was evaluated by mechanical tests such as ring compression test and 3-point bend test. Evaluation of the absorbed contents such as hydrogen and oxygen were also carried out. The results showed that Zircaloy-4 cladding failed during thermal shock when the ECR (equivalent cladding reacted) value exceeded 20%. Lower boundary of brittle failure at thermal shock corresponds to 20% of ECR line calculated by the Baker-Just equation regardless of test temperature. On the other hand, boundary of ductile failure by the mechanical test did not followed after the ECR line. It rapidly decreased above 1000 °C to show that all Zircaloy-4 claddings behaved brittle fracture above 1150 °C when it oxidized at 300 s. Microstructural analysis revealed that boundary of ductile failure by the mechanical test fitted well when the absorbed oxygen content inside the prior-β layer was below 0.5 wt%.

  8. Microsecond-long lasing delays in thin P-clad InGaAs QW lasers

    SciTech Connect

    Wu, C.H.; Miester, C.F; Zory, P.S.; Emanuel, M.A.

    1996-06-01

    Microsecond-long lasing delays have been observed in wide-stripe, thin p-clad, InGaAs single quantum well (QW) lasers with ``thick`` p{sup +} cap layers. Computer modeling indicates that localized refractive index changes in the cap layer due to ohmic heating from the con- tact resistance may be the root cause.

  9. Laser cladding of a Mg based Mg-Gd-Y-Zr alloy with Al-Si powders

    NASA Astrophysics Data System (ADS)

    Chen, Erlei; Zhang, Kemin; Zou, Jianxin

    2016-03-01

    In the present work, a Mg based Mg-Gd-Y-Zr alloy was subjected to laser cladding with Al-Si powders at different laser scanning speeds in order to improve its surface properties. It is observed that the laser clad layer mainly contains Mg2Si, Mg17Al12 and Al2(Gd,Y) phases distributed in the Mg matrix. The depth of the laser clad layer increases with decreasing the scanning speed. The clad layer has graded microstructures and compositions. Both the volume fraction and size of Mg2Si, Mg17Al12 and Al2(Gd,Y) phases decreases with the increasing depth. Due to the formation of these hardening phases, the hardness of clad layer reached a maximum value of HV440 when the laser scanning speed is 2 mm/s, more than 5 times of the substrate (HV75). Besides, the corrosion properties of the untreated and laser treated samples were all measured in a NaCl (3.5 wt.%) aqueous solution. The corrosion potential was increased from -1.77 V for the untreated alloy to -1.13 V for the laser clad alloy with scanning rate of 2 mm/s, while the corrosion current density was reduced from 2.10 × 10-5 A cm-2 to 1.64 × 10-6 A cm-2. The results show that laser cladding is an efficient method to improve surface properties of Mg-Rare earth alloys.

  10. Evaluation of the fabricability of advanced iron aluminide-clad austenitic stainless steel tubing

    SciTech Connect

    Mohn, W.R.; Topolski, M.J.

    1993-07-01

    Researchers at Babcock & Wilcox Alliance Research Center have investigated methods to produce bimetallic tubing consisting of iron aluminide-clad austenitic stainless steel for practical use in fossil fueled energy equipment. In the course of this work, the compatibility of iron aluminide with four candidate austenitic stainless steel substrates was first evaluated using diffusion couples. Based on these results, a combination of iron aluminide and 304 stainless steel was selected for further development. Two composite billets of this combination were then prepared and extruded in separate trails at 2200F and 2000F. Both extrusions yielded 2-inch OD clad tubes, each approximately 18 feet long. Results of the evaluation show that the tube extruded at 2000F had a sound, integrally bonded clad layer throughout its entire length. However, the tube extruded at 2200F exhibited regions of disbonding between the clad layer and the substrate. In supplement to this work, an assessment of the technical and economic merits of iron aluminide-clad austenitic stainless steel components in power generation systems was conducted by B&W Fossil Power Division. Future activities should include an investigation of lower extrusion processing temperatures to optimize the fabrication of high quality iron-aluminide clad tubing.

  11. Wear Characteristics of Ni-Based Hardfacing Alloy Deposited on Stainless Steel Substrate by Laser Cladding

    NASA Astrophysics Data System (ADS)

    Awasthi, Reena; Limaye, P. K.; Kumar, Santosh; Kushwaha, Ram P.; Viswanadham, C. S.; Srivastava, Dinesh; Soni, N. L.; Patel, R. J.; Dey, G. K.

    2015-03-01

    In this study, dry sliding wear characteristics of the Ni-based hardfacing alloy (Ni-Mo-Cr-Si) deposited on stainless steel SS316L substrate by laser cladding have been presented. Dry sliding wear behavior of the laser clad layer was evaluated against two different counter bodies, AISI 52100 chromium steel (~850 VHN) and tungsten carbide ball (~2200 VHN) to study both adhesive and abrasive wear characteristics, in comparison with the substrate SS316L using ball on plate reciprocating wear tester. The wear resistance was evaluated as a function of load and sliding speed for a constant sliding amplitude and sliding distance. The wear mechanisms were studied on the basis of wear surface morphology and microchemical analysis of the wear track using SEM-EDS. Laser clad layer of Ni-Mo-Cr-Si on SS316L exhibited much higher hardness (~700 VHN) than that of substrate SS316L (~200 VHN). The laser clad layer exhibited higher wear resistance as compared to SS316L substrate while sliding against both the counterparts. However, the improvement in the wear resistance of the clad layer as compared to the substrate was much higher while sliding against AISI 52100 chromium steel than that while sliding against WC, at the same contact stress intensity.

  12. Advanced Fuels Campaign Cladding & Coatings Meeting Summary

    SciTech Connect

    Not Listed

    2013-03-01

    The Fuel Cycle Research and Development (FCRD) Advanced Fuels Campaign (AFC) organized a Cladding and Coatings operational meeting February 12-13, 2013, at Oak Ridge National Laboratory (ORNL). Representatives from the U.S. Department of Energy (DOE), national laboratories, industry, and universities attended the two-day meeting. The purpose of the meeting was to discuss advanced cladding and cladding coating research and development (R&D); review experimental testing capabilities for assessing accident tolerant fuels; and review industry/university plans and experience in light water reactor (LWR) cladding and coating R&D.

  13. Protective claddings for high strength chromium alloys

    NASA Technical Reports Server (NTRS)

    Collins, J. F.

    1971-01-01

    The application of a Cr-Y-Hf-Th alloy as a protective cladding for a high strength chromium alloy was investigated for its effectiveness in inhibiting nitrogen embrittlement of a core alloy. Cladding was accomplished by a combination of hot gas pressure bonding and roll cladding techniques. Based on bend DBTT, the cladding alloy was effective in inhibiting nitrogen embrittlement of the chromium core alloy for up to 720 ks (200hours) in air at 1422 K (2100 F). A significant increase in the bend DBTT occurred with longer time exposures at 1422 K or short time exposures at 1589 K (2400 F).

  14. Characterization of Fuel-Cladding Bond Strength Using Laser Shock

    SciTech Connect

    James A. Smith; David L. Cottle; Barry H. Rabin

    2014-04-01

    This paper describes new laser-based capabilities for characterization of fuel-cladding bond strength in nuclear fuels, and presents preliminary results obtained from studies on as-fabricated monolithic fuel consisting of uranium-10 wt.% molybdenum alloys clad in 6061 aluminum by hot isostatic pressing. Two complementary experimental methods are employed, laser-shock testing and laser-ultrasonic imaging. Measurements are spatially localized, non-contacting and require minimum specimen preparation, and are therefore ideally suited for applications involving radioactive materials, including irradiated materials. The theoretical principles and experimental approaches employed in characterization of nuclear fuel plates are described. The ability to measure layer thicknesses, elastic properties of the constituents, and the location and nature of laser-shock induced debonds is demonstrated, and preliminary bond strength measurement results are discussed.

  15. Deep ultraviolet photoluminescence of Tm-doped AlGaN alloys

    SciTech Connect

    Nepal, N.; Zavada, J. M.; Lee, D. S.; Steckl, A. J.; Sedhain, A.; Lin, J. Y.; Jiang, H. X.

    2009-03-16

    The ultraviolet (UV) photoluminescence (PL) properties of Tm-doped Al{sub x}Ga{sub 1-x}N (0.39{<=}x{<=}1) alloys grown by solid-source molecular beam epitaxy were probed using above-bandgap excitation from a laser source at 197 nm. The PL spectra show dominant UV emissions at 298 and 358 nm only for samples with x=1 and 0.81. Temperature dependence of the PL intensities of these emission lines reveals exciton binding energies of 150 and 57 meV, respectively. The quenching of these UV emissions appears related to the thermal activation of the excitons bound to rare-earth structured isovalent (RESI) charge traps, which transfer excitonic energy to Tm{sup 3+} ions resulting in the UV emissions. A model of the RESI trap levels in AlGaN alloys is presented.

  16. Engineering the Carrier Dynamics of InGaN Nanowire White Light-Emitting Diodes by Distributed p-AlGaN Electron Blocking Layers

    PubMed Central

    Nguyen, Hieu Pham Trung; Djavid, Mehrdad; Woo, Steffi Y.; Liu, Xianhe; Connie, Ashfiqua T.; Sadaf, Sharif; Wang, Qi; Botton, Gianluigi A.; Shih, Ishiang; Mi, Zetian

    2015-01-01

    We report on the demonstration of a new type of axial nanowire LED heterostructures, with the use of self-organized InGaN/AlGaN dot-in-a-wire core-shell nanowire arrays. The large bandgap AlGaN shell is spontaneously formed on the sidewall of the nanowire during the growth of AlGaN barrier of the quantum dot active region. As such, nonradiative surface recombination, that dominates the carrier dynamics of conventional axial nanowire LED structures, can be largely eliminated, leading to significantly increased carrier lifetime from ~0.3 ns to 4.5 ns. The luminescence emission is also enhanced by orders of magnitude. Moreover, the p-doped AlGaN barrier layers can function as distributed electron blocking layers (EBLs), which is found to be more effective in reducing electron overflow, compared to the conventional AlGaN EBL. The device displays strong white-light emission, with a color rendering index of ~95. An output power of >5 mW is measured for a 1 mm × 1 mm device, which is more than 500 times stronger than the conventional InGaN axial nanowire LEDs without AlGaN distributed EBLs. PMID:25592057

  17. Engineering the Carrier Dynamics of InGaN Nanowire White Light-Emitting Diodes by Distributed p-AlGaN Electron Blocking Layers

    NASA Astrophysics Data System (ADS)

    Nguyen, Hieu Pham Trung; Djavid, Mehrdad; Woo, Steffi Y.; Liu, Xianhe; Connie, Ashfiqua T.; Sadaf, Sharif; Wang, Qi; Botton, Gianluigi A.; Shih, Ishiang; Mi, Zetian

    2015-01-01

    We report on the demonstration of a new type of axial nanowire LED heterostructures, with the use of self-organized InGaN/AlGaN dot-in-a-wire core-shell nanowire arrays. The large bandgap AlGaN shell is spontaneously formed on the sidewall of the nanowire during the growth of AlGaN barrier of the quantum dot active region. As such, nonradiative surface recombination, that dominates the carrier dynamics of conventional axial nanowire LED structures, can be largely eliminated, leading to significantly increased carrier lifetime from ~0.3 ns to 4.5 ns. The luminescence emission is also enhanced by orders of magnitude. Moreover, the p-doped AlGaN barrier layers can function as distributed electron blocking layers (EBLs), which is found to be more effective in reducing electron overflow, compared to the conventional AlGaN EBL. The device displays strong white-light emission, with a color rendering index of ~95. An output power of >5 mW is measured for a 1 mm × 1 mm device, which is more than 500 times stronger than the conventional InGaN axial nanowire LEDs without AlGaN distributed EBLs.

  18. Texture Evolution of Single-Pass Hot-Rolled 5052/AZ31/5052 Clad Sheets

    NASA Astrophysics Data System (ADS)

    Nie, Huihui; Liang, Wei; Yang, Fuqian; Zheng, Liuwei; Li, Xianrong; Fan, Haiwei

    2016-06-01

    Three-layered 5052/AZ31/5052 clad sheets with maximum rolling reductions of 33% and 48% were prepared, using single-pass hot rolling followed by thermal annealing at 200°C for 1 h. The evolutions of microstructures and textures were analyzed. The experimental results show that the AZ31 layer exhibited a typical deformation microstructure with rolling-induced twins. The AZ31 layer with the 33% rolling reduction possessed a texture with the basal pole tilting about 35° away from normal direction to transverse direction and the majority of twins consists of {10 bar{1} 1}-{10 bar{1} 2} double twins and {10 bar{1} 2} tensile twins. The AZ31 layer with the 48% rolling reduction possessed a typical basal texture because {10 bar{1} 1} compression twins were activated by c-axis strain to compete with the tensile twins. No intermetallics were observed after annealing, and recrystallization occurred preferentially at the interface between AZ31 and 5052. The typical rolling texture of the 5052 layer disappeared, and the stable {001} <110> rotation cube component was dominant. The tensile test of the rolled three-layered 5052/AZ31/5052 clad sheets was performed. The tensile experimental results show that the annealed clad sheets with 33% rolling reduction and smaller degree of recrystallization have the largest elongation of 22.5% and larger ultimate tensile strength (UTS) than the annealed clad sheets with 48% rolling reduction.

  19. Interaction of a fuel cladding with uranium carbonitride in electrogenerating channel

    NASA Astrophysics Data System (ADS)

    Vasil'ev, I. V.; Ivanov, A. S.; Kaynov, V. B.; Churin, V. A.

    2013-12-01

    Samples of the fuel cladding of electrogenerating channel no. 30, which was included in the setup Ya-82 during nuclear power tests, are studied. The structure of the samples and the distribution of U, Mo, Nb, Cs, C, and N over the cladding thickness are investigated. The X-ray spectrometry microanalysis of the samples is performed at the MAR-3 modernized microanalyzer. A layered structure of the cladding is revealed using the method of scanning electron microscopy. Clusters of pores and other defects are observed at the boundaries of the layers. It is found that the uranium concentration profiles in different passages (at different points of the sample) are distinguished qualitatively. Three types of profiles are observed: firstly, profiles with no visible concentration of uranium above the background level; secondly, monotonically decaying profiles corresponding to the diffusion-induced penetration of uranium; and, thirdly, nonmonotonic concentration profiles. The depth of penetration of uranium into the cladding is ˜105 nm. The peaks of uranium concentration are near the boundaries of the observed layers. It is found that cesium penetrates the tungsten coating and molybdenum cladding. Domains with the increased carbon content are revealed. A stepwise growth in the nitrogen concentration is observed in the region occupied by the tungsten coating.

  20. AlGaN Channel High Electron Mobility Transistors: Device Performance and Power-Switching Figure of Merit

    NASA Astrophysics Data System (ADS)

    Raman, Ajay; Dasgupta, Sansaptak; Rajan, Siddharth; Speck, James S.; Mishra, Umesh K.

    2008-05-01

    In this paper, AlGaN channels for high electron mobility transistors (HEMTs) have been evaluated based on a power device figure of merit. AlGaN-channel HEMTs grown on SiC substrates by plasma-assisted molecular beam epitaxy (PAMBE) were fabricated. Maximum saturation current of 0.55 A/mm was obtained at VGS=1 V. Current-gain cutoff ( ft) and power-gain cutoff ( fmax) frequencies obtained from small signal measurements were ft=13.2 GHz and fmax=41 GHz. Pulsed current-voltage (I-V) measurements at 200 ns showed no dispersion in I-V curves. Large signal continuous wave (CW) measurement yielded an output power density of 4.5 W/mm with power added efficiency (PAE) of 59% at 4 GHz. This work demonstrates the potential of AlGaN channel HEMTs for high voltage switching and microwave power applications.

  1. Ultrasonic monitoring of material processing using clad buffer rod sensors

    NASA Astrophysics Data System (ADS)

    Ramos Franca, Demartonne

    Ultrasonic sensors and techniques are developed for in-line monitoring of polymer extrusion, cleanliness of molten metals and liquid flow speed at elevated temperature. Pulse-echo mode is used for the first two processes, while the through-transmission mode is applied in the third one. The ultrasonic probe consists of high performance clad buffer rods with different dimensions to thermally isolate the commercial ultrasonic transducer from materials at high temperature. The clad buffer rods are made of steel, polymer and ceramic. Steel clad buffer rods are introduced for in-line monitoring of polymer extrusion processes. Owing to its superior performance in pulse-echo mode, for the first time such a probe is installed and performs ultrasonic monitoring in the die of a co-extrusion machine and in the barrel section of a twin-screw extruder. It can reveal a variety of information relevant to process parameters, such as polymer layer thickness, interface location and adhesion quality, stability, or polymer composition change. For the ultrasonic monitoring of polymer processes, probes with acoustic impedance that matches that of the processed polymer may offer certain advantages such as quantitative viscoelastic evaluation; thus high temperature polymer clad buffer rods, in particular PEEK, are developed. It is demonstrated that this new probe exhibits unique advantages for in-line monitoring of the cure of epoxies and polymer extrusion process. Long steel clad buffer rods with a spherical focus lens machined at the probing end are proposed for cleanliness evaluation of molten metals. The potential of this focusing probe is demonstrated by means of high-resolution imaging and particles detection in molten zinc at temperatures higher than 600°C, using a single probe operated at pulse-echo mode. A contrapropagating ultrasonic flowmeter employing steel clad buffer rods is devised to operate at high temperature. It is demonstrated that these rods guide ultrasonic signals

  2. Parametric Study and Multi-Criteria Optimization in Laser Cladding by a High Power Direct Diode Laser

    NASA Astrophysics Data System (ADS)

    Farahmand, Parisa; Kovacevic, Radovan

    2014-12-01

    In laser cladding, the performance of the deposited layers subjected to severe working conditions (e.g., wear and high temperature conditions) depends on the mechanical properties, the metallurgical bond to the substrate, and the percentage of dilution. The clad geometry and mechanical characteristics of the deposited layer are influenced greatly by the type of laser used as a heat source and process parameters used. Nowadays, the quality of fabricated coating by laser cladding and the efficiency of this process has improved thanks to the development of high-power diode lasers, with power up to 10 kW. In this study, the laser cladding by a high power direct diode laser (HPDDL) as a new heat source in laser cladding was investigated in detail. The high alloy tool steel material (AISI H13) as feedstock was deposited on mild steel (ASTM A36) by a HPDDL up to 8kW laser and with new design lateral feeding nozzle. The influences of the main process parameters (laser power, powder flow rate, and scanning speed) on the clad-bead geometry (specifically layer height and depth of the heat affected zone), and clad microhardness were studied. Multiple regression analysis was used to develop the analytical models for desired output properties according to input process parameters. The Analysis of Variance was applied to check the accuracy of the developed models. The response surface methodology (RSM) and desirability function were used for multi-criteria optimization of the cladding process. In order to investigate the effect of process parameters on the molten pool evolution, in-situ monitoring was utilized. Finally, the validation results for optimized process conditions show the predicted results were in a good agreement with measured values. The multi-criteria optimization makes it possible to acquire an efficient process for a combination of clad geometrical and mechanical characteristics control.

  3. Cladding Attachment Over Thick Exterior Insulating Sheathing

    SciTech Connect

    Baker, P.; Eng, P.; Lepage, R.

    2014-01-01

    The addition of insulation to the exterior of buildings is an effective means of increasing the thermal resistance of both wood framed walls as well as mass masonry wall assemblies. For thick layers of exterior insulation (levels greater than 1.5 inches), the use of wood furring strips attached through the insulation back to the structure has been used by many contractors and designers as a means to provide a convenient cladding attachment location (Straube and Smegal 2009, Pettit 2009, Joyce 2009, Ueno 2010). The research presented in this report is intended to help develop a better understanding of the system mechanics involved and the potential for environmental exposure induced movement between the furring strip and the framing. BSC sought to address the following research questions: 1. What are the relative roles of the mechanisms and the magnitudes of the force that influence the vertical displacement resistance of the system? 2. Can the capacity at a specified deflection be reliably calculated using mechanics based equations? 3. What are the impacts of environmental exposure on the vertical displacement of furring strips attached directly through insulation back to a wood structure?

  4. Cladding Attachment Over Thick Exterior Insulating Sheathing

    SciTech Connect

    Baker, P.; Eng, P.; Lepage, R.

    2014-01-01

    The addition of insulation to the exterior of buildings is an effective means of increasing the thermal resistance of both wood framed walls as well as mass masonry wall assemblies. For thick layers of exterior insulation (levels greater than 1.5 inches), the use of wood furring strips attached through the insulation back to the structure has been used by many contractors and designers as a means to provide a convenient cladding attachment location (Straube and Smegal 2009, Pettit 2009, Joyce 2009, Ueno 2010). The research presented in this report is intended to help develop a better understanding of the system mechanics involved and the potential for environmental exposure induced movement between the furring strip and the framing. BSC sought to address the following research questions: 1.What are the relative roles of the mechanisms and the magnitudes of the force that influence the vertical displacement resistance of the system? 2.Can the capacity at a specified deflection be reliably calculated using mechanics based equations? 3.What are the impacts of environmental exposure on the vertical displacement of furring strips attached directly through insulation back to a wood structure?

  5. Impact of stress relaxation in GaAsSb cladding layers on quantum dot creation in InAs/GaAsSb structures grown on GaAs (001)

    SciTech Connect

    Bremner, S. P.; Ban, K.-Y.; Faleev, N. N.; Honsberg, C. B.; Smith, D. J.

    2013-09-14

    We describe InAs quantum dot creation in InAs/GaAsSb barrier structures grown on GaAs (001) wafers by molecular beam epitaxy. The structures consist of 20-nm-thick GaAsSb barrier layers with Sb content of 8%, 13%, 15%, 16%, and 37% enclosing 2 monolayers of self-assembled InAs quantum dots. Transmission electron microscopy and X-ray diffraction results indicate the onset of relaxation of the GaAsSb layers at around 15% Sb content with intersected 60° dislocation semi-loops, and edge segments created within the volume of the epitaxial structures. 38% relaxation of initial elastic stress is seen for 37% Sb content, accompanied by the creation of a dense net of dislocations. The degradation of In surface migration by these dislocation trenches is so severe that quantum dot formation is completely suppressed. The results highlight the importance of understanding defect formation during stress relaxation for quantum dot structures particularly those with larger numbers of InAs quantum-dot layers, such as those proposed for realizing an intermediate band material.

  6. Development of clad boiler tubes extruded from bimetallic centrifugal castings

    NASA Astrophysics Data System (ADS)

    Sponseller, D. L.; Timmons, G. A.; Bakker, W. T.

    1998-04-01

    Wrought tubes of T-11 steel, externally clad with SS310, have been produced by a new method (U.S. Patent 5,558,150). The alloys were united directly from the molten state by centrifugal casting. In the optimum process, temperatures were controlled to prevent meltback of the SS310 outer layer by the higher melting T-11 stream. Hollow extrusion billets were prepared from the heavy-walled cast bimetallic tubes and successfully hot extruded (at a ratio of 13.4) to 84-mm (3.3 in.) OD X 64-mm (2.5-in.) ID tubes, and (at a ratio of 37.6) to 51-mm (2-in.) OD X 38-mm (1.5-in.) ID tubes. In all, 10 castings were produced, and 12 billets were extruded to tubes. For the most part, thicknesses of the cladding and of the tube wall are rather uniform around the circumference and from end to end of the tubes. Hardness and tensile properties of annealed 51-mm (2-in.) tubes are uniform from end to end of a tube, and between tubes, and readily conform to ASTM A 213; tubes satisfy the flattening and flaring requirements of ASTM A 450. The cladding is metallurgically bonded to the base metal, as revealed by metallography, and by two tests developed for this study: a bond shear strength test and a twist test. In the latter test, rings 3.1 mm (0.125 in.) in thickness are slotted and severely twisted with a special tool. In tubes made by the optimum process, minute fissures that form adjacent to some of the pressure points during twist testing occupy just 3 % of the bond-line length. Cost estimates for commercial production of 51-mm (2-in.) tubes via the centrifugal casting route suggest that such tubes should be considerably less expensive than conventionally clad tubes (extruded from composite billets assembled from heavy-walled wrought tubes).

  7. Evolution of pores in the fuel cladding of the electrogenerating channel

    SciTech Connect

    Vasil’ev, I. V. Ivanov, A. S.

    2014-12-15

    The results of reactor tests of carbonitride fuel in a monocrystalline cladding from a molybdenum-based alloy that were carried out earlier on an experimental setup Ya-82 for 8 to 300 h at a temperature of ∼1500°C can be used in order to prove the operational reliability of fuel elements in the design of a megawatt nuclear power plant for a spacecraft. A raster image of the surface of a sample of cladding shows that the interfaces between the layers are decorated by pores. This result is explained in this work by the theory of coalescence. The mechanisms responsible for the evolution of pores taking place at the parameters of a Ya-82 setup are considered. The effect of decoration by pores of the interfaces between the layers of a sample of cladding of the electrogenerating channel by carrying out reactor tests is explained. The dependence of the average radius of pores on the duration of the experiment is obtained. An evaluation of the average sizes of pores arising under the conditions of the experiment gives a value of ∼2 μm, which is in agreement with the experimental data. A computational study of swelling of the cladding material in the process of irradiation is performed. Predictive estimates of the behavior of the porous system and swelling of the cladding material for a megawatt class nuclear power plant are made.

  8. The impact of the initial state on the kinetics of oxidation ion- modified fuel cladding alloy E110

    NASA Astrophysics Data System (ADS)

    Kalin, B. A.; Volkov, N. V.; Valikov, R. A.; Yashin, A. S.; Yakutkina, T. V.

    2016-04-01

    The paper examines the impact of the initial state (the presence of impurities, surface preparation), and surface alloying on the kinetics of the oxidation of fuel cladding alloy E110. The studies concluded that the use of ionic polishing instead of traditional chemical polishing helps to reduce the rate of oxidation of zirconium alloys. Also studied the effect of alloying elements introduced in the surface layers of claddings by ion mixing on the kinetics of the oxidation of the alloy E110.

  9. Bioactivity of calcium phosphate bioceramic coating fabricated by laser cladding

    NASA Astrophysics Data System (ADS)

    Zhu, Yizhi; Liu, Qibin; Xu, Peng; Li, Long; Jiang, Haibing; Bai, Yang

    2016-05-01

    There were always strong expectations for suitable biomaterials used for bone regeneration. In this study, to improve the biocompatiblity of titanium alloy, calcium phosphate bioceramic coating was obtained by laser cladding technology. The microstructure, phases, bioactivity, cell differentiation, morphology and resorption lacunae were investigated by optical microscope (OM), x-ray diffraction (XRD), methyl thiazolyl tetrazolium (MTT) assay, tartrate-resistant acid phosphatase (TRAP) staining and scanning electronic microscope (SEM), respectively. The results show that bioceramic coating consists of three layers, which are a substrate, an alloyed layer and a ceramic layer. Bioactive phases of β-tricalcium phosphate (β-TCP) and hydroxyapatite (HA) were found in ceramic coating. Osteoclast precursors have excellent proliferation on the bioceramic surface. The bioceramics coating could be digested by osteoclasts, which led to the resorption lacunae formed on its surface. It revealed that the gradient bioceramic coating has an excellent bioactivity.

  10. Testing of uranium nitride fuel in T-111 cladding at 1200 K cladding temperature

    NASA Technical Reports Server (NTRS)

    Rohal, R. G.; Tambling, T. N.; Smith, R. L.

    1973-01-01

    Two groups of six fuel pins each were assembled, encapsulated, and irradiated in the Plum Brook Reactor. The fuel pins employed uranium mononitride (UN) in a tantalum alloy clad. The first group of fuel pins was irradiated for 1500 hours to a maximum burnup of 0.7-atom-percent uranium. The second group of fuel pins was irradiated for about 3000 hours to a maximum burnup of 1.0-atom-percent uranium. The average clad surface temperature during irradiation of both groups of fuel pins was approximately 1200 K. The postirradiation examination revealed the following: no clad failures or fuel swelling occurred; less than 1 percent of the fission gases escaped from the fuel; and the clad of the first group of fuel pins experienced clad embrittlement whereas the second group, which had modified assembly and fabrication procedures to minimize contamination, had a ductile clad after irradiation.

  11. Pellet-clad interaction (PCI) failures of zirconium alloy fuel cladding — A review

    NASA Astrophysics Data System (ADS)

    Cox, B.

    1990-08-01

    This review summarizes the history of the appearance and cure of pellet-cladding interaction (PCI) failures during the operation of Zircaloy clad UO 2 fuel in a number of reactors. The work carried out to permit unrestricted operation of reactors without causing PCI failures has led to the universal adoption of the CANLUB-graphite coated cladding in CANDU reactors, and to the wide adoption of Zr-liner cladding in BWRs. There has only been a low incidence of PCI failures in PWR cladding, and the problem has not loomed large enough to require the adoption of either of the above protective methods in these reactors, although experimental liner cladding has been tested. The extensive work on the mechanism of PCI failures (leading to the conclusion that an SCC process induced by fission product iodine is the most probable cause) is summarised.

  12. Cascaded-cladding-pumped cascaded Raman fiber amplifier.

    PubMed

    Jiang, Huawei; Zhang, Lei; Feng, Yan

    2015-06-01

    The conversion efficiency of double-clad Raman fiber laser is limited by the cladding-to-core area ratio. To get high conversion efficiency, the inner-cladding-to-core area ratio has to be less than about 8, which limits the brightness enhancement. To overcome the problem, a cascaded-cladding-pumped cascaded Raman fiber laser with multiple-clad fiber as the Raman gain medium is proposed. A theoretical model of Raman fiber amplifier with multiple-clad fiber is developed, and numerical simulation proves that the proposed scheme can improve the conversion efficiency and brightness enhancement of cladding pumped Raman fiber laser. PMID:26072764

  13. Nuclear analyses of supercritical water cooled reactor with carbon nano-tube cladding

    SciTech Connect

    Uenohara, Y.; Yamano, N.

    2012-07-01

    The authors have confirmed the feasibility of the dual layer clad comprised of iron and carbon nano-tube to problems of Super Critical Water Reactor cores. Continuous energy Monte Carlo method was applied. The difference between JENDL-3.3 and ENDF-6 was confirmed. Depletion was carried out. (authors)

  14. Fabrication of Very High Efficiency 5.8 GHz Power Amplifiers using AlGaN HFETs on SiC Substrates for Wireless Power Transmission

    NASA Technical Reports Server (NTRS)

    Sullivan, Gerry

    2001-01-01

    For wireless power transmission using microwave energy, very efficient conversion of the DC power into microwave power is extremely important. Class E amplifiers have the attractive feature that they can, in theory, be 100% efficient at converting, DC power to RF power. Aluminum gallium nitride (AlGaN) semiconductor material has many advantageous properties, relative to silicon (Si), gallium arsenide (GaAs), and silicon carbide (SiC), such as a much larger bandgap, and the ability to form AlGaN/GaN heterojunctions. The large bandgap of AlGaN also allows for device operation at higher temperatures than could be tolerated by a smaller bandgap transistor. This could reduce the cooling requirements. While it is unlikely that the AlGaN transistors in a 5.8 GHz class E amplifier can operate efficiently at temperatures in excess of 300 or 400 C, AlGaN based amplifiers could operate at temperatures that are higher than a GaAs or Si based amplifier could tolerate. Under this program, AlGaN microwave power HFETs have been fabricated and characterized. Hybrid class E amplifiers were designed and modeled. Unfortunately, within the time frame of this program, good quality HFETs were not available from either the RSC laboratories or commercially, and so the class E amplifiers were not constructed.

  15. Deep ultraviolet detection dynamics of AlGaN based devices

    NASA Astrophysics Data System (ADS)

    Mazzeo, G.; Conte, G.; Reverchon, J.-L.; Dussaigne, A.; Duboz, J.-Y.

    2006-11-01

    The photoconductive response of AlGaN based UV detectors to 193nm excimer laser radiation is presented. Two devices have been tested: a metal-semiconductor-metal (MSM) planar structure and a Schottky diode. The transient response of the MSM device closely follows the laser pulses, with a photoconductive decay time constant shorter than 3ns. Conversely, the Schottky diode shows a slower photoconductive rise and decay kinetics due to the material series resistance coupled with the junction capacitance. Moreover, a longer time constant tail is also evident in this case with a characteristic time of about 40ns, due to the presence of trap states localized at 0.2-0.3eV from the band edge. The detection dynamics has been evaluated by changing the beam energy density between 2×10-5 and 0.2mJ/mm2. The signal increases linearly in the case of the MSM device up to 0.001mJ/mm2, whereas, for a further intensity rise, the response shows a sublinear behavior. On the contrary, the Schottky diode showed a linear trend inside the reduced 2×10-3-1.5×10-2mJ/mm2 range.

  16. Electrical and optical properties of Fe doped AlGaN grown by molecular beam epitaxy

    SciTech Connect

    Polyakov, A. Y.; Smirnov, N. B.; Govorkov, A. V.; Kozhukhova, E. A.; Dabiran, A. M.; Chow, P. P.; Wowchak, A. M.; Pearton, S. J.

    2010-01-15

    Electrical and optical properties of AlGaN grown by molecular beam epitaxy were studied in the Al composition range 15%-45%. Undoped films were semi-insulating, with the Fermi level pinned near E{sub c}-0.6-0.7 eV. Si doping to (5-7)x10{sup 17} cm{sup -3} rendered the 15% Al films conducting n-type, but a large portion of the donors were relatively deep (activation energy 95 meV), with a 0.15 eV barrier for capture of electrons giving rise to strong persistent photoconductivity (PPC) effects. The optical threshold of this effect was {approx}1 eV. Doping with Fe to a concentration of {approx}10{sup 17} cm{sup -3} led to decrease in concentration of uncompensated donors, suggesting compensation by Fe acceptors. Addition of Fe strongly suppressed the formation of PPC-active centers in favor of ordinary shallow donors. For higher Al compositions, Si doping of (5-7)x10{sup 17} cm{sup -3} did not lead to n-type conductivity. Fe doping shifted the bandedge luminescence by 25-50 meV depending on Al composition. The dominant defect band in microcathodoluminescence spectra was the blue band near 3 eV, with the energy weakly dependent on composition.

  17. Light emission and microstructure of Mg-doped AlGaN grown on patterned sapphire

    NASA Astrophysics Data System (ADS)

    Bell, A.; Liu, R.; Ponce, F. A.; Amano, H.; Akasaki, I.; Cherns, D.

    2003-01-01

    Distinct crystalline and optical properties have been observed in Mg-doped Al0.03Ga0.97N grown on a patterned sapphire substrate; the pattern consisting of etched trenches along the sapphire <112¯0> direction. The epilayer has two distinct regions: one grown directly onto the sapphire mesa and the other an epitaxial lateral overgrowth (ELO) region that overhangs the trench. Transmission electron microscopy shows the presence of pyramidal defects as well as large dislocation densities in the region grown directly on sapphire. In contrast, the ELO region is defect free and contains no Mg-related pyramidal defects. Cathodoluminescence measurements show superior near-band-edge emission in the ELO region, suggesting that the emission is susceptible to nonradiative centers caused by the high defect density in the rest of the sample. The Mg-related donor-acceptor-pair emission is fairly uniform throughout the film, indicating that it is not affected by the nonradiative centers. These optical and structural properties of AlGaN are closely related to the direction of the growth front.

  18. Detection of halide ions with AlGaN /GaN high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Kang, B. S.; Ren, F.; Kang, M. C.; Lofton, C.; Tan, Weihong; Pearton, S. J.; Dabiran, A.; Osinsky, A.; Chow, P. P.

    2005-04-01

    AlGaN /GaN high electron mobility transistors (HEMTs) both with and without a Au gate are found to exhibit significant changes in channel conductance upon exposing the gate region to various halide ions. The polar nature of the halide ions leads to a change of surface charge in the gate region on the HEMT, producing a change in the surface potential at the semiconductor/liquid interface. HEMTs with a Au-gate electrode not only doubled the sensitivity of changing the channel conductance as compared to gateless HEMT, but also showed the opposite conductance behavior. When anions adsorbed on the Au, they produced a counter charge for electrovalence. These anions drag some counter ions from the bulk solution or create an image positive charge on the metal for the required neutrality. The gateless HEMTs can be used as sensors for a range of chemicals through appropriate modification with covalently bonded halide functional groups on the Au surface. This creates many possibilities to functionalize the surface for a wide range of integrated biological, chemical, and fluid monitoring sensors.

  19. Electrical defects in AlGaN and InAlN

    NASA Astrophysics Data System (ADS)

    Johnstone, D.; Leach, Jacob H.; Kovalskii, Vladimir A.; Fan, Qian; Xie, Jingqiao; Morkoç, Hadis

    2009-02-01

    Compound semiconductors based on GaN have multiple functional applications. Useful compositions include GaN, and ternary and quaternary compositions of (AlGaIn)N. Defects arising from lattice mismatch, point defects, or impurities may act as electrical trapping centers and degrade device efficiency. Current-voltage, capacitance-voltage, thermal admittance spectroscopy (TAS), and deep level transient spectroscopy (DLTS) measurements are applied to characterize the defects in Al0.40Ga0.80N and In0.18Al0.82N in this report. Broad peaks with a shoulder at high temperature dominate the DLTS spectra in each of the materials. An acceptor trap associated with a dislocation appears at 340 K in AlGaN. The defect has an energy of 0.2 eV and capture cross section of 10-21 cm2. A second trap at 0.35 eV, 10-14 cm2 appears in the TAS measurements in addition to the trap at 0.2 eV. Defects in InAlN are dominated by a peak near 150 K. Two traps appear in the TAS measurements. Both traps in the InAlN are acceptors, based on a lack of field dependent emission rates using double pulse DLTS (DDLTS). The two energy levels in InAlN appear to be coupled, with only one state occupied at a time.

  20. Double-clad nuclear fuel safety rod

    DOEpatents

    McCarthy, William H.; Atcheson, Donald B.; Vaidyanathan, Swaminathan

    1984-01-01

    A device for shutting down a nuclear reactor during an undercooling or overpower event, whether or not the reactor's scram system operates properly. This is accomplished by double-clad fuel safety rods positioned at various locations throughout the reactor core, wherein melting of a secondary internal cladding of the rod allows the fuel column therein to shift from the reactor core to place the reactor in a subcritical condition.

  1. Structure and Properties of Ti-Nb-C Coatings Obtained by Non-vacuum Electron Beam Cladding

    NASA Astrophysics Data System (ADS)

    Lenivtseva, O. G.; Polyakov, I. A.; Lazurenko, D. V.; Lozhkin, V. S.

    2015-10-01

    In this study the structure and properties of surface-alloyed cp-titanium layers obtained by non-vacuum electron beam cladding of niobium carbide powders were analyzed. A thickness of coatings fabricated by single-layer cladding was 1.3 mm. Cladding of the second layer led to an increase in the thickness by 0.8 mm. It was found that titanium carbide particles of different morphology acted as strengthening structural elements. The X-ray diffraction (XRD) analysis revealed the presence of α-Ti (α'-Ti), β-Ti, and TiC in the cladded layer. The results of the energy dispersive X-ray (EDX) analysis indicated the presence of Nb in the titanium matrix as well as in the carbide phase. However, such phases as NbC and (Nb, Ti)C were not identified by the XRD analysis. Transmission electron microscopy (TEM) revealed zones containing an increased amount of Nb. The structure of these zones was represented by the β-Ti and ω-Ti precipitation. An average microhardness value of cladded layers was approximately 330 HV.

  2. Plasmonic gap-mode nanocavities with metallic mirrors in high-index cladding.

    PubMed

    Cheng, Pi-Ju; Weng, Chen-Ya; Chang, Shu-Wei; Lin, Tzy-Rong; Tien, Chung-Hao

    2013-06-01

    We theoretically analyze plasmonic gap-mode nanocavities covered by a thick cladding layer at telecommunication wavelengths. In the presence of high-index cladding materials such as semiconductors, the first-order hybrid gap mode becomes more promising for lasing than the fundamental one. Still, the significant mirror loss remains the main challenge to lasing. Using silver coatings within a decent thickness range at two end facets, we show that the reflectivity is substantially enhanced above 95 %. At a coating thickness of 50 nm and cavity length of 1.51 μm, the quality factor is about 150, and the threshold gain is lower than 1500 cm(-1). PMID:23736601

  3. Clad Degradation- Summary and Abstraction for LA

    SciTech Connect

    D. Stahl

    2004-10-01

    The purpose of this model report is to develop the summary cladding degradation abstraction that will be used in the Total System Performance Assessment for the License Application (TSPA-LA). Most civilian commercial nuclear fuel is encased in Zircaloy cladding. The model addressed in this report is intended to describe the postulated condition of commercial Zircaloy-clad fuel as a function of postclosure time after it is placed in the repository. Earlier total system performance assessments analyzed the waste form as exposed UO{sub 2}, which was available for degradation at the intrinsic dissolution rate. Water in the waste package quickly became saturated with many of the radionuclides, limiting their release rate. In the total system performance assessments for the Viability Assessment and the Site Recommendation, cladding was analyzed as part of the waste form, limiting the amount of fuel available at any time for degradation. The current model is divided into two stages. The first considers predisposal rod failures (most of which occur during reactor operation and associated activities) and postdisposal mechanical failure (from static loading of rocks) as mechanisms for perforating the cladding. Other fuel failure mechanisms including those caused by handling or transportation have been screened out (excluded) or are treated elsewhere. All stainless-steel-clad fuel, which makes up a small percentage of the overall amount of fuel to be stored, is modeled as failed upon placement in the waste packages. The second stage of the degradation model is the splitting of the cladding from the reaction of water or moist air and UO{sub 2}. The splitting has been observed to be rapid in comparison to the total system performance assessment time steps and is modeled to be instantaneous. After the cladding splits, the rind buildup inside the cladding widens the split, increasing the diffusion area from the fuel rind to the waste package interior. This model report summarizes

  4. Tunable polarization beam splitting based on a symmetrical metal-cladding waveguide structure.

    PubMed

    Wang, Yi; Cao, Zhuangqi; Li, Honggen; Shen, Qishun; Yuan, Wen; Xiao, Pingping

    2009-08-01

    Electrical tuning of polarization beam splitting is demonstrated in the structure of symmetrical metal-cladding waveguide by introducing optically nonlinear material into both the coupling prism and the guiding layer. Due to the anisotropy of the coupling material, different excitation conditions for TE and TM modes are obtained, which results in polarization-dependent reflections and transmissions. And the splitting effect of the two orthogonally polarized beams can be manipulated through an electrical modulation of the guiding layer properties. PMID:19654735

  5. Yb-doped large mode area fibers with depressed clad and dopant confinement

    NASA Astrophysics Data System (ADS)

    Roy, Vincent; Paré, Claude; Laperle, Pierre; Desbiens, Louis; Taillon, Yves

    2016-03-01

    Large mode area fibers with depressed-index cladding layer and confinement of rare-earth dopants can provide effective suppression of high-order modes. A polarization-maintaining Yb-doped double-clad fiber with 35/250 μm core/clad diameter has been fabricated from conventional methods according to this design. The fiber which has an effective mode area close to 500 μm2 yields near diffraction-limited output with beam quality factor M2 close to 1.1 when tested as a power amplifier with a coherent seed light source. Beam pointing measurements provide further evidence for near single-mode behavior as the pointing fluctuations are shown to be negligible once the fiber is coiled to a given diameter.

  6. Effect of zirconium oxide on the stress-corrosion susceptibility of irradiated Zircaloy cladding

    SciTech Connect

    Mattas, R.F.; Yaggee, F.L.; Neimark, L.A.

    1982-01-01

    Cladding specimens were obtained from two fuel rods irradiated in the Big Rock Point Reactor to a burnup of approximately 8 gigawatt days per ton. Both claddings had a uniform, thick (approximately 4/mu/m) zirconium oxide layer on the inner surface. The significant difference between the two rods was the degree of fission-gas release (0.2 versus 14.3 percent). The cladding specimens, with the fuel removed, were subjected to stress-rupture tests to evaluate their stress corrosion cracking (SCC) susceptibility at an initial iodine concentration of 0.6 mg/cm/sup 2/ and a temperature of 325 degree C. Specimens from the high-gas-release rod exhibited significantly increased susceptibility to iodine SCC. The results suggest that the inner-surface oxide provides a barrier to iodine penetration. 10 refs.

  7. Hydrides reorientation investigation of high burn-up PWR fuel cladding

    NASA Astrophysics Data System (ADS)

    Valance, Stéphane; Bertsch, Johannes

    2015-09-01

    The direction of formation of hydride in fuel cladding tube is a major issue for the assessment of the cladding remaining ductility after service. This behavior is quite well known for fresh material, but few results exist for irradiated material. The reorientation behavior of a Zircaloy-4 fuel cladding (AREVA duplex DX-D4) at a burn-up of around 72 GWd t-1 is investigated here. The increase of the fraction of reoriented hydrides through repeated thermo-mechanical loading is inspected; as well, the possibility to recover a state with a minimized quantity of reoriented hydrides is tested using pure thermal loading cycles. The study is completed by a qualitative assessment of the hydrogen density in the duplex layer, where a dependence of the hydrides density on the hoop stress state is observed.

  8. High power operation of cladding pumped holmium-doped silica fibre lasers.

    PubMed

    Hemming, Alexander; Bennetts, Shayne; Simakov, Nikita; Davidson, Alan; Haub, John; Carter, Adrian

    2013-02-25

    We report the highest power operation of a resonantly cladding-pumped, holmium-doped silica fibre laser. The cladding pumped all-glass fibre utilises a fluorine doped glass layer to provide low loss cladding guidance of the 1.95 µm pump radiation. The operation of both single mode and large-mode area fibre lasers was demonstrated, with up to 140 W of output power achieved. A slope efficiency of 59% versus launched pump power was demonstrated. The free running emission was measured to be 2.12-2.15 µm demonstrating the potential of this architecture to address the long wavelength operation of silica based fibre lasers with high efficiency. PMID:23481989

  9. Fuel cladding behavior under rapid loading conditions

    NASA Astrophysics Data System (ADS)

    Yueh, K.; Karlsson, J.; Stjärnsäter, J.; Schrire, D.; Ledergerber, G.; Munoz-Reja, C.; Hallstadius, L.

    2016-02-01

    A modified burst test (MBT) was used in an extensive test program to characterize fuel cladding failure behavior under rapid loading conditions. The MBT differs from a normal burst test with the use of a driver tube to simulate the expansion of a fuel pellet, thereby producing a partial strain driven deformation condition similar to that of a fuel pellet expansion in a reactivity insertion accident (RIA). A piston/cylinder assembly was used to pressurize the driver tube. By controlling the speed and distance the piston travels the loading rate and degree of sample deformation could be controlled. The use of a driver tube with a machined gauge section localizes deformation and allows for continuous monitoring of the test sample diameter change at the location of maximum hoop strain, during each test. Cladding samples from five irradiated fuel rods were tested between 296 and 553 K and loading rates from 1.5 to 3.5/s. The test rods included variations of Zircaloy-2 with different liners and ZIRLO, ranging in burn-up from 41 to 74 GWd/MTU. The test results show cladding ductility is strongly temperature and loading rate dependent. Zircaloy-2 cladding ductility degradation due to operational hydrogen pickup started to recover at approximately 358 K for test condition used in the study. This recovery temperature is strongly loading rate dependent. At 373 K, ductility recovery was small for loading rates less than 8 ms equivalent RIA pulse width, but longer than 8 ms the ductility recovery increased exponentially with increasing pulse width, consistent with literature observations of loading rate dependent brittle-to-ductile (BTD) transition temperature. The cladding ductility was also observed to be strongly loading rate/pulse width dependent for BWR cladding below the BTD temperature and Pressurized Water Reactor (PWR) cladding at both 296 and 553 K.

  10. Fixed interface charges between AlGaN barrier and gate stack composed of in situ grown SiN and Al{sub 2}O{sub 3} in AlGaN/GaN high electron mobility transistors with normally off capability

    SciTech Connect

    Capriotti, M. Alexewicz, A.; Fleury, C.; Gavagnin, M.; Bethge, O.; Wanzenböck, H. D.; Bertagnolli, E.; Pogany, D.; Strasser, G.; Visalli, D.; Derluyn, J.

    2014-03-17

    Using a generalized extraction method, the fixed charge density N{sub int} at the interface between in situ deposited SiN and 5 nm thick AlGaN barrier is evaluated by measurements of threshold voltage V{sub th} of an AlGaN/GaN metal insulator semiconductor high electron mobility transistor as a function of SiN thickness. The thickness of the originally deposited 50 nm thick SiN layer is reduced by dry etching. The extracted N{sub int} is in the order of the AlGaN polarization charge density. The total removal of the in situ SiN cap leads to a complete depletion of the channel region resulting in V{sub th} = +1 V. Fabrication of a gate stack with Al{sub 2}O{sub 3} as a second cap layer, deposited on top of the in situ SiN, is not introducing additional fixed charges at the SiN/Al{sub 2}O{sub 3} interface.

  11. Dilution and Ferrite Number Prediction in Pulsed Current Cladding of Super-Duplex Stainless Steel Using RSM

    NASA Astrophysics Data System (ADS)

    Eghlimi, Abbas; Shamanian, Morteza; Raeissi, Keyvan

    2013-12-01

    Super-duplex stainless steels have an excellent combination of mechanical properties and corrosion resistance at relatively low temperatures and can be used as a coating to improve the corrosion and wear resistance of low carbon and low alloy steels. Such coatings can be produced using weld cladding. In this study, pulsed current gas tungsten arc cladding process was utilized to deposit super-duplex stainless steel on high strength low alloy steel substrates. In such claddings, it is essential to understand how the dilution affects the composition and ferrite number of super-duplex stainless steel layer in order to be able to estimate its corrosion resistance and mechanical properties. In the current study, the effect of pulsed current gas tungsten arc cladding process parameters on the dilution and ferrite number of super-duplex stainless steel clad layer was investigated by applying response surface methodology. The validity of the proposed models was investigated by using quadratic regression models and analysis of variance. The results showed an inverse relationship between dilution and ferrite number. They also showed that increasing the heat input decreases the ferrite number. The proposed mathematical models are useful for predicting and controlling the ferrite number within an acceptable range for super-duplex stainless steel cladding.

  12. U-Mo Foil/Cladding Interactions in Friction Stir Welded Monolithic RERTR Fuel Plates

    SciTech Connect

    D.D. Keiser; J.F. Jue; C.R. Clark

    2006-10-01

    Interaction between U-Mo fuel and Al has proven to dramatically impact the overall irradiation performance of RERTR dispersion fuels. It is of interest to better understand how similar interactions may affect the performance of monolithic fuel plates, where a uranium alloy fuel is sandwiched between aluminum alloy cladding. The monolithic fuel plate removes the fuel matrix entirely, which reduces the total surface area of the fuel that is available to react with the aluminum and moves the interface between the fuel and cladding to a colder region of the fuel plate. One of the major fabrication techniques for producing monolithic fuel plates is friction stir welding. This paper will discuss the interactions that can occur between the U-Mo foil and 6061 Al cladding when applying this fabrication technique. It has been determined that the time at high temperatures should be limited as much as is possible during fabrication or any post-fabrication treatment to reduce as much as possible the interactions between the foil and cladding. Without careful control of the fabrication process, significant interaction between the U-Mo foil and Al alloy cladding can result. The reaction layers produced from such interactions can exhibit notably different morphologies vis-à-vis those typically observed for dispersion fuels.

  13. Microstructure evolution and properties of Al/Al-Mg-Si alloy clad wire during heat treatment

    NASA Astrophysics Data System (ADS)

    Wang, Xiang; Guan, Ren-guo; Zhang, Yang; Su, Ning; Ji, Lian-ze; Li, Yuan-dong; Chen, Ti-jun

    2016-06-01

    In this paper, heat treatment was carried out on Al/Al-Mg-Si alloy clad wire, and microstructure evolution and properties of Al/Al-Mg-Si alloy clad wire during heat treatment were investigated. During solution, contents of Mg and Si in inner matrix increased due to dissolution of primary Mg2Si, and they also increased in outer matrix because Mg and Si diffused across the interface. Tensile strength of the clad wire increased firstly and then decreased, and elongation continuously increased, while conductivity continuously decreased with the increase in solution time. In aging process, Mg2Si precipitated in both inner core and outer layer, and the content and average diameter of the precipitate increased with the increase in aging time. The content of precipitate was higher, and the average diameter was bigger in inner core. Tensile strength of the clad wire increased firstly and then decreased with the increase in aging time, and the elongation continuously decreased, while the conductivity continuously increased. The peak tensile strength of 202 MPa occurred at 8 h, when the corresponding elongation was 20 % and the conductivity reached 56.07 %IACS. Even tensile strength of the prepared clad wire approximately equaled to that of Al-0.5Mg-0.35Si alloy 203 MPa, the conductivity was obviously improved from 54.2 to 56.07 %IACS.

  14. Corrosion Resistant Cladding by YAG Laser Welding in Underwater Environment

    SciTech Connect

    Tsutomi Kochi; Toshio Kojima; Suemi Hirata; Ichiro Morita; Katsura Ohwaki

    2002-07-01

    It is known that stress-corrosion cracking (SCC) will occur in nickel-base alloys used in Reactor Pressure Vessel (RPV) and Internals of nuclear power plants. A SCC sensitivity has been evaluated by IHI in each part of RPV and Internals. There are several water level instrumentation nozzles installed in domestic BWR RPV. In water level instrumentation nozzles, 182 type nickel-base alloys were used for the welding joint to RPV. It is estimated the SCC potential is high in this joint because of a higher residual stress than the yield strength (about 400 MPa). This report will describe a preventive maintenance method to these nozzles Heat Affected Zone (HAZ) and welds by a corrosion resistant cladding (CRC) by YAG Laser in underwater environment (without draining a reactor water). There are many kinds of countermeasures for SCC, for example, Induction Heating Stress Improvement (IHSI), Mechanical Stress Improvement Process (MSIP) and so on. A YAG laser CRC is one of them. In this technology a laser beam is used for heat source and irradiated through an optical fiber to a base metal and SCC resistant material is used for welding wires. After cladding the HAZ and welds are coated by the corrosion resistant materials so their surfaces are improved. A CRC by gas tungsten arc welding (GTAW) in an air environment had been developed and already applied to a couple of operating plants (16 Nozzles). This method was of course good but it spent much time to perform because of an installation of some water-proof working boxes to make a TIG-weldability environment. CRC by YAG laser welding in underwater environment has superior features comparing to this conventional TIG method as follows. At the viewpoint of underwater environment, (1) an outage term reduction (no drainage water). (2) a radioactive exposure dose reduction for personnel. At that of YAG laser welding, (1) A narrower HAZ. (2) A smaller distortion. (3) A few cladding layers. A YAG laser CRC test in underwater

  15. Effects of irradiation on strength and toughness of commercial LWR vessel cladding

    SciTech Connect

    Haggag, F.M.; Corwin, W.R.; Alexander, D.J.; Nanstad, R.K.

    1987-01-01

    The potential for stainless steel cladding to improve the fracture behavior of an operating nuclear reactor pressure vessel, particularly during certain overcooling transients, may depend greatly on the properties of the irradiated cladding. Therefore, weld overlay cladding irradiated at temperatures and to fluences relevant to power reactor operation was examined. The cladding was applied to a pressure vessel steel plate by the three-wire series-arc commercial method. Cladding was applied in three layers to provide adequate thickness for the fabrication of test specimens. The three-wire series-arc procedure, developed by Combustion Engineering, Inc., Chattanooga, Tennessee, produced a highly controlled weld chemistry, microstructure, and fracture properties in all three layers of the weld. Charpy V-notch and tensile specimens were irradiated at 288/sup 0/C to fluence levels of 2 and 5 x 10/sup 19/ neutrons/cm/sup 2/ (>1 MeV). Postirradiation testing results show that, in the test temperature range from -125 to 288/sup 0/C, the yield strength increased by 8 to 30%, ductility insignificantly increased, while there was almost no change in ultimate tensile strength. All cladding exhibited ductile-to-brittle transition behavior during Charpy impact testing, due to the dominance of delta-ferrite failures at low temperatures. On the upper shelf, energy was reduced, due to irradiation exposure, 15 and 20%, while the lateral expansion was reduced 43 and 41%, at 2 and 5 x 10/sup 19/ neutrons/cm/sup 2/ (>1 MeV), respectively. In addition, radiation damage resulted in 13 and 28/sup 0/C shifts of the Charpy impact transition temperature at the 41-J level for the low and high fluences, respectively.

  16. Ultraviolet light-emitting diodes with polarization-doped p-type layer

    NASA Astrophysics Data System (ADS)

    Hu, Wenxiao; Qin, Ping; Song, Weidong; Zhang, Chongzhen; Wang, Rupeng; Zhao, Liangliang; Xia, Chao; Yuan, Songyang; Yin, Yian; Li, Shuti

    2016-09-01

    We report ultraviolet light emitting diode (LEDs) with polarization doped p-type layer. Fabricated LEDs with polarization doped p-type layer exhibited reduced forward voltage and enhanced light output power, compared to those with traditional p-type AlGaN layer. The improvement is attributed to improved hole concentration and the smooth valence band by the polarization enhanced p-type doping. Our simulated results reveal that this p-type layer can further enhance the performance of ultraviolet LEDs by removing the electron blocking layer (EBL).

  17. Improved LWR Cladding Performance by EPD Surface Modification Technique

    SciTech Connect

    Corradini, Michael; Sridharan, Kumar

    2012-11-26

    This project will utilize the electro-phoretic deposition technique (EPD) in conjunction with nanofluids to deposit oxide coatings on prototypic zirconium alloy cladding surfaces. After demonstrating that this surface modification is reproducible and robust, the team will subject the modified surface to boiling and corrosion tests to characterize the improved nucleate boiling behavior and superior corrosion performance. The scope of work consists of the following three tasks: The first task will employ the EPD surface modification technique to coat the surface of a prototypic set of zirconium alloy cladding tube materials (e.g. Zircaloy and advanced alloys such as M5) with a micron-thick layer of zirconium oxide nanoparticles. The team will characterize the modified surface for uniformity using optical microscopy and scanning-electron microscopy, and for robustness using standard hardness measurements. After zirconium alloy cladding samples have been prepared and characterized using the EPD technique, the team will begin a set of boiling experiments to measure the heat transfer coefficient and critical heat flux (CHF) limit for each prepared sample and its control sample. This work will provide a relative comparison of the heat transfer performance for each alloy and the surface modification technique employed. As the boiling heat transfer experiments begin, the team will also begin corrosion tests for these zirconium alloy samples using a water corrosion test loop that can mimic light water reactor (LWR) operational environments. They will perform extended corrosion tests on the surface-modified zirconium alloy samples and control samples to examine the robustness of the modified surface, as well as the effect on surface oxidation

  18. Microstructural Characterization of the U-9.1Mo Fuel/AA6061 Cladding Interface in Friction-Bonded Monolithic Fuel Plates Irradiated in the RERTR-6 Experiment

    SciTech Connect

    Keiser, Dennis D.; Jue, Jan-Fong; Miller, Brandon; Gan, Jian; Robinson, Adam; Medvedev, Pavel; Madden, James; Wachs, Dan; Clark, Curtis; Meyer, Mitch

    2015-09-01

    Low-enrichment (U-235 < 20%) U-Mo monolithic fuel is being developed for use in research and test reactors. The earliest design for this fuel that was investigated via reactor testing was comprised of a nominally U-10Mo fuel foil encased in AA6061 (Al-6061) cladding. For a fuel design to be deemed adequate for final use in a reactor, it must maintain dimensional stability and retain fission products throughout irradiation, which means that there must be good integrity at the fuel foil/cladding interface. To investigate the nature of the fuel/cladding interface for this fuel type after irradiation, fuel plates that were tested in INL's Advanced Test Reactor (ATR) were subsequently characterized using optical metallography, scanning electron microscopy, and transmission electron microscopy. Results of this characterization showed that the fuel/cladding interaction layers present at the U-Mo fuel/AA6061 cladding interface after fabrication became amorphous during irradiation. Up to two main interaction layers, based on composition, could be found at the fuel/cladding interface, depending on location. After irradiation, an Al-rich layer contained very few fission gas bubbles, but did exhibit Xe enrichment near the AA6061 cladding interface. Another layer, which contained more Si, had more observable fission gas bubbles. Adjacent to the AA6061 cladding were Mg-rich precipitates, which was in close proximity to the region where Xe is observed to be enriched. In samples produced using a focused ion beam at the interaction zone/AA6061 cladding interface were possible indications of porosity/debonding, which suggested that the interface in this location is relatively weak.

  19. Potential effects of gallium on cladding materials

    SciTech Connect

    Wilson, D.F.; Beahm, E.C.; Besmann, T.M.; DeVan, J.H.; DiStefano, J.R.; Gat, U.; Greene, S.R.; Rittenhouse, P.L.; Worley, B.A.

    1997-10-01

    This paper identifies and examines issues concerning the incorporation of gallium in weapons derived plutonium in light water reactor (LWR) MOX fuels. Particular attention is given to the more likely effects of the gallium on the behavior of the cladding material. The chemistry of weapons grade (WG) MOX, including possible consequences of gallium within plutonium agglomerates, was assessed. Based on the calculated oxidation potentials of MOX fuel, the effect that gallium may have on reactions involving fission products and possible impact on cladding performance were postulated. Gallium transport mechanisms are discussed. With an understanding of oxidation potentials and assumptions of mechanisms for gallium transport, possible effects of gallium on corrosion of cladding were evaluated. Potential and unresolved issues and suggested research and development (R and D) required to provide missing information are presented.

  20. Capturing reflected cladding modes from a fiber Bragg grating with a double-clad fiber coupler.

    PubMed

    Baiad, Mohamad Diaa; Gagné, Mathieu; Lemire-Renaud, Simon; De Montigny, Etienne; Madore, Wendy-Julie; Godbout, Nicolas; Boudoux, Caroline; Kashyap, Raman

    2013-03-25

    We present a novel measurement scheme using a double-clad fiber coupler (DCFC) and a fiber Bragg grating (FBG) to resolve cladding modes. Direct measurement of the optical spectra and power in the cladding modes is obtained through the use of a specially designed DCFC spliced to a highly reflective FBG written into slightly etched standard photosensitive single mode fiber to match the inner cladding diameter of the DCFC. The DCFC is made by tapering and fusing two double-clad fibers (DCF) together. The device is capable of capturing backward propagating low and high order cladding modes simply and efficiently. Also, we demonstrate the capability of such a device to measure the surrounding refractive index (SRI) with an extremely high sensitivity of 69.769 ± 0.035 μW/RIU and a resolution of 1.433 × 10(-5) ± 8 × 10(-9) RIU between 1.37 and 1.45 RIU. The device provides a large SRI operating range from 1.30 to 1.45 RIU with sufficient discrimination for all individual captured cladding modes. The proposed scheme can be adapted to many different types of bend, temperature, refractive index and other evanescent wave based sensors. PMID:23546069

  1. 3D analysis of thermal and stress evolution during laser cladding of bioactive glass coatings.

    PubMed

    Krzyzanowski, Michal; Bajda, Szymon; Liu, Yijun; Triantaphyllou, Andrew; Mark Rainforth, W; Glendenning, Malcolm

    2016-06-01

    Thermal and strain-stress transient fields during laser cladding of bioactive glass coatings on the Ti6Al4V alloy basement were numerically calculated and analysed. Conditions leading to micro-cracking susceptibility of the coating have been investigated using the finite element based modelling supported by experimental results of microscopic investigation of the sample coatings. Consecutive temperature and stress peaks are developed within the cladded material as a result of the laser beam moving along the complex trajectory, which can lead to micro-cracking. The preheated to 500°C base plate allowed for decrease of the laser power and lowering of the cooling speed between the consecutive temperature peaks contributing in such way to achievement of lower cracking susceptibility. The cooling rate during cladding of the second and the third layer was lower than during cladding of the first one, in such way, contributing towards improvement of cracking resistance of the subsequent layers due to progressive accumulation of heat over the process. PMID:26953962

  2. Characterization of hard coatings produced by laser cladding using laser-induced breakdown spectroscopy technique

    NASA Astrophysics Data System (ADS)

    Varela, J. A.; Amado, J. M.; Tobar, M. J.; Mateo, M. P.; Yañez, A.; Nicolas, G.

    2015-05-01

    Protective coatings with a high abrasive wear resistance can be obtained from powders by laser cladding technique, in order to extend the service life of some industrial components. In this work, laser clad layers of self-fluxing NiCrBSi alloy powder mixed with WC powder have been produced on stainless steel substrates of austenitic type (AISI 304) in a first step and then chemically characterized by laser-induced breakdown spectroscopy (LIBS) technique. With the suitable laser processing parameters (mainly output power, beam scan speed and flow rate) and powders mixture proportions between WC ceramics and NiCrBSi alloys, dense pore free layers have been obtained on single tracks and on large areas with overlapped tracks. The results achieved by LIBS technique and applied for the first time to the analysis of laser clads provided the chemical composition of the tungsten carbides in metal alloy matrix. Different measurement modes (multiple point analyses, depth profiles and chemical maps) have been employed, demonstrating the usefulness of LIBS technique for the characterization of laser clads based on hardfacing alloys. The behavior of hardness can be explained by LIBS maps which evidenced the partial dilution of some WC spheres in the coating.

  3. High internal quantum efficiency in AlGaN multiple quantum wells grown on bulk AlN substrates

    SciTech Connect

    Bryan, Zachary Bryan, Isaac; Sitar, Zlatko; Collazo, Ramón; Xie, Jinqiao; Mita, Seiji

    2015-04-06

    The internal quantum efficiency (IQE) of Al{sub 0.55}Ga{sub 0.45}N/AlN and Al{sub 0.55}Ga{sub 0.45}N/Al{sub 0.85}Ga{sub 0.15}N UVC MQW structures was analyzed. The use of bulk AlN substrates enabled us to undoubtedly distinguish the effect of growth conditions, such as V/III ratio, on the optical quality of AlGaN based MQWs from the influence of dislocations. At a high V/III ratio, a record high IQE of ∼80% at a carrier density of 10{sup 18 }cm{sup −3} was achieved at ∼258 nm. The high IQE was correlated with the decrease of the non-radiative coefficient A and a reduction of midgap defect luminescence, all suggesting that, in addition to dislocations, point defects are another major factor that strongly influences optical quality of AlGaN MQW structures.

  4. Optically confined polarized resonance Raman studies in identifying crystalline orientation of sub-diffraction limited AlGaN nanostructure

    SciTech Connect

    Sivadasan, A. K. Patsha, Avinash; Dhara, Sandip

    2015-04-27

    An optical characterization tool of Raman spectroscopy with extremely weak scattering cross section tool is not popular to analyze scattered signal from a single nanostructure in the sub-diffraction regime. In this regard, plasmonic assisted characterization tools are only relevant in spectroscopic studies of nanoscale object in the sub-diffraction limit. We have reported polarized resonance Raman spectroscopic (RRS) studies with strong electron-phonon coupling to understand the crystalline orientation of a single AlGaN nanowire of diameter ∼100 nm. AlGaN nanowire is grown by chemical vapor deposition technique using the catalyst assisted vapor-liquid-solid process. The results are compared with the high resolution transmission electron microscopic analysis. As a matter of fact, optical confinement effect due to the dielectric contrast of nanowire with respect to that of surrounding media assisted with electron-phonon coupling of RRS is useful for the spectroscopic analysis in the sub-diffraction limit of 325 nm (λ/2N.A.) using an excitation wavelength (λ) of 325 nm and near ultraviolet 40× far field objective with a numerical aperture (N.A.) value of 0.50.

  5. Novel Accident-Tolerant Fuel Meat and Cladding

    SciTech Connect

    Robert D. Mariani; Pavel G Medvedev; Douglas L Porter; Steven L Hayes; James I. Cole; Xian-Ming Bai

    2013-09-01

    A novel accident-tolerant fuel meat and cladding are here proposed. The fuel meat design incorporates annular fuel with inserts and discs that are fabricated from a material having high thermal conductivity, for example niobium. The inserts are rods or tubes. Discs separate the fuel pellets. Using the BISON fuel performance code it was found that the peak fuel temperature can be lowered by more than 600 degrees C for one set of conditions with niobium metal as the thermal conductor. In addition to improved safety margin, several advantages are expected from the lower temperature such as decreased fission gas release and fuel cracking. Advantages and disadvantages are discussed. An enrichment of only 7.5% fully compensates the lost reactivity of the displaced UO2. Slightly higher enrichments, such as 9%, allow uprates and increased burnups to offset the initial costs for retooling. The design has applications for fast reactors and transuranic burning, which may accelerate its development. A zirconium silicide coating is also described for accident tolerant applications. A self-limiting degradation behavior for this coating is expected to produce a glassy, self-healing layer that becomes more protective at elevated temperature, with some similarities to MoSi2 and other silicides. Both the fuel and coating may benefit from the existing technology infrastructure and the associated wide expertise for a more rapid development in comparison to other, more novel fuels and cladding.

  6. Cladding Attachment Over Thick Exterior Insulating Sheathing (Fact Sheet)

    SciTech Connect

    Not Available

    2013-11-01

    The addition of insulation to the exterior of buildings is an effective means of increasing the thermal resistance of wood-framed walls and mass masonry wall assemblies. The location of the insulation on the exterior of the structure has many direct benefits, including better effective R-value from reduced thermal bridging, better condensation resistance, reduced thermal stress on the structure, as well as other commonly associated improvements such as increased airtightness and improved water management. For thick layers of exterior insulation (more than 1.5 in.), the use of wood furring strips attached through the insulation back to the structure has been used by many contractors and designers as a means to provide a convenient cladding attachment location. Although the approach has proven effective, there is significant resistance to its widespread implementation due to a lack of research and understanding of the mechanisms involved in the development of the vertical displacement resistance capacity. In addition, the long-term in-service performance of the system has been questioned due to potential creep effects of the assembly under the sustained dead load of the cladding and effects of varying environmental conditions. In addition, the current International Building Code (IBC) and International Residential Code (IRC) do not have a provision that specifically allows this assembly.

  7. Development of clad boiler tubes extruded from bimetallic centrifugal castings

    SciTech Connect

    Sponseller, D.L.; Bakker, W.T.; Timmons, G.A.

    1998-04-01

    Wrought tubes of T-11 steel, externally clad with SS310, have been produced by a new method. The alloys were united directly from the molten state by centrifugal casting. In the optimum process, temperatures were controlled to prevent meltback of the SS310 outer layer by the higher melting T-11 stream. Hollow extrusion billets were prepared from the heavy-walled cast bimetallic tubes and successfully hot extruded to 84-mm OD x 64-mm ID tubes, and to 51-mm OD x 38-mm ID tubes. For the most part, thicknesses of the cladding and of the tube wall are rather uniform around the circumference and from end to end of the tubes. Hardness and tensile properties of annealed 51-mm tubes are uniform from end to end of a tube, and between tubes, and readily conform to ASTM A 213; tubes satisfy the flattening and flaring requirements of ASTM A 450. The cladding is metallurgically bonded to be base metal, as revealed by metallography, and by two tests developed for this study: a bond shear strength test and a twist test. In the latter test, rings 3.1 mm in thickness are slotted and severely twisted with a special tool. In tubes made by the optimum process, minute fissures that form adjacent to some of the pressure points during twist testing occupy just 3% of the bond-line length. Cost estimates for commercial production of 51-mm tubes via the centrifugal casting route suggest that such tubes should be considerably less expensive than conventionally clad tubes (extruded from composite billets assembled from heavy-walled wrought tubes). Such tubes should be attractive for the following applications in utility boilers: high-corrosion areas of existing coal-fired boilers, in both steam-generating tubes and superheaters; water walls, screen tubes, and superheater tubes of municipal waste-incineration boilers; future ultra super-critical boilers operating a higher temperatures and pressures; and steam-generating tubes of Syngas coolers of integrated coal gasification power plants.

  8. Enhancement of blue InGaN light-emitting diodes by using AlGaN increased composition-graded barriers

    NASA Astrophysics Data System (ADS)

    Yan, Lei; Zhiqiang, Liu; Miao, He; Xiaoyan, Yi; Junxi, Wang; Jinmin, Li; Shuwen, Zheng; Shuti, Li

    2015-05-01

    The characteristics of nitride-based blue light-emitting diodes (LEDs) with AlGaN composition-graded barriers are analyzed numerically. The carrier concentrations in the quantum wells (QWs), the energy band diagrams, the electrostatic fields, and the light output power are investigated by APSYS software. The simulation results show that the LED with AlGaN composition-graded barriers has a better performance than its AlGaN/InGaN counterpart owing to the increase of hole injection and the enhancement of electron confinement. The simulation results also suggest that the output power is enhanced significantly and the efficiency droop is markedly improved when the AlGaN barriers are replaced by AlGaN composition-graded barriers. Project supported by the National High Technology Program of China (Nos. 2011AA03A105, 2013AA03A101), the National Natural Science Foundation of China (Nos. 61306051, 61306050, 11474105), the Beijing Municipal Science and Technology Project (No. D12110300140000), the National Basic Research Program of China (No. 2011CB301902), the Industry-Academia-Research Union Special Fund of Guangdong Province of China (No. 2012B091000169), the Science & Technology Innovation Platform of Industry-Academia-Research Union of Guangdong Province-Ministry Cooperation Special Fund of China (No. 2012B090600038), the Specialized Research Fund for the Doctoral Program of Higher Education (No. 20134407110008), and the Science research innovation foundation of South China Normal University of China (No. 2013kyjj041).

  9. AlGaN UV LED and Photodiodes Radiation Hardness and Space Qualifications and Their Applications in Space Science and High Energy Density Physics

    SciTech Connect

    Sun, K. X.

    2011-05-31

    This presentation provides an overview of robust, radiation hard AlGaN optoelectronic devices and their applications in space exploration & high energy density physics. Particularly, deep UV LED and deep UV photodiodes are discussed with regard to their applications, radiation hardness and space qualification. AC charge management of UV LED satellite payload instruments, which were to be launched in late 2012, is covered.

  10. Surface modification of AISI H13 tool steel by laser cladding with NiTi powder

    NASA Astrophysics Data System (ADS)

    Norhafzan, B.; Aqida, S. N.; Chikarakara, E.; Brabazon, D.

    2016-04-01

    This paper presents laser cladding of NiTi powder on AISI H13 tool steel surface for surface properties enhancement. The cladding process was conducted using Rofin DC-015 diffusion-cooled CO2 laser system with wavelength of 10.6 µm. NiTi powder was pre-placed on H13 tool steel surface. The laser beam was focused with a spot size of 90 µm on the sample surface. Laser parameters were set to 1515 and 1138 W peak power, 18 and 24 % duty cycle and 2300-3500 Hz laser pulse repetition frequency. Hardness properties of the modified layer were characterized by Wilson Hardness tester. Metallographic study and chemical composition were conducted using field emission scanning electron microscope and energy-dispersive X-ray spectrometer (EDXS) analysis. Results showed that hardness of NiTi clad layer increased three times that of the substrate material. The EDXS analysis detected NiTi phase presence in the modified layer up to 9.8 wt%. The metallographic study shows high metallurgical bonding between substrate and modified layer. These findings are significant to both increased hardness and erosion resistance of high-wear-resistant components and elongating their lifetime.

  11. Cladding For Transversely-Pumped Laser Rod

    NASA Technical Reports Server (NTRS)

    Byer, Robert L.; Fan, Tso Yee

    1989-01-01

    Combination of suitable dimensioning and cladding of neodymium:yttrium aluminum garnet of similar solid-state laser provides for more efficient utilization of transversely-incident pump light from diode lasers. New design overcomes some of limitations of longitudinal- and older transverse-pumping concepts and promotes operation at higher output powers in TEM00 mode.

  12. Advanced ceramic cladding for water reactor fuel

    SciTech Connect

    Feinroth, H.

    2000-07-01

    Under the US Department of Energy's Nuclear Energy Research Initiatives (NERI) program, continuous fiber ceramic composites (CFCCs) are being developed as cladding for water reactor fuel elements. The purpose is to substantially increase the passive safety of water reactors. A development effort was initiated in 1991 to fabricate CFCC-clad tubes using commercially available fibers and a sol-gel process developed by McDermott Technologies. Two small-diameter CFCC tubes were fabricated using pure alumina and alumina-zirconia fibers in an alumina matrix. Densities of {approximately}60% of theoretical were achieved. Higher densities are required to guarantee fission gas containment. This NERI work has just begun, and only preliminary results are presented herein. Should the work prove successful, further development is required to evaluate CFCC cladding and performance, including in-pile tests containing fuel and exploring a marriage of CFCC cladding materials with suitable advanced fuel and core designs. The possibility of much higher temperature core designs, possibly cooled with supercritical water, and achievement of plant efficiencies {ge}50% would be examined.

  13. Pellet cladding mechanical interactions of ceramic claddings fuels under light water reactor conditions

    NASA Astrophysics Data System (ADS)

    Li, Bo-Shiuan

    Ceramic materials such as silicon carbide (SiC) are promising candidate materials for nuclear fuel cladding and are of interest as part of a potential accident tolerant fuel design due to its high temperature strength, dimensional stability under irradiation, corrosion resistance, and lower neutron absorption cross-section. It also offers drastically lower hydrogen generation in loss of coolant accidents such as that experienced at Fukushima. With the implementation of SiC material properties to the fuel performance code, FRAPCON, performances of the SiC-clad fuel are compared with the conventional Zircaloy-clad fuel. Due to negligible creep and high stiffness, SiC-clad fuel allows gap closure at higher burnup and insignificant cladding dimensional change. However, severe degradation of SiC thermal conductivity with neutron irradiation will lead to higher fuel temperature with larger fission gas release. High stiffness of SiC has a drawback of accumulating large interfacial pressure upon pellet-cladding mechanical interactions (PCMI). This large stress will eventually reach the flexural strength of SiC, causing failure of SiC cladding instantly in a brittle manner instead of the graceful failure of ductile metallic cladding. The large interfacial pressure causes phenomena that were previously of only marginal significance and thus ignored (such as creep of the fuel) to now have an important role in PCMI. Consideration of the fuel pellet creep and elastic deformation in PCMI models in FRAPCON provide for an improved understanding of the magnitude of accumulated interfacial pressure. Outward swelling of the pellet is retarded by the inward irradiation-induced creep, which then reduces the rate of interfacial pressure buildup. Effect of PCMI can also be reduced and by increasing gap width and cladding thickness. However, increasing gap width and cladding thickness also increases the overall thermal resistance which leads to higher fuel temperature and larger fission

  14. High temperature and low pressure chemical vapor deposition of silicon nitride on AlGaN: Band offsets and passivation studies

    NASA Astrophysics Data System (ADS)

    Reddy, Pramod; Washiyama, Shun; Kaess, Felix; Hayden Breckenridge, M.; Hernandez-Balderrama, Luis H.; Haidet, Brian B.; Alden, Dorian; Franke, Alexander; Sarkar, Biplab; Kohn, Erhard; Collazo, Ramon; Sitar, Zlatko

    2016-04-01

    In this work, we employed X-ray photoelectron spectroscopy to determine the band offsets and interface Fermi level at the heterojunction formed by stoichiometric silicon nitride deposited on AlxGa1-xN (of varying Al composition "x") via low pressure chemical vapor deposition. Silicon nitride is found to form a type II staggered band alignment with AlGaN for all Al compositions (0 ≤ x ≤ 1) and present an electron barrier into AlGaN even at higher Al compositions, where Eg(AlGaN) > Eg(Si3N4). Further, no band bending is observed in AlGaN for x ≤ 0.6 and a reduced band bending (by ˜1 eV in comparison to that at free surface) is observed for x > 0.6. The Fermi level in silicon nitride is found to be at 3 eV with respect to its valence band, which is likely due to silicon (≡Si0/-1) dangling bonds. The presence of band bending for x > 0.6 is seen as a likely consequence of Fermi level alignment at Si3N4/AlGaN hetero-interface and not due to interface states. Photoelectron spectroscopy results are corroborated by current-voltage-temperature and capacitance-voltage measurements. A shift in the interface Fermi level (before band bending at equilibrium) from the conduction band in Si3N4/n-GaN to the valence band in Si3N4/p-GaN is observed, which strongly indicates a reduction in mid-gap interface states. Hence, stoichiometric silicon nitride is found to be a feasible passivation and dielectric insulation material for AlGaN at any composition.

  15. Analysis of microstructure and properties of multilayer coatings produced by laser cladding

    NASA Astrophysics Data System (ADS)

    Bykovskiy, D. P.; Petrovskiy, V. N.; Dzhumaev, P. S.; Polskiy, V. I.; Yermachenko, V. M.

    2016-02-01

    Purpose of the work is to prepare multilayer coatings corresponding to specified requirements to recovery and improvement of surface details. Requirements to coatings: providing durable and reliable adhesion base and filler materials, absence of pores, cracks, delaminations, reducing mixing metal base and cladding. We used iron-based PR-10R6M5 and tungsten carbide Hoganas 44712 powders. Experimental determination of the optimal technological mode of application of the single track, the coefficient of overlapping tracks to create a full layer, the angle of the second cladding layer, relative to the first one and, finally, the determination of the optimal additive tungsten carbide to achieve increased durability were produced to fulfill these requirements.

  16. Nondestructive evaluation of explosively welded clad rods by resonance acoustic spectroscopy.

    PubMed

    Fan, Y; Tysoe, B; Sim, J; Mirkhani, K; Sinclair, A N; Honarvar, F; Sildva, Harry; Szecket, Alexander; Hardwick, Roy

    2003-07-01

    A resonance acoustic spectroscopy technique is assessed for nondestructive evaluation of explosively welded clad rods. Each rod is modeled as a two-layered cylinder with a spring-mass system to represent a thin interfacial layer containing the weld. A range of interfacial profiles is generated in a set of experimental samples by varying the speed of the explosion that drives the copper cladding into the aluminum core. Excellent agreement is achieved between measured and calculated values of the resonant frequencies of the system, through appropriate adjustment of the interfacial mass and spring constants used in the wave scattering calculations. Destructive analysis of the interface in the experimental specimens confirms that key features of the interfacial profile may be inferred from resonance acoustic spectroscopy analysis applied to ultrasonic measurements. PMID:12788219

  17. High-niobium bearing steel for base material of CRA clad UOE pipe

    SciTech Connect

    Terada, Y.; Tamehiro, H.; Uemori, R.; Maruyama, N.; Ogawa, H.; Takahashi, A.

    1994-12-31

    The manufacturing technology of corrosion resistant alloy (CRA) clad UOE pipe by applying thermomechanical control process (TMCP) has been studied. In order to obtain good pitting corrosion resistance in the Incoloy 825 layer, it is necessary to ensure complete recrystallization and suppress the precipitation of chromium carbides in the Incoloy 825 layer after rolling. To this end the clad plate was finish-rolled at high temperature and water-cooled after appropriate air cooling. However, in conventional steel, high temperature rolling considerably deteriorates the low-temperature toughness, therefore, it was found that increasing the niobium content causes the microstructure to refine remarkably and provides an excellent balance of strength and low-temperature toughness at a niobium content of about 0.1% even in high temperature rolling. The grain refinement by adding high niobium is attributable to suppression of austenite grain coarsening during slab-reheating by Nb(CN) particles, a rise in recrystallization stop temperature of austenite.

  18. Microstructural Characterization of the U-9.1Mo Fuel/AA6061 Cladding Interface in Friction-Bonded Monolithic Fuel Plates Irradiated in the RERTR-6 Experiment

    NASA Astrophysics Data System (ADS)

    Keiser, Dennis D.; Jue, Jan-Fong; Miller, Brandon; Gan, Jian; Robinson, Adam; Medvedev, Pavel; Madden, James; Wachs, Dan; Clark, Curtis; Meyer, Mitch

    2015-09-01

    Low-enrichment (235U < 20 pct) U-Mo monolithic fuel is being developed for use in research and test reactors. The earliest design for this fuel that was investigated via reactor testing consisted of a nominally U-10Mo fuel foil encased in AA6061 (Al-6061) cladding. For a fuel design to be deemed adequate for final use in a reactor, it must maintain dimensional stability and retain fission products throughout irradiation, which means that there must be good integrity at the fuel foil/cladding interface. To investigate the nature of the fuel/cladding interface for this fuel type after irradiation, fuel plates were fabricated using a friction bonding process, tested in INL's advanced test reactor (ATR), and then subsequently characterized using optical metallography, scanning electron microscopy, and transmission electron microscopy. Results of this characterization showed that the fuel/cladding interaction layers present at the U-Mo fuel/AA6061 cladding interface after fabrication became amorphous during irradiation. Up to two main interaction layers, based on composition, could be found at the fuel/cladding interface, depending on location. After irradiation, an Al-rich layer contained very few fission gas bubbles, but did exhibit Xe enrichment near the AA6061 cladding interface. Another layer, which contained more Si, had more observable fission gas bubbles. In the samples produced using a focused ion beam at the interaction zone/AA6061 cladding interface, possible indications of porosity/debonding were found, which suggested that the interface in this location is relatively weak.

  19. Modeling Cladding-Coolant Heat Transfer of High-Burnup Fuel During RIA

    SciTech Connect

    Wenfeng Liu; Kazimi, Mujid S.

    2006-07-01

    This paper describes a model for the cladding-coolant heat transfer of high burnup fuel during a Reactivity Initiated Accident (RIA) which is implemented in the fuel performance code FRAPTRAN 1.2. The minimum stable film boiling temperature, affected by the subcooling and the clad oxidation, is modeled by a modified Henry correlation. This accounts for the effects of thermal properties of the cladding surface on the transient temperature drop during liquid-solid contact. The transition boiling regime is described as the interpolation of the heat flux between two anchor points on the boiling curve: the Critical Heat Flux (CHF) and minimum stable film boiling. The CHF correlation is based on the Zuber hydrodynamic model multiplied by a subcooling factor. Frederking correlation is chosen to model the film boiling regime. The heat conduction through the oxide layer of the cladding surface of high burnup fuel is calculated by solving heat conduction equations with thermal properties of zirconia taken from MATPRO. This model is validated in the FRAPTRAN code for test cases of both high burnup and fresh test fuel rods including the burnup level (0--56 MW d/kg), peak fuel enthalpy deposit (70--190 cal/g), degree of subcooling (0--80 deg. C), and extent of oxidation (0--25 micron). The modified code demonstrates the capability of differentiating between the departure from nucleate boiling (DNB) and none-DNB cases. The predicted peak cladding temperature (PCT) and duration of DNB achieves generally good agreement with the experimental data. It is found that the cladding surface oxidation of high burnup fuel causes an early rewetting of cladding or suppresses DNB due to two factors: 1) Thick zirconia layer may delay the heat conducted to the surface while keeping the surface heat transfer in the most effective nucleate boiling regime. 2) The transient liquid-solid contact resulting from vapor breaking down would cause a lower interface temperature for an oxidized surface

  20. Electron microscopy structure study of laser-clad TiC-Ni particle-reinforced coating

    SciTech Connect

    Ouyang, J.H.; Li, X.; Lei, T.C.

    2000-04-01

    The microstructure of a laser-clad TiC-Ni particle-reinforced coating on 1045 steel was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ion microprobe mass spectroscopy (IMMS). The microstructural constituents of the clad layers (CLs) were analyzed to be TiC particles, {gamma}-Ni primary dendrites, and interdendritic eutectics of {gamma}{sub E}-Ni plus M{sub 23}(CB){sub 6} and M{sub 6}(CB) carboborides. Three growth mechanisms of the original TiC particles were found: (1) stepped lateral growth at the edges, (2) radiated and cylindrically coupled growth at the edges, and (3) bridging growth of the clustered particles. Ordered and modulated structures were found in the original TiC particles. In addition to the original TiC particles, fine TiC particles precipitated from the liquid phase and {gamma}-Ni solid solution during laser cladding. The microstructures of the bonding zones (BZs) were intimately associated with laser processing parameters. The BZs of the clad coatings can be categorized into three types according to the combination of the CL with heat-affected zone (HAZ): (1) straight interface combination, (2) zigzag connection, and (3) combination by partial melting of prior austenitic grain boundaries of the substrate. The microstructural evolution of the CLs was discussed. The formation and phase transformation models of the BZs were proposed.

  1. Wear properties of compact graphite cast iron with bionic units processed by deep laser cladding WC

    NASA Astrophysics Data System (ADS)

    Zhou, Hong; Zhang, Peng; Sun, Na; Wang, Cheng-tao; Lin, Peng-yu; Ren, Lu-quan

    2010-08-01

    By simulating the cuticles of some soil animals, the wear resistance of compact graphite cast iron (CGI) processed by laser remelting gets a conspicuous improvement. In order to get a further anti-wear enhancement of CGI, a new method of deep laser cladding was used to process bionic units. By preplacing grooves then filling with WC powders and laser cladding, the bionic units had a larger dimension in depth and higher microhardness. Fe powder with different proportions from 30% (wt.) to 60% (wt.) was added into WC before laser processing for a good incorporation with CGI substrate. The improved laser cladding units turned out to induce higher wear resistance in comparison with laser remelting ones. The depth of the layer reached up to 1 mm. The results of dry sliding wear tests indicated that the specimen processed by laser cladding has a remarkable improvement than the ones processed by laser remelting. It should be noted that the wear mass loss was essentially dependent on the increase in WC proportion.

  2. Use of plasma arc welding process to combat hydrogen metallic disbonding of austenitic stainless steel claddings

    SciTech Connect

    Alexandrov, O.A. ); Steklov, O.I.; Alexeev, A.V. )

    1993-11-01

    A separation type crack, metallic disbonding, occurred between austenitic stainless steel weld metal cladding and 2 1/4Cr-1Mo base metal in the hydrodesulfurizing reactor of an oil refining plant. For stainless steel cladding, the submerged arc welding (SAW) process with a strip electrode is usually applied, but the authors experimented with the plasma arc welding (PAW) process with hot wire electrode for the cladding. The metallic disbonding is considered to be attributed to hydrogen accumulation at the transition zone and has been generally studied on a laboratory scale using an autoclave. The authors used a electrolytic hydrogen charging technique for the sake of experimental simplicity and made a comparison with the results for gaseous hydrogen charging. The main conclusions obtained were follows: The PAW stainless steel weld metal cladding is more resistant to metallic disbonding with the PAW process is explained by the desirable microstructure and properties of the first layer of weld metal at the transition zone. Electrolytic hydrogen charging pretty well reproduces the results of autoclave gas phase charging.

  3. Mode size and loss in strongly asymmetric plasmonic waveguide with dielectric cladding

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Mei, Ting; Li, Yicen; Zhu, Ning; Jin, Gui

    2015-12-01

    The effect of dielectric cladding on modifying a mode field based on a multilayer planar surface plasmon polariton (SPP) waveguide is investigated at the telecom wavelength of 1.55 μm. Through numerical calculations based on the transfer matrix method and Cauchy integration method, we point out that the mode loss and the mode size can be efficiently engineered via tailoring the dielectric cladding layer. With appropriately optimized thickness and refractive index of the dielectric cladding, the mode size and mode loss of the long-range SPP modes supported by the proposed structure could reach their minima simultaneously such that the figure of merit exhibits a maximum, which breaks the trade-off relationship between confinement and attenuation of SPP waveguide to a certain degree. Furthermore, benefiting from the dielectric cladding effect, the adjustability of field distribution in the dielectric region provides a simple and effective means for improving the light-matter interaction strength for the purpose of SPP signal modulating, detecting or sensing.

  4. Characterization of Brazed Joints of C-C Composite to Cu-clad-Molybdenum

    NASA Technical Reports Server (NTRS)

    Singh, M.; Asthana, R.

    2008-01-01

    Carbon-carbon composites with either pitch+CVI matrix or resin-derived matrix were joined to copper-clad molybdenum using two active braze alloys, Cusil-ABA (1.75% Ti) and Ticusil (4.5% Ti). The brazed joints revealed good interfacial bonding, preferential precipitation of Ti at the composite/braze interface, and a tendency toward de-lamination in resin-derived C-C composite due to its low inter-laminar shear strength. Extensive braze penetration of the inter-fiber channels in the pitch+CVI C-C composites was observed. The relatively low brazing temperatures (<950 C) precluded melting of the clad layer and restricted the redistribution of alloying elements but led to metallurgically sound composite joints. The Knoop microhardness (HK) distribution across the joint interfaces revealed sharp gradients at the Cu-clad-Mo/braze interface and higher hardness in Ticusil (approx.85-250 HK) than in Cusil-ABA (approx.50-150 HK). These C-C/Cu-clad-Mo joints with relatively low thermal resistance may be promising for thermal management applications.

  5. Correlation of waterside corrosion and cladding microstructure in high-burnup fuel and gadolinia rods

    SciTech Connect

    Chung, H.M. )

    1989-09-01

    Waterside corrosion of the Zircaloy cladding has been examined in high-burnup fuel rods from several BWRs and PWRs, as well as in 3 wt % gadolinia burnable poison rods obtained from a BWR. The corrosion behavior of the high-burnup rods was then correlated with results from a microstructural characterization of the cladding by optical, scanning-electron, and transmission-electron microscopy (OM, SEM, and TEM). OM and SEM examination of the BWR fuel cladding showed both uniform and nodular oxide layers 2 to 45 {mu}m in thickness after burnups of 11 to 30 MWd/kgU. For one of the BWRs, which was operated at 307{degree}C rather than the normal 288{degree}C, a relatively thick (50 to 70 {mu}m) uniform oxide, rather than nodular oxides, was observed after a burnup of 27 to 30 MWd/kgU. TEM characterization revealed a number of microstructural features that occurred in association with the intermetallic precipitates in the cladding metal, apparently as a result of irradiation-induced or -enhanced processes. The BWR rods that exhibited white nodular oxides contained large precipitates (300 to 700 nm in size) that were partially amorphized during service, indicating that a distribution of the large intermetallic precipitates is conductive to nodular oxidation. 23 refs., 9 figs.

  6. Interfacial Characterization of Dissimilar Joints Between Al/Mg/Al-Trilayered Clad Sheet to High-Strength Low-Alloy Steel

    NASA Astrophysics Data System (ADS)

    Macwan, A.; Jiang, X. Q.; Chen, D. L.

    2015-07-01

    Magnesium (Mg) alloys are increasingly used in the automotive and aerospace sectors to reduce vehicle weight. Al/Mg/Al tri-layered clad sheets are deemed as a promising alternative to improve the corrosion resistance and formability of Mg alloys. The structural application of Al/Mg/Al tri-layered clad sheets inevitably involves welding and joining in the multi-material vehicle body manufacturing. This study aimed to characterize the bonding interface microstructure of the Al/Mg/Al-clad sheet to high-strength low-alloy steel with and without Zn coating using ultrasonic spot welding at different levels of welding energy. It was observed that the presence of Zn coating improved the bonding at the interface due to the formation of Al-Zn eutectic structure via enhanced diffusion. At a higher level of welding energy, characteristic flow patterns of Zn into Al-clad layer were observed with an extensive penetration mainly along some high angle grain boundaries. The dissimilar joints without Zn coating made at a high welding energy of 800 J failed partially from the Al/Fe weld interface and partially from the Al/Mg clad interface, while the joints with Zn coating failed from the Al/Mg clad interface due to the presence of brittle Al12Mg17 phase.

  7. Novel strip-cast Mg/Al clad sheets with excellent tensile and interfacial bonding properties

    NASA Astrophysics Data System (ADS)

    Kim, Jung-Su; Lee, Dong Ho; Jung, Seung-Pill; Lee, Kwang Seok; Kim, Ki Jong; Kim, Hyoung Seop; Lee, Byeong-Joo; Chang, Young Won; Yuh, Junhan; Lee, Sunghak

    2016-06-01

    In order to broaden industrial applications of Mg alloys, as lightest-weight metal alloys in practical uses, many efforts have been dedicated to manufacture various clad sheets which can complement inherent shortcomings of Mg alloys. Here, we present a new fabrication method of Mg/Al clad sheets by bonding thin Al alloy sheet on to Mg alloy melt during strip casting. In the as-strip-cast Mg/Al clad sheet, homogeneously distributed equi-axed dendrites existed in the Mg alloy side, and two types of thin reaction layers, i.e., γ (Mg17Al12) and β (Mg2Al3) phases, were formed along the Mg/Al interface. After post-treatments (homogenization, warm rolling, and annealing), the interfacial layers were deformed in a sawtooth shape by forming deformation bands in the Mg alloy and interfacial layers, which favorably led to dramatic improvement in tensile and interfacial bonding properties. This work presents new applications to multi-functional lightweight alloy sheets requiring excellent formability, surface quality, and corrosion resistance as well as tensile and interfacial bonding properties.

  8. Novel strip-cast Mg/Al clad sheets with excellent tensile and interfacial bonding properties

    PubMed Central

    Kim, Jung-Su; Lee, Dong Ho; Jung, Seung-Pill; Lee, Kwang Seok; Kim, Ki Jong; Kim, Hyoung Seop; Lee, Byeong-Joo; Chang, Young Won; Yuh, Junhan; Lee, Sunghak

    2016-01-01

    In order to broaden industrial applications of Mg alloys, as lightest-weight metal alloys in practical uses, many efforts have been dedicated to manufacture various clad sheets which can complement inherent shortcomings of Mg alloys. Here, we present a new fabrication method of Mg/Al clad sheets by bonding thin Al alloy sheet on to Mg alloy melt during strip casting. In the as-strip-cast Mg/Al clad sheet, homogeneously distributed equi-axed dendrites existed in the Mg alloy side, and two types of thin reaction layers, i.e., γ (Mg17Al12) and β (Mg2Al3) phases, were formed along the Mg/Al interface. After post-treatments (homogenization, warm rolling, and annealing), the interfacial layers were deformed in a sawtooth shape by forming deformation bands in the Mg alloy and interfacial layers, which favorably led to dramatic improvement in tensile and interfacial bonding properties. This work presents new applications to multi-functional lightweight alloy sheets requiring excellent formability, surface quality, and corrosion resistance as well as tensile and interfacial bonding properties. PMID:27245687

  9. Novel strip-cast Mg/Al clad sheets with excellent tensile and interfacial bonding properties.

    PubMed

    Kim, Jung-Su; Lee, Dong Ho; Jung, Seung-Pill; Lee, Kwang Seok; Kim, Ki Jong; Kim, Hyoung Seop; Lee, Byeong-Joo; Chang, Young Won; Yuh, Junhan; Lee, Sunghak

    2016-01-01

    In order to broaden industrial applications of Mg alloys, as lightest-weight metal alloys in practical uses, many efforts have been dedicated to manufacture various clad sheets which can complement inherent shortcomings of Mg alloys. Here, we present a new fabrication method of Mg/Al clad sheets by bonding thin Al alloy sheet on to Mg alloy melt during strip casting. In the as-strip-cast Mg/Al clad sheet, homogeneously distributed equi-axed dendrites existed in the Mg alloy side, and two types of thin reaction layers, i.e., γ (Mg17Al12) and β (Mg2Al3) phases, were formed along the Mg/Al interface. After post-treatments (homogenization, warm rolling, and annealing), the interfacial layers were deformed in a sawtooth shape by forming deformation bands in the Mg alloy and interfacial layers, which favorably led to dramatic improvement in tensile and interfacial bonding properties. This work presents new applications to multi-functional lightweight alloy sheets requiring excellent formability, surface quality, and corrosion resistance as well as tensile and interfacial bonding properties. PMID:27245687

  10. Stimulated emission and optical gain in AlGaN heterostructures grown on bulk AlN substrates

    SciTech Connect

    Guo, Wei Bryan, Zachary; Kirste, Ronny; Bryan, Isaac; Hussey, Lindsay; Bobea, Milena; Haidet, Brian; Collazo, Ramón; Sitar, Zlatko; Xie, Jinqiao; Mita, Seiji; Gerhold, Michael

    2014-03-14

    Optical gain spectra for ∼250 nm stimulated emission were compared in three different AlGaN-based structures grown on single crystalline AlN substrates: a single AlGaN film, a double heterostructure (DH), and a Multiple Quantum Well (MQW) structure; respective threshold pumping power densities of 700, 250, and 150 kW/cm{sup 2} were observed. Above threshold, the emission was transverse-electric polarized and as narrow as 1.8 nm without a cavity. The DH and MQW structures showed gain values of 50–60 cm{sup −1} when pumped at 1 MW/cm{sup 2}. The results demonstrated the excellent optical quality of the AlGaN-based heterostructures grown on AlN substrates and their potential for realizing electrically pumped sub-280 nm laser diodes.

  11. Microstructure characteristics of Ni/WC composite cladding coatings

    NASA Astrophysics Data System (ADS)

    Yang, Gui-rong; Huang, Chao-peng; Song, Wen-ming; Li, Jian; Lu, Jin-jun; Ma, Ying; Hao, Yuan

    2016-02-01

    A multilayer tungsten carbide particle (WCp)-reinforced Ni-based alloy coating was fabricated on a steel substrate using vacuum cladding technology. The morphology, microstructure, and formation mechanism of the coating were studied and discussed in different zones. The microstructure morphology and phase composition were investigated by scanning electron microscopy, optical microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. In the results, the coating presents a dense and homogeneous microstructure with few pores and is free from cracks. The whole coating shows a multilayer structure, including composite, transition, fusion, and diffusion-affected layers. Metallurgical bonding was achieved between the coating and substrate because of the formation of the fusion and diffusion-affected layers. The Ni-based alloy is mainly composed of γ-Ni solid solution with finely dispersed Cr7C3/Cr23C6, CrB, and Ni+Ni3Si. WC particles in the composite layer distribute evenly in areas among initial Ni-based alloying particles, forming a special three-dimensional reticular microstructure. The macrohardness of the coating is HRC 55, which is remarkably improved compared to that of the substrate. The microhardness increases gradually from the substrate to the composite zone, whereas the microhardness remains almost unchanged in the transition and composite zones.

  12. Tailoring of polarization in electron blocking layer for electron confinement and hole injection in ultraviolet light-emitting diodes

    SciTech Connect

    Lu, Yu-Hsuan; Pilkuhn, Manfred H.; Fu, Yi-Keng; Chu, Mu-Tao; Huang, Shyh-Jer E-mail: totaljer48@gmail.com; Su, Yan-Kuin E-mail: totaljer48@gmail.com; Wang, Kang L.

    2014-03-21

    The influence of the AlGaN electron blocking layer (EBL) with graded aluminum composition on electron confinement and hole injection in AlGaN-based ultraviolet light-emitting diodes (LEDs) are investigated. The light output power of LED with graded AlGaN EBL was markedly improved, comparing to LED with conventional EBL. In experimental results, a high increment of 86.7% can be obtained in light output power. Simulation analysis shows that via proper modification of the barrier profile from the last barrier of the active region to EBL, not only the elimination of electron overflow to p-type layer can be achieved but also the hole injection into the active region can be enhanced, compared to a conventional LED structure. The dominant factor to the performance improvement is shown to be the modulation of polarization field by the graded Al composition in EBL.

  13. Improving hole injection and carrier distribution in InGaN light-emitting diodes by removing the electron blocking layer and including a unique last quantum barrier

    SciTech Connect

    Cheng, Liwen Chen, Haitao; Wu, Shudong

    2015-08-28

    The effects of removing the AlGaN electron blocking layer (EBL), and using a last quantum barrier (LQB) with a unique design in conventional blue InGaN light-emitting diodes (LEDs), were investigated through simulations. Compared with the conventional LED design that contained a GaN LQB and an AlGaN EBL, the LED that contained an AlGaN LQB with a graded-composition and no EBL exhibited enhanced optical performance and less efficiency droop. This effect was caused by an enhanced electron confinement and hole injection efficiency. Furthermore, when the AlGaN LQB was replaced with a triangular graded-composition, the performance improved further and the efficiency droop was lowered. The simulation results indicated that the enhanced hole injection efficiency and uniform distribution of carriers observed in the quantum wells were caused by the smoothing and thinning of the potential barrier for the holes. This allowed a greater number of holes to tunnel into the quantum wells from the p-type regions in the proposed LED structure.

  14. PWR cores with silicon carbide cladding

    SciTech Connect

    Dobisesky, J. P.; Carpenter, D.; Pilat, E.; Kazimi, M. S.

    2012-07-01

    The feasibility of using silicon carbide rather than Zircaloy cladding, to reach higher power levels and higher discharge burnups in PWRs has been evaluated. A preliminary fuel design using fuel rods with the same dimensions as in the Westinghouse Robust Fuel Assembly but with fuel pellets having 10 vol% central void has been adopted to mitigate the higher fuel temperatures that occur due to the lower thermal conductivity of the silicon carbide and to the persistence of the open clad-pellet gap over most of the fuel life. With this modified fuel design, it is possible to achieve 18 month cycles that meet present-day operating constraints on peaking factor, boron concentration, reactivity coefficients and shutdown margin, while allowing batch average discharge burnups up to 80 MWD/kgU and peak rod burnups up to 100 MWD/kgU. Power uprates of 10% and possibly 20% also appear feasible. For non-uprated cores, the silicon carbide-clad fuel has a clear advantage that increases with increasing discharge burnup. Even for comparable discharge burnups, there is a savings in enriched uranium. Control rod configuration modifications may be required to meet the shutdown margin criterion for the 20% up-rate. Silicon carbide's ability to sustain higher burnups than Zircaloy also allows the design of a licensable two year cycle with only 96 fresh assemblies, avoiding the enriched uranium penalty incurred with use of larger batch sizes due to their excessive leakage. (authors)

  15. Bioactivity of fluorapatite/alumina composite coatings deposited on Ti6Al4V substrates by laser cladding

    NASA Astrophysics Data System (ADS)

    Chien, C. S.; Liu, C. W.; Kuo, T. Y.; Wu, C. C.; Hong, T. F.

    2016-04-01

    Hydroxyapatite (HA) is one of the most commonly used coating materials for metal implants. However, following high-temperature deposition, HA easily decomposes into an unstable phase or forms an amorphous phase, and hence, the long-term stability of the implant is reduced. Accordingly, the present study investigates the use of fluorapatite (FA) fortified with 20 wt% alumina (α-Al2O3) as an alternative biomedical coating material. The coatings are deposited on Ti6Al4V substrates using a Nd:YAG laser cladding process performed with laser powers and travel speeds of 400 W/200 mm/min, 800 W/400 mm/min and 1200 W/600 mm/min, respectively. The results show that for all of the specimens, a strong metallurgical bond is formed at the interface between the coating layer and the transition layer due to melting and diffusion. The XRD analysis results reveal that the cladding layers in all of the specimens consist mainly of FA, β-TCP, CaF2, Ti and θ-Al2O3 phases. In addition, the cladding layers of the specimens prepared using laser powers of 400 and 800 W also contain CaTiO3 and CaAl2O4, while that of the specimen clad using a power of 1200 W contains TTCP and CaO. Following immersion in simulated body fluid for 14 days, all of the specimens precipitate dense bone-like apatite and exhibit excellent bioactivity. However, among all of the specimens, the specimen that is prepared with a laser power of 800 W shows the best biological activity due to the presence of residual FA, apatite-generating CaTiO3 and a rough cladding layer surface.

  16. Improvement of AlGaN/GaN high electron mobility transistor structures by in situ deposition of a Si3N4 surface layer

    NASA Astrophysics Data System (ADS)

    Derluyn, J.; Boeykens, S.; Cheng, K.; Vandersmissen, R.; Das, J.; Ruythooren, W.; Degroote, S.; Leys, M. R.; Germain, M.; Borghs, G.

    2005-09-01

    We have made AlGaN/GaN high electron mobility transistors with a Si3N4 passivation layer that was deposited in situ in our metal-organic chemical-vapor deposition reactor in the same growth sequence as the rest of the layer stack. The Si3N4 is shown to be of high quality and stoichiometric in composition. It reduces the relaxation, cracking, and surface roughness of the AlGaN layer. It also neutralizes the charges at the top AlGaN interface, which leads to a higher two-dimensional electron-gas density. Moreover, it protects the surface during processing and improves the Ohmic source and drain contacts. This leads to devices with greatly improved characteristics.

  17. Measuring the depth profiles of strain/composition in AlGaN-graded layer by high-resolution x-ray diffraction

    SciTech Connect

    Kuchuk, A. V.; Stanchu, H. V.; Kladko, V. P.; Belyaev, A. E.; Li, Chen; Ware, M. E.; Mazur, Yu. I.; Salamo, G. J.

    2014-12-14

    Here, we demonstrate X-ray fitting through kinematical simulations of the intensity profiles of symmetric reflections for epitaxial compositionally graded layers of AlGaN grown by molecular beam epitaxy pseudomorphically on [0001]-oriented GaN substrates. These detailed simulations depict obvious differences between changes in thickness, maximum concentration, and concentration profile of the graded layers. Through comparison of these simulations with as-grown samples, we can reliably determine these parameters, most important of which are the profiles of the concentration and strain which determine much of the electrical properties of the film. In addition to learning about these parameters for the characterization of thin film properties, these fitting techniques create opportunities to calibrate growth rates and control composition profiles of AlGaN layers with a single growth rather than multiple growths as has been done traditionally.

  18. Electrically heated ex-reactor pellet-cladding interaction (PCI) simulations utilizing irradiated Zircaloy cladding. [PWR

    SciTech Connect

    Barner, J.O.; Fitzsimmons, D.E.

    1985-02-01

    In a program sponsored by the Fuel Systems Research Branch of the US Nuclear Regulatory Commission, a series of six electrically heated fuel rod simulation tests were conducted at Pacific Northwest Laboratory. The primary objective of these tests was to determine the susceptibility of irradiated pressurized-water reactor (PWR) Zircaloy-4 cladding to failures caused by pellet-cladding mechanical interaction (PCMI). A secondary objective was to acquire kinetic data (e.g., ridge growth or relaxation rates) that might be helpful in the interpretation of in-reactor performance results and/or the modeling of PCMI. No cladding failures attributable to PCMI occurred during the six tests. This report describes the testing methods, testing apparatus, fuel rod diametral strain-measuring device, and test matrix. Test results are presented and discussed.

  19. Static and dynamic oxidation of Pt-clad Mo-47Re alloy

    SciTech Connect

    Clark, R.K.; Wallace, T.A. )

    1994-06-15

    Molybdenum-based alloys have the potential for meeting the materials requirements of many applications requiring strength values as high as 140 MPa at temperatures as high as 1,300 C. The addition of Re to Mo provides greater ductility and a lower ductile-to-brittle transition temperature than for unalloyed Mo. The alloy Mo-47Re (wt %) is one alloy from the Mo-Re system that is a candidate for use in hydrogen-fueled engines of hypersonic vehicles. Potential applications for the alloy in engines include heat exchanger tubes at temperatures up to 1,260 C and combustion chamber linings at temperatures to 1,370 C and hydrogen pressures to 175 ATM. The projected service life at peak temperature in such an application is about 12 h. Because of the reactivity of molybdenum and rhenium with oxygen in air at high temperatures, some means of protecting the alloy must be devised. One approach to protecting the alloy is to clad it with a non-reactive impermeable barrier layer. Platinum is proposed as a candidate for use as a cladding because of its high melting point (1,790 C) and chemical stability at high temperature. This paper presents results from a study of the oxidation performance of Pt-clad Mo-47Re. Pt-clad samples were tested under static and dynamic oxidation conditions at 1,260 C. A single unclad sample was tested under dynamic oxidation conditions at 595 C. The static oxidation tests were conducted in an ambient pressure furnace with laboratory air. The dynamic oxidation tests were conducted in an electric arc-heated wind tunnel. Weight change, metallography, and microscopy results are presented to show the effects of oxidation on the alloy and interaction between the cladding and the alloy.

  20. Microstructure and Mechanical Properties of Laser Clad and Post-cladding Tempered AISI H13 Tool Steel

    NASA Astrophysics Data System (ADS)

    Telasang, Gururaj; Dutta Majumdar, Jyotsna; Wasekar, Nitin; Padmanabham, G.; Manna, Indranil

    2015-05-01

    This study reports a detailed investigation of the microstructure and mechanical properties (wear resistance and tensile strength) of hardened and tempered AISI H13 tool steel substrate following laser cladding with AISI H13 tool steel powder in as-clad and after post-cladding conventional bulk isothermal tempering [at 823 K (550 °C) for 2 hours] heat treatment. Laser cladding was carried out on AISI H13 tool steel substrate using a 6 kW continuous wave diode laser coupled with fiber delivering an energy density of 133 J/mm2 and equipped with a co-axial powder feeding nozzle capable of feeding powder at the rate of 13.3 × 10-3 g/mm2. Laser clad zone comprises martensite, retained austenite, and carbides, and measures an average hardness of 600 to 650 VHN. Subsequent isothermal tempering converted the microstructure into one with tempered martensite and uniform dispersion of carbides with a hardness of 550 to 650 VHN. Interestingly, laser cladding introduced residual compressive stress of 670 ± 15 MPa, which reduces to 580 ± 20 MPa following isothermal tempering. Micro-tensile testing with specimens machined from the clad zone across or transverse to cladding direction showed high strength but failure in brittle mode. On the other hand, similar testing with samples sectioned from the clad zone parallel or longitudinal to the direction of laser cladding prior to and after post-cladding tempering recorded lower strength but ductile failure with 4.7 and 8 pct elongation, respectively. Wear resistance of the laser surface clad and post-cladding tempered samples (evaluated by fretting wear testing) registered superior performance as compared to that of conventional hardened and tempered AISI H13 tool steel.

  1. Investigation of Clad Metals for Use as Bipolar Plate Material in PEM Fuel Cell Stacks

    SciTech Connect

    Rich, John S.; Meier, Alan M.; Kim, Jin Yong; Xia, Guanguang; Yang, Zhenguo; Weil, K. Scott

    2006-07-21

    Although metal interconnects offer many advantages over their carbon-based counterparts, they suffer from surface corrosion which leads to a release of metal ions that can contaminate the electrolyte membrane and poison the electrode catalysts. In addition, the formation of a passivating oxide or oxyhydroxide layer on the surface of the metal will increase the contact resistance between the bipolar plate and the graphite electrode backing. The approach currently under development employs an inexpensive clad metal laminate as the primary material for the bipolar plate. The key in making this work is in identifying an appropriate surface passivation layer that mitigates corrosion while at the same time allows for good electronic conduction. The current study investigated the kinetics of nitride formation on Nb and Ti foils as a function of time, temperature, atmosphere (N2-H2 gas composition), and the corrosion behavior. These two metals are being considered for use as a thin external cladding layer over an inexpensive steel core layer. As the nitride layer formation temperature was increased, the surface morphologies for both niobium and titanium substrates became coarser and more pitted, the nitride thicknesses of both increased non-linearly, and in the titanium system an oxide layer product layer on the outer surface grew as well. As the isothermal hold time was increased, the surface morphologies of both niobium and titanium reaction product layers did not change noticeably, and the thicknesses of the nitride layers increased. As the amount of hydrogen in the atmosphere was increased the surface morphologies for both the niobium and titanium did not change detectably, the thicknesses of the nitride layers increased, and titanium thicknesses of the oxide layers decreased. The nitrided niobium exhibited much better corrosion behavior than the nitrided titanium but no improvement was obtained relative to the pure Nb corrosion rates.

  2. The light-matter interaction of a single semiconducting AlGaN nanowire and noble metal Au nanoparticles in the sub-diffraction limit.

    PubMed

    Sivadasan, A K; Madapu, Kishore K; Dhara, Sandip

    2016-08-24

    Near field scanning optical microscopy (NSOM) is not only a tool for imaging of sub-diffraction limited objects but also a prominent characteristic tool for understanding the intrinsic properties of nanostructures. In order to understand light-matter interactions in the near field regime using a NSOM technique with an excitation of 532 nm (2.33 eV), we selected an isolated single semiconducting AlGaN nanowire (NW) of diameter ∼120 nm grown via a vapor liquid solid (VLS) mechanism along with a metallic Au nanoparticle (NP) catalyst. The role of electronic transitions from different native defect related energy states of AlGaN is discussed in understanding the NSOM images for the semiconducting NW. The effect of strong surface plasmon resonance absorption of an excitation laser on the NSOM images for Au NPs, involved in the VLS growth mechanism of NWs, is also observed. PMID:27511614

  3. Angular distribution of polarized light and its effect on light extraction efficiency in AlGaN deep-ultraviolet light-emitting diodes.

    PubMed

    Chen, Xinjuan; Ji, Cheng; Xiang, Yong; Kang, Xiangning; Shen, Bo; Yu, Tongjun

    2016-05-16

    Angular distribution of polarized light and its effect on light extraction efficiency (LEE) in AlGaN deep-ultraviolet (DUV) light-emitting diodes (LEDs) are investigated in this paper. A united picture is presented to describe polarized light's emission and propagation processes. It is found that the electron-hole recombinations in AlGaN multiple quantum wells produce three kinds of angularly distributed polarized emissions and propagation process can change their intensity distributions. By investigation the change of angular distributions in 277nm and 215nm LEDs, this work reveals that LEE can be significantly enhanced by modulating the angular distributions of polarized light of DUV LEDs. PMID:27409966

  4. Traps and defects in pre- and post-proton irradiated AlGaN-GaN high electron mobility transistors and AlGaN Schottky diodes

    NASA Astrophysics Data System (ADS)

    Sin, Yongkun; Foran, Brendan; Presser, Nathan; LaLumondiere, Stephen; Lotshaw, William; Moss, Steven C.

    2013-03-01

    High electron mobility transistors (HEMTs) based on AlGaN-GaN hetero-structures are promising for both commercial and military applications that require high voltage, high power, and high efficiency operation. Study of reliability and radiation effects of AlGaN-GaN HEMTs is necessary before solid state power amplifiers based on GaN HEMT technology are successfully deployed in satellite communication systems. Several AlGaN HEMT manufacturers have recently reported encouraging reliability data, but long-term reliability of these devices in the space environment still remains a major concern because a large number of traps and defects are present both in the bulk as well as at the surface leading to undesirable characteristics. This study is to investigate the effects of the AlGaN-GaN HEMTs and AlGaN Schottky diodes irradiated with protons.

  5. Transversely polarized source cladding for an optical fiber

    NASA Technical Reports Server (NTRS)

    Egalon, Claudio Oliveira (Inventor); Rogowski, Robert S. (Inventor)

    1994-01-01

    An optical fiber comprising a fiber core having a longitudinal symmetry axis is provided. An active cladding surrounds a portion of the fiber core and comprises light-producing sources which emit light in response to chemical or light excitation. The cladding sources are oriented transversely with respect to the longitudinal axis of the fiber core. This polarization results in a superior power efficiency compared to active cladding sources that are randomly polarized or longitudinally polarized parallel with the longitudinal symmetry axis.

  6. Development and characterisations of WC–12Co microwave clad

    SciTech Connect

    Zafar, Sunny Sharma, Apurbba Kumar

    2014-10-15

    In the present work, WC–12Co based cermet clad was developed on AISI 304 stainless steel using microwave hybrid heating technique. The experimental trials were carried out in a 1.4 kW industrial multimode microwave applicator. The paper explains the major events occurring during microwave irradiation and formation of clad. The developed clads were subsequently characterised through field emission scanning electron microscopy equipped with energy dispersive X-ray spectroscopy, X-ray diffraction, assessment of porosity and microhardness. The WC–12Co clads developed with an approximate thickness of 1 mm, illustrated excellent metallurgical bonding with substrate. The microstructure of the WC–12Co clad mainly consists of skeleton structured carbides embedded in tough metallic phase. The phase analysis of the developed clads indicate the presence of various stable and complex carbides like Co{sub 6}W{sub 6}C, Co{sub 3}W{sub 3}C and Fe{sub 6}W{sub 6}C. The uniform distribution of such carbides with skeleton-like morphology in the microstructure is indicative of high hardness of the clad. The developed clads were free from visible interfacial cracking and the clad porosity was found in the order of approximately 0.98%. The average microhardness of the WC–12Co microwave clads was observed to be 1135 ± 88 HV. - Highlights: • Microwave cladding of WC–12Co on AISI 304 stainless steel is carried out. • Skeleton-like structures of W–Co based carbides are embedded in metallic matrix. • Clad–substrate interface is free from un-melted and un-dissolved carbide particles. • Hardness of clad (1135 ± 88 HV) is 3.5 times that of the substrate (325 ± 49 HV)

  7. Clad fiber capacitor and method of making same

    SciTech Connect

    Tuncer, Enis

    2012-12-11

    A clad capacitor and method of manufacture includes assembling a preform comprising a ductile, electrically conductive fiber; a ductile, electrically insulating cladding positioned on the fiber; and a ductile, electrically conductive sleeve positioned over the cladding. One or more preforms are then bundled, heated and drawn along a longitudinal axis to decrease the diameter of the ductile components of the preform and fuse the preform into a unitized strand.

  8. Clad fiber capacitor and method of making same

    SciTech Connect

    Tuncer, Enis

    2013-11-26

    A clad capacitor and method of manufacture includes assembling a preform comprising a ductile, electrically conductive fiber; a ductile, electrically insulating cladding positioned on the fiber; a ductile, electrically conductive sleeve positioned over the cladding. One or more of the preforms are then bundled, heated and drawn along a longitudinal axis to decrease the diameter of the ductile components of the preform and fuse the preform into a unitized strand.

  9. Microstructure and high temperature oxidation resistance of Ti-Ni gradient coating on TA2 titanium alloy fabricated by laser cladding

    NASA Astrophysics Data System (ADS)

    Liu, Fencheng; Mao, Yuqing; Lin, Xin; Zhou, Baosheng; Qian, Tao

    2016-09-01

    To improve the high temperature oxidation resistance of TA2 titanium alloy, a gradient Ni-Ti coating was laser cladded on the surface of the TA2 titanium alloy substrate, and the microstructure and oxidation behavior of the laser cladded coating were investigated experimentally. The gradient coating with a thickness of about 420-490 μm contains two different layers, e.g. a bright layer with coarse equiaxed grain and a dark layer with fine and columnar dendrites, and a transition layer with a thickness of about 10 μm exists between the substrate and the cladded coating. NiTi, NiTi2 and Ni3Ti intermetallic compounds are the main constructive phases of the laser cladded coating. The appearance of these phases enhances the microhardness, and the dense structure of the coating improves its oxidation resistance. The solidification procedure of the gradient coating is analyzed and different kinds of solidification processes occur due to the heat dissipation during the laser cladding process.

  10. An acoustic vibration sensor based on tapered triple cladding fiber

    NASA Astrophysics Data System (ADS)

    Xu, Hui; Pang, Fufei; Zhao, Shiqi; Chen, Zhenyi; Wang, Tingyun

    2014-05-01

    An acoustic vibration sensor is investigated and demonstrated by using a tapered triple cladding fiber (TCF). It is fabricated by tapering a length of 2 cm TCF which is spliced between two single mode fibers (SMF). The TCF consists of core, inner cladding, middle cladding and outer cladding. After the tapering process, this structure becomes a tapered coaxial fiber coupler which presents a periodic filtering transmission spectrum. The surrounding vibration perturbation can be directly demodulated by intensity detection of the transmission power at a particular wavelength. The experimental result shows that the maximum frequency response of 700 kHz is achieved.

  11. Effects of different binders on microstructure and phase composition of hydroxyapatite Nd-YAG laser clad coatings

    NASA Astrophysics Data System (ADS)

    Chien, C. S.; Hong, T. F.; Han, T. J.; Kuo, T. Y.; Liao, T. Y.

    2011-01-01

    The laser clad coating technique can help to produce metallurgical bonding with high bonding strength between the coating layer and the substrate, which has been gradually applied for hydroxyapatite (HA) coating on metallic substrates. In this study, HA powder is mixed with two different binders, namely water glass (WG) and polyvinyl alcohol (PVA), respectively, and is then clad on Ti-6Al-4V substrates using an Nd:YAG laser system under various processing conditions. The microstructure, chemical composition and hardness of the coating layer and transition layer of the various samples are then systematically explored. The experimental results show that the coating layers of the various samples all contain both cellular dendrites and rod-like piled structures, while the transition layers contain only cellular dendrites. For all samples, the coating layer consists mostly of CaTiO 3, Ca 2P 2O 7, CaO and HA phases, whereas the transition layer contains primarily CaTiO 3, Ca 2P 2O 7, Ti 3P, Ti and HA phases. In addition, the transition layer of the WG samples also contains SiO 2 and Si 2Ti phases. In all of the specimens, the transition layer has a higher average hardness than the substrate or coating layer. Moreover, the transition layer in the WG sample is harder than that in the PVA sample.

  12. Deformation potentials in AlGaN and InGaN alloys and their impact on optical polarization properties of nitride quantum wells

    NASA Astrophysics Data System (ADS)

    Łepkowski, S. P.; Gorczyca, I.; Stefańska-Skrobas, K.; Christensen, N. E.; Svane, A.

    2013-08-01

    The deformation potentials acz-D1, act-D2, D3, D4, and D5 are determined for random AlGaN and InGaN alloys using electronic band structure calculations based on the density functional theory. A sublinear composition dependence is obtained for acz-D1 and D3 in AlGaN, and D3 in InGaN, whereas superlinear behavior on composition is found for act-D2, D4, and D5 in AlGaN, and act-D2 and D5 in InGaN. The optical polarization properties of nitride quantum wells are very well described by the k·p method when the obtained deformation potentials are included. In m-plane AlGaN/AlN and InGaN/GaN quantum wells, the difference between the interband transition energies for light polarized parallel and orthogonal to the crystalline c axis compares more favorably to experimental data, than when deformation potentials previously reported in literature are used.

  13. Fabrication of polyaniline-HCl cladding modified fiber optic intrinsic biosensor for glucose detection

    NASA Astrophysics Data System (ADS)

    Pahurkar, Vikas; Tamgadge, Yuoraj; Muley, Gajanan

    2016-05-01

    In the present study, we have fabricated and studied response of cladding modified fiber optic intrinsic glucose biosensor (FOIGB). The optical fiber was used as a light transforming waveguide and sensing element fabricated over it by applying a thin layer of polymer. The cladding of the sensor was modified with the polyaniline-hydrochloric acid (PANI-HCl) polymer matrix. The PANI-HCl matrix provides an amorphous morphology useful to immobilize glucose oxidase (GOx) biomolecules through cross-linking technique via glutaraldehyde. The present sensor was used to detect the glucose analyte in the solution. In the sensing response study of FOIGB toward glucose, novel modal power distribution (MPD) technique was used. The reaction between GOx and glucose changes the optical properties of prepared FOIGB and hence modify MPD at output as a function of glucose concentration. The nature and surface morphology of PANI-HCl matrix has been studied.

  14. A Novel Inter Core-Cladding Lithium Niobate Thin Film Coated Fiber Modulator/Sensor

    NASA Technical Reports Server (NTRS)

    Jamison, Tracee L.; Komriech, Phillip; Yu, Chung

    2004-01-01

    A fiber modulator/sensor has been fabricated by depositing a lithium niobate sol-gel thin film between the core and cladding of a fiber preform. The preform is then drawn into 125 micron fiber. The proposed design of lithium niobate cylinder fibers can enhance the existing methodology for detecting sound waves under water utilizing the acoustooptic properties of lithium niobate. Upon application of a stress or strain, light propagating inside the core, according to the principle of total internal reflection, escapes, into the cladding because of the photoelastic boundary layer of lithium niobate. Test results of the lithium niobate fiber reveal a reduction in the 1550 nm, 4mW source with applied tension. The source power from an ordinary quartz fiber under the same stress condition remained invariant to applied tension.

  15. Graded-index thin-film stack for cladding and coupling.

    PubMed

    Lim, Kim Peng; Ng, Doris Keh Ting; Pu, Jing; Toh, Yeow Teck; Febiana, Tjiptoharsono; Vivek, Krishnamurthy; Wang, Qian

    2016-08-20

    A graded-index multilayer thin-film stack is optimized to act as a cladding layer on top of a silicon (Si) nanowaveguide and also a collimator for chip coupling where the waveguide ends. The numerical example shows an optimized graded-index profile from 2.35 to 1.45 provides an optical coupling to the standard single-mode fiber with efficiency close to 90% while retaining tight light confinement for the Si nanowaveguide. The corresponding material realization of a graded-index profile with a Si-rich nitride SiNx/SiON/SiO2 system is explored using inductively coupled plasma chemical vapor deposition, and a SiNx cladded Si waveguide is demonstrated. PMID:27556999

  16. Photonic lantern with cladding-removable fibers

    NASA Astrophysics Data System (ADS)

    Sun, Weimin; Yan, Qi; Bi, Yao; Yu, Haijiao; Liu, Xiaoqi; Xue, Jiuling; Tian, He; Liu, Yongjun

    2014-07-01

    Recently, spectral measurement becomes an important tool in astronomy to find exoplanets etc. The fibers are used to transfer light from the focal plate to spectrometers. To get high-resolution spectrum, the input slits of the spectrometers should be as narrow as possible. In opposite, the light spots from the fibers are circle, which diameters are clearly wider than the width of the spectrometer slits. To reduce the energy loss of the fiber-guide star light, many kinds of image slicers were designed and fabricated to transform light spot from circle to linear. Some different setup of fiber slicers are introduced by different research groups around the world. The photonic lanterns are candidates of fiber slicers. Photonic lantern includes three parts: inserted fibers, preform or tubing, taped part of the preform or tubing. Usually the optical fields concentrate in the former-core area, so the light spots are not uniform from the tapered end of the lantern. We designed, fabricated and tested a special kind of photonic lantern. The special fibers consist polymer cladding and doped high-index core. The polymer cladding could be easily removed using acetone bath, while the fiber core remains in good condition. We inserted the pure high-index cores into a pure silica tubing and tapered it. During the tapering process, the gaps between the inserted fibers disappeared. Finally we can get a uniform tapered multimode fiber end. The simulation results show that the longer the taper is, the lower the loss is. The shape of the taper should be controlled carefully. A large-zone moving-flame taper machine was fabricated to make the special photonic lantern. Three samples of photonic lanterns were fabricated and tested. The lanterns with cladding-removable fibers guide light uniform in the tapered ends that means these lanterns could collect more light from those ends.

  17. COMPARISON OF CLADDING CREEP RUPTURE MODELS

    SciTech Connect

    P. Macheret

    2000-06-12

    The objective of this calculation is to compare several creep rupture correlations for use in calculating creep strain accrued by the Zircaloy cladding of spent nuclear fuel when it has been emplaced in the repository. These correlations are used to calculate creep strain values that are then compared to a large set of experimentally measured creep strain data, taken from four different research articles, making it possible to determine the best fitting correlation. The scope of the calculation extends to six different creep rupture correlations.

  18. Thermomechanical loading applied on the cladding tube during the pellet cladding mechanical interaction phase of a rapid reactivity initiated accident

    NASA Astrophysics Data System (ADS)

    Hellouin de Menibus, Arthur; Sercombe, Jerome; Auzoux, Quentin; Poussard, Christophe

    2014-10-01

    Calculations of the CABRI REP-Na5 pulse were performed with the ALCYONE code in order to determine the evolution of the thermomechanical loading applied on the cladding tube during the Pellet-Cladding Mechanical Interaction (PCMI) phase of a rapid Reactivity Initiated Accident (RIA) initiated at 280 °C that lasted 8.8 ms. The evolution of the following parameters are reported: the cladding temperature, heating rate, strain rate and loading biaxiality. The impact of these parameters on the cladding mechanical behavior and fracture are then briefly reviewed.

  19. Microstructure, Wear, and Corrosion Characteristics of TiC-Laser Surface Cladding on Low-Carbon Steel

    NASA Astrophysics Data System (ADS)

    El-Labban, Hashem F.; Mahmoud, Essam Rabea Ibrahim; Algahtani, Ali

    2016-04-01

    Laser cladding was used to produce surface composite layer reinforced with TiC particles on low-carbon steel alloy for improving the wear and corrosion resistances. The cladding process was carried out at powers of 2800, 2000, 1500, and 1000 W, and a fixed traveling speed of 4 mm/s. The produced layers are free from any cracks. Some of the TiC particles were melted and then re-solidified in the form of fine acicular dendrites. The amount of the melted TiC was increased by increasing the laser power. The hardness of the produced layers was improved by about 19 times of the base metal. Decreasing laser power led to hardness increment at the free surface. The improvement in wear resistance was reached to about 25 times (in case of 1500 W) of the base metal. Moreover, the corrosion resistance shows remarkable improvement after the laser treatment.

  20. Structural and optical investigations of AlGaN MQWs grown on a relaxed AlGaN buffer on AlN templates for emission at 280 nm

    NASA Astrophysics Data System (ADS)

    Li, X.; Le Gac, G.; Bouchoule, S.; El Gmili, Y.; Patriarche, G.; Sundaram, S.; Disseix, P.; Réveret, F.; Leymarie, J.; Streque, J.; Genty, F.; Salvestrini, J.-P.; Dupuis, R. D.; Li, X.-H.; Voss, P. L.; Ougazzaden, A.

    2015-12-01

    10-period Al0.57Ga0.43N/Al0.38Ga0.62N multi-quantum wells (MQWs) were grown on a relaxed Al0.58Ga0.42N buffer on AlN templates on sapphire. The threading dislocations and V-pits were characterized and their origin is discussed. The influence of V-pits on the structural quality of the MQWs and on optical emission at 280 nm was analyzed. It was observed that near-surface V-pits were always associated with grain boundaries consisting of edge threading dislocations originating from the AlN/Al2O3 interface. Although the high density of V-pits disrupted MQWs growth, it did not affect the internal quantum efficiency which was measured to be ~1% at room temperature even when V-pit density was increased from 7×107 cm-2 to 2×109 cm-2. The results help to understand the origin, propagation and influences of the typical defects in AlGaN MQWs grown on AlN/Al2O3 templates which may lead to further improvement of the performance of DUV devices.

  1. Image processing applied to laser cladding process

    SciTech Connect

    Meriaudeau, F.; Truchetet, F.

    1996-12-31

    The laser cladding process, which consists of adding a melt powder to a substrate in order to improve or change the behavior of the material against corrosion, fatigue and so on, involves a lot of parameters. In order to perform good tracks some parameters need to be controlled during the process. The authors present here a low cost performance system using two CCD matrix cameras. One camera provides surface temperature measurements while the other gives information relative to the powder distribution or geometric characteristics of the tracks. The surface temperature (thanks to Beer Lambert`s law) enables one to detect variations in the mass feed rate. Using such a system the authors are able to detect fluctuation of 2 to 3g/min in the mass flow rate. The other camera gives them information related to the powder distribution, a simple algorithm applied to the data acquired from the CCD matrix camera allows them to see very weak fluctuations within both gaz flux (carriage or protection gaz). During the process, this camera is also used to perform geometric measurements. The height and the width of the track are obtained in real time and enable the operator to find information related to the process parameters such as the speed processing, the mass flow rate. The authors display the result provided by their system in order to enhance the efficiency of the laser cladding process. The conclusion is dedicated to a summary of the presented works and the expectations for the future.

  2. Material Selection for Accident Tolerant Fuel Cladding

    SciTech Connect

    Pint, Bruce A.; Terrani, Kurt A.; Yamamoto, Yukinori; Snead, Lance Lewis

    2015-01-01

    Alternative cladding materials to Zr-based alloys are being investigated for accident tolerance, which can be defined as > 100X improvement (compared to Zr-based alloys) in oxidation resistance to steam or steam-H2 environments at ≥ 1200°C for short times. After reviewing a wide range of candidates, current steam oxidation testing is being conducted on Mo, MAX phases and FeCrAl alloys. Recently reported low mass losses for Mo in steam at 800°C could not be reproduced. Both FeCrAl and MAX phase Ti2AlC form a protective alumina scale in steam. However, commercial Ti2AlC that was not single phase, formed a much thicker oxide at 1200°C in steam and significant TiO2, and therefore Ti2AlC may be challenging to form as a cladding or a coating. Alloy development for FeCrAl is seeking to maintain its steam oxidation resistance to 1475°C, while reducing its Cr content to minimize susceptibility to irradiation-assisted α´ formation. The composition effects and critical limits to retaining protective scale formation at > 1400°C are still being evaluated.

  3. Material selection for accident tolerant fuel cladding

    SciTech Connect

    Pint, B. A.; Terrani, K. A.; Yamamoto, Y.; Snead, L. L.

    2015-09-14

    Alternative cladding materials are being investigated for accident tolerance, which can be defined as >100X improvement (compared to current Zr-based alloys) in oxidation resistance in steam environments at ≥1200°C for short (≤4 h) times. After reviewing a wide range of candidates, current steam oxidation testing is being conducted on Mo, MAX phases and FeCrAl alloys. Recently reported low mass losses for Mo in steam at 800°C could not be reproduced. Both FeCrAl and MAX phase Ti2AlC form a protective alumina scale in steam. Therefore, commercial Ti2AlC that is not single phase, formed a much thicker oxide at 1200°C in steam and significant TiO2, and therefore may be challenging to use as a cladding or a coating. Alloy development for FeCrAl is seeking to maintain its steam oxidation resistance to 1475°C, while reducing its Cr content to minimize susceptibility to irradiation assisted Cr-rich α’ formation. The composition effects and critical limits to retaining protective scale formation at >1400°C are still being evaluated.

  4. Material selection for accident tolerant fuel cladding

    DOE PAGESBeta

    Pint, B. A.; Terrani, K. A.; Yamamoto, Y.; Snead, L. L.

    2015-09-14

    Alternative cladding materials are being investigated for accident tolerance, which can be defined as >100X improvement (compared to current Zr-based alloys) in oxidation resistance in steam environments at ≥1200°C for short (≤4 h) times. After reviewing a wide range of candidates, current steam oxidation testing is being conducted on Mo, MAX phases and FeCrAl alloys. Recently reported low mass losses for Mo in steam at 800°C could not be reproduced. Both FeCrAl and MAX phase Ti2AlC form a protective alumina scale in steam. Therefore, commercial Ti2AlC that is not single phase, formed a much thicker oxide at 1200°C in steammore » and significant TiO2, and therefore may be challenging to use as a cladding or a coating. Alloy development for FeCrAl is seeking to maintain its steam oxidation resistance to 1475°C, while reducing its Cr content to minimize susceptibility to irradiation assisted Cr-rich α’ formation. The composition effects and critical limits to retaining protective scale formation at >1400°C are still being evaluated.« less

  5. Material Selection for Accident Tolerant Fuel Cladding

    NASA Astrophysics Data System (ADS)

    Pint, B. A.; Terrani, K. A.; Yamamoto, Y.; Snead, L. L.

    2015-09-01

    Alternative cladding materials to Zr-based alloys are being investigated for accident tolerance, which can be defined as >100X improvement (compared to Zr-based alloys) in oxidation resistance to steam or steam-H2 environments at ≥1473 K (1200 °C) for short times. After reviewing a wide range of candidates, current steam oxidation testing is being conducted on Mo, MAX phases, and FeCrAl alloys. Recently reported low-mass losses for Mo in steam at 1073 K (800 °C) could not be reproduced. Both FeCrAl and MAX phase Ti2AlC form a protective alumina scale in steam. However, commercial Ti2AlC that was not single phase, formed a much thicker oxide at 1473 K (1200 °C) in steam and significant TiO2, and therefore, Ti2AlC may be challenging to form as a cladding or a coating. Alloy development for FeCrAl is seeking to maintain its steam oxidation resistance to 1748 K (1475 °C), while reducing its Cr content to minimize susceptibility to irradiation-assisted α' formation. The composition effects and critical limits to retaining protective scale formation at >1673 K (1400 °C) are still being evaluated.

  6. Metal clad aramid fibers for aerospace wire and cable

    NASA Astrophysics Data System (ADS)

    Tokarsky, Edward W.; Dunham, Michael G.; Hunt, James E.; Santoleri, E. David; Allen, David B.

    1995-11-01

    High strength light weight metal clad aramid fibers can provide significant weight savings when used to replace conventional metal wire in aerospace cable. An overview of metal clad aramid fiber materials and information on performance and use in braided electrical shielding and signal conductors is provided.

  7. Metal clad aramid fibers for aerospace wire and cable

    NASA Technical Reports Server (NTRS)

    Tokarsky, Edward W.; Dunham, Michael G.; Hunt, James E.; Santoleri, E. David; Allen, David B.

    1995-01-01

    High strength light weight metal clad aramid fibers can provide significant weight savings when used to replace conventional metal wire in aerospace cable. An overview of metal clad aramid fiber materials and information on performance and use in braided electrical shielding and signal conductors is provided.

  8. Influence of laser cladding regimes on structural features and mechanical properties of coatings on titanium substrates

    NASA Astrophysics Data System (ADS)

    Malyutina, Yulia N.; Lazurenko, Daria V.; Bataev, Ivan A.; Movtchan, Igor A.

    2015-10-01

    In this paper an influence of the tantalum content on the structure and properties of surface layers of the titanium alloy doped using a laser treatment technology was investigated. It was found that an increase of a quantity of filler powder per one millimeter of a track length contributed to a rise of the content of undissolved particles in coatings. The maximum thickness of a cladded layer was reached at the mass of powder per the length unit equaled to 5.5 g/cm. Coatings were characterized by the formation of a dendrite structure with attributes of segregation. The width of a quenched fusion zone grew with an increase in the rate of powder feed to the treated area. Significant strengthening of the titanium surface layer alloyed with tantalum was not observed; however, the presence of undissolved tantalum particles can decrease the hardness of titanium surface layers.

  9. Influence of laser cladding regimes on structural features and mechanical properties of coatings on titanium substrates

    SciTech Connect

    Malyutina, Yulia N. Lazurenko, Daria V. Bataev, Ivan A.; Movtchan, Igor A.

    2015-10-27

    In this paper an influence of the tantalum content on the structure and properties of surface layers of the titanium alloy doped using a laser treatment technology was investigated. It was found that an increase of a quantity of filler powder per one millimeter of a track length contributed to a rise of the content of undissolved particles in coatings. The maximum thickness of a cladded layer was reached at the mass of powder per the length unit equaled to 5.5 g/cm. Coatings were characterized by the formation of a dendrite structure with attributes of segregation. The width of a quenched fusion zone grew with an increase in the rate of powder feed to the treated area. Significant strengthening of the titanium surface layer alloyed with tantalum was not observed; however, the presence of undissolved tantalum particles can decrease the hardness of titanium surface layers.

  10. Mechanical properties of silver halide core/clad IR fibers

    NASA Astrophysics Data System (ADS)

    Shalem, Shaul; German, Alla; Moser, Frank; Katzir, Abraham

    1996-04-01

    We have developed core/clad polycrystalline silver halide optical fibers with a loss of roughly 0.3 dB/m at 10.6 micrometers. Such fibers, with core diameters 0.3 - 0.6 mm and lengths of 1 to 2 meters are capable of continuously delivering output power densities as high as 14 KW/cm2. The fibers were repetitively bent in the plastic and elastic regimes and the optical transmission monitored during bending. The mechanical properties of the core/clad fibers and of the core only fibers are similar. It was also demonstrated that the 'bending' properties of the core/clad fibers are determined by the cladding material. Our investigations suggest that proper design of the core/clad structure may give significant improvement in mechanical properties such as more cycles to optical failure. This will be very important especially for endoscopic laser surgery and other medical applications.

  11. Effect of Annealing on Microstructure and Tensile Properties of 5052/AZ31/5052 Clad Sheets

    NASA Astrophysics Data System (ADS)

    Nie, Huihui; Liang, Wei; Chi, Chengzhong; Li, Xianrong; Fan, Haiwei; Yang, Fuqian

    2016-05-01

    Three-layered 5052Al/AZ31Mg/5052Al (5052/AZ31/5052) clad sheets were fabricated by four-pass rolling and annealed under different conditions. Under the optimal annealing condition, homogeneous and equiaxial grains with an average AZ31 grain size of 5.24 µm were obtained and the maximum values of ultimate tensile strength and elongation of the clad sheet reached 230 MPa and 18%, respectively. Electron backscatter diffraction analysis showed that the AZ31 layer had a typical rolling texture with its c-axis parallel to the normal direction. The fraction of low-angle grain boundaries in the 5052 layer was nearly four times more than that in the AZ31 layer because of different deformation extent and recrystallization driving forces. The textures of Al3Mg2 and Mg17Al12 were similar to that of 5052 because of the deformation coordination during the rolling and recrystallization process. The orientation relationship between Mg17Al12 and AZ31 seemed to be (110) Mg17Al12//(10-11) AZ31.

  12. An elegant route to overcome fundamentally-limited light extraction in AlGaN deep-ultraviolet light-emitting diodes: Preferential outcoupling of strong in-plane emission

    PubMed Central

    Lee, Jong Won; Kim, Dong Yeong; Park, Jun Hyuk; Schubert, E. Fred; Kim, Jungsub; Lee, Jinsub; Kim, Yong-Il; Park, Youngsoo; Kim, Jong Kyu

    2016-01-01

    While there is an urgent need for semiconductor-based efficient deep ultraviolet (DUV) sources, the efficiency of AlGaN DUV light-emitting diodes (LEDs) remains very low because the extraction of DUV photons is significantly limited by intrinsic material properties of AlGaN. Here, we present an elegant approach based on a DUV LED having multiple mesa stripes whose inclined sidewalls are covered by a MgF2/Al omni-directional mirror to take advantage of the strongly anisotropic transverse-magnetic polarized emission pattern of AlGaN quantum wells. The sidewall-emission-enhanced DUV LED breaks through the fundamental limitations caused by the intrinsic properties of AlGaN, thus shows a remarkable improvement in light extraction as well as operating voltage. Furthermore, an analytic model is developed to understand and precisely estimate the extraction of DUV photons from AlGaN DUV LEDs, and hence to provide promising routes for maximizing the power conversion efficiency. PMID:26935402

  13. An elegant route to overcome fundamentally-limited light extraction in AlGaN deep-ultraviolet light-emitting diodes: Preferential outcoupling of strong in-plane emission

    NASA Astrophysics Data System (ADS)

    Lee, Jong Won; Kim, Dong Yeong; Park, Jun Hyuk; Schubert, E. Fred; Kim, Jungsub; Lee, Jinsub; Kim, Yong-Il; Park, Youngsoo; Kim, Jong Kyu

    2016-03-01

    While there is an urgent need for semiconductor-based efficient deep ultraviolet (DUV) sources, the efficiency of AlGaN DUV light-emitting diodes (LEDs) remains very low because the extraction of DUV photons is significantly limited by intrinsic material properties of AlGaN. Here, we present an elegant approach based on a DUV LED having multiple mesa stripes whose inclined sidewalls are covered by a MgF2/Al omni-directional mirror to take advantage of the strongly anisotropic transverse-magnetic polarized emission pattern of AlGaN quantum wells. The sidewall-emission-enhanced DUV LED breaks through the fundamental limitations caused by the intrinsic properties of AlGaN, thus shows a remarkable improvement in light extraction as well as operating voltage. Furthermore, an analytic model is developed to understand and precisely estimate the extraction of DUV photons from AlGaN DUV LEDs, and hence to provide promising routes for maximizing the power conversion efficiency.

  14. An elegant route to overcome fundamentally-limited light extraction in AlGaN deep-ultraviolet light-emitting diodes: Preferential outcoupling of strong in-plane emission.

    PubMed

    Lee, Jong Won; Kim, Dong Yeong; Park, Jun Hyuk; Schubert, E Fred; Kim, Jungsub; Lee, Jinsub; Kim, Yong-Il; Park, Youngsoo; Kim, Jong Kyu

    2016-01-01

    While there is an urgent need for semiconductor-based efficient deep ultraviolet (DUV) sources, the efficiency of AlGaN DUV light-emitting diodes (LEDs) remains very low because the extraction of DUV photons is significantly limited by intrinsic material properties of AlGaN. Here, we present an elegant approach based on a DUV LED having multiple mesa stripes whose inclined sidewalls are covered by a MgF2/Al omni-directional mirror to take advantage of the strongly anisotropic transverse-magnetic polarized emission pattern of AlGaN quantum wells. The sidewall-emission-enhanced DUV LED breaks through the fundamental limitations caused by the intrinsic properties of AlGaN, thus shows a remarkable improvement in light extraction as well as operating voltage. Furthermore, an analytic model is developed to understand and precisely estimate the extraction of DUV photons from AlGaN DUV LEDs, and hence to provide promising routes for maximizing the power conversion efficiency. PMID:26935402

  15. Strongly transverse-electric-polarized emission from deep ultraviolet AlGaN quantum well light emitting diodes

    SciTech Connect

    Reich, Christoph Guttmann, Martin; Wernicke, Tim; Mehnke, Frank; Kuhn, Christian; Feneberg, Martin; Goldhahn, Rüdiger; Rass, Jens; Kneissl, Michael; Lapeyrade, Mickael; Einfeldt, Sven; Knauer, Arne; Kueller, Viola; Weyers, Markus

    2015-10-05

    The optical polarization of emission from ultraviolet (UV) light emitting diodes (LEDs) based on (0001)-oriented Al{sub x}Ga{sub 1−x}N multiple quantum wells (MQWs) has been studied by simulations and electroluminescence measurements. With increasing aluminum mole fraction in the quantum well x, the in-plane intensity of transverse-electric (TE) polarized light decreases relative to that of the transverse-magnetic polarized light, attributed to a reordering of the valence bands in Al{sub x}Ga{sub 1−x}N. Using k ⋅ p theoretical model calculations, the AlGaN MQW active region design has been optimized, yielding increased TE polarization and thus higher extraction efficiency for bottom-emitting LEDs in the deep UV spectral range. Using (i) narrow quantum wells, (ii) barriers with high aluminum mole fractions, and (iii) compressive growth on patterned aluminum nitride sapphire templates, strongly TE-polarized emission was observed at wavelengths as short as 239 nm.

  16. Improved p-type conductivity in Al-rich AlGaN using multidimensional Mg-doped superlattices.

    PubMed

    Zheng, T C; Lin, W; Liu, R; Cai, D J; Li, J C; Li, S P; Kang, J Y

    2016-01-01

    A novel multidimensional Mg-doped superlattice (SL) is proposed to enhance vertical hole conductivity in conventional Mg-doped AlGaN SL which generally suffers from large potential barrier for holes. Electronic structure calculations within the first-principle theoretical framework indicate that the densities of states (DOS) of the valence band nearby the Fermi level are more delocalized along the c-axis than that in conventional SL, and the potential barrier significantly decreases. Hole concentration is greatly enhanced in the barrier of multidimensional SL. Detailed comparisons of partial charges and decomposed DOS reveal that the improvement of vertical conductance may be ascribed to the stronger pz hybridization between Mg and N. Based on the theoretical analysis, highly conductive p-type multidimensional Al0.63Ga0.37N/Al0.51Ga0.49N SLs are grown with identified steps via metalorganic vapor-phase epitaxy. The hole concentration reaches up to 3.5 × 10(18) cm(-3), while the corresponding resistivity reduces to 0.7 Ω cm at room temperature, which is tens times improvement in conductivity compared with that of conventional SLs. High hole concentration can be maintained even at 100 K. High p-type conductivity in Al-rich structural material is an important step for the future design of superior AlGaN-based deep ultraviolet devices. PMID:26906334

  17. Improved p-type conductivity in Al-rich AlGaN using multidimensional Mg-doped superlattices

    NASA Astrophysics Data System (ADS)

    Zheng, T. C.; Lin, W.; Liu, R.; Cai, D. J.; Li, J. C.; Li, S. P.; Kang, J. Y.

    2016-02-01

    A novel multidimensional Mg-doped superlattice (SL) is proposed to enhance vertical hole conductivity in conventional Mg-doped AlGaN SL which generally suffers from large potential barrier for holes. Electronic structure calculations within the first-principle theoretical framework indicate that the densities of states (DOS) of the valence band nearby the Fermi level are more delocalized along the c-axis than that in conventional SL, and the potential barrier significantly decreases. Hole concentration is greatly enhanced in the barrier of multidimensional SL. Detailed comparisons of partial charges and decomposed DOS reveal that the improvement of vertical conductance may be ascribed to the stronger pz hybridization between Mg and N. Based on the theoretical analysis, highly conductive p-type multidimensional Al0.63Ga0.37N/Al0.51Ga0.49N SLs are grown with identified steps via metalorganic vapor-phase epitaxy. The hole concentration reaches up to 3.5 × 1018 cm-3, while the corresponding resistivity reduces to 0.7 Ω cm at room temperature, which is tens times improvement in conductivity compared with that of conventional SLs. High hole concentration can be maintained even at 100 K. High p-type conductivity in Al-rich structural material is an important step for the future design of superior AlGaN-based deep ultraviolet devices.

  18. Ultralow-threshold electrically injected AlGaN nanowire ultraviolet lasers on Si operating at low temperature.

    PubMed

    Li, K H; Liu, X; Wang, Q; Zhao, S; Mi, Z

    2015-02-01

    Ultraviolet laser radiation has been adopted in a wide range of applications as diverse as water purification, flexible displays, data storage, sterilization, diagnosis and bioagent detection. Success in developing semiconductor-based, compact ultraviolet laser sources, however, has been extremely limited. Here, we report that defect-free disordered AlGaN core-shell nanowire arrays, formed directly on a Si substrate, can be used to achieve highly stable, electrically pumped lasers across the entire ultraviolet AII (UV-AII) band (∼320-340 nm) at low temperatures. The laser threshold is in the range of tens of amps per centimetre squared, which is nearly three orders of magnitude lower than those of previously reported quantum-well lasers. This work also reports the first demonstration of electrically injected AlGaN-based ultraviolet lasers monolithically grown on a Si substrate, and offers a new avenue for achieving semiconductor lasers in the ultraviolet B (UV-B) (280-320 nm) and ultraviolet C (UV-C) (<280 nm) bands. PMID:25599190

  19. Ultralow-threshold electrically injected AlGaN nanowire ultraviolet lasers on Si operating at low temperature

    NASA Astrophysics Data System (ADS)

    Li, K. H.; Liu, X.; Wang, Q.; Zhao, S.; Mi, Z.

    2015-02-01

    Ultraviolet laser radiation has been adopted in a wide range of applications as diverse as water purification, flexible displays, data storage, sterilization, diagnosis and bioagent detection. Success in developing semiconductor-based, compact ultraviolet laser sources, however, has been extremely limited. Here, we report that defect-free disordered AlGaN core-shell nanowire arrays, formed directly on a Si substrate, can be used to achieve highly stable, electrically pumped lasers across the entire ultraviolet AII (UV-AII) band (˜320-340 nm) at low temperatures. The laser threshold is in the range of tens of amps per centimetre squared, which is nearly three orders of magnitude lower than those of previously reported quantum-well lasers. This work also reports the first demonstration of electrically injected AlGaN-based ultraviolet lasers monolithically grown on a Si substrate, and offers a new avenue for achieving semiconductor lasers in the ultraviolet B (UV-B) (280-320 nm) and ultraviolet C (UV-C) (<280 nm) bands.

  20. Improved p-type conductivity in Al-rich AlGaN using multidimensional Mg-doped superlattices

    PubMed Central

    Zheng, T. C.; Lin, W.; Liu, R.; Cai, D. J.; Li, J. C.; Li, S. P.; Kang, J. Y.

    2016-01-01

    A novel multidimensional Mg-doped superlattice (SL) is proposed to enhance vertical hole conductivity in conventional Mg-doped AlGaN SL which generally suffers from large potential barrier for holes. Electronic structure calculations within the first-principle theoretical framework indicate that the densities of states (DOS) of the valence band nearby the Fermi level are more delocalized along the c-axis than that in conventional SL, and the potential barrier significantly decreases. Hole concentration is greatly enhanced in the barrier of multidimensional SL. Detailed comparisons of partial charges and decomposed DOS reveal that the improvement of vertical conductance may be ascribed to the stronger pz hybridization between Mg and N. Based on the theoretical analysis, highly conductive p-type multidimensional Al0.63Ga0.37N/Al0.51Ga0.49N SLs are grown with identified steps via metalorganic vapor-phase epitaxy. The hole concentration reaches up to 3.5 × 1018 cm−3, while the corresponding resistivity reduces to 0.7 Ω cm at room temperature, which is tens times improvement in conductivity compared with that of conventional SLs. High hole concentration can be maintained even at 100 K. High p-type conductivity in Al-rich structural material is an important step for the future design of superior AlGaN-based deep ultraviolet devices. PMID:26906334

  1. Initial and Long-Term Movement of Cladding Installed Over Exterior Rigid Insulation

    SciTech Connect

    Baker, P.

    2014-09-01

    Changes in the International Energy Conservation Code (IECC) from 2009 to 2012 have resulted in the use of exterior rigid insulation becoming part of the prescriptive code requirements. With more jurisdictions adopting the 2012 IECC builders are going to finding themselves required to incorporate exterior insulation in the construction of their exterior wall assemblies. For thick layers of exterior insulation (levels greater than 1.5 inches), the use wood furring strips attached through the insulation back to the structure has been used by many contractors and designers as a means to provide a convenient cladding attachment location. However, there has been a significant resistance to its widespread implementation due to a lack of research and understanding of the mechanisms involved and potential creep effects of the assembly under the sustained dead load of a cladding. This research was an extension on previous research conducted by BSC in 2011, and 2012. Each year the understanding of the system discrete load component interactions, as well as impacts of environmental loading has increased. The focus of the research was to examine more closely the impacts of screw fastener bending on the total system capacity, effects of thermal expansion and contraction of materials on the compressive forces in the assembly, as well as to analyze a full years worth of cladding movement data from assemblies constructed in an exposed outdoor environment.

  2. Laser cladding of tungsten carbides (Spherotene ®) hardfacing alloys for the mining and mineral industry

    NASA Astrophysics Data System (ADS)

    Amado, J. M.; Tobar, M. J.; Alvarez, J. C.; Lamas, J.; Yáñez, A.

    2009-03-01

    The abrasive nature of the mechanical processes involved in mining and mineral industry often causes significant wear to the associated equipment and derives non-negligible economic costs. One of the possible strategies to improve the wear resistance of the various components is the deposition of hardfacing layers on the bulk parts. The use of high power lasers for hardfacing (laser cladding) has attracted a great attention in the last decade as an alternative to other more standard methods (arc welding, oxy-fuel gas welding, thermal spraying). In laser cladding the hardfacing material is used in powder form. For high hardness applications Ni-, Co- or Fe-based alloys containing hard phase carbides at different ratios are commonly used. Tungsten carbides (WC) can provide coating hardness well above 1000 HV (Vickers). In this respect, commercially available WC powders normally contain spherical micro-particles consisting of crushed WC agglomerates. Some years ago, Spherotene ® powders consisting of spherical-fused monocrystaline WC particles, being extremely hard, between 1800 and 3000 HV, were patented. Very recently, mixtures of Ni-based alloy with Spherotene powders optimized for laser processing were presented (Technolase ®). These mixtures have been used in our study. Laser cladding tests with these powders were performed on low carbon steel (C25) substrates, and results in terms of microstructure and hardness will be discussed.

  3. Hydrogen uptake in Zircaloy-2 reactor fuel claddings studied with elastic recoil detection

    SciTech Connect

    Rajasekhara, S.; Doyle, B. L.; Enos, D. G.; Clark, B. G.

    2013-04-19

    The recent trend towards a high burn-up discharge spent nuclear fuel necessitates a thorough understanding of hydrogen uptake in Zr-based cladding materials that encapsulate spent nuclear fuel. Although it is challenging to experimentally replicate exact conditions in a nuclear reactor that lead to hydrogen uptake in claddings, in this study we have attempted to understand the kinetics of hydrogen uptake by first electrolytically charging Zircaloy-2 (Zr-2) cladding material for various durations (100 to 2,600 s), and subsequently examining hydrogen ingress with elastic recoil detection (ERD) and transmission electron microscopy (TEM). To understand the influence of irradiation damage defects on hydrogen uptake, an analogous study was performed on ion - irradiated (0.1, 1 and 25 dpa) Zr-2. Analysis of ERD data from the un-irradiated Zr-2 suggests that the growth of the hydride layer is diffusion controlled, and preliminary TEM results support this assertion. In un-irradiated Zr-2, the diffusivity of hydrogen in the hydride phase was found to be approximately 1.1 Multiplication-Sign 10{sup -11} cm{sup 2}/s, while the diffusivity in the hydride phase for lightly irradiated (0.1 and 1 dpa) Zr-2 is an order of magnitude lower. Irradiation to 25 dpa results in a hydrogen diffusivity that is comparable to the un-irradiated Zr-2. These results are compared with existing literature on hydrogen transport in Zr - based materials.

  4. Tensile Hoop Behavior of Irradiated Zircaloy-4 Nuclear Fuel Cladding

    SciTech Connect

    Jaramillo, Roger A; Hendrich, WILLIAM R; Packan, Nicolas H

    2007-03-01

    A method for evaluating the room temperature ductility behavior of irradiated Zircaloy-4 nuclear fuel cladding has been developed and applied to evaluate tensile hoop strength of material irradiated to different levels. The test utilizes a polyurethane plug fitted within a tubular cladding specimen. A cylindrical punch is used to compress the plug axially, which generates a radial displacement that acts upon the inner diameter of the specimen. Position sensors track the radial displacement of the specimen outer diameter as the compression proceeds. These measurements coupled with ram force data provide a load-displacement characterization of the cladding response to internal pressurization. The development of this simple, cost-effective, highly reproducible test for evaluating tensile hoop strain as a function of internal pressure for irradiated specimens represents a significant advance in the mechanical characterization of irradiated cladding. In this project, nuclear fuel rod assemblies using Zircaloy-4 cladding and two types of mixed uranium-plutonium oxide (MOX) fuel pellets were irradiated to varying levels of burnup. Fuel pellets were manufactured with and without thermally induced gallium removal (TIGR) processing. Fuel pellets manufactured by both methods were contained in fuel rod assemblies and irradiated to burnup levels of 9, 21, 30, 40, and 50 GWd/MT. These levels of fuel burnup correspond to fast (E > 1 MeV) fluences of 0.27, 0.68, 0.98, 1.4 and 1.7 1021 neutrons/cm2, respectively. Following irradiation, fuel rod assemblies were disassembled; fuel pellets were removed from the cladding; and the inner diameter of cladding was cleaned to remove residue materials. Tensile hoop strength of this cladding material was tested using the newly developed method. Unirradiated Zircaloy-4 cladding was also tested. With the goal of determining the effect of the two fuel types and different neutron fluences on clad ductility, tensile hoop strength tests were

  5. Laser Cladding of Composite Bioceramic Coatings on Titanium Alloy

    NASA Astrophysics Data System (ADS)

    Xu, Xiang; Han, Jiege; Wang, Chunming; Huang, Anguo

    2016-02-01

    In this study, silicon nitride (Si3N4) and calcium phosphate tribasic (TCP) composite bioceramic coatings were fabricated on a Ti6Al4V (TC4) alloy using Nd:YAG pulsed laser, CO2 CW laser, and Semiconductor CW laser. The surface morphology, cross-sectional microstructure, mechanical properties, and biological behavior were carefully investigated. These investigations were conducted employing scanning electron microscope, energy-dispersive x-ray spectroscopy, and other methodologies. The results showed that both Si3N4 and Si3N4/TCP composite coatings were able to form a compact bonding interface between the coating and the substrate by using appropriate laser parameters. The coating layers were dense, demonstrating a good surface appearance. The bioceramic coatings produced by laser cladding have good mechanical properties. Compared with that of the bulk material, microhardness of composite ceramic coatings on the surface significantly increased. In addition, good biological activity could be obtained by adding TCP into the composite coating.

  6. Eddy Current Measurements of Corrosion and Metal Loss in Zircaloy Cladding with Ferromagnetic Crud

    SciTech Connect

    Yagnik, Suresh K.; Johnson, Duane P.; Kervinen, John A

    2004-08-15

    The routine method of monitoring Zircaloy cladding corrosion in nuclear fuel pools is based on eddy current (EC) measurements at a single high frequency in the range of 1-3 MHz. At this frequency the rf wave does not penetrate through the cladding wall and, ideally, the EC response can be correlated to the thickness of the oxide layer that separates the sensor head from the metal substrate. In practice, however, the cladding corrosion is often overestimated by this method due to the primary circuit corrosion products (or crud) that are deposited on the fuel rod surface. In addition, the crud, which is primarily nickel ferrite oxides, may significantly interfere with the EC response due to its ferromagnetic nature. We describe a two-frequency method with four-dimensional vector analyses of the EC response to more precisely assess the cladding corrosion. Two independent approaches for measuring the corrosion damage are suggested in this study. First, the four-dimensional data treatment enables a direct measure of the oxide thickness, even in the presence of ferromagnetic crud. Second, it can also provide a direct measure of the substrate wall thickness, and hence the degree of corrosion, provided the original wall thickness is known. By comparison, the approaches to crud correction currently available prove inadequate, especially if both the thickness and permeability of the crud deposits vary over the fuel rod surface, as is generally the case. The new method has been applied to inactive samples with and without the ferromagnetic crud effect. In the reported laboratory simulations, the oxide thickness and wall thinning were measured independently to within {+-}4 {mu}m, irrespective of unknown crud thickness and permeability.

  7. Weld overlay cladding with iron aluminides

    SciTech Connect

    Goodwin, G.M.

    1995-08-01

    The hot and cold cracking tendencies of some early iron aluminide alloy compositions have limited their use in applications where good weldability is required. Using hot crack testing techniques invented at ORNL, and experimental determinations of preheat and postweld heat treatment needed to avoid cold cracking, we have developed iron aluminide filler metal compositions which can be successfully used to weld overlay clad various substrate materials, including 9Cr-1Mo steel, 2-1/4Cr-1Mo steel, and 300-series austenitic stainless steels. Dilution must be carefully controlled to avoid crack-sensitive deposit compositions. The technique used to produce the current filler metal compositions is aspiration-casting, i.e. drawing the liquid from the melt into glass rods. Future development efforts will involve fabrication of composite wires of similar compositions to permit mechanized gas tungsten arc (GTA) and/or gas metal arc (GMA) welding.

  8. Reliability of hard plastic clad silica fibers

    NASA Astrophysics Data System (ADS)

    Skutnik, Bolesh J.; Spaniol, Stefan

    2006-04-01

    New formulations of cladding materials have become available in recent times for Hard Plastic Clad Silica (HPCS) fibers, Initial data showed gains in some properties, particularly dynamic strength, especially for high numerical aperture (NA) fibers. A systematic study has been undertaken to determine the full strength and fatigue behavior of these HPCS fibers and to make comparisons to earlier HPCS fibers. Preliminary results, now confirmed, has shown improved median dynamic strength and higher Weibull slope. Full results are presented below including fatigue behavior and optical properties. These fibers have many applications and benefits in the high power delivery and medical laser uses as highlighted below. High power diode laser systems with their laser diode bars and arrays not only require special fibers to couple directly to the diode emitters, but also require special fibers to couple from the laser to application sites. These latter power delivery fibers are much larger than the internal fibers but still must be flexible, and have not only good strength but also good fatigue behavior. This particularly important industrial systems using robotic arms to apply the high power laser energy at a treatment site. The optical properties of HPCS fibers are well suited for the needs of the delivery of high power from diode laser bars and arrays to an application site. Benefits of strong median dynamic strengths and tighter flaw distributions in such cases will be discussed. Many medical applications, especially endoscopic ones, can benefit from the use of highly flexible, high NA, cost effective, HPCS optical fibers. Benefits of high strength and good fatigue behavior for such fibers in endoscopic procedures, including laser surgery, are discussed briefly including implications for mechanical reliability in medical and industrial settings.

  9. Temperature and burnup correlated fuel-cladding chemical interaction in U-10ZR metallic fuel

    NASA Astrophysics Data System (ADS)

    Carmack, William J.

    Metallic fuels are proposed for use in advanced sodium cooled fast reactors and provide a number of advantages over other fuel types considering their fabricability, performance, recyclability, and safety. Resistance to cladding "breach" and subsequent release of fission products and fuel constituents to the nuclear power plant primary coolant system is a key performance parameter for a nuclear fuel system. In metallic fuel, FCCI weakens the cladding, especially at high power-high temperature operation, contributing to fuel pin breach. Empirical relationships for FCCI have been developed from a large body of data collected from in-pile (EBR-II) and out-of-pile experiments [1]. However, these relationships are unreliable in predicting FCCI outside the range of EBR-II experimental data. This dissertation examines new FCCI data extracted from the MFF-series of prototypic length metallic fuel irradiations performed in the Fast Flux Test Facility (FFTF). The fuel in these assemblies operated a temperature and burnup conditions similar to that in EBR-II but with axial fuel height three times longer than EBR-II experiments. Comparing FCCI formation data from FFTF and EBR-II provides new insight into FCCI formation kinetics. A model is developed combining both production and diffusion of lanthanides to the fuel-cladding interface and subsequent reaction with the cladding. The model allows these phenomena to be influenced by fuel burnup (lanthanide concentrations) and operating temperature. Parameters in the model are adjusted to reproduce measured FCCI layer thicknesses from EBR-II and FFTF. The model predicts that, under appropriate conditions, rate of FCCI formation can be controlled by either fission product transport or by the reaction rate of the interaction species at the fuel-cladding interface. This dissertation will help forward the design of metallic fuel systems for advanced sodium cooled fast reactors by allowing the prediction of FCCI layer formation in full

  10. Femtosecond writing of depressed cladding waveguides in strongly cumulative regime

    NASA Astrophysics Data System (ADS)

    Bukharin, Mikhail A.; Khudyakov, Dmitriy V.; Vartapetov, Sergey K.

    2015-05-01

    We proposed a novel approach for direct femtosecond inscription of waveguides. It consisted in formation of cladding with reduced refractive index in fused silica. Depressed cladding was based on peripheral regions of individually written neighbored tracks, which should be inscribed in strongly cumulative regime. It was shown, that due to shot time interval between femtosecond laser pulses and relatively slow thermal diffusion, the exposed focal region surrounds by significantly wide cladding with reduced refracted index. Based on proposed approach we demonstrated depressed cladding waveguide inscription in fused silica using emission directly from commercially available femtosecond oscillator without correcting optical systems and second harmonic generation. It was shown, that the new approach provides formation of easily adjustable single mode waveguides with desired mode field diameter. Such depressed cladding waveguides exploit both advantages of fused silica material and depressed cladding geometry. We also verified our suggestion by experiment and inscribed depressed cladding waveguides with two different mode field diameters at similar femtosecond pulse characteristics. The obtained structures provided low propagation losses and good coupling with Gaussian mode. The waveguides supported propagation of both polarizations with nearly identical characteristics. Obtained experimental results were in good agreement with numerical simulation.

  11. Laser cladding of quasi-crystal-forming Al-Cu-Fe-Bi on an Al-Si alloy substrate

    NASA Astrophysics Data System (ADS)

    Biswas, Krishanu; Chattopadhyay, Kamanio; Galun, Rolf; Mordike, Barry L.

    2005-07-01

    We report here the results of an investigation aimed at producing coatings containing phases closely related to the quasi-crystalline phase with dispersions of soft Bi particles using an Al-Cu-Fe-Bi elemental powder mixture on Al-10.5 at. pct Si substrates. A two-step process of cladding followed by remelting is used to fine-tune the alloying, phase distribution, and microstructure. A powder mix of Al64Cu22.3Fe11.7Bi2 has been used to form the clads. The basic reason for choosing Bi lies in the fact that it is immiscible with each of the constituent elements. Therefore, it is expected that Bi will solidify in the form of dispersoids during the rapid solidification. A detailed microstructural analysis has been carried out by using the backscattered imaging mode in a scanning electron microscope (SEM) and transmission electron microscope (TEM). The microstructural features are described in terms of layers of different phases. Contrary to our expectation, the quasi-crystalline phase could not form on the Al-Si substrate. The bottom of the clad and remelted layers shows the regrowth of aluminum. The formation of phases such as blocky hexagonal Al-Fe-Si and a ternary eutectic (Al + CuAl2 + Si) have been found in this layer. The middle layer shows the formation of long plate-shaped Al13Fe4 along with hexagonal Al-Fe-Si phase growing at the periphery of the former. The formation of metastable Al-Al6Fe eutectic has also been found in this layer. The top layer, in the case of the as-clad track, shows the presence of plate-shaped Al13Fe4 along with a 1/1 cubic rational approximant of a quasi-crystal. The top layer of the remelted track shows the presence of a significant amount of a 1/1 cubic rational approximant. In addition, the as-clad and remelted microstructures show a fine-scale dispersion of Bi particles of different sizes formed during monotectic solidification. The remelting is found to have a strong effect on the size and distribution of Bi particles. The dry

  12. Structure and mechanical properties of coatings fabricated by nonvacuum electron beam cladding of Ti-Ta-Zr powder mixtures

    NASA Astrophysics Data System (ADS)

    Samoylenko, Vitaliy V.; Lenivtseva, Olga G.; Polyakov, Igor A.; Laptev, Ilya S.

    2015-10-01

    In this paper structural investigations and mechanical tests of Ti-Ta-Zr coatings obtained on surfaces of cp-titanium workpieces were carried out. It was found that the coatings had a dendrite structure; investigations at high-power magnifications revealed a platelet structure. An increase of tantalum concentration led to refinement of structural components. The microhardness level of all coatings, excepting a specimen with the maximum tantalum content, was 370 HV. The microhardness of this coating reached 400 HV. The ultimate tensile strength of cladded layers varied from 697 to 947 MPa. Adhesion tests showed that bimetallic composites were characterized by high bond strength of cladded layers to the substrate, which exceeded cp-titanium strength characteristics.

  13. Structure and mechanical properties of coatings fabricated by nonvacuum electron beam cladding of Ti-Ta-Zr powder mixtures

    SciTech Connect

    Samoylenko, Vitaliy V. Lenivtseva, Olga G. Polyakov, Igor A. Laptev, Ilya S.

    2015-10-27

    In this paper structural investigations and mechanical tests of Ti-Ta-Zr coatings obtained on surfaces of cp-titanium workpieces were carried out. It was found that the coatings had a dendrite structure; investigations at high-power magnifications revealed a platelet structure. An increase of tantalum concentration led to refinement of structural components. The microhardness level of all coatings, excepting a specimen with the maximum tantalum content, was 370 HV. The microhardness of this coating reached 400 HV. The ultimate tensile strength of cladded layers varied from 697 to 947 MPa. Adhesion tests showed that bimetallic composites were characterized by high bond strength of cladded layers to the substrate, which exceeded cp-titanium strength characteristics.

  14. Optical-assembly periodic structure of ferrofluids in a liquid core/metal cladding optical waveguide.

    PubMed

    Wang, Xianping; Yin, Cheng; Sun, Jingjing; Han, Qingbang; Li, Honggen; Sang, Minghuang; Yuan, Wen; Cao, Zhuangqi

    2013-11-01

    We present a novel and simple mechanism for the fabrication of periodic microstructure based on a ferrofluids core/metal cladding optical waveguide chip. The ultrahigh-order modes excited in the millimeter scale guiding layer lead to the ordered particle aggregates in ferrofluids without applying a magnetic field. Since the absorption of photons by the extremely dilute ferrofluids is extremely small and the Soret effect is not noticeable, a tentative explanation in terms of the optical trapping effect is proposed. Furthermore, this scheme exhibits all-optically tunable reflectivity and lateral Goos-Hänchen shift, which potentially may be for practical use in novel optical devices. PMID:24216657

  15. Ion beam mixed oxidation protective coating on Zry-4 cladding

    NASA Astrophysics Data System (ADS)

    Park, Jae-Won; Kim, Jae-Un; Park, Jeong-Yong

    2016-06-01

    In this study, SiC was coated on the surface of Zry-4 cladding to improve the oxidation protectiveness. In the coating of SiC onto Zry-4, the prime concern was adhesion at an elevated temperature. Here, a 70 keV N ion beam was irradiated onto a SiC coating layer of ∼100 nm in thickness; this was deposited via the e-beam evaporation method. Additional coating to a target thickness was then carried out. The films deposited without ion-beam mixing (IBM) often peeled-off at an elevated temperature, while the IBM SiC film always adhered to Zry-4, even after heating to ∼1000 °C; at such a temperature, however, cracks formed in the film. X-ray photoelectron spectroscopy (XPS) analysis showed that the deposited SiC film contained about 20 at.% of O, while after annealing in air, 76 at.% of O was found on the surface layer. This implied that both the surface of SiC film and Zry-4 in the crack lines were oxidized. Comparing the Zr3d peak positions across the interface, a shift of binding energy by ∼1 eV was detected, representing that, in view of favorable thermodynamics, SiC/Zry-4 seems to be an acceptable system to apply IBM. To heal the crack, the process of IBM for a 1 μm thick coating and annealing was repeated. High-resolution field emission secondary electron microscopy (FE-SEM) showed that the crack lines, the main places at which oxidation occurred, were gradually covered as the process was repeated, ensuring enhanced oxidation protectiveness.

  16. Microstructure and corrosion resistance of TC2 Ti alloy by laser cladding with Ti/TiC/TiB2 powders

    NASA Astrophysics Data System (ADS)

    Diao, Yunhua; Zhang, Kemin

    2015-10-01

    In the present work, a TiC/TiB2 composite coating was produced onto a TC2 Ti alloy by laser cladding with Ti/TiC/TiB2 powders. The surface microstructure, phase components and compositions were characterized with methods of optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffractometry (XRD), and energy dispersive spectrometry (EDS). The cladding layer is consisted of Ti, TiC and TiB2. And the surface microhardness was measured. After laser cladding, a maximum hardness of 1100 HV is achieved in the laser cladding surface layer, which is more three times higher than that of the TC2 substrate (∼300 HV). Due to the formation of TiC and TiB2 intermetallic compounds in the alloyed region and grain refinement, the microhardness of coating is higher than TC2 Ti alloy. In this paper, the corrosion property of matrix material and treated samples were both measured in NaCl (3.5 wt%) aqueous solution. From the result we can see that the laser cladding specimens' corrosion property is clearly becoming better than that of the substrate.

  17. Fabrication of oxide dispersion strengthened ferritic clad fuel pins

    SciTech Connect

    Zirker, L.R. ); Bottcher, J.H. ); Shikakura, S. ); Tsai, C.L. . Dept. of Welding Engineering); Hamilton, M.L. )

    1991-01-01

    A resistance butt welding procedure was developed and qualified for joining ferritic fuel pin cladding to end caps. The cladding are INCO MA957 and PNC ODS lots 63DSA and 1DK1, ferritic stainless steels strengthened by oxide dispersion, while the end caps are HT9 a martensitic stainless steel. With adequate parameter control the weld is formed without a residual melt phase and its strength approaches that of the cladding. This welding process required a new design for fuel pin end cap and weld joint. Summaries of the development, characterization, and fabrication processes are given for these fuel pins. 13 refs., 6 figs., 1 tab.

  18. Increasing corrosion resistance of carbon steels by surface laser cladding

    NASA Astrophysics Data System (ADS)

    Polsky, V. I.; Yakushin, V. L.; Dzhumaev, P. S.; Petrovsky, V. N.; Safonov, D. V.

    2016-04-01

    This paper presents results of investigation of the microstructure, elemental composition and corrosion resistance of the samples of low-alloy steel widely used in the engineering, after the application of laser cladding. The level of corrosion damage and the corrosion mechanism of cladded steel samples were established. The corrosion rate and installed discharge observed at the total destruction of cladding were obtained. The regularities of structure formation in the application of different powder compositions were obtained. The optimal powder composition that prevents corrosion of samples of low-carbon low-alloy steel was established.

  19. Oxidation performance of platinum-clad Mo-47Re alloy

    NASA Technical Reports Server (NTRS)

    Clark, Ronald K.; Wallace, Terryl A.

    1994-01-01

    The alloy Mo-47Re has favorable mechanical properties at temperatures above 1400 C, but it undergoes severe oxidation when used in air with no protective coating. To shield the alloy from oxidation, platinum cladding has been evaluated. The unprotected alloy undergoes catastrophic oxidation under static and dynamic oxidation conditions. The platinum cladding provides good protection from static and dynamic oxidation for moderate times at 1260 C. Samples tested for longer times under static oxidation conditions experienced severe oxidation. The data suggest that oxidation results from the transport of oxygen through the grain boundaries and through the pinhole defects of the platinum cladding.

  20. Glass-clad semiconductor core optical fibers

    NASA Astrophysics Data System (ADS)

    Morris, Stephanie Lynn

    Glass-clad optical fibers comprising a crystalline semiconductor core have garnered considerable recent attention for their potential utility as novel waveguides for applications in nonlinear optics, sensing, power delivery, and biomedicine. As research into these fibers has progressed, it has become evident that excessive losses are limiting performance and so greater understanding of the underlying materials science, coupled with advances in fiber processing, is needed. More specifically, the semiconductor core fibers possess three performance-limiting characteristics that need to be addressed: (a) thermal expansion mismatches between crystalline core and glass cladding that lead to cracks, (b) the precipitation of oxide species in the core upon fiber cooling, which results from partial dissolution of the cladding glass by the core melt, and (c) polycrystallinity; all of which lead to scattering and increased transmission losses. This dissertation systematically studies each of these effects and develops both a fundamental scientific understanding of and practical engineering methods for reducing their impact. With respect to the thermal expansion mismatch and, in part, the dissolution of oxides, for the first time to our knowledge, oxide and non-oxide glass compositions are developed for a series of semiconductor cores based on two main design criteria: (1) matching the thermal expansion coefficient between semiconductor core and glass cladding to minimize cracking and (2) matching the viscosity-temperature dependences, such that the cladding glass draws into fiber at a temperature slightly above the melting point of the semiconductor in order to minimize dissolution and improve the fiber draw process. The x[Na 2O:Al2O3] + (100 - 2x)SiO2 glass compositional family was selected due to the ability to tailor the glass properties to match the aforementioned targets through slight variations in composition and adjusting the ratios of bridging and non-bridging oxygen

  1. View of building 11050, showing metal clad addition on east ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of building 11050, showing metal clad addition on east elevation, looking southwest. - Naval Ordnance Test Station Inyokern, China Lake Pilot Plant, Machine Shop, C Street, China Lake, Kern County, CA

  2. Chalcogenide optical microwires cladded with fluorine-based CYTOP.

    PubMed

    Li, Lizhu; Abdukerim, Nurmemet; Rochette, Martin

    2016-08-22

    We demonstrate optical transmission results of highly nonlinear As2Se3 optical microwires cladded with fluorine-based CYTOP, and compare them with microwires cladded with typical hydrogen-based polymers. In the linear optics regime, the CYTOP-cladded microwire transmits light in the spectral range from 1.3 µm up to >2.5 µm without trace of absorption peaks such as those observed using hydrogen-based polymer claddings. The microwire is also pumped in the nonlinear optics regime, showing multiple-orders of four-wave mixing and supercontinuum generation spanning from 1.0 µm to >4.3 µm. We conclude that with such a broadband transparency and high nonlinearity, the As2Se3-CYTOP microwire is an appealing solution for nonlinear optical processing in the mid-infrared. PMID:27557174

  3. Liquid-core, liquid-cladding photonic crystal fibers.

    PubMed

    De Matos, Christiano J; Cordeiro, Cristiano M B; Dos Santos, Eliane M; Ong, Jackson S; Bozolan, Alexandre; Brito Cruz, Carlos H

    2007-09-01

    We experimentally demonstrate a simple and novel technique to simultaneously insert a liquid into the core of a hollow-core photonic crystal fiber (PCF) and a different liquid into its cladding. The result is a liquid-core, liquid-cladding waveguide in which the two liquids can be selected to yield specific guidance characteristics. As an example, we tuned the core-cladding index difference by proper choice of the inserted liquids to obtain control over the number of guided modes. Single-mode guidance was achieved for a particular choice of liquids. We also experimentally and theoretically investigated the nature of light confinement and observed the transition from photonic bandgap to total internal reflection guidance both with the core-cladding index contrast and with the PCF length. PMID:19547475

  4. Composite polymer: Glass edge cladding for laser disks

    DOEpatents

    Powell, H.T.; Wolfe, C.A.; Campbell, J.H.; Murray, J.E.; Riley, M.O.; Lyon, R.E.; Jessop, E.S.

    1987-11-02

    Large neodymium glass laser disks for disk amplifiers such as those used in the Nova laser require an edge cladding which absorbs at 1 micrometer. This cladding prevents edge reflections from causing parasitic oscillations which would otherwise deplete the gain. Nova now utilizes volume-absorbing monolithic-glass claddings which are fused at high temperature to the disks. These perform quite well but are expensive to produce. Absorbing glass strips are adhesively bonded to the edges of polygonal disks using a bonding agent whose index of refraction matches that of both the laser and absorbing glass. Optical finishing occurs after the strips are attached. Laser disks constructed with such claddings have shown identical gain performance to the previous Nova disks and have been tested for hundreds of shots without significant degradation. 18 figs.

  5. Composite polymer-glass edge cladding for laser disks

    DOEpatents

    Powell, Howard T.; Riley, Michael O.; Wolfe, Charles R.; Lyon, Richard E.; Campbell, John H.; Jessop, Edward S.; Murray, James E.

    1989-01-01

    Large neodymium glass laser disks for disk amplifiers such as those used in the Nova laser require an edge cladding which absorbs at 1 micrometer. This cladding prevents edge reflections from causing parasitic oscillations which would otherwise deplete the gain. Nova now utilizes volume-absorbing monolithic-glass claddings which are fused at high temperature to the disks. These perform quite well but are expensive to produce. Absorbing glass strips are adhesively bonded to the edges of polygonal disks using a bonding agent whose index of refraction matches that of both the laser and absorbing glass. Optical finishing occurs after the strips are attached. Laser disks constructed with such claddings have shown identical gain performance to the previous Nova disks and have been tested for hundreds of shots without significant degradation.

  6. Chemical vapor deposition for silicon cladding on advanced ceramics

    NASA Technical Reports Server (NTRS)

    Goela, Jitendra S.; Taylor, Raymond L.

    1989-01-01

    Polycrystalline Si was used to clad several advanced ceramic materials such as SiC, Si3N4, sapphire Al2O3, pyrolytic BN, and Si by a CVD process. The thickness of Si cladding ranged from 0.025 to 3.0 mm. CVD Si adhered quite well to all the above materials except Al3O, where the Si cladding was highly stressed and cracked or delaminated. A detailed material characterization of Si-clad SiC samples showed that Si adherence to SiC does not depend much on the substrate surface preparation; that the thermal cycling and polishing of the samples do not cause delamination; and that, in four-point bend tests, the Si-SiC bond remains intact, with the failure occurring in the Si.

  7. High Temperature Steam Corrosion of Cladding for Nuclear Applications: Experimental

    SciTech Connect

    McHugh, Kevin M; Garnier, John E; Sergey Rashkeev; Michael V. Glazoff; George W. Griffith; Shannong M. Bragg-Sitton

    2013-01-01

    Stability of cladding materials under off-normal conditions is an important issue for the safe operation of light water nuclear reactors. Metals, ceramics, and metal/ceramic composites are being investigated as substitutes for traditional zirconium-based cladding. To support down-selection of these advanced materials and designs, a test apparatus was constructed to study the onset and evolution of cladding oxidation, and deformation behavior of cladding materials, under loss-of-coolant accident scenarios. Preliminary oxidation tests were conducted in dry oxygen and in saturated steam/air environments at 1000OC. Tube samples of Zr-702, Zr-702 reinforced with 1 ply of a ß-SiC CMC overbraid, and sintered a-SiC were tested. Samples were induction heated by coupling to a molybdenum susceptor inside the tubes. The deformation behavior of He-pressurized tubes of Zr-702 and SiC CMC-reinforced Zr-702, heated to rupture, was also examined.

  8. Explosion Clad for Upstream Oil and Gas Equipment

    SciTech Connect

    Banker, John G.; Massarello, Jack; Pauly, Stephane

    2011-01-17

    Today's upstream oil and gas facilities frequently involve the combination of high pressures, high temperatures, and highly corrosive environments, requiring equipment that is thick wall, corrosion resistant, and cost effective. When significant concentrations of CO{sub 2} and/or H{sub 2}S and/or chlorides are present, corrosion resistant alloys (CRA) can become the material of choice for separator equipment, piping, related components, and line pipe. They can provide reliable resistance to both corrosion and hydrogen embrittlement. For these applications, the more commonly used CRA's are 316L, 317L and duplex stainless steels, alloy 825 and alloy 625, dependent upon the application and the severity of the environment. Titanium is also an exceptional choice from the technical perspective, but is less commonly used except for heat exchangers. Explosion clad offers significant savings by providing a relatively thin corrosion resistant alloy on the surface metallurgically bonded to a thick, lower cost, steel substrate for the pressure containment. Developed and industrialized in the 1960's the explosion cladding technology can be used for cladding the more commonly used nickel based and stainless steel CRA's as well as titanium. It has many years of proven experience as a reliable and highly robust clad manufacturing process. The unique cold welding characteristics of explosion cladding reduce problems of alloy sensitization and dissimilar metal incompatibility. Explosion clad materials have been used extensively in both upstream and downstream oil, gas and petrochemical facilities for well over 40 years. The explosion clad equipment has demonstrated excellent resistance to corrosion, embrittlement and disbonding. Factors critical to insure reliable clad manufacture and equipment design and fabrication are addressed.

  9. Double-clad nuclear-fuel safety rod

    DOEpatents

    McCarthy, W.H.; Atcheson, D.B.

    1981-12-30

    A device for shutting down a nuclear reactor during an undercooling or overpower event, whether or not the reactor's scram system operates properly. This is accomplished by double-clad fuel safety rods positioned at various locations throughout the reactor core, wherein melting of a secondary internal cladding of the rod allows the fuel column therein to shift from the reactor core to place the reactor in a subcritical condition.

  10. Explosion Clad for Upstream Oil and Gas Equipment

    NASA Astrophysics Data System (ADS)

    Banker, John G.; Massarello, Jack; Pauly, Stephane

    2011-01-01

    Today's upstream oil and gas facilities frequently involve the combination of high pressures, high temperatures, and highly corrosive environments, requiring equipment that is thick wall, corrosion resistant, and cost effective. When significant concentrations of CO2 and/or H2S and/or chlorides are present, corrosion resistant alloys (CRA) can become the material of choice for separator equipment, piping, related components, and line pipe. They can provide reliable resistance to both corrosion and hydrogen embrittlement. For these applications, the more commonly used CRA's are 316L, 317L and duplex stainless steels, alloy 825 and alloy 625, dependent upon the application and the severity of the environment. Titanium is also an exceptional choice from the technical perspective, but is less commonly used except for heat exchangers. Explosion clad offers significant savings by providing a relatively thin corrosion resistant alloy on the surface metallurgically bonded to a thick, lower cost, steel substrate for the pressure containment. Developed and industrialized in the 1960's the explosion cladding technology can be used for cladding the more commonly used nickel based and stainless steel CRA's as well as titanium. It has many years of proven experience as a reliable and highly robust clad manufacturing process. The unique cold welding characteristics of explosion cladding reduce problems of alloy sensitization and dissimilar metal incompatibility. Explosion clad materials have been used extensively in both upstream and downstream oil, gas and petrochemical facilities for well over 40 years. The explosion clad equipment has demonstrated excellent resistance to corrosion, embrittlement and disbonding. Factors critical to insure reliable clad manufacture and equipment design and fabrication are addressed.

  11. Cladding for transverse-pumped solid-state laser

    NASA Technical Reports Server (NTRS)

    Byer, Robert L. (Inventor); Fan, Tso Y. (Inventor)

    1989-01-01

    In a transverse pumped, solid state laser, a nonabsorptive cladding surrounds a gain medium. A single tranverse mode, namely the Transverse Electromagnetic (TEM) sub 00 mode, is provided. The TEM sub 00 model has a cross sectional diameter greater than a transverse dimension of the gain medium but less than a transverse dimension of the cladding. The required size of the gain medium is minimized while a threshold for laser output is lowered.

  12. HYDRIDE-RELATED DEGRADATION OF SNF CLADDING UNDER REPOSITORY CONDITIONS

    SciTech Connect

    K. McCoy

    2000-12-12

    The purpose and scope of this analysis/model report is to analyze the degradation of commercial spent nuclear fuel (CSNF) cladding under repository conditions by the hydride-related metallurgical processes, such as delayed hydride cracking (DHC), hydride reorientation and hydrogen embrittlement, thereby providing a better understanding of the degradation process and clarifying which aspects of the process are known and which need further evaluation and investigation. The intended use is as an input to a more general analysis of cladding degradation.

  13. Material development for thermionic fuel-cladding systems.

    NASA Technical Reports Server (NTRS)

    Yang, L.; Hudson, R. G.; Johnson, H.; Horner, H.; Allen, D. T.

    1972-01-01

    Fuel-cladding systems capable of maintaining stable dimension and electron emission characteristics at high temperatures under irradiation are essential to the successful operation of nuclear thermionic power sources. Studies regarding two possible systems, involving tungsten clad uranium carbide and uranium oxide, are considered. Out-of-pile developmental efforts and the in-pile evaluation results for the two systems are described. Prototypical emitters have been tested for 8000 hours for the carbide system and 4000 hours for the oxide system.

  14. Optimization of Laser Cladding for Al Coating Production

    NASA Astrophysics Data System (ADS)

    Riveiro, A.; Mejías, A.; Lusquiños, F.; del Val, J.; Comesaña, R.; Pardo, J.; Pou, J.

    The production of aluminum based coatings on a stainless steel (AISI 304) substrate by side laser cladding, and using a high power diode laser was experimentally studied. Relevant processing parameters were found and correlations between them were determined. Furthermore, the influence of the processing parameters on the costs associated to the process was examined. These relationships can be used as a guideline for the selection of proper processing parameters for laser cladding of this kind of materials.

  15. Neutron-absorbing amorphous alloys for cladding coatings

    NASA Astrophysics Data System (ADS)

    Sevryukov, O. N.; Fedotov, V. T.; Polyansky, A. A.

    2016-04-01

    This paper shows developed compositions of neutron-absorbing cladding alloys based on nickel and containing such elements as B, Gd, Hf, and Mn. The techniques for application of coatings from these alloys on the surface of structural steels have been improved. It has been shown that the amorphous neutron-absorbing coating is more uniform than the crystalline one. The experimental data on the adhesion of cladding coatings with a steel substrate and their neutron-absorbing capacity have been obtained.

  16. Supercontinuum Generation in a Microstructured Fiber with an Irregular Cladding

    NASA Astrophysics Data System (ADS)

    Minkovich, V. P.; Sotsky, A. B.; Vaca Pereira G., M.; Dzen, I. S.; Sotskaya, L. I.

    2016-05-01

    A broad-band supercontinuum generation was obtained at excitation of a microstructured optical fiber with an irregular cladding by femtosecond laser pulses. To explain the experimental data, calculations of the mode characteristics of microstructured fibers were performed. It was shown that the creation of air channels with different radii in the fiber cladding makes it possible to involve both the fundamental and high fiber modes in the supercontinuum generation that helps to increase the width of the generation spectrum.

  17. Selectivity control of photosensitivity of Ag-GaP and Ag- AlGaN structures

    NASA Astrophysics Data System (ADS)

    Lamkin, I. A.; Tarasov, S. A.; Solomonov, A. V.; Andreev, M. Y.; Kurin, S. Yu

    2015-12-01

    Design, growth and studies of photosensitive structures based on Ag-GaP and Ag- AlxGa1-xN contacts are reported. Methods for structure selectivity control, which allow changing the sensitivity spectrum half-width in a range of 11-210 nm were worked out. By varying the metal layer thickness, a set of Ag-GaP short-wavelength photodetectors (PD) was fabricated. The set includes PDs from broadband (spectrum half-width Δλ=210 nm, sensitivity SI = 0,19 A/W) to visible-blind (Δλ=15 nm, SI = 0,034 A/W). The use of Ag-AlxGa1-xN structures provided increased sensitivity (SI = 0,071 A/W) and Δλ reduced to 11 nm due to special selection of solid solution composition.

  18. Real-time laser cladding control with variable spot size

    NASA Astrophysics Data System (ADS)

    Arias, J. L.; Montealegre, M. A.; Vidal, F.; Rodríguez, J.; Mann, S.; Abels, P.; Motmans, F.

    2014-03-01

    Laser cladding processing has been used in different industries to improve the surface properties or to reconstruct damaged pieces. In order to cover areas considerably larger than the diameter of the laser beam, successive partially overlapping tracks are deposited. With no control over the process variables this conduces to an increase of the temperature, which could decrease mechanical properties of the laser cladded material. Commonly, the process is monitored and controlled by a PC using cameras, but this control suffers from a lack of speed caused by the image processing step. The aim of this work is to design and develop a FPGA-based laser cladding control system. This system is intended to modify the laser beam power according to the melt pool width, which is measured using a CMOS camera. All the control and monitoring tasks are carried out by a FPGA, taking advantage of its abundance of resources and speed of operation. The robustness of the image processing algorithm is assessed, as well as the control system performance. Laser power is decreased as substrate temperature increases, thus maintaining a constant clad width. This FPGA-based control system is integrated in an adaptive laser cladding system, which also includes an adaptive optical system that will control the laser focus distance on the fly. The whole system will constitute an efficient instrument for part repair with complex geometries and coating selective surfaces. This will be a significant step forward into the total industrial implementation of an automated industrial laser cladding process.

  19. Laser cladding: repairing and manufacturing metal parts and tools

    NASA Astrophysics Data System (ADS)

    Sexton, Leo

    2003-03-01

    Laser cladding is presently used to repair high volume aerospace, automotive, marine, rail or general engineering components where excessive wear has occurred. It can also be used if a one-off high value component is either required or has been accidentally over-machined. The ultimate application of laser cladding is to build components up from nothing, using a laser cladding system and a 3D CAD drawing of the component. It is thus emerging that laser cladding can be classified as a special case of Rapid Prototyping (RP). Up to this point in time RP was seen, and is still seen, as in intermediately step between the design stage of a component and a finished working product. This can now be extended so that laser cladding makes RP a one-stop shop and the finished component is made from tool-steel or some alloy-base material. The marriage of laser cladding with RP is an interesting one and offers an alternative to traditional tool builders, re-manufacturers and injection mould design/repair industries. The aim of this paper is to discuss the emergence of this new technology, along with the transference of the process out of the laboratory and into the industrial workplace and show it is finding its rightful place in the manufacturing/repair sector. It will be shown that it can be used as a cost cutting, strategic material saver and consequently a green technology.

  20. HIP clad nickel base Alloy 625 for deep sour wells

    SciTech Connect

    Uhl, W.K.; Pendley, M.R.

    1984-05-01

    The hot isostatic pressing (HIP) process was used to clad nickel base Alloy 625 to AISI 4130 low alloy steel. The performance of the HIP clad material in the corrosive environment characteristic of deep, sour oil and gas wells was evaluated in laboratory tests. Included in the test program were NACE TM-01-77 sulfide stress cracking tests, chloride stress corrosion cracking tests in boiling MgCl /SUB 2'/ , and pitting and crevice corrosion tests. The HIP clad 625 performed excellently, displaying essentially the same corrosion resistance as wrought 625. Specifically the HIP clad 625 resisted sulfide stress cracking at applied stresses as high as 120% of yield strength and resisted chloride stress corrosion cracking at stresses exceeding 100% of yield. The HIP clad 625 also displayed immunity to pitting and crevice corrosion, with corrosion rates of <0.025 mm/y (1 mil/y). The 4130 base metal, however, was attacked severly in all tests. SEM/EDX analysis of the 625/4130 interface demonstrated that dilution of the cladding by the base metal was essentially eliminated.

  1. Hollow cylindrical plasma filament waveguide with discontinuous finite thickness cladding

    SciTech Connect

    Alshershby, Mostafa; Hao Zuoqiang; Lin Jingquan

    2013-01-15

    We have explored here a hollow cylindrical laser plasma multifilament waveguide with discontinuous finite thickness cladding, in which the separation between individual filaments is in the range of several millimeters and the waveguide cladding thickness is in the order of the microwave penetration depth. Such parameters give a closer representation of a realistic laser filament waveguide sustained by a long stable propagation of femtosecond (fs) laser pulses. We report how the waveguide losses depend on structural parameters like normalized plasma filament spacing, filament to filament distance or pitch, normal spatial frequency, and radius of the plasma filament. We found that for typical plasma parameters, the proposed waveguide can support guided modes of microwaves in extremely high frequency even with a cladding consisting of only one ring of plasma filaments. The loss of the microwave radiation is mainly caused by tunneling through the discontinuous finite cladding, i.e., confinement loss, and is weakly dependent on the plasma absorption. In addition, the analysis indicates that the propagation loss is fairly large compared with the loss of a plasma waveguide with a continuous infinite thickness cladding, while they are comparable when using a cladding contains more than one ring. Compared to free space propagation, this waveguide still presents a superior microwave transmission to some distance in the order of the filamentation length; thus, the laser plasma filaments waveguide may be a potential channel for transporting pulsed-modulated microwaves if ensuring a long and stable propagation of fs laser pulses.

  2. Residual Stress Measurements of Explosively Clad Cylindrical Pressure Vessels

    SciTech Connect

    Taylor, Douglas J; Watkins, Thomas R; Hubbard, Camden R; Hill, M. R.; Meith, W. A.

    2012-01-01

    Tantalum refractory liners were explosively clad into cylindrical pressure vessels, some of which had been previously autofrettaged. Using explosive cladding, the refractory liner formed a metallurgical bond with the steel of the pressure vessel at a cost of induced strain. Two techniques were employed to determine the residual stress state of the clad steel cylinders: neutron diffraction and mechanical slitting. Neutron diffraction is typically nondestructive; however, due to attenuation along the beam path, the cylinders had to be sectioned into rings that were nominally 25 mm thick. Slitting is a destructive method, requiring the sectioning of the cylindrical samples. Both techniques provided triaxial stress data and useful information on the effects of explosive cladding. The stress profiles in the hoop and radial directions were similar for an autofrettaged, nonclad vessel and a clad, nonautofrettaged vessel. The stress profiles in the axial direction appeared to be different. Further, the data suggested that residual stresses from the autofrettage and explosive cladding processes were not additive, in part due to evidence of reverse yielding. The residual stress data are presented, compared and discussed.

  3. Polymer materials as modified optical fiber cladding for chemical sensors

    NASA Astrophysics Data System (ADS)

    Yuan, Jianming

    An intrinsic fiber optic chemical sensor has been designed and developed by using a polymer material as a modified fiber cladding. The sensor is constructed by replacing a certain portion of the original cladding with a chemically sensitive material, specifically, polyaniline or polypyrrole. Both the light absorption coefficient and the refractive index of the polymers change upon the exposure to different chemical vapors. These changes induce the optical intensity modulation of the fiber optic sensor. Polyaniline or polypyrrole is coated as the modified cladding by either spin-cast or in-situ deposition method for sensing HCl, NH3, H 2O2, and H4N2 vapors. All sensors show rapid and strong response to the chemical vapors. Thus, these sensors demonstrate that polyaniline and polypyrrole are viable candidate materials for the detection of volatile toxic gases. Sensors exhibit better performance when correct parameters, such as modification area, in-situ deposition time, and spin-rate, are used in the cladding modification process. The reversibility of the sensor depends on the reaction between the modified cladding material and the chemical vapors. Polyaniline cladding has better reversibility than polypyrrole. The optimized sensor response and sensitivity can be achieved by selecting an incident light with suitable wavelength, power, and incident angle.

  4. Uranium and cesium diffusion in fuel cladding of electrogenerating channel

    SciTech Connect

    Vasil’ev, I. V. Ivanov, A. S.; Churin, V. A.

    2014-12-15

    The results of reactor tests of a carbonitride fuel in a single-crystal cladding from a molybdenum-based alloy can be used in substantiating the operational reliability of fuels in developing a project of a megawatt space nuclear power plant. The results of experimental studies of uranium and cesium penetration into the single-crystal cladding of fuel elements with a carbonitride fuel are interpreted. Those fuel elements passed nuclear power tests in the Ya-82 pilot plant for 8300 h at a temperature of about 1500°C. It is shown that the diffusion coefficients for uranium diffusion into the cladding are virtually coincident with the diffusion coefficients measured earlier for uranium diffusion into polycrystalline molybdenum. It is found that the penetration of uranium into the cladding is likely to occur only in the case of a direct contact between the cladding and fuel. The experimentally observed nonmonotonic uranium-concentration profiles are explained in terms of predominant uranium diffusion along grain boundaries. It is shown that a substantially nonmonotonic behavior observed in our experiment for the uranium-concentration profile may be explained by the presence of a polycrystalline structure of the cladding in the surface region from its inner side. The diffusion coefficient is estimated for the grain-boundary diffusion of uranium. The diffusion coefficients for cesium are estimated on the basis of experimental data obtained in the present study.

  5. Characterization of dilution action in laser-induction hybrid cladding

    NASA Astrophysics Data System (ADS)

    Huang, Yongjun

    2011-07-01

    Based on an experimental study of laser-induction hybrid cladding by powder feeding, the dilution action and elemental composition distribution were investigated in detail. The results indicate that, compared with individual laser cladding, by using laser-induction hybrid cladding it is easier to form a metallurgical bonding coating and the change range of dilution is much larger. Moreover, at the bottom of molten region, the morphology exhibits nearly a straight line. The processing parameters have great influence on dilution in hybrid cladding. With the increase of scanning speed, the tendency of dilution presents a U-shaped profile, i.e., the middle dilution is much less than those of two ends. The dilution increases with the induction energy. Furthermore, the bigger the dilution, the more uniform is the elemental composition throughout coating. In laser-induction hybrid cladding, the microstructure of low dilution coating is relatively fine due to the low hybrid cladding energy. By adjusting the laser energy and induction energy appropriately, i.e., high induction energy—low laser energy, the low dilution coating with fine microstructure and good mechanical properties can be achieved.

  6. Weld overlay cladding with iron aluminides

    SciTech Connect

    Goodwin, G.M.

    1997-12-01

    The author has established a range of compositions for these alloys within which hot cracking resistance is very good, and within which cold cracking can be avoided in many instances by careful control of welding conditions, particularly preheat and postweld heat treatment. For example, crack-free butt welds have been produced for the first time in 12-mm thick wrought Fe{sub 3}Al plate. Cold cracking, however, still remains an issue in many cases. The author has developed a commercial source for composite weld filler metals spanning a wide range of achievable aluminum levels, and are pursuing the application of these filler metals in a variety of industrial environments. Welding techniques have been developed for both the gas tungsten arc and gas metal arc processes, and preliminary work has been done to utilize the wire arc process for coating of boiler tubes. Clad specimens have been prepared for environmental testing in-house, and a number of components have been modified and placed in service in operating kraft recovery boilers. In collaboration with a commercial producer of spiral weld overlay tubing, the author is attempting to utilize the new filler metals for this novel application.

  7. Aluminum alloy clad fiber optic corrosion sensor

    NASA Astrophysics Data System (ADS)

    Rutherford, Paul S.; Ikegami, Roy; Shrader, John E.; Sherrer, David; Zabaronick, Noel; Zeakes, Jason S.; Murphy, Kent A.; Claus, Richard O.

    1997-06-01

    Life extension programs for military metallic aircraft are becoming increasingly important as defense budgets shrink and world economies realign themselves to an uncertain future. For existing military weapon systems, metallic corrosion damage costs as estimated $DOL8 billion per year. One approach to reducing this cost is to develop a reliable method to detect and monitor corrosion in hidden metallic structure with the use of corrosion sensors which would give an early indication of corrosion without significant disassembly, thereby reducing maintenance costs. This presentation describes the development, analysis, and testing of a fiber optic corrosion sensor developed jointly with the Virginia Polytechnic Fiber and Electro-Optics Research Center and sponsored by Wright Laboratory Materials Directorate. In the sensor which was researched, the normal cladding is removed in the sensor region, and replaced with aluminum alloy and allowed to corrode on coupons representative of C/KC-135 body structure in an ASTM B117 salt spray chamber and a Boeing developed Crevice Corrosion Cell. In this approach, the optical signal output of the sensor was originally designed to increase as corrosion takes place, however interaction with the corrosion byproducts yielded different results than anticipated. These test results to determine a correlation between the sensor output and the structural degradation due to corrosion are discussed.

  8. Demonstration of transverse-magnetic deep-ultraviolet stimulated emission from AlGaN multiple-quantum-well lasers grown on a sapphire substrate

    SciTech Connect

    Li, Xiao-Hang E-mail: dupuis@gatech.edu; Kao, Tsung-Ting; Satter, Md. Mahbub; Shen, Shyh-Chiang; Yoder, P. Douglas; Detchprohm, Theeradetch; Dupuis, Russell D. E-mail: dupuis@gatech.edu; Wei, Yong O.; Wang, Shuo; Xie, Hongen; Fischer, Alec M.; Ponce, Fernando A.

    2015-01-26

    We demonstrate transverse-magnetic (TM) dominant deep-ultraviolet (DUV) stimulated emission from photo-pumped AlGaN multiple-quantum-well lasers grown pseudomorphically on an AlN/sapphire template by means of photoluminescence at room temperature. The TM-dominant stimulated emission was observed at wavelengths of 239, 242, and 243 nm with low thresholds of 280, 250, and 290 kW/cm{sup 2}, respectively. In particular, the lasing wavelength of 239 nm is shorter compared to other reports for AlGaN lasers grown on foreign substrates including sapphire and SiC. The peak wavelength difference between the transverse-electric (TE)-polarized emission and TM-polarized emission was approximately zero for the lasers in this study, indicating the crossover of crystal-field split-off hole and heavy-hole valence bands. The rapid variation of polarization between TE- and TM-dominance versus the change in lasing wavelength from 243 to 249 nm can be attributed to a dramatic change in the TE-to-TM gain coefficient ratio for the sapphire-based DUV lasers in the vicinity of TE-TM switch.

  9. High-performance AlGaN metal-semiconductor-metal solar-blind ultraviolet photodetectors by localized surface plasmon enhancement

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Xu, Jin; Ye, Wei; Li, Yang; Qi, Zhiqiang; Dai, Jiangnan; Wu, Zhihao; Chen, Changqing; Yin, Jun; Li, Jing; Jiang, Hao; Fang, Yanyan

    2015-01-01

    AlGaN-based solar-blind ultraviolet photodetectors have attractive potential applications in the fields of missile plume detection, biochemical sensing, solar astronomy, etc. In this work, significant deep ultraviolet detection enhancement is demonstrated on AlGaN-based metal-semiconductor-metal (MSM) solar-blind ultraviolet photodetectors by introducing the coupling of localized surface plasmon from Al nanoparticles with the high-Al-content AlGaN epilayer. The size-controlled Al nanoparticle arrays fabricated by nanosphere lithography can not only reduce the detectors' dark current but also bring about greatly enhanced responsivity. The peak responsivity of AlGaN-based MSM solar-blind ultraviolet photodetectors with Al nanoparticles can reach 2.34 A/W at 269 nm under 20 V bias, enhanced more than 25 times than that without Al nanoparticles. Our approach shows an efficient fabrication technique of high-performance and low-cost plasmonic enhanced AlGaN solar-blind MSM ultraviolet photodetectors.

  10. Strain dependence on polarization properties of AlGaN and AlGaN-based ultraviolet lasers grown on AlN substrates

    SciTech Connect

    Bryan, Zachary Bryan, Isaac; Sitar, Zlatko; Collazo, Ramón; Mita, Seiji; Tweedie, James

    2015-06-08

    Since the band ordering in AlGaN has a profound effect on the performance of UVC light emitting diodes (LEDs) and even determines the feasibility of surface emitting lasers, the polarization properties of emitted light from c-oriented AlGaN and AlGaN-based laser structures were studied over the whole composition range, as well as various strain states, quantum confinements, and carrier densities. A quantitative relationship between the theoretical valence band separation, determined using k•p theory, and the experimentally measured degree of polarization is presented. Next to composition, strain was found to have the largest influence on the degree of polarization while all other factors were practically insignificant. The lowest crossover point from the transverse electric to transverse magnetic polarized emission of 245 nm was found for structures pseudomorphically grown on AlN substrates. This finding has significant implications toward the efficiency and feasibility of surface emitting devices below this wavelength.

  11. Preparation and characterization of laser cladding wollastonite derived bioceramic coating on titanium alloy.

    PubMed

    Li, Huan-cai; Wang, Dian-gang; Chen, Chuan-zhong; Weng, Fei; Shi, Hua

    2015-01-01

    The bioceramic coating is fabricated on titanium alloy (Ti6Al4V) by laser cladding the preplaced wollastonite (CaSiO3) powders. The coating on Ti6Al4V is characterized by x-ray diffraction, scanning electron microscopy coupled with energy dispersive spectroscopy, and attenuated total reflection Fourier-transform infrared. The interface bonding strength is measured using the stretching method using an RGD-5-type electronic tensile machine. The microhardness distribution of the cross-section is determined using an indentation test. The in vitro bioactivity of the coating on Ti6Al4V is evaluated using the in vitro simulated body fluid (SBF) immersion test. The microstructure of the laser cladding sample is affected by the process parameters. The coating surface is coarse, accidented, and microporous. The cross-section microstructure of the ceramic layer from the bottom to the top gradually changes from cellular crystal, fine cellular-dendrite structure to underdeveloped dendrite crystal. The coating on Ti6Al4V is composed of CaTiO3, CaO, α-Ca2SiO4, SiO2, and TiO2. After soaking in the SBF solution, the calcium phosphate layer is formed on the coating surface. PMID:26307502

  12. French investigations of high burnup effect on LOCA thermomecanical behavior. Part two. Oxidation and quenching experiments under simulated LOCA conditions with high burnup clad material

    SciTech Connect

    GrandJean, C.; Cauvin, R.; Lebuffe, C.

    1997-01-01

    In the frame of the high burnup fuel studies to support a possible extension of the current discharge burnup limit, experimental programs have been undertaken, jointly by EDF and IPSN in order to study the thermal-shock behavior of high burnup fuel claddings under typical LOCA conditions. The TAGUS program used unirradiated cladding samples, bare or bearing a pre-corrosion state simulating the end-of-life state of high burnup fuel claddings: the TAGCIR program used actually irradiated cladding samples taken from high burnup rods irradiated over 5 cycles in a commercial EDF PWR and having reached a rod burnup close to 60 GWd/tU. The thermal-shock failure tests consisted in oxidizing the cladding samples under steam flow, on both inner and outer faces or on the outer face alone, and subjecting them to a final water quench. The heating was provided by an inductive furnace the power of which being regulated through monitoring of the sample surface temperature with use of a single-wave optical pyrometer. Analysis of the irradiated tests (TAGCIR series) evidenced an increased oxidation rate as compared to similar tests on unirradiated samples. Results of the quenching tests series on unirradiated and irradiated samples are plotted under the usual presentation of failure maps relative to the oxidation parameters ECR (equivalent cladding reacted) or e{sub {beta}} (thickness of the remaining beta phase layer) as a function of the oxidation temperature. Comparison of the failure limits for irradiated specimens to those for unirradiated specimens indicates a lower brittleness under two side oxidation and possibly the opposite under one-side oxidation. The tentative analysis of the oxidation and quenching tests results on irradiated samples reveals the important role played by the hydrogen charged during in-reactor corrosion on the oxidation kinetics and the failure bearing capability of the cladding under LOCA transient conditions.

  13. Enhanced conductivity of sol-gel silica cladding for efficient poling in electro-optic polymer/TiO2 vertical slot waveguide modulators.

    PubMed

    Enami, Yasufumi; Jouane, Youssef; Luo, Jingdong; Jen, Alex K-Y

    2014-12-01

    We report the enhanced conductivity of sol-gel silica under-cladding for efficient poling of electro-optic (EO) polymer in a hybrid EO polymer/TiO2 vertical slot waveguide modulator. The electrical volume conductivity of sol-gel silica cladding increases approximately 30 times when the calcining time of the cladding layer is critically reduced to 45 minutes, which increases the in-device EO coefficient of the 600-nm-thick EO polymer film in modulators and reduces the lower halfwave voltage (Vπ) of the modulators. The lowest driving voltage (Vπ) of the TiO2 slot waveguide modulator is 2.0 V for an electrode length (Le) of 10 mm and wavelength of 1550 nm (VπLe = 2.0 V·cm) for the low-index guest-host EO polymer SEO125. The optical propagation loss is reduced to 7 dB/cm. PMID:25606950

  14. Ti Alloys Processed By Selective Laser Melting And By Laser Cladding: Microstructures And Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Mertens, Anne; Contrepois, Quentin; Dormal, Thierry; Lemaire, Olivier; Lecomte-Beckers, Jacqueline

    2012-07-01

    In this study, samples of alloy Ti-6Al-4V have been processed by Selective Laser Melting (SLM) and by Laser Cladding (LC), two layer-by-layer near-net-shape processes allowing for economic production of complex parts. The resulting microstructures have been characterised in details, so as to allow for a better understanding of the solidification process and of the subsequent phase transformations taking place upon cooling for both techniques. On the one hand, a new “MesoClad” laser with a maximum power of 300 W has been used successfully to produce thin wall samples by LC. On the other hand, the influence of processing parameters on the mechanical properties was investigated by means of uniaxial tensile testing performed on samples produced by SLM with different orientations with respect to the direction of mechanical solicitation. A strong anisotropy in mechanical behaviour was thus interpreted in relations with the microstructures and processing conditions.

  15. Weld overlay cladding with iron aluminides

    SciTech Connect

    Goodwin, G.M.

    1996-11-01

    The hot and cold cracking tendencies of some early iron aluminide alloy compositions limited their use to applications where good weldability was not required. Considerable progress has been made toward improving this situation. Using hot crack testing techniques developed at ORNL and a systematic study of alloy compositional effects, we have established a range of compositions within which hot cracking resistance is very good, essentially equivalent to stainless steel. Cold cracking, however, remains an issue, and extensive efforts are continuing to optimize composition and welding parameters, especially preheat and postweld heat treatment, to minimize its occurrence. In terms of filler metal and process development, we have progressed from sheared strip through aspiration cast rod and shielded metal arc electrodes to the point where we can now produce composite wire with a steel sheath and aluminum core in coil form, which permits the use of both the gas tungsten arc and gas metal arc processes. This is a significant advancement in that the gas metal arc process lends itself well to automated welding, and is the process of choice for commercial weld overlay applications. Using the newly developed filler metals, we have prepared clad specimens for testing in a variety of environments both in-house and outside ORNL, including laboratory and commercial organizations. As a means of assessing the field performance of this new type of material, we have modified several non-pressure boundary boiler components, including fuel nozzles and port shrouds, by introducing areas of weld overlay in strategic locations, and have placed these components in service in operating boilers for a side-by-side comparison with conventional corrosion-resistant materials.

  16. Technology Solutions Case Study: Initial and Long-Term MOvement of Cladding Installed Over Exterior Rigid Insulation

    SciTech Connect

    2014-10-01

    Changes in the International Energy Conservation Code (IECC) from 2009 to 2012 have resulted in the use of exterior rigid insulation becoming part of the prescriptive code requirements. With more jurisdictions adopting the 2012 IECC, builders will be required to incorporate exterior insulation in the construction of their exterior wall assemblies. For thick layers of exterior insulation (levels greater than 1.5 inches), the use of wood of furring strips attached through the insulation back to the structure has been used by many contractors and designers as a means to provide a convenient cladding attachment location. However, there has been resistance to its widespread implementation due to a lack of research and understanding of the mechanisms involved and potential creep effects of the assembly under the sustained dead load of a cladding. This research conducted by Building Science Corporation evaluated the system mechanics and long-term performance of this technique.

  17. Zr electrorefining process for the treatment of cladding hull waste in LiCl-KCl molten salts

    SciTech Connect

    Lee, Chang Hwa; Lee, You Lee; Jeon, Min Ku; Kang, Kweon Ho; Choi, Yong Taek; Park, Geun Il

    2013-07-01

    Zr electrorefining for the treatment of Zircaloy-4 cladding hull waste is demonstrated in LiCl-KCl-ZrCl{sub 4} molten salts. Although a Zr oxide layer thicker than 5 μm strongly inhibits the Zr dissolution process, pre-treatment processes increases the dissolution kinetics. For 10 g-scale experiments, the purities of the recovered Zr were 99.54 wt.% and 99.74 wt.% for fresh and oxidized cladding tubes, respectively, with no electrical contact issue. The optimal condition for Zr electrorefining has been found to improve the morphological feature of the recovered Zr, which reduces the salt incorporation by examining the effect of the process parameters such as the ZrCl{sub 4} concentration and the applied potential.

  18. Fracture analysis of full-thickness clad beam specimens

    SciTech Connect

    Keeney, J.A.; Bass, B.R.; McAfee, W.J.

    1997-12-01

    Finite-element analyses were performed on full-thickness clad beam specimens to quantify fracture toughness for shallow cracks in material for which metallurgical conditions are prototypic of those found in reactor pressure vessels (RPVs). The beam specimens are fabricated from a section of an RPV wall (removed from a canceled nuclear plant) that includes weld, plate, and clad material with metallurgical factors potentially influencing fracture toughness for shallow cracks. A summary of the testing program is provided and the analyses of the test data are discussed, including comparisons of measured displacements with finite-element analysis results, applications of toughness estimation techniques, and interpretations of constraint conditions implied by stress-based constraint methodologies. Fracture toughness estimates were obtained from displacement data using finite-element techniques and estimation schemes based on the {eta}-factor method. The J-Q methodology was used to assess crack-tip stress triaxiality in the clad beam specimens. The shallow-crack clad beam specimens showed a significant loss of constraint similar to that of other shallow-crack single-edge notch bend specimens. The stress-based Dodds-Anderson scaling model was also utilized to analyze constraint conditions in the clad beam specimens and appears to be effective in adjusting the test data to account for loss of in-plane constraint for uniaxially tested beams.

  19. Accident Performance of Light Water Reactor Cladding Materials

    SciTech Connect

    Nelson, Andrew T.

    2012-07-24

    During a loss of coolant accident as experienced at Fukushima, inadequate cooling of the reactor core forces component temperatures ever higher where they must withstand aggressive chemical environments. Conventional zirconium cladding alloys will readily oxidize in the presence of water vapor at elevated temperatures, rapidly degrading and likely failing. A cladding breach removes the critical barrier between actinides and fission products and the coolant, greatly increasing the probability of the release of radioactivity in the event of a containment failure. These factors have driven renewed international interest in both study and improvement of the materials used in commercial light water reactors. Characterization of a candidate cladding alloy or oxidation mitigation technique requires understanding of both the oxidation kinetics and hydrogen production as a function of temperature and atmosphere conditions. Researchers in the MST division supported by the DOE-NE Fuel Cycle Research and Development program are working to evaluate and quantify these parameters across a wide range of proposed cladding materials. The primary instrument employed is a simultaneous thermal analyzer (STA) equipped with a specialized water vapor furnace capable of maintaining temperatures above 1200 C in a range of atmospheres and water vapor contents. The STA utilizes thermogravimetric analysis and a coupled mass spectrometer to measure in situ oxidation and hydrogen production of candidate materials. This capability is unprecedented in study of materials under consideration for reactor cladding use, and is currently being expanded to investigate proposed coating techniques as well as the effect of coating defects on corrosion resistance.

  20. Fatigue crack growth testing of sub-clad defects

    SciTech Connect

    Jones, D.P.; Leax, T.R.

    1998-04-01

    Fatigue crack growth tests were performed on four point bend specimens with crack like defects intentionally placed in A302B low-alloy pressure vessel steel clad with 308/309L weld deposited stainless steel. The defects were placed in the base metal under the cladding by machining a cavity from the side opposite the cladding, electric-discharge machining a very sharp flaw, fatigue pre-cracking the flaw, and then filling up the cavity by a weld repair process. The specimens were stress relieved before fatigue testing. The specimens were fatigue cycled at positive load ratios until the defects broke through to the surface. The specimens were then fractured at liquid nitrogen temperatures to reveal the fracture surfaces. Seven different sub-clad flaw specimens were tested in room temperature air and each test provides a record of cycles to defect break-through. Changes in defect size and shape as a function of applied load cycles were obtained by benchmarking the crack at various stages of the load history. The results provide a set of embedded defect data which can be used for qualifying fatigue crack growth analysis procedures such as those in Section XI of the ASME Boiler and Pressure Vessel Code. A comparison between calculated and measured values shows that the ASME B and PV Section XI fatigue crack growth procedures conservatively predict cycles to defect break-through for small sub-clad defects.

  1. The Corrosion and Corrosion Fatigue Behavior of Nickel Based Alloy Weld Overlay and Coextruded Claddings

    NASA Astrophysics Data System (ADS)

    Stockdale, Andrew

    The use of low NOx boilers in coal fired power plants has resulted in sulfidizing corrosive conditions within the boilers and a reduction in the service lifetime of the waterwall tubes. As a solution to this problem, Ni-based weld overlays are used to provide the necessary corrosion resistance however; they are susceptible to corrosion fatigue. There are several metallurgical factors which give rise to corrosion fatigue that are associated with the localized melting and solidification of the weld overlay process. Coextruded coatings offer the potential for improved corrosion fatigue resistance since coextrusion is a solid state coating process. The corrosion and corrosion fatigue behavior of alloy 622 weld overlays and coextruded claddings was investigated using a Gleeble thermo-mechanical simulator retrofitted with a retort. The experiments were conducted at a constant temperature of 600°C using a simulated combustion gas of N2-10%CO-5%CO2-0.12%H 2S. An alternating stress profile was used with a minimum tensile stress of 0 MPa and a maximum tensile stress of 300 MPa (ten minute fatigue cycles). The results have demonstrated that the Gleeble can be used to successfully simulate the known corrosion fatigue cracking mechanism of Ni-based weld overlays in service. Multilayer corrosion scales developed on each of the claddings that consisted of inner and outer corrosion layers. The scales formed by the outward diffusion of cations and the inward diffusion of sulfur and oxygen anions. The corrosion fatigue behavior was influenced by the surface finish and the crack interactions. The initiation of a large number of corrosion fatigue cracks was not necessarily detrimental to the corrosion fatigue resistance. Finally, the as-received coextruded cladding exhibited the best corrosion fatigue resistance.

  2. High-power blue laser diodes with indium tin oxide cladding on semipolar (202{sup ¯}1{sup ¯}) GaN substrates

    SciTech Connect

    Pourhashemi, A. Farrell, R. M.; Cohen, D. A.; Speck, J. S.; DenBaars, S. P.; Nakamura, S.

    2015-03-16

    We demonstrate a high power blue laser diode (LD) using indium tin oxide as a cladding layer on semipolar oriented GaN. These devices show peak output powers and external quantum efficiencies comparable to state-of-the-art commercial c-plane devices. Ridge waveguide LDs were fabricated on (202{sup ¯}1{sup ¯}) oriented GaN substrates using InGaN waveguiding layers and GaN cladding layers. At a lasing wavelength of 451 nm at room temperature, an output power of 2.52 W and an external quantum efficiency of 39% were measured from a single facet under a pulsed injection current of 2.34 A. The measured differential quantum efficiency was 50%.

  3. Performance of HT9 clad metallic fuel at high temperature

    SciTech Connect

    Pahl, R.G.; Lahm, C.E.; Hayes, S.L.

    1992-12-01

    Steady-state testing of HT9 clad metallic fuel at high temperatures was initiated in EBR-II in November of 1987. At that time U-10 wt. % Zr fuel clad with the low-swelling ferritic/martensitic alloy HT9 was being considered as driver fuel options for both EBR-II and FFTF. The objective of the X447 test described here was to determine the lifetime of HT9 cladding when operated with metallic fuel at beginning of life inside wall temperatures approaching {approximately}660{degree}C. Though stress-temperature design limits for HT9 preclude its use for high burnup applications under these conditions due to excessive thermal creep, the X447 test was carried out to obtain data on high temperature breach phenomena involving metallic fuel since little data existed in that area.

  4. Performance of HT9 clad metallic fuel at high temperature

    SciTech Connect

    Pahl, R.G.; Lahm, C.E.; Hayes, S.L.

    1992-01-01

    Steady-state testing of HT9 clad metallic fuel at high temperatures was initiated in EBR-II in November of 1987. At that time U-10 wt. % Zr fuel clad with the low-swelling ferritic/martensitic alloy HT9 was being considered as driver fuel options for both EBR-II and FFTF. The objective of the X447 test described here was to determine the lifetime of HT9 cladding when operated with metallic fuel at beginning of life inside wall temperatures approaching [approximately]660[degree]C. Though stress-temperature design limits for HT9 preclude its use for high burnup applications under these conditions due to excessive thermal creep, the X447 test was carried out to obtain data on high temperature breach phenomena involving metallic fuel since little data existed in that area.

  5. Clad photon sieve for generating localized hollow beams

    NASA Astrophysics Data System (ADS)

    Cheng, Yiguang; Tong, Junmin; Zhu, Jiangping; Liu, Junbo; Hu, Song; He, Yu

    2016-02-01

    A novel photon sieve structure called clad photon sieve is proposed to generate localized hollow beams and its design principle and focusing properties are studied. The clad photon sieve is composed of the internal zone and external zone with pinholes being positioned on the dark zones. Pinholes in the internal zone and in the external zone give destructive interference to the focus, leading to localized hollow beams being generated on the focal plane. Focusing properties of clad photon sieve with different focal lengths, zone numbers and modulation factors are also studied by theoretical calculations, numerical simulations and experiments, showing that the central dark spot size can be controlled by the focal length and rings number, and the intensity of the central dark spot varies with different modulation factors related with the internal zone and the external zone. This photon sieve can be useful for trapping and manipulating of particles and cooling of atoms.

  6. Nanoscale light-matter interactions in atomic cladding waveguides.

    PubMed

    Stern, Liron; Desiatov, Boris; Goykhman, Ilya; Levy, Uriel

    2013-01-01

    Alkali vapours, such as rubidium, are being used extensively in several important fields of research such as slow and stored light nonlinear optics quantum computation, atomic clocks and magnetometers. Recently, there is a growing effort towards miniaturizing traditional centimetre-size vapour cells. Owing to the significant reduction in device dimensions, light-matter interactions are greatly enhanced, enabling new functionalities due to the low power threshold needed for nonlinear interactions. Here, taking advantage of the mature platform of silicon photonics, we construct an efficient and flexible platform for tailored light-vapour interactions on a chip. Specifically, we demonstrate light-matter interactions in an atomic cladding waveguide, consisting of a silicon nitride nano-waveguide core with a rubidium vapour cladding. We observe the efficient interaction of the electromagnetic guided mode with the rubidium cladding and show that due to the high confinement of the optical mode, the rubidium absorption saturates at powers in the nanowatt regime. PMID:23462991

  7. Fracture behavior and microstructural characteristics of irradiated Zircaloy cladding

    SciTech Connect

    Chung, H.M.; Yaggee, F.L.; Kassner, T.F.

    1985-06-01

    Zircaloy cladding tube specimens from commercial power reactor fuel assemblies (burnup >22 MWd/kgU) have been deformed to fracture at 325/sup 0/C by either the internal gas-pressurization or the expanding-mandrel technique in a helium or argon environment containing no fission product species (e.g., I, Cs, or Cd). The fracture surfaces of 11 irradiated specimens fractured by internal gas pressurization were examined by scanning electron microscopy, and 7 specimens were found to contain various degrees of the pseudocleavage feature that is characteristic of pellet-cladding interaction failures. Out of 10 test specimens fractured by expanding-mandrel loading, 5 were found to contain regions of pseudocleavage on the fracture surfaces. The specimens exhibited ''X-marks'' on the outer surface and brittle incipient cracks distributed on the inner surface, which are also characteristic of pellet-cladding interaction failures.

  8. Nanoscale light–matter interactions in atomic cladding waveguides

    PubMed Central

    Stern, Liron; Desiatov, Boris; Goykhman, Ilya; Levy, Uriel

    2013-01-01

    Alkali vapours, such as rubidium, are being used extensively in several important fields of research such as slow and stored light nonlinear optics quantum computation, atomic clocks and magnetometers. Recently, there is a growing effort towards miniaturizing traditional centimetre-size vapour cells. Owing to the significant reduction in device dimensions, light–matter interactions are greatly enhanced, enabling new functionalities due to the low power threshold needed for nonlinear interactions. Here, taking advantage of the mature platform of silicon photonics, we construct an efficient and flexible platform for tailored light–vapour interactions on a chip. Specifically, we demonstrate light–matter interactions in an atomic cladding waveguide, consisting of a silicon nitride nano-waveguide core with a rubidium vapour cladding. We observe the efficient interaction of the electromagnetic guided mode with the rubidium cladding and show that due to the high confinement of the optical mode, the rubidium absorption saturates at powers in the nanowatt regime. PMID:23462991

  9. Fabrication of stainless steel clad tubing. [gas pressure bonding

    NASA Technical Reports Server (NTRS)

    Kovach, C. W.

    1978-01-01

    The feasibility of producing stainless steel clad carbon steel tubing by a gas pressure bonding process was evaluated. Such a tube product could provide substantial chromium savings over monolithic stainless tubing in the event of a serious chromium shortage. The process consists of the initial assembly of three component tubesets from conventionally produced tubing, the formation of a strong metallurgical bond between the three components by gas pressure bonding, and conventional cold draw and anneal processing to final size. The quality of the tubes produced was excellent from the standpoint of bond strength, mechanical, and forming properties. The only significant quality problem encountered was carburization of the stainless clad by the carbon steel core which can be overcome by further refinement through at least three different approaches. The estimated cost of clad tubing produced by this process is greater than that for monolithic stainless tubing, but not so high as to make the process impractical as a chromium conservation method.

  10. Metal-clad optical waveguides: analytical and experimental study.

    PubMed

    Kaminow, I P; Mammel, W L; Weber, H P

    1974-02-01

    Planar optical waveguides consisting of thin dielectric films with metal cladding have been investigated theoretically and experimentally. A computer program was devised to provide the phase and attenuation constants and wavefunctions for TE and TM modes in symmetric and asymmetric guides. Approximate expressions suitable for slide-rule calculation were also derived. Numerical results and illustrations are given for films of photoresist with Al, Ag, and Au cladding. Direct measurements of the attenuation and phase constants at 0.633 microm of numerous experimental waveguides are in reasonable agreement with theory. Attenuations <1 dB/cm, which is sufficiently small for application in devices, were measured. Calculated wavefunctions illustrate the mismatch of modes at transitions between unclad and metal-clad waveguides. Experimentally, we find substantial losses at such abrupt junctions. They can be overcome by simple tapered transitions. PMID:20125992

  11. Microstructures of mixed group III-nitride epitaxial layers

    NASA Astrophysics Data System (ADS)

    Westmeyer, Andrew Nathan

    InGaN and AlGaN epitaxial layers were deposited by metalorganic chemical vapor deposition on sapphire substrates with GaN buffer layers. For the growth of InGaN at a given temperature, the trimethylgallium flow rate has the greatest influence on the In incorporation, whereas the trimethylindium flow rate has little influence. These effects are attributed to the suppression of In desorption by increasing the growth rate and the saturation of the surface with In adatoms, respectively. If the growth temperature is increased by 2.4°C, then the In content is lowered by 1% for the investigated temperature range of 785--845°C. For the growth of AlGaN, the solid fraction of Al has a sub-linear dependence on the gas composition. This was attributed to the composition pulling effect, in which incoming species are rejected in order to reduce the strain with the underlying buffer layer. A strain analysis was performed on all samples by X-ray diffraction in order to determine the composition and degree of relaxation. These values were compared to those obtained by Rutherford backscattering spectroscopy. By this method the varied reported values for elastic constants were evaluated to ascertain which set provided the best correlation. Transmission electron microscopy was performed. Plan-view images of InGaN contain domains differing in the direction of the modulations. Zone-axis diffraction patterns reveal sidebands adjacent to several Bragg reflections. These observations can be explained by diffraction effects resulting from periodic composition modulations, which are an intermediate stage in the process of phase separation. Since Young's modulus for the nitrides is isotropic in the (0001) plane, no particular direction is favored for the modulations based on strain energy considerations. In the case of AlGaN, periodic composition modulations are observed not in the growth plane (0001) but in the growth direction [0001]. Satellites in diffraction patterns are aligned in this

  12. The Influence of the In-Situ Clad Staining on the Corrosion of Zircaloy in PWR Water Environment

    SciTech Connect

    Kammenzind, B.F., Eklund, K.L. and Bajaj, R.

    2001-06-21

    Zircaloy cladding tubes strain in-situ during service life in the corrosive environment of a Pressurized Water Reactor for a variety of reasons. First, the tube undergoes stress free growth due to the preferential alignment of irradiation induced vacancy loops on basal planes. Positive strains develop in the textured tubes along prism orientations while negative strains develop along basal orientations (Reference (a)). Second, early in life, free standing tubes will often shrink by creep in the diametrical direction under the external pressure of the water environment, but potentially grow later in life in the diametrical direction once the expanding fuel pellet contacts the cladding inner wall (Reference (b)). Finally, the Zircaloy cladding absorbs hydrogen as a by product of the corrosion reaction (Reference (c)). Once above the solubility limit in Zircaloy, the hydride precipitates as zirconium hydride (References (c) through (j)). Both hydrogen in solid solution and precipitated as Zirconium hydride cause a volume expansion of the Zircaloy metal (Reference (k)). Few studies are reported on that have investigated the influence that in-situ clad straining has on corrosion of Zircaloy. If Zircaloy corrosion rates are governed by diffusion of anions through a thin passivating boundary layer at the oxide-to-metal interface (References (l) through (n)), in-situ straining of the cladding could accelerate the corrosion process by prematurely breaking that passivating oxide boundary layer. References (o) through (q) investigated the influence that an applied tensile stress has on the corrosion resistance of Zircaloy. Knights and Perkins, Reference (o), reported that the applied tensile stress increased corrosion rates above a critical stress level in 400 C and 475 C steam, but not at lower temperatures nor in dry oxygen environments. This latter observation suggested that hydrogen either in the oxide or at the oxide-to-metal interface is involved in the observed stress

  13. Results of NDE Technique Evaluation of Clad Hydrides

    SciTech Connect

    Dennis C. Kunerth

    2014-09-01

    This report fulfills the M4 milestone, M4FT-14IN0805023, Results of NDE Technique Evaluation of Clad Hydrides, under Work Package Number FT-14IN080502. During service, zirconium alloy fuel cladding will degrade via corrosion/oxidation. Hydrogen, a byproduct of the oxidation process, will be absorbed into the cladding and eventually form hydrides due to low hydrogen solubility limits. The hydride phase is detrimental to the mechanical properties of the cladding and therefore it is important to be able to detect and characterize the presence of this constituent within the cladding. Presently, hydrides are evaluated using destructive examination. If nondestructive evaluation techniques can be used to detect and characterize the hydrides, the potential exists to significantly increase test sample coverage while reducing evaluation time and cost. To demonstrate the viability this approach, an initial evaluation of eddy current and ultrasonic techniques were performed to demonstrate the basic ability to these techniques to detect hydrides or their effects on the microstructure. Conventional continuous wave eddy current techniques were applied to zirconium based cladding test samples thermally processed with hydrogen gas to promote the absorption of hydrogen and subsequent formation of hydrides. The results of the evaluation demonstrate that eddy current inspection approaches have the potential to detect both the physical damage induced by hydrides, e.g. blisters and cracking, as well as the combined effects of absorbed hydrogen and hydride precipitates on the electrical properties of the zirconium alloy. Similarly, measurements of ultrasonic wave velocities indicate changes in the elastic properties resulting from the combined effects of absorbed hydrogen and hydride precipitates as well as changes in geometry in regions of severe degradation. However, for both approaches, the signal responses intended to make the desired measurement incorporate a number of contributing

  14. Deformation and fracture characteristics of spent Zircaloy fuel cladding

    SciTech Connect

    Chung, H.M.; Yaggee, F.L.

    1982-09-01

    For a better understanding of Zircaloy fuel-rod failure by the pellet-cladding interaction (PCI) phenomenon, a mechanistic study of deformation and fracture behavior of spent power reactor fuel cladding under simulated PCI conditions was conducted. Zircaloy-2 cladding specimens, obtained from fuel assemblies of operating power reactors, were deformed to fracture at 325/sup 0/C by internal gas pressurization in the absence of fission product simulants. Fracture characteristics and microstructures were examined via SEM, TEM, and HVEM. Numerous dislocation tangles and cell structures, observed in TEM specimens of cladding tubes that failed in a ductile manner, were consistent with SEM observations of a limited number of dimples characteristic of microvoid coalescence. A number of brittle-type failures were produced without the influence of fission product simulants. The brittle cracks occurred near the areas compressed by the Swagelok fittings of the internally pressurized tube and propagated from the outer to the inner surface. Since the outer surface was isolated and maintained under a flowing stream of pure helium, it is unlikely that the brittle-type failure was influenced by any fission product traces. SEM fractography of the brittle-type failure revealed a large area of transgranular pseudocleavage with limited areas of ductile fluting, which were similar in appearance to the surfaces produced by in-reactor PCI-type failures. A TEM evaluation of the cladding in the vicinity of the through-wall crack revealed numerous locations that contained an extensive amount of second-phase precipitate (Zr/sub 3/O). We believe that the brittle-type failures of the irradiated spent fuel cladding in the stress rupture experiments are associated with segregation of oxygen, which leads to the formation of the order structure, an immobilization of dislocations, and minimal plastic deformation in the material.

  15. Structure and properties of titanium surface layers after electron beam alloying with powder mixtures containing carbon

    NASA Astrophysics Data System (ADS)

    Lenivtseva, O. G.; Bataev, I. A.; Golkovskii, M. G.; Bataev, A. A.; Samoilenko, V. V.; Plotnikova, N. V.

    2015-11-01

    The structure and tribological properties of commercially pure titanium (cp-Ti) samples after non-vacuum electron beam surface alloying with carbon were studied. Two types of powders were used to introduce carbon in surface layer of cp-Ti: titanium carbide (TiC) and mixture of pure titanium and graphite ("Ti + C"). Single layer and multilayer coatings were studied. Application of electron beam for alloying provided cladding rate of 4.5 m2/h. The thickness of the clad coatings was 1.6-2.0 mm. The main phases received after "Ti + C" powder cladding were α-titanium, TiC, and retained graphite. In the samples obtained by cladding of TiC, graphite was not observed. A factor determining the microhardness and tribological properties of the cladded layer was the volume fraction of TiC. Maximum coating microhardness of 8 GPa was obtained by cladding of single layer of TiC powder or two layers of the "Ti + C" mixture. Two types of tests were carried out to evaluate the wear resistance of the samples. In friction tests against loose abrasive particles, the wear rate of the best samples was 9.3 times lower than that of cp-Ti. In wear tests using fixed abrasive particles, the relative wear resistance of the best samples was 2.3 times higher than that of cp-Ti.

  16. In situ plasma enhanced atomic layer deposition half cycle study of Al{sub 2}O{sub 3} on AlGaN/GaN high electron mobility transistors

    SciTech Connect

    Qin, Xiaoye; Wallace, Robert M.

    2015-08-24

    A half cycle study of plasma enhanced atomic layer deposited (PEALD) Al{sub 2}O{sub 3} on AlGaN is investigated using in situ X-ray photoelectron spectroscopy, low energy ion scattering, and ex situ electrical characterizations. A faster nucleation or growth is detected from PEALD relative to purely thermal ALD using an H{sub 2}O precursor. The remote O{sub 2} plasma oxidizes the AlGaN surface slightly at the initial stage, which passivates the surface and reduces the OFF-state leakage. This work demonstrates that PEALD is a useful strategy for Al{sub 2}O{sub 3} growth on AlGaN/GaN devices.

  17. Study of the response of Zircaloy- 4 cladding to thermal shock during water quenching after double sided steam oxidation at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Sawarn, Tapan K.; Banerjee, Suparna; Kumar, Sunil

    2016-05-01

    This study investigates the failure of embrittled Zircaloy-4 cladding in a simulated loss of coolant accident condition and correlates it with the evolved stratified microstructure. Isothermal steam oxidation of Zircaloy-4 cladding at high temperatures (900-1200 °C) with soaking periods in the range 60-900 s followed by water quenching was carried out. The combined oxide + oxygen stabilized α-Zr layer thickness and the fraction of the load bearing phase (recrystallised α-Zr grains + prior β-Zr or only prior β-Zr) of clad tube specimens were correlated with the %ECR calculated using Baker-Just equation. Average oxygen concentration of the load bearing phase corresponding to different oxidation conditions was calculated from the average microhardness using an empirical correlation. The results of these experiments are presented in this paper. Thermal shock sustainability of the clad was correlated with the %ECR, combined oxide+α-Zr(O) layer thickness, fraction of the load bearing phase and its average oxygen concentration.

  18. Influence of irradiation on KISCC of Zr-1%Nb claddings

    NASA Astrophysics Data System (ADS)

    Bibilashvili, Yu. K.; Medvedev, A. V.; Nesterov, B. I.; Novikov, V. V.; Golovanov, V. N.; Eremin, S. G.; Yurtchenko, A. D.

    2000-06-01

    Experimental results on iodine induced stress corrosion cracking (SCC) in irradiated claddings from Zr-1%Nb alloy are analyzed. Fatigue cracks were grown at their inner surfaces. The irradiation was carried on in the liquid sodium cooled BOR-60 to the fluence not lower than 10 22 n/cm 2. The SCC-test was carried at 350°C, in argon gas at constant pressure and iodine surface concentration of 0.2 mg/cm 2. The threshold stress intensity factor for the irradiated Zr-1%Nb claddings was determined to be ˜2.0 MPa√m.

  19. Method and system for edge cladding of laser gain media

    SciTech Connect

    Bayramian, Andrew James; Caird, John Allyn; Schaffers, Kathleen Irene

    2014-03-25

    A gain medium operable to amplify light at a gain wavelength and having reduced transverse ASE includes an input surface and an output surface opposing the input surface. The gain medium also includes a central region including gain material and extending between the input surface and the output surface along a longitudinal optical axis of the gain medium. The gain medium further includes an edge cladding region surrounding the central region and extending between the input surface and the output surface along the longitudinal optical axis of the gain medium. The edge cladding region includes the gain material and a dopant operable to absorb light at the gain wavelength.

  20. Welding fixture for nuclear fuel pin cladding assemblies

    DOEpatents

    Oakley, David J.; Feld, Sam H.

    1986-01-01

    A welding fixture for locating a driver sleeve about the open end of a nuclear fuel pin cladding. The welding fixture includes a holder provided with an open cavity having shoulders for properly positioning the driver sleeve, the end cap, and a soft, high temperature resistant plastic protective sleeve that surrounds a portion of the end cap stem. Ejected contaminant particles spewed forth by closure of the cladding by pulsed magnetic welding techniques are captured within a contamination trap formed in the holder for ultimate removal and disposal of contaminating particles along with the holder.

  1. Welding fixture for nuclear fuel pin cladding assemblies

    DOEpatents

    Oakley, D.J.; Feld, S.H.

    1984-02-22

    A welding fixture is described for locating a driver sleeve about the open end of a nuclear fuel pin cladding. The welding fixture includes a holder provided with an open cavity having shoulders for properly positioning the driver sleeve, the end cap, and a soft, high temperature resistant plastic protective sleeve that surrounds a portion of the end cap stem. Ejected contaminant particles spewed forth by closure of the cladding by pulsed magnetic welding techniques are captured within a contamination trap formed in the holder for ultimate removal and disposal of contaminating particles along with the holder.

  2. CHARACTERIZATION OF HYDROGEN CONTENT IN ZIRCALOY-4 NUCLEAR FUEL CLADDING

    SciTech Connect

    Pfeif, E. A.; Mishra, B.; Olson, D. L.; Lasseigne, A. N.; Krzywosz, K.; Mader, E. V.

    2010-02-22

    Assessment of hydrogen uptake of underwater nuclear fuel clad and component materials will enable improved monitoring of fuel health. Zirconium alloys are used in nuclear reactors as fuel cladding, fuel channels, guide tubes and spacer grids, and are available for inspection in spent fuel pools. With increasing reactor exposure zirconium alloys experience hydrogen ingress due to neutron interactions and water-side corrosion that is not easily quantified without destructive hot cell examination. Contact and non-contact nondestructive techniques, using Seebeck coefficient measurements and low frequency impedance spectroscopy, to assess the hydrogen content and hydride formation within zircaloy 4 material that are submerged to simulate spent fuel pools are presented.

  3. Laser cladding of Stellite #6: a detailed analysis

    NASA Astrophysics Data System (ADS)

    Kathuria, Yash P.; Tsuboi, Akihiko

    1996-09-01

    Potential applications such as hard facing of engine valve seat, turbine engine blade shroud interlock and leading edge of steam turbine blade, with controlled dilution have stimulated the use of laser cladding recently. In this paper, based on the laser beam interaction time, the microscopical study of dendrite structure formation in laser cladding of stellite number 6 on mild steel and Cr-Ni base materials is investigated. The effect of the various parameters such as heat input, beam interaction time, scanning frequency and transverse speed are considered. The applications in the rapid prototyping industries are also discussed.

  4. Photoluminescence efficiency of BGaN epitaxial layers with high boron content

    NASA Astrophysics Data System (ADS)

    Jurkevičius, J.; Mickevičius, J.; Kadys, A.; Kolenda, M.; Tamulaitis, G.

    2016-07-01

    High-boron-content epitaxial layers of BGaN intended for lattice-matching with AlGaN in UV light emitters were grown on SiC substrate and GaN and AlN templates on sapphire. Photoluminescence (PL) of these layers was studied under quasi-steady-state conditions by varying temperature and excitation intensity. The PL spectra in the samples with different boron content and their dynamics evidence formation of boron-rich regions occupying a small fraction of the total layer volume and acting as the emission killers. The room-temperature PL efficiency of the BGaN epilayers was estimated and shown to drastically decrease at increasing boron content with no significant correlation with either the type of substrate/template or technological conditions of the layer deposition.

  5. Pulsed growth techniques in plasma-assisted molecular beam epitaxy of AlxGa1-xN layers with medium Al content (x=0.4-0.6)

    NASA Astrophysics Data System (ADS)

    Nechaev, D. V.; Brunkov, P. N.; Troshkov, S. I.; Jmerik, V. N.; Ivanov, S. V.

    2015-09-01

    Paper presents the comparative analysis of Metal Modulated Epitaxy (MME) and Droplet Elimination by Thermal Annealing (DETA) techniques in the low-temperature plasma-assisted MBE of thick AlxGa1-xN layers with the medium Al content (x=0.4-0.6) grown under the highly metal-rich conditions. Atomically smooth surface with RMS of about 0.4 nm across the area of 2×2 μm2 has been achieved for AlGaN layers grown at FIII/FN flux ratio of 2.5 and substrate temperature of 700 °C by using DETA. The MME growth of AlGaN epilayers leads to their cracking due to the tensile stress introduced by relaxed GaN interlayers which are formed during the nitrogen exposure of the Ga-enriched AlGaN surface. A new technique based on IR-pyrometry measurements has been developed to monitor in situ metal accumulation and depletion on the growth surface.

  6. Influence Of The Laser Cladding Strategies On The Mechanical Properties Of Inconel 718

    SciTech Connect

    Lamikiz, A.; Tabernero, I.; Ukar, E.; Lopez de Lacalle, L. N.

    2011-01-17

    This work presents different experimental results of the mechanical properties of Inconel registered 718 test parts built-up by laser cladding. Recently, turbine manufacturers for aeronautical sector have presented high interest on laser cladding processes. This process allows building fully functional structures on superalloys, such as Inconel registered 718, with high flexibility on complex shapes. However, there is limited data on mechanical properties of the laser cladding structures. Moreover, the available data do not include the influence of process parameters and laser cladding strategies. Therefore, a complete study of the influence of the laser cladding parameters and mainly, the variation of the tensile strength with the laser cladding strategy is presented. The results show that there is a high directionality of mechanical properties, depending on the strategies of laser cladding process. In other words, the test parts show a fiber -like structure that should be considered on the laser cladding strategy selection.

  7. Dielectric tube waveguides with absorptive cladding for broadband, low-dispersion and low loss THz guiding.

    PubMed

    Bao, Hualong; Nielsen, Kristian; Bang, Ole; Jepsen, Peter Uhd

    2015-01-01

    Research on terahertz waveguides is experiencing a tremendous growth due to their importance for compact and robust THz systems. However, designing compact, broadband, mechanically stable and environmentally shielded THz waveguides is still a challenge due to high losses of both metals and dielectrics in this frequency range. Here we report on a novel twist on the classical tube waveguide where we deliberately introduce a thick and highly lossy cladding layer. By this we attenuate the field in the cladding and thus prevent interference with the core field. This mechanism breaks the well-known ARROW guiding mechanism, and as a result, extremely broad bandwidth and low dispersion can be achieved with a very simple design. Since the main part of the field propagates inside the air-core, the propagation loss is still kept at a very low level. Simulations, analytical modelling and experiments verify our findings. The proposed THz waveguide is robust, insensitive to external perturbation and easy to handle, and thus the design represents a significant advance of the field of THz dielectric waveguides suitable for the 0.3-1 THz band which in the future will be important for ultrafast wireless communication systems. PMID:25557284

  8. Dielectric tube waveguides with absorptive cladding for broadband, low-dispersion and low loss THz guiding

    NASA Astrophysics Data System (ADS)

    Bao, Hualong; Nielsen, Kristian; Bang, Ole; Jepsen, Peter Uhd

    2015-01-01

    Research on terahertz waveguides is experiencing a tremendous growth due to their importance for compact and robust THz systems. However, designing compact, broadband, mechanically stable and environmentally shielded THz waveguides is still a challenge due to high losses of both metals and dielectrics in this frequency range. Here we report on a novel twist on the classical tube waveguide where we deliberately introduce a thick and highly lossy cladding layer. By this we attenuate the field in the cladding and thus prevent interference with the core field. This mechanism breaks the well-known ARROW guiding mechanism, and as a result, extremely broad bandwidth and low dispersion can be achieved with a very simple design. Since the main part of the field propagates inside the air-core, the propagation loss is still kept at a very low level. Simulations, analytical modelling and experiments verify our findings. The proposed THz waveguide is robust, insensitive to external perturbation and easy to handle, and thus the design represents a significant advance of the field of THz dielectric waveguides suitable for the 0.3-1 THz band which in the future will be important for ultrafast wireless communication systems.

  9. Initial and Long-Term Movement of Cladding Installed Over Exterior Rigid Insulation

    SciTech Connect

    Baker, Peter

    2014-09-01

    Changes in the International Energy Conservation Code (IECC) from 2009 to 2012 have resulted in the use of exterior rigid insulation becoming part of the prescriptive code requirements. With more jurisdictions adopting the 2012 IECC builders will be required to incorporate exterior insulation in the construction of their exterior wall assemblies. For thick layers of exterior insulation (levels greater than 1.5 inches), the use of wood furring strips attached through the insulation back to the structure has been used by many contractors and designers as a means to provide a convenient cladding attachment location. This research was an extension on previous research conducted by Building Science Corporation in 2011, and 2012. Each year the understanding of the system discrete load component interactions, as well as impacts of environmental loading, has increased. The focus of the research was to examine more closely the impacts of screw fastener bending on the total system capacity, effects of thermal expansion and contraction of materials on the compressive forces in the assembly, as well as to analyze a full year’s worth of cladding movement data from assemblies constructed in an exposed outdoor environment.

  10. U.S. Department of Energy Accident Resistant SiC Clad Nuclear Fuel Development

    SciTech Connect

    George W. Griffith

    2011-10-01

    A significant effort is being placed on silicon carbide ceramic matrix composite (SiC CMC) nuclear fuel cladding by Light Water Reactor Sustainability (LWRS) Advanced Light Water Reactor Nuclear Fuels Pathway. The intent of this work is to invest in a high-risk, high-reward technology that can be introduced in a relatively short time. The LWRS goal is to demonstrate successful advanced fuels technology that suitable for commercial development to support nuclear relicensing. Ceramic matrix composites are an established non-nuclear technology that utilizes ceramic fibers embedded in a ceramic matrix. A thin interfacial layer between the fibers and the matrix allows for ductile behavior. The SiC CMC has relatively high strength at high reactor accident temperatures when compared to metallic cladding. SiC also has a very low chemical reactivity and doesn't react exothermically with the reactor cooling water. The radiation behavior of SiC has also been studied extensively as structural fusion system components. The SiC CMC technology is in the early stages of development and will need to mature before confidence in the developed designs can created. The advanced SiC CMC materials do offer the potential for greatly improved safety because of their high temperature strength, chemical stability and reduced hydrogen generation.

  11. Microstructure and corrosion properties of thick WC composite coating formed by plasma cladding

    NASA Astrophysics Data System (ADS)

    Guozhi, Xie; Xiaolong, Song; Dongjie, Zhang; Yuping, Wu; Pinghua, Lin

    2010-08-01

    The thick Ni-coated WC coatings, in a matrix of Nickel-based alloys, were prepared on AISI 1045 steel using plasma cladding equipment. A pre-placed layer of uniform mixture, with different weight fractions of Ni-coated WC powder and Nickel-based alloy powder, on the steel substrate was melted at the high temperature of the plasma jet. The coating composition, microstructure and microhardness were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectrometer (EDS) and microhardness testing. The experimental results show that the metallurgical bond was formed between the coating and substrate. The XRD results show that the coatings contain γ-Ni, carbides (such as M 23C 6 and M 7C 3) and boride (such as Fe 2B, Fe 3B phases). SEM shows that all the coatings are crack-free with lower porosity (<1%). It is found that the microhardness and the electrochemical behavior of the coatings are depended on the content of Ni-coated WC powder. The corrosion mechanism for the coatings may be due to the microgalvance corrosion between the phases in the cladding coatings.

  12. Influence of optical polarization on the improvement of light extraction efficiency from reflective scattering structures in AlGaN ultraviolet light-emitting diodes

    SciTech Connect

    Wierer, J. J. Allerman, A. A.; Montaño, I.; Moseley, M. W.

    2014-08-11

    The improvement in light extraction efficiency from reflective scattering structures in AlGaN ultraviolet light-emitting diodes (UVLEDs) emitting at ∼270 nm is shown to be influenced by optical polarization. Three UVLEDs with different reflective scattering structures are investigated and compared to standard UVLEDs without scattering structures. The optical polarization and therefore the direction of light propagation within the various UVLEDs are altered by changes in the quantum well (QW) thickness. The improvement in light extraction efficiency of the UVLEDs with reflective scattering structures increases, compared to the UVLEDs without scattering structures, as the fraction of emitted light propagating parallel to the QW plane increases. Additionally, the light extraction efficiency increases as the average distance to the reflective scattering structures decreases.

  13. Migration enhanced lateral epitaxial overgrowth of AlN and AlGaN for high reliability deep ultraviolet light emitting diodes

    NASA Astrophysics Data System (ADS)

    Jain, R.; Sun, W.; Yang, J.; Shatalov, M.; Hu, X.; Sattu, A.; Lunev, A.; Deng, J.; Shturm, I.; Bilenko, Y.; Gaska, R.; Shur, M. S.

    2008-08-01

    We report on the growth of low-defect thick films of AlN and AlGaN on trenched AlGaN/sapphire templates using migration enhanced lateral epitaxial overgrowth. Incoherent coalescence-related defects were alleviated by controlling the tilt angle of growth fronts and by allowing Al adatoms sufficient residence time to incorporate at the most energetically favorable lattice sites. Deep ultraviolet light emitting diode structures (310nm) deposited over fully coalesced thick AlN films exhibited cw output power of 1.6mW at 50mA current with extrapolated lifetime in excess of 5000hours. The results demonstrate substantial improvement in the device lifetime, primarily due to the reduced density of growth defects.

  14. Report on Reactor Physics Assessment of Candidate Accident Tolerant Fuel Cladding Materials in LWRs

    SciTech Connect

    Powers, Jeffrey J.; George, Nathan; Maldonado, G. Ivan; Worrall, Andrew

    2015-08-28

    This work focuses on ATF concepts being researched at Oak Ridge National Laboratory (ORNL), expanding on previous studies of using alternate cladding materials in pressurized water reactors (PWRs). The neutronic performance of two leading alternate cladding materials were assessed in boiling water reactors (BWRs): iron-chromium-aluminum (FeCrAl) cladding, and silicon carbide (SiC)-based composite cladding. This report fulfills ORNL Milestone M3FT-15OR0202332 within the fiscal year 2015 (FY15)

  15. Spot weld attachment of thermocouples to a fuel rod cladding interior surface

    SciTech Connect

    Page, R.E.; Bates, S.O.; Pilger, J.P.

    1984-08-01

    Research was conducted by Pacific Northwest Laboratory to weld 0.020-inch-diameter thermocouples to the interior surface of Zircaloy 4 light-water reactor fuel cladding. Inconel sheathed Type K thermocouples were attached to fuel cladding to register cladding temperatures during loss-of-coolant accident testing. This report describes the development of welding parameters and the effects of thermocouple attachment on the burst strength and integrity of the cladding at temperatures up to 1550/sup 0/F.

  16. Towards refractive index sensitivity of long-period gratings at level of tens of µm per refractive index unit: fiber cladding etching and nano-coating deposition.

    PubMed

    Śmietana, Mateusz; Koba, Marcin; Mikulic, Predrag; Bock, Wojtek J

    2016-05-30

    In this work we report experimental results on optimizing the refractive index (RI) sensitivity of long-period gratings (LPGs) by fiber cladding etching and thin aluminum oxide (Al2O3) overlay deposition. The presented LPG takes advantage of work in the dispersion turning point (DTP) regime as well as the mode transition (MT) effect for higher-order cladding modes (LP09 and LP010). The MT was obtained by depositing Al2O3 overlays with single-nanometer precision using the Atomic Layer Deposition method (ALD). Etching of both the overlay and the fiber cladding was performed using hydrofluoric acid (HF). For shallow etching of the cladding, i.e., DTP observed at next = 1.429 and 1.439 RIU for an LPG with no overlay, followed by deposition of an overlay of up to 167 nm in thickness, HF etching allowed for post-deposition fine-tuning of the overlay thickness resulting in a significant increase in RI sensitivity mainly at the DTP of the LP09 cladding mode. However, at an external RI (next) above 1.39 RIU, the DTP of LP010 was noticed, and its RI sensitivity exceeded 9,000 nm/RIU. Deeper etching of the cladding, i.e., DTP observed for next above 1.45 RIU, followed by the deposition of thicker overlays (up to 201 nm in thickness) allowed the sensitivity to reach values of over 40,000 nm/RIU in a narrow RI range. Sensitivity exceeding 20,000 nm/RIU was obtained in an RI range suitable for label-free biosensing applications. PMID:27410112

  17. ELECTROLYTIC CLADDING OF ZIRCONIUM ON URANIUM

    DOEpatents

    Wick, J.J.

    1959-09-22

    A method is presented for coating uranium with zircoalum by rendering the uranium surface smooth and oxidefree, immersing it in a molten electrolytic bath in NaCI, K/sub 2/ZrF/sub 6/, KF, and ZrO/sub 2/, and before the article reaches temperature equilibrium with the bath, applying an electrolyzing current of 60 amperes per square dectmeter at approximately 3 volts to form a layer of zirconium metal on the uranium.

  18. Effect of Auxiliary Preheating of the Filler Wire on Quality of Gas Metal Arc Stainless Steel Claddings

    NASA Astrophysics Data System (ADS)

    Shahi, Amandeep S.; Pandey, Sunil

    2008-02-01

    Weld cladding is a process for producing surfaces with good corrosion resistant properties by means of depositing/laying of stainless steels on low-carbon steel components with an objective of achieving maximum economy and enhanced life. The aim of the work presented here was to investigate the effect of auxiliary preheating of the solid filler wire in mechanized gas metal arc welding (GMAW) process (by using a specially designed torch to preheat the filler wire independently, before its emergence from the torch) on the quality of the as-welded single layer stainless steel overlays. External preheating of the filler wire resulted in greater contribution of arc energy by resistive heating due to which significant drop in the main welding current values and hence low dilution levels were observed. Metallurgical aspects of the as welded overlays such as chemistry, ferrite content, and modes of solidification were studied to evaluate their suitability for service and it was found that claddings obtained through the preheating arrangement, besides higher ferrite content, possessed higher content of chromium, nickel, and molybdenum and lower content of carbon as compared to conventional GMAW claddings, thereby giving overlays with superior mechanical and corrosion resistance properties. The findings of this study not only establish the technical superiority of the new process, but also, owing to its productivity-enhanced features, justify its use for low-cost surfacing applications.

  19. Building America Case Study: Initial and Long-Term Movement of Cladding Installed Over Exterior Rigid Insulation (Fact Sheet)

    SciTech Connect

    Not Available

    2014-10-01

    Changes in the International Energy Conservation Code (IECC) from 2009 to 2012 have resulted in the use of exterior rigid insulation becoming part of the prescriptive code requirements. With more jurisdictions adopting the 2012 IECC builders are going to finding themselves required to incorporate exterior insulation in the construction of their exterior wall assemblies. For thick layers of exterior insulation (levels greater than 1.5 inches), the use wood furring strips attached through the insulation back to the structure has been used by many contractors and designers as a means to provide a convenient cladding attachment location. However, there has been a significant resistance to its widespread implementation due to a lack of research and understanding of the mechanisms involved and potential creep effects of the assembly under the sustained dead load of a cladding. This research was an extension on previous research conducted by BSC in 2011, and 2012. Each year the understanding of the system discrete load component interactions, as well as impacts of environmental loading has increased. The focus of the research was to examine more closely the impacts of screw fastener bending on the total system capacity, effects of thermal expansion and contraction of materials on the compressive forces in the assembly, as well as to analyze a full years worth of cladding movement data from assemblies constructed in an exposed outdoor environment.

  20. Experimental and numerical investigation on cladding of corrosion-erosion resistant materials by a high power direct diode laser

    NASA Astrophysics Data System (ADS)

    Farahmand, Parisa

    In oil and gas industry, soil particles, crude oil, natural gas, particle-laden liquids, and seawater can carry various highly aggressive elements, which accelerate the material degradation of component surfaces by combination of slurry erosion, corrosion, and wear mechanisms. This material degradation results into the loss of mechanical properties such as strength, ductility, and impact strength; leading to detachment, delamination, cracking, and ultimately premature failure of components. Since the failure of high valued equipment needs considerable cost and time to be repaired or replaced, minimizing the tribological failure of equipment under aggressive environment has been gaining increased interest. It is widely recognized that effective management of degradation mechanisms will contribute towards the optimization of maintenance, monitoring, and inspection costs. The hardfacing techniques have been widely used to enhance the resistance of surfaces against degradation mechanisms. Applying a surface coating improves wear and corrosion resistance and ensures reliability and long-term performance of coated parts. A protective layer or barrier on the components avoids the direct mechanical and chemical contacts of tool surfaces with process media and will reduce the material loss and ultimately its failure. Laser cladding as an advanced hardfacing technique has been widely used for industrial applications in order to develop a protective coating with desired material properties. During the laser cladding, coating material is fused into the base material by means of a laser beam in order to rebuild a damaged part's surface or to enhance its surface function. In the hardfacing techniques such as atmospheric plasma spraying (APS), high velocity oxygen-fuel (HVOF), and laser cladding, mixing of coating materials with underneath surface has to be minimized in order to utilize the properties of the coating material most effectively. In this regard, laser cladding offers

  1. Polarization-matched quaternary superlattice electron blocking layer in blue InGaN light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Kuo, Yen-Kuang; Chen, Fang-Ming; Chang, Jih-Yuan; Lin, Bing-Cheng

    2016-05-01

    The effect of polarization-matched AlInGaN/AlGaN superlattice (SL) electron blocking layer (EBL) on the physical characteristics of blue InGaN light-emitting diodes (LEDs) is investigated numerically. Simulation results show that the optical performance of the LEDs with polarization-matched SL EBL can be markedly improved due to the effectively suppressed polarization effect, enhanced hole injection efficiency, and reduced electron overflow. Comparing to the LEDs with conventional AlGaN EBL, an improvement of 53% in light output power is achieved for the proposed LED structure.

  2. Microstructure and properties of the Ti/Al2O3/NiCr composites fabricated by explosive compaction/cladding.

    PubMed

    Wang, Bingfeng; Xie, Fangyu; Wang, Bin; Luo, Xiaozhou

    2015-05-01

    Titanium/aluminum oxide/nickel chromium (Ti/Al2O3/NiCr) composite bar prepared by explosive compaction/cladding technique represents a new kind of sandwich-structural composites for medical application. Formation of the interfaces of Ti/Al2O3 and Al2O3/NiCr govern the properties of the composite material. The electrical resistivity and microstructure of the intermediate layer and the interfaces of the Ti/Al2O3/NiCr explosive compaction/cladding bar are investigated by means of four-point probe analysis, optical microscopy, scanning electron microscopy, electron microprobe analysis, and X-ray diffraction. The Ti/Al2O3/NiCr composite bar is characterized by the consolidated ceramic intermediate layer and the metallurgical bonding interfaces. The intermediate ceramic layer plays a role of insulation and thermal conductance in this composite. The average shear strength of the composite bar is about 9.36 MPa. The heat affected zone characterized by relatively larger sizes of grains is distinguished from the other part of the Ti tube. The intermetallics AlTi3 and Al0.9Ni4.22 are generated at the intermediate ceramic layer. Formation mechanism of the interfaces of the explosive compaction/cladding bar are described. PMID:25746277

  3. Iridium alloy Clad Vent Set manufacturing qualification studies

    NASA Astrophysics Data System (ADS)

    Ulrich, George B.

    Metallurgical qualification studies to demonstrate the manufacturing readiness of the iridium alloy Clad Vent Set (CVS) for the General Purpose Heat Source program at the Oak Ridge Y-12 Plant are described. Microstructural data for various materials/test conditions are presented.

  4. 78 FR 7451 - Clad Steel Plate From Japan; Determination

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-01

    ..., 2012 (77 FR 5052) and determined on May 7, 2012 that it would conduct a full review (77 FR 37439, June..., 2012 (77 FR 38825). The hearing was held in Washington, DC, on December 6, 2012, and all persons who... COMMISSION Clad Steel Plate From Japan; Determination On the basis of the record \\1\\ developed in the...

  5. Cladding burst behavior of Fe-based alloys under LOCA

    DOE PAGESBeta

    Terrani, Kurt A.; Dryepondt, Sebastien N.; Pint, Bruce A.; Massey, Caleb P.

    2015-12-17

    Burst behavior of austenitic and ferritic Fe-based alloy tubes has been examined under a simulated large break loss of coolant accident. Specifically, type 304 stainless steel (304SS) and oxidation resistant FeCrAl tubes were studied alongside Zircaloy-2 and Zircaloy-4 that are considered reference fuel cladding materials. Following the burst test, characterization of the cladding materials was carried out to gain insights regarding the integral burst behavior. Given the widespread availability of a comprehensive set of thermo-mechanical data at elevated temperatures for 304SS, a modeling framework was implemented to simulate the various processes that affect burst behavior in this Fe-based alloy. Themore » most important conclusion is that cladding ballooning due to creep is negligible for Fe-based alloys. Thus, unlike Zr-based alloys, cladding cross-sectional area remains largely unchanged up to the point of burst. Furthermore, for a given rod internal pressure, the temperature onset of burst in Fe-based alloys appears to be simply a function of the alloy's ultimate tensile strength, particularly at high rod internal pressures.« less

  6. PERSPECTIVE WITH WEST PORTAL. THE BRIDGE IS CLAD IN HORIZONTAL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    PERSPECTIVE WITH WEST PORTAL. THE BRIDGE IS CLAD IN HORIZONTAL CLAPBOARD SIDING AND HAS A SHEET METAL ROOF. NOTE THE TWO OPENINGS THAT RUN THE LENGTH OF THE BRIDGE; ONE IS AT THE EAVES AND THE OTHER IS ABOUT 4’ ABOVE THE DECK. - Dreibelbis Station Bridge, Spanning Maiden Creek, Balthaser Road (TR 745), Lenhartsville, Berks County, PA

  7. Cladding burst behavior of Fe-based alloys under LOCA

    SciTech Connect

    Terrani, Kurt A.; Dryepondt, Sebastien N.; Pint, Bruce A.; Massey, Caleb P.

    2015-12-17

    Burst behavior of austenitic and ferritic Fe-based alloy tubes has been examined under a simulated large break loss of coolant accident. Specifically, type 304 stainless steel (304SS) and oxidation resistant FeCrAl tubes were studied alongside Zircaloy-2 and Zircaloy-4 that are considered reference fuel cladding materials. Following the burst test, characterization of the cladding materials was carried out to gain insights regarding the integral burst behavior. Given the widespread availability of a comprehensive set of thermo-mechanical data at elevated temperatures for 304SS, a modeling framework was implemented to simulate the various processes that affect burst behavior in this Fe-based alloy. The most important conclusion is that cladding ballooning due to creep is negligible for Fe-based alloys. Thus, unlike Zr-based alloys, cladding cross-sectional area remains largely unchanged up to the point of burst. Furthermore, for a given rod internal pressure, the temperature onset of burst in Fe-based alloys appears to be simply a function of the alloy's ultimate tensile strength, particularly at high rod internal pressures.

  8. Optimization of Hydride Rim Formation in Unirradiated Zr 4 Cladding

    SciTech Connect

    Shimskey, Rick W.; Hanson, Brady D.; MacFarlan, Paul J.

    2013-09-30

    The purpose of this work is to build on the results reported in the M2 milestone M2FT 13PN0805051, document number FCRD-USED-2013-000151 (Hanson, 2013). In that work, it was demonstrated that unirradiated samples of zircaloy-4 cladding could be pre-hydrided at temperatures below 400°C in pure hydrogen gas and that the growth of hydrides on the surface could be controlled by changing the surface condition of the samples and form a desired hydride rim on the outside diameter of the cladding. The work performed at Pacific Northwest National Laboratory since the issuing of the M2 milestone has focused its efforts to optimize the formation of a hydride rim on available zircaloy-4 cladding samples by controlling temperature variation and gas flow control during pre-hydriding treatments. Surface conditioning of the outside surface was also examined as a variable. The results of test indicate that much of the variability in the hydride thickness is due to temperature variation occurring in the furnaces as well as how hydrogen gas flows across the sample surface. Efforts to examine other alloys, gas concentrations, and different surface conditioning plan to be pursed in the next FY as more cladding samples become available

  9. Crack resistance curves determination of tube cladding material

    NASA Astrophysics Data System (ADS)

    Bertsch, J.; Hoffelner, W.

    2006-06-01

    Zirconium based alloys have been in use as fuel cladding material in light water reactors since many years. As claddings change their mechanical properties during service, it is essential for the assessment of mechanical integrity to provide parameters for potential rupture behaviour. Usually, fracture mechanics parameters like the fracture toughness KIC or, for high plastic strains, the J-integral based elastic-plastic fracture toughness JIC are employed. In claddings with a very small wall thickness the determination of toughness needs the extension of the J-concept beyond limits of standards. In the paper a new method based on the traditional J approach is presented. Crack resistance curves (J-R curves) were created for unirradiated thin walled Zircaloy-4 and aluminium cladding tube pieces at room temperature using the single sample method. The procedure of creating sharp fatigue starter cracks with respect to optical recording was optimized. It is shown that the chosen test method is appropriate for the determination of complete J-R curves including the values J0.2 (J at 0.2 mm crack length), Jm (J corresponding to the maximum load) and the slope of the curve.

  10. Viscoelastic modelling of Zircaloy cladding in-pile transient creep

    NASA Astrophysics Data System (ADS)

    Tulkki, Ville; Ikonen, Timo

    2015-02-01

    In fuel behaviour modelling accurate description of the cladding stress response is important for both operational and safety considerations. The cladding creep determines in part the width of the gas gap, the duration to pellet-cladding contact and the stresses to the cladding due to the pellet expansion. Conventionally the strain hardening rule has been used to describe the creep response to transient loads in engineering applications. However, it has been well documented that the strain hardening rule does not describe well results of tests with load drops or reversals. In our earlier work we have developed a model for primary creep which can be used to simulate the in- and out-of-pile creep tests. Since then several creep experiments have entered into public domain. In this paper we develop the model formulation based on the theory of viscoelasticity, and show that this model can reproduce the new experimental results. We also show that the creep strain recovery encountered in experimental measurements can be explained by viscoelastic behaviour.

  11. Controlling the stress of growing GaN on 150-mm Si (111) in an AlN/GaN strained layer superlattice

    NASA Astrophysics Data System (ADS)

    Lin, Po-Jung; Huang, Shih-Yung; Wang, Wei-Kai; Chen, Che-Lin; Chung, Bu-Chin; Wuu, Dong-Sing

    2016-01-01

    For growing a thicker GaN epilayer on a Si substrate, generally, a larger wafer bowing with tensile stress caused by the mismatch of thermal expansion coefficients between GaN and Si easily generates a cracked surface during cool down. In this work, wafer bowing was investigated to control stress by changing the thickness of a GaN layer from 18.6 to 27.8 nm in a 80-paired AlN/GaN strained layer superlattice (SLS) grown on a 150-mm Si (111) substrate. The results indicated that wafer bowing was inversely proportional to the total thickness of epilayer and the thickness of the GaN layer in the AlN/GaN SLS, since higher compressive stress caused by a thicker GaN layer during SLS growth could compensate for the tensile stress generated during cool down. After returning to room temperature, the stress of the AlN/GaN SLS was still compressive and strained in the a-axis. This is due to an unintended AlGaN grading layer was formed in the AlN/GaN SLS. This AlGaN layer reduced the lattice mismatch between AlN and GaN and efficiently accumulated stress without causing relaxation.

  12. Perform Tests and Document Results and Analysis of Oxide Layer Effects and Comparisons

    SciTech Connect

    Collins, E. D.; DelCul, G. D.; Spencer, B. B.; Hunt, R. D.; Ausmus, C.

    2014-08-30

    During the initial feasibility test using actual used nuclear fuel (UNF) cladding in FY 2012, an incubation period of 30–45 minutes was observed in the initial dry chlorination. The cladding hull used in the test had been previously oxidized in a dry air oxidation pretreatment prior to removal of the fuel. The cause of this incubation period was attributed to the resistance to chlorination of an oxide layer imparted by the dry oxidation pretreatment on the cladding. Subsequently in 2013, researchers at the Korea Atomic Energy Institute (KAERI) reported on their chlorination study [R1] on ~9-gram samples of unirradiated ZirloTM cladding tubes that had been previously oxidized in air at 500oC for various time periods to impart oxide layers of varying thickness. In early 2014, discussions with Indefinite Delivery, Indefinite Quantity (IDIQ) contracted technical consultants from Westinghouse described their previous development (and patents) [R2] on methods of chemical washing to remove some or all of the hydrous oxide layer imparted on UNF cladding during irradiation in light water reactors (LWRs) . Thus, the Oak Ridge National Laboratory (ORNL) study, described herein, was planned to extend the KAERI study on the effects of anhydrous oxide layers, but on larger ~100-gram samples of unirradiated zirconium alloy cladding tubes, and to investigate the effects of various methods of chemical pretreatment prior to chlorination with 100% chlorine on the average reaction rates and Cl2 usage efficiencies.

  13. Effects of thermal aging and neutron irradiation on the mechanical properties of stainless steel weld overlay cladding

    SciTech Connect

    Haggag, F.M.; Nanstad, R.K.

    1991-01-01

    Stainless steel weld overlay cladding was fabricated using the three-wire, series-arc method. Three layers of cladding were applied to a pressure vessel plate to provide adequate thickness for fabrication of test specimens. Since irradiation of the stainless steel cladding to 5 {times} 10{sup 19} neutrons/cm{sup 2} (>1 MeV) was conducted at 288{degrees}C for 1605 h, tensile, Charpy V-notch (CVN), precracked Charpy V-notch (PCVN), and compact fracture toughness specimens were thermally aged at 288{degrees}C for 1605 h. Additional specimens are being aged to 20,000 and 50,000 h. Thermal aging of three-wire, series-arc stainless steel weld overlay cladding at 288{degrees}C for 1604 h resulted in appreciable decrease (16%) in the CVN upper-shelf energy, but the effect on the 41-J transition temperature shift was very small (3{degrees}C). The combined effect, following neutron irradiation at 288{degrees}C to a fluence of 5 {times} 10{sup 19} neutrons/cm{sup 2} (>MeV), was a 22% reduction in the CVN upper-shelf energy and a 29{degrees}C shift at the 41-J level. The effect of thermal aging on tensile properties was very small or negligible. However, the combined effect after neutron irradiation was an increase in the yield strength (6 to 34% at test temperatures from 288 to {minus}125{degrees}C) and no apparent change in ultimate strength and total elongation. Also, neutron irradiation reduced the initiation fracture toughness (J{sub Ic}) much more than did thermal aging. However, irradiation slightly decreased the tearing modulus, but no reduction was caused by thermal aging alone. The effects of long-term thermal exposure times (20,000 and 50,000 h) will be investigated when the specimen become available.

  14. Effects of thermal aging and neutron irradiation on the mechanical properties of stainless steel weld overlay cladding

    SciTech Connect

    Haggag, F.M.; Nanstad, R.K.

    1991-12-31

    Stainless steel weld overlay cladding was fabricated using the three-wire, series-arc method. Three layers of cladding were applied to a pressure vessel plate to provide adequate thickness for fabrication of test specimens. Since irradiation of the stainless steel cladding to 5 {times} 10{sup 19} neutrons/cm{sup 2} (>1 MeV) was conducted at 288{degrees}C for 1605 h, tensile, Charpy V-notch (CVN), precracked Charpy V-notch (PCVN), and compact fracture toughness specimens were thermally aged at 288{degrees}C for 1605 h. Additional specimens are being aged to 20,000 and 50,000 h. Thermal aging of three-wire, series-arc stainless steel weld overlay cladding at 288{degrees}C for 1604 h resulted in appreciable decrease (16%) in the CVN upper-shelf energy, but the effect on the 41-J transition temperature shift was very small (3{degrees}C). The combined effect, following neutron irradiation at 288{degrees}C to a fluence of 5 {times} 10{sup 19} neutrons/cm{sup 2} (>MeV), was a 22% reduction in the CVN upper-shelf energy and a 29{degrees}C shift at the 41-J level. The effect of thermal aging on tensile properties was very small or negligible. However, the combined effect after neutron irradiation was an increase in the yield strength (6 to 34% at test temperatures from 288 to {minus}125{degrees}C) and no apparent change in ultimate strength and total elongation. Also, neutron irradiation reduced the initiation fracture toughness (J{sub Ic}) much more than did thermal aging. However, irradiation slightly decreased the tearing modulus, but no reduction was caused by thermal aging alone. The effects of long-term thermal exposure times (20,000 and 50,000 h) will be investigated when the specimen become available.

  15. Oxidation of SiC cladding under Loss of Coolant Accident (LOCA) conditions in LWRs

    SciTech Connect

    Lee, Y.; Yue, C.; Arnold, R. P.; McKrell, T. J.; Kazimi, M. S.

    2012-07-01

    An experimental assessment of Silicon Carbide (SiC) cladding oxidation rate in steam under conditions representative of Loss of Coolant Accidents (LOCA) in light water reactors (LWRs) was conducted. SiC oxidation tests were performed with monolithic alpha phase tubular samples in a vertical quartz tube at a steam temperature of 1140 deg. C and steam velocity range of 1 to 10 m/sec, at atmospheric pressure. Linear weight loss of SiC samples due to boundary layer controlled reaction of silica scale (SiO{sub 2} volatilization) was experimentally observed. The weight loss rate increased with increasing steam flow rate. Over the range of test conditions, SiC oxidation rates were shown to be about 3 orders of magnitude lower than the oxidation rates of zircaloy 4. A SiC volatilization correlation for developing laminar flow in a vertical channel is formulated. (authors)

  16. Enhanced Raman scattering assisted by ultrahigh order modes of the double metal cladding waveguide

    SciTech Connect

    Xu, Tian; Huang, Liming; Jin, Yonglong; Fang, Jinghuai E-mail: fjhuai@ntu.edu.cn; Yin, Cheng E-mail: fjhuai@ntu.edu.cn; Huang, Meizhen

    2014-10-20

    Distinguished from the usual strategy to enhance the Raman scattering such as creating hot spots in the surface-enhanced Raman scattering, this paper takes a quite different approach based on the double metal cladding waveguide. The target analyte is located in the guiding layer of sub-millimeter scale, where several ultrahigh order modes with high intensity are simultaneously excited via a focused laser beam. The experimental setup is simple, and both simulation and experimental results confirm the enhancement mechanism of these oscillating modes. Other appealing features include the large detection area and the ability to excite guided modes via both polarizations. This scheme can be applied to large molecules detection and readily integrated with other Raman enhancement techniques.

  17. Examination of frit vent from Sixty-Watt Heat Source simulant fueled clad vent set

    SciTech Connect

    Ulrich, G.B.

    1995-11-01

    The flow rate and the metallurgical condition of a frit vent from a simulant-fueled clad vent set (CVS) that had been hot isostatically pressed (HIP) for the Sixty-Watt Heat Source program were evaluated. The flow rate form the defueled vent cup subassembly was reduced approximately 25% from the original flow rate. No obstructions were found to account for the reduced flow rate. Measurements indicate that the frit vent powder thickness was reduced about 30%. Most likely, the powder was compressed during the HIP operation, which increased the density of the powder layer and thus reduced the flow rate of the assembly. All other observed manufacturing attributes appeared to be normal, but the vent hole activation technique needs further refinement before it is used in applications requiring maximum CVS integrity.

  18. Double-cladding photonic crystal fibers with reduced cladding symmetry for Tm-doped lasers

    NASA Astrophysics Data System (ADS)

    Coscelli, Enrico; Molardi, Carlo; Poli, Federica; Cucinotta, Annamaria; Selleri, Stefano

    2014-05-01

    Innovative Photonic Crystal Fibers (PCF) with optimized air-hole matrix, designed to break the C6ν symmetry of the inner cladding while preserving their feasibility through the well-established stack-and-draw technique, are presented. The possibility to provide stable SM guiding at λ = 2 μm with core diameter up to 80 μm and a coupled pump power exceeding 300 W is analyzed by means of a full-vector modal solver based on the finiteelement method with embedded thermal model, to account for the effects of heating on the mode confinement. Simulation results have shown this approach is effective in providing modal discrimination, allowing selective amplification of the sole fundamental mode due to the delocalization of the high-order modes with mirrorsymmetric field distributions. Effective suppression of the high-order modes under a heat load of 340 W/m, while keeping an effective area exceeding 2500 μm2 has been demonstrated.

  19. Cladding hull decontamination and densification process. Part 1. The prototype cladding hull decontamination system

    SciTech Connect

    Lambright, T.M.; Montgomery, D.R.

    1980-04-01

    A prototype system for decontaminating Zircaloy-4 cladding hulls has been assembled and tested at Pacific Northwest Laboratory. The decontamination process consists of treatment with a gaseous mixture of hydrogen fluoride (HF) and argon (Ar) followed by a dilute aqueous etch of ammonium oxalate, ammonium citrate, ammonium fluoride, and hydrogen peroxide. The continuous cleaning process described in this report successfully descaled small portions of most charges, but was unable to handle the original design capacity of 4 kg/hr because of problems in the following areas: control of HF reactor temperatures, regulation of HF and argon mixtures and flows, isolation of the HF reactor atmosphere from the aqueous washer/rinser atmosphere, regulation of undesirable side reactions, and control over hull transport through the system. Due to the limited time available to solve these problems, the system did not attain fully operational status. The work was performed with unirradiated hulls that simulated irradiated hulls. The system was not built to be remotely operable. The process chemistry and system equipment are described in this report with particular emphasis on critical operating areas. Recommendations for improved system operation are included.

  20. Orientation-Dependent Displacement Sensor Using an Inner Cladding Fiber Bragg Grating.

    PubMed

    Yang, Tingting; Qiao, Xueguang; Rong, Qiangzhou; Bao, Weijia

    2016-01-01

    An orientation-dependent displacement sensor based on grating inscription over a fiber core and inner cladding has been demonstrated. The device comprises a short piece of multi-cladding fiber sandwiched between two standard single-mode fibers (SMFs). The grating structure is fabricated by a femtosecond laser side-illumination technique. Two well-defined resonances are achieved by the downstream both core and cladding fiber Bragg gratings (FBGs). The cladding resonance presents fiber bending dependence, together with a strong orientation dependence because of asymmetrical distribution of the "cladding" FBG along the fiber cross-section. PMID:27626427

  1. Alloy inhomogeneity and carrier localization in AlGaN sections and AlGaN/AlN nanodisks in nanowires with 240–350 nm emission

    SciTech Connect

    Himwas, C.; Hertog, M. den; Dang, Le Si; Songmuang, R.; Monroy, E.

    2014-12-15

    We present structural and optical studies of AlGaN sections and AlGaN/AlN nanodisks (NDs) in nanowires grown by plasma-assisted molecular beam epitaxy. The Al-Ga intermixing at Al(Ga)N/GaN interfaces and the chemical inhomogeneity in AlGaN NDs evidenced by scanning transmission electron microscopy are attributed to the strain relaxation process. This interpretation is supported by the three-dimensional strain distribution calculated by minimizing the elastic energy in the structure. The alloy inhomogeneity increases with the Al content, leading to enhanced carrier localization signatures in the luminescence characteristics, i.e., red shift of the emission, s-shaped temperature dependence, and linewidth broadening. Despite these effects, the emission energy of AlGaN/AlN NDs can be tuned in the 240–350 nm range with internal quantum efficiencies around 30%.

  2. A Novel Method of Modeling the Deformation Resistance for Clad Sheet

    SciTech Connect

    Hu Jianliang; Yi Youping; Xie Mantang

    2011-08-22

    Because of the excellent thermal conductivity, the clad sheet (3003/4004/3003) of aluminum alloy is extensively used in various heat exchangers, such as radiator, motorcar air conditioning, evaporator, and so on. The deformation resistance model plays an important role in designing the process parameters of hot continuous rolling. However, the complex behaviors of the plastic deformation of the clad sheet make the modeling very difficult. In this work, a novel method for modeling the deformation resistance of clad sheet was proposed by combining the finite element analysis with experiments. The deformation resistance model of aluminum 3003 and 4004 was proposed through hot compression test on the Gleeble-1500 thermo-simulation machine. And the deformation resistance model of clad sheet was proposed through finite element analysis using DEFORM-2D software. The relationship between cladding ratio and the deformation resistance was discussed in detail. The results of hot compression simulation demonstrate that the cladding ratio has great effects on the resistance of the clad sheet. Taking the cladding ratio into consideration, the mathematical model of the deformation resistance for clad sheet has been proved to have perfect forecasting precision of different cladding ratio. Therefore, the presented model can be used to predict the rolling force of clad sheet during the hot continuous rolling process.

  3. On microstructure and flexural strength of metal-ceramic composite cladding developed through microwave heating

    NASA Astrophysics Data System (ADS)

    Sharma, Apurbba Kumar; Gupta, Dheeraj

    2012-05-01

    A domestic multimode microwave applicator was used to develop carbide reinforced (tungsten-based) metal-matrix composite cladding on austenitic stainless steel substrate. Cladding was developed through microwave irradiation of the preplaced clad materials at 2.45 GHz for 420 s. Clads show metallurgical bonding with substrate by partial dilution of materials. Back scattered images of clad section confirm uniformly distributed reinforced particles in the metallic matrix. Presence of WC, W2C, NiSi, NiW and Co3W3C phases was detected in the clad. Flexural characteristics show two distinct load transitions attributable to deformations of the matrix and the reinforced particles. Clads fail at the upper transition load; further load is taken by the SS-316 substrate. Clads exhibit good stiffness and good adhesion with the substrate. Multi directional cracks were observed at the clad surface; on further loading, cracks get propagated into the clad thickness without getting peeled-off. Mechanism of clad development has been introduced.

  4. Phase Evolution and Properties of Al2CrFeNiMo x High-Entropy Alloys Coatings by Laser Cladding

    NASA Astrophysics Data System (ADS)

    Wu, Wei; Jiang, Li; Jiang, Hui; Pan, Xuemin; Cao, Zhiqiang; Deng, Dewei; Wang, Tongmin; Li, Tingju

    2015-10-01

    A series of Al2CrFeNiMo x ( x = 0 to 2.0 at.%) high-entropy alloys coatings was synthesized on stainless steel by laser cladding. The effect of Mo content on the microstructures and mechanical properties of Al2CrFeNiMo x coatings was studied. The results show that the laser clad layer consists of the cladding zone, bonding zone, and heat-affected zone. The Al2CrFeNiMo x coatings are composed of two simple body-center cubic phases and the cladding zone is mainly composed of equiaxed grains. When the content of Mo reaches 2 at.%, a eutectic structure is found in the interdendritic regions. The surface microhardness of the Al2CrFeNiMo2 coating is 678 HV, which is about three times higher than that of the substrate (243 HV). Compared with stainless steel, the wear resistance of the coatings has been improved greatly. The wear mass loss of the Al2CrFeNiMo alloy is 9.8 mg, which is much less than that of the substrate (18.9 mg) and its wear scar width is the lowest among the Al2CrFeNiMo x coatings, indicating that the wear resistance of the Al2CrFeNiMo is the best.

  5. Filtration and Leach Testing for PUREX Cladding Sludge and REDOX Cladding Sludge Actual Waste Sample Composites

    SciTech Connect

    Shimskey, Rick W.; Billing, Justin M.; Buck, Edgar C.; Casella, Amanda J.; Crum, Jarrod V.; Daniel, Richard C.; Draper, Kathryn E.; Edwards, Matthew K.; Hallen, Richard T.; Kozelisky, Anne E.; MacFarlan, Paul J.; Peterson, Reid A.; Swoboda, Robert G.

    2009-03-02

    A testing program evaluating actual tank waste was developed in response to Task 4 from the M-12 External Flowsheet Review Team (EFRT) issue response plan (Barnes and Voke 2006). The test program was subdivided into logical increments. The bulk water-insoluble solid wastes that are anticipated to be delivered to the Hanford Waste Treatment and Immobilization Plant (WTP) were identified according to type such that the actual waste testing could be targeted to the relevant categories. Under test plan TP RPP WTP 467 (Fiskum et al. 2007), eight broad waste groupings were defined. Samples available from the 222S archive were identified and obtained for testing. Under this test plan, a waste testing program was implemented that included: • Homogenizing the archive samples by group as defined in the test plan. • Characterizing the homogenized sample groups. • Performing parametric leaching testing on each group for compounds of interest. • Performing bench-top filtration/leaching tests in the hot cell for each group to simulate filtration and leaching activities if they occurred in the UFP2 vessel of the WTP Pretreatment Facility. This report focuses on a filtration/leaching test performed using two of the eight waste composite samples. The sample groups examined in this report were the plutonium-uranium extraction (PUREX) cladding waste sludge (Group 3, or CWP) and reduction-oxidation (REDOX) cladding waste sludge (Group 4, or CWR). Both the Group 3 and 4 waste composites were anticipated to be high in gibbsite, thus requiring caustic leaching. WTP RPT 167 (Snow et al. 2008) describes the homogenization, characterization, and parametric leaching activities before benchtop filtration/leaching testing of these two waste groups. Characterization and initial parametric data in that report were used to plan a single filtration/leaching test using a blend of both wastes. The test focused on filtration testing of the waste and caustic leaching for aluminum, in the form

  6. Fabrication of a tantalum-clad tungsten target for KENS

    NASA Astrophysics Data System (ADS)

    Kawai, Masayoshi; Kikuchi, Kenji; Kurishita, Hiroaki; Li, Jing-Feng; Furusaka, Michihiro

    2001-07-01

    Since the cold neutron source intensity of KENS (the spallation neutron source at High Energy Accelerator Research Organization) was decreased into about a third of the designed value because a cadmium liner at the cold neutron source deformed and obstructed the neutron beam line, the target-moderator-and-reflector assembly (TMRA) has been replaced by a new one aimed at improving the neutron performance and recovering the cold neutron source. The tantalum target has also been replaced by a tantalum-clad tungsten one. In order to bond the tantalum-clad with the tungsten block, a hot isostatic press (HIP) process was applied and optimized. It was found that gaseous interstitial impurity elements severely attacked tantalum and embrittled, and that the getter materials such as zirconium and tantalum were effective to reduce the embrittlement.

  7. HIP-clad products for the plastics industry

    NASA Astrophysics Data System (ADS)

    Bishop, Morley F.; Nickel, Clinton F.

    1999-07-01

    The production of plastics and plastics components requires equipment that can withstand severe wear and, in a high percentage of cases, wear and corrosion environments. There are two basic elements of plastic extrusion equipment: the barrels and the screws. Both must manifest similar properties, but since screw elements are less costly and easier to replace, they are usually designed to wear out first. Due to the high cost of wear/corrosion-resistance materials, the industry used clad (i.e., bimetallic) components. Barrel sections and screw segments are both produced as hot-isostatic press clad components using similar processes. There are any number of material combinations that are used and that are possible for the right application.

  8. Pulsed Magnetic Welding for Advanced Core and Cladding Steel

    SciTech Connect

    Cao, Guoping; Yang, Yong

    2013-12-19

    To investigate a solid-state joining method, pulsed magnetic welding (PMW), for welding the advanced core and cladding steels to be used in Generation IV systems, with a specific application for fuel pin end-plug welding. As another alternative solid state welding technique, pulsed magnetic welding (PMW) has not been extensively explored on the advanced steels. The resultant weld can be free from microstructure defects (pores, non-metallic inclusions, segregation of alloying elements). More specifically, the following objectives are to be achieved: 1. To design a suitable welding apparatus fixture, and optimize welding parameters for repeatable and acceptable joining of the fuel pin end-plug. The welding will be evaluated using tensile tests for lap joint weldments and helium leak tests for the fuel pin end-plug; 2 Investigate the microstructural and mechanical properties changes in PMW weldments of proposed advanced core and cladding alloys; 3. Simulate the irradiation effects on the PWM weldments using ion irradiation.

  9. Clad — Automatic Differentiation Using Clang and LLVM

    NASA Astrophysics Data System (ADS)

    Vassilev, V.; Vassilev, M.; Penev, A.; Moneta, L.; Ilieva, V.

    2015-05-01

    Differentiation is ubiquitous in high energy physics, for instance in minimization algorithms and statistical analysis, in detector alignment and calibration, and in theory. Automatic differentiation (AD) avoids well-known limitations in round-offs and speed, which symbolic and numerical differentiation suffer from, by transforming the source code of functions. We will present how AD can be used to compute the gradient of multi-variate functions and functor objects. We will explain approaches to implement an AD tool. We will show how LLVM, Clang and Cling (ROOT's C++11 interpreter) simplifies creation of such a tool. We describe how the tool could be integrated within any framework. We will demonstrate a simple proof-of-concept prototype, called Clad, which is able to generate n-th order derivatives of C++ functions and other language constructs. We also demonstrate how Clad can offload laborious computations from the CPU using OpenCL.

  10. High Power 938nm Cladding Pumped Fiber Laser

    SciTech Connect

    Dawson, J; Beach, R; Brobshoff, A; Liao, Z; Payne, S; Pennington, D; Taylor, L; Hackenberg, W; Bonaccini, D

    2002-12-26

    We have developed a Nd:doped cladding pumped fiber amplifier, which operates at 938nm with greater than 2W of output power. The core co-dopants were specifically chosen to enhance emission at 938nm. The fiber was liquid nitrogen cooled in order to achieve four-level laser operation on a laser transition that is normally three level at room temperature, thus permitting efficient cladding pumping of the amplifier. Wavelength selective attenuation was induced by bending the fiber around a mandrel, which permitted near complete suppression of amplified spontaneous emission at 1088nm. We are presently seeking to scale the output of this laser to 10W. We will discuss the fiber and laser design issues involved in scaling the laser to the 10W power level and present our most recent results.

  11. Release of fission tritium through Zircaloy-4 fuel cladding tubes

    NASA Astrophysics Data System (ADS)

    Andrieu, C.; Ravel, S.; Ducros, G.; Lemaignan, C.

    2005-12-01

    In order to analyse a potential fission tritium migration from the fuel to the coolant trough the cladding, two experiments of effusion and permeation types, have been performed on 3H release from Zry4 claddings. During the tests at 350 °C, the 3H released activities were measured at regular intervals. In both cases, very fast release rates have been obtained in the first few days, followed by more steady release rates. A correlation has been obtained between the 3H releases measured and the oxide formation kinetics after the initial burst. A mechanism of 3H transport is proposed based on the behaviour of the precipitates during the oxidation of Zry4. Applied to the conditions of PWR fuels, the measurements performed and the mechanisms considered lead to an insignificant contribution of fission tritium permeation to the total inventory of the tritium in the primary coolant.

  12. Package Impact Models as a Precursor to Cladding Analysis

    SciTech Connect

    Klymyshyn, Nicholas A.; Adkins, Harold E.; Bajwa, C.; Piotter, Jason

    2010-07-22

    The evaluation of spent nuclear fuel casks under impact loading is an important safety topic that is reviewed as part of cask certification by the United States Nuclear Regulatory Commission. Explicit dynamic finite element models of full cask systems are increasingly common in industry for determining structural integrity during hypothetical drop accidents. Full cask model results are also used as the loading basis for single fuel pin impact models, which evaluate the response of fuel cladding under drop conditions. In this paper, a simplified cask system is evaluated to illustrate several important structural dynamic phenomena, including the effect of gaps between components, the difference in local response at various points on a cask during impact, and the effect of modeling various simplified representations of the basket and fuel assemblies contained within the cask. This paper focuses on the cask impact analysis, and how loading conditions for a subsequent fuel assembly or fuel cladding analysis can be extracted.

  13. Retrospective dosimetry analyses of reactor vessel cladding samples

    SciTech Connect

    Greenwood, L. R.; Soderquist, C. Z.; Fero, A. H.

    2011-07-01

    Reactor pressure vessel cladding samples for Ringhals Units 3 and 4 in Sweden were analyzed using retrospective reactor dosimetry techniques. The objective was to provide the best estimates of the neutron fluence for comparison with neutron transport calculations. A total of 51 stainless steel samples consisting of chips weighing approximately 100 to 200 mg were removed from selected locations around the pressure vessel and were sent to Pacific Northwest National Laboratory for analysis. The samples were fully characterized and analyzed for radioactive isotopes, with special interest in the presence of Nb-93m. The RPV cladding retrospective dosimetry results will be combined with a re-evaluation of the surveillance capsule dosimetry and with ex-vessel neutron dosimetry results to form a comprehensive 3D comparison of measurements to calculations performed with 3D deterministic transport code. (authors)

  14. Evaluation of Tritium Content and Release from Pressurized Water Reactor Fuel Cladding

    SciTech Connect

    Robinson, Sharon M.; Chattin, Marc Rhea; Giaquinto, Joseph; Jubin, Robert Thomas

    2015-09-01

    It is expected that tritium pretreatment will be required in future reprocessing plants to prevent the release of tritium to the environment (except for long-cooled fuels). To design and operate future reprocessing plants in a safe and environmentally compliant manner, the amount and form of tritium in the used nuclear fuel (UNF) must be understood and quantified. Tritium in light water reactor (LWR) fuel is dispersed between the fuel matrix and the fuel cladding, and some tritium may be in the plenum, probably as tritium labelled water (THO) or T2O. In a standard processing flowsheet, tritium management would be accomplished by treatment of liquid streams within the plant. Pretreating the fuel prior to dissolution to release the tritium into a single off-gas stream could simplify tritium management, so the removal of tritium in the liquid streams throughout the plant may not be required. The fraction of tritium remaining in the cladding may be reduced as a result of tritium pretreatment. Since Zircaloy® cladding makes up roughly 25% by mass of UNF in the United States, processes are being considered to reduce the volume of reprocessing waste for Zircaloy® clad fuel by recovering the zirconium from the cladding for reuse. These recycle processes could release the tritium in the cladding. For Zircaloy-clad fuels from light water reactors, the tritium produced from ternary fission and other sources is expected to be divided between the fuel, where it is generated, and the cladding. It has been previously documented that a fraction of the tritium produced in uranium oxide fuel from LWRs can migrate and become trapped in the cladding. Estimates of the percentage of tritium in the cladding typically range from 0–96%. There is relatively limited data on how the tritium content of the cladding varies with burnup and fuel history (temperature, power, etc.) and how pretreatment impacts its release. To gain a better understanding of how tritium in cladding

  15. Measurement of dispersion in optical fibres with a microstructure cladding

    SciTech Connect

    Levchenko, A E; Kurkov, Andrei S; Semenov, S L

    2005-09-30

    Based on the interferometric technique, a setup is built for measuring the spectral dependence of chromatic dispersion in fibres with a microstructure cladding. The setup provides measurements in a broad spectral range from 670 to 1550 nm taking birefringence in the fibre into account. The results of measurements of dispersion in a standard fibre with this setup and a commercial device are in good agreement. (optical fibres)

  16. DISSOLUTION OF ZIRCALOY 2 CLAD UO2 COMMERCIAL REACTOR FUEL

    SciTech Connect

    Kessinger, G.; Thompson, M.

    2009-08-07

    The primary goal of this investigation was to evaluate the effectiveness of the chop-leach process, with nitric acid solvent, to produce a nominally 300 g/L [U] and 1 M [H{sup +}] product solution. The results of this study show that this processing technique is appropriate for applications in which a low free acid and moderately high U content are desired. The 7.75 L of product solution, which was over 450 g/L in U, was successfully diluted to produce about 13 L of solvent extraction feed that was 302 g/L in U with a [H{sup +}] in the range 0.8-1.2 M. A secondary goal was to test the effectiveness of this treatment for the removal of actinides from Zircaloy cladding to produce a low-level radioactive waste (LLW) cladding product. Analysis of the cladding shows that actinides are present in the cladding at a concentration of about 5000 {eta}Ci/g, which is about 50 times greater than the acceptable transuranium element limit in low level radioactive waste. It appears that the concentration of nitric acid used for this dissolution study (initial concentration 4 M, with 10 M added as the dissolution proceeded) was inadequate to completely digest the UO{sub 2} present in the spent fuel. The mass of insoluble material collected from the initial treatments with nitric acid, 340 g, was much higher than expected, and analysis of this insoluble residue showed that it contained at least 200 g U.

  17. Ion irradiation testing of Improved Accident Tolerant Cladding Materials

    SciTech Connect

    Anderoglu, Osman; Tesmer, Joseph R.; Maloy, Stuart A.

    2014-01-14

    This report summarizes the results of ion irradiations conducted on two FeCrAl alloys (named as ORNL A&B) for improving the accident tolerance of LWR nuclear fuel cladding. After irradiation with 1.5 MeV protons to ~0.5 to ~1 dpa and 300°C nanoindentations were performed on the cross-sections along the ion range. An increase in hardness was observed in both alloys. Microstructural analysis shows radiation induced defects.

  18. Multiresponse Optimization of Laser Cladding Steel + VC Using Grey Relational Analysis in the Taguchi Method

    NASA Astrophysics Data System (ADS)

    Zhang, Zhe; Kovacevic, Radovan

    2016-05-01

    Laser cladding of metal matrix composite coatings (MMCs) has become an effective and economic method to improve the wear resistance of mechanical components. The clad quality characteristics such as clad height, carbide fraction, carbide dissolution, and matrix hardness in MMCs determine the wear resistance of the coatings. These clad quality characteristics are influenced greatly by the laser cladding processing parameters. In this study, American Iron and Steel Institute (AISI) 420 + 20% vanadium carbide (VC) was deposited on mild steel with a high powder direct diode laser. The Taguchi-based Grey relational method was used to optimize the laser cladding processing parameters (laser power, scanning speed, and powder feed rate) with the consideration of multiple clad characteristics related to wear resistance (clad height, carbide volume fraction, and Fe-matrix hardness). A Taguchi L9 orthogonal array was designed to study the effects of processing parameters on each response. The contribution and significance of each processing parameter on each clad characteristic were investigated by the analysis of variance (ANOVA). The Grey relational grade acquired from Grey relational analysis was used as the performance characteristic to obtain the optimal combination of processing parameters. Based on the optimal processing parameters, the phases and microstructure of the laser-cladded coating were characterized by using x-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS).

  19. A specimen and method for evaluating the effect of cladding on the behavior of subclad flaws

    SciTech Connect

    McAfee, W.J.; Bryson, J.W.; Cheverton, R.D.; Robinson, G.C.

    1991-01-01

    A specimen that reveals important fracture-related properties of cladding in the presence of a subclad flaw is under development at the Oak Ridge National Laboratory (ORNL). Information developed from testing these specimens, referred to as Jo-Blocks, is being used by the Heavy-Section Steel Technology (HSST) Program in evaluating the behavior of subclad flaws in Pressurized Water Reactors (PWR) pressure vessels during pressurized-thermal-shock (PTS) loading conditions. The cladding can be idealized as a force that holds an otherwise surface flaw closed'' at the surface, reducing the stress intensity factor along the portion of the crack front in the base material. This closing force is approximately equal to the average stress in the cladding, which for postulated severe PTS transients is at yield, multiplied by the cladding thickness. There is a critical amount of stretching of the cladding that results in through-clad flaw propagation, i.e., cladding failure, thus converting the subclad flaw to a surface flaw. The Jo-Block specimen consists of two steel (base metal) blocks with ends butted together to form a crack'' and with opposite edges clad so that the crack terminates at the two fusion zones. Testing of Jo-Block specimens reveals as a minimum the effective yield point'' of the cladding, in the presence of a subclad crack, and the critical value of clad stretching (crack opening displacement). 15 refs., 10 figs.

  20. Multiresponse Optimization of Laser Cladding Steel + VC Using Grey Relational Analysis in the Taguchi Method

    NASA Astrophysics Data System (ADS)

    Zhang, Zhe; Kovacevic, Radovan

    2016-07-01

    Laser cladding of metal matrix composite coatings (MMCs) has become an effective and economic method to improve the wear resistance of mechanical components. The clad quality characteristics such as clad height, carbide fraction, carbide dissolution, and matrix hardness in MMCs determine the wear resistance of the coatings. These clad quality characteristics are influenced greatly by the laser cladding processing parameters. In this study, American Iron and Steel Institute (AISI) 420 + 20% vanadium carbide (VC) was deposited on mild steel with a high powder direct diode laser. The Taguchi-based Grey relational method was used to optimize the laser cladding processing parameters (laser power, scanning speed, and powder feed rate) with the consideration of multiple clad characteristics related to wear resistance (clad height, carbide volume fraction, and Fe-matrix hardness). A Taguchi L9 orthogonal array was designed to study the effects of processing parameters on each response. The contribution and significance of each processing parameter on each clad characteristic were investigated by the analysis of variance (ANOVA). The Grey relational grade acquired from Grey relational analysis was used as the performance characteristic to obtain the optimal combination of processing parameters. Based on the optimal processing parameters, the phases and microstructure of the laser-cladded coating were characterized by using x-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS).

  1. Microbial biofilm growth on irradiated, spent nuclear fuel cladding

    NASA Astrophysics Data System (ADS)

    Bruhn, D. F.; Frank, S. M.; Roberto, F. F.; Pinhero, P. J.; Johnson, S. G.

    2009-02-01

    A fundamental criticism regarding the potential for microbial influenced corrosion in spent nuclear fuel cladding or storage containers concerns whether the required microorganisms can, in fact, survive radiation fields inherent in these materials. This study was performed to unequivocally answer this critique by addressing the potential for biofilm formation, the precursor to microbial-influenced corrosion, in radiation fields representative of spent nuclear fuel storage environments. This study involved the formation of a microbial biofilm on irradiated spent nuclear fuel cladding within a hot cell environment. This was accomplished by introducing 22 species of bacteria, in nutrient-rich media, to test vessels containing irradiated cladding sections and that was then surrounded by radioactive source material. The overall dose rate exceeded 2 Gy/h gamma/beta radiation with the total dose received by some of the bacteria reaching 5 × 10 3 Gy. This study provides evidence for the formation of biofilms on spent-fuel materials, and the implication of microbial influenced corrosion in the storage and permanent deposition of spent nuclear fuel in repository environments.

  2. Laser surface texturization for high power cladding light stripper

    NASA Astrophysics Data System (ADS)

    Berisset, Michael; Lebrun, Léo.; Faucon, Marc; Kling, Rainer; Boullet, Johan; Aguergaray, Claude

    2016-03-01

    We demonstrated herein a new type of cladding light strippers suitable for high power systems. By precisely micro-machining the surface of the fiber we create CLS with efficiencies as high as 97 % for large NA, multi-mode, cladding light (NA = 0.3), and 70 % for single-mode, low NA, light. The NA of the cladding light is reduced from 0.3 down to 0.08. The CLS exhibit a 1°C/stripped-Watt temperature elevation making them very suitable for high power applications. This fabrication method is simple and reliable. We have tested different texturization geometries on several different fibers: 20/400 from Nufern, KAGOME, and LMA 10 and LMA 15 fibers (results not shown herein) and we observed good efficiencies and temperature elevation behavior for all of them. Finally, large scale production of CLS with this method is possible since the time necessary to prepare on CLS is very small, in the order of few seconds.

  3. Behavior of Zr1%Nb Fuel Cladding under Accident Conditions

    SciTech Connect

    Perez-Fero, E.; Hozer, Z.; Windberg, P.; Nagy, I.; Vimi, A.; Ver, N.; Matus, L.; Kunstar, M.; Novotny, T.; Horvath, M.; Gyori, Cs.

    2007-07-01

    The behavior of the VVER fuel (E110) cladding under accident conditions has been investigated at the AEKI in order to study the role of oxidation and hydrogen uptake on the cladding embrittlement and to understand the phenomena that took place during the Paks-2 cleaning tank incident (2003). The test programme covered small scale tests and large scale tests with electrically heated 7-rod bundles in the CODEX (Core Degradation Experiment) facility. Since a hydrogen rich atmosphere could have been formed in the closed tank, the experiments were carried out in hydrogen-steam mixture. According to the results of the small scale tests, a former correlation for the ductile-brittle transitions of E110 in pure steam remained valid in hydrogen rich steam atmosphere as well. During the large scale tests the main conditions of the incident were reconstructed. The test characterized the high temperature oxidation and embrittlement of zirconium in hydrogen rich steam. The observed cladding failure phenomena and the extent of the damage of the test bundle in the quenching phase were very similar to those of the VVER assemblies in the incident. The simulation of the cleaning tank incident provided detailed information on the most probable scenario of the incident. (authors)

  4. Microbial Biofilm Growth on Irradiated, Spent Nuclear Fuel Cladding

    SciTech Connect

    S.M. Frank

    2009-02-01

    A fundamental criticism regarding the potential for microbial influenced corrosion in spent nuclear fuel cladding or storage containers concerns whether the required microorganisms can, in fact, survive radiation fields inherent in these materials. This study was performed to unequivocally answer this critique by addressing the potential for biofilm formation, the precursor to microbial-influenced corrosion, in radiation fields representative of spent nuclear fuel storage environments. This study involved the formation of a microbial biofilm on irradiated spent nuclear fuel cladding within a hot cell environment. This was accomplished by introducing 22 species of bacteria, in nutrient-rich media, to test vessels containing irradiated cladding sections and that was then surrounded by radioactive source material. The overall dose rate exceeded 2 Gy/h gamma/beta radiation with the total dose received by some of the bacteria reaching 5 × 103 Gy. This study provides evidence for the formation of biofilms on spent-fuel materials, and the implication of microbial influenced corrosion in the storage and permanent deposition of spent nuclear fuel in repository environments.

  5. Failure of TRIGA fuel cladding at the Berkeley research reactor

    SciTech Connect

    Denton, Michael M.; Lim, Tek H.

    1986-07-01

    Following a long maintenance shutdown during which a fission chamber was refurbished and a compensated ion chamber replaced, concentrations of radioisotopes were detected in the reactor-room air on a Constant (CAM) after two and a half hours of full-power operation. Following test lead to identification of three fission-product gasses in the reactor room air: Kr{sup 85m}, Kr{sup 87} , and Kr{sup 88} . Conservative estimates indicated the maximum concentrations of all fission gasses to be about 1.1x10{sup -8} {mu}Ci/ml with a total release of less than 1 mCi. It was concluded that the gasses come from a leaking fuel element. Three old, instrumented elements with defective thermocouples were removed first and the reactor was tested at full-power. No abnormal activities were detected during or following the operation. Each of the suspected fuel elements are instrumented with leadout tubes extending 15 feet to above the pool surface. This suggests some possible causes for the cladding failure. First, flexing due to daily movement of the core could have weakened the tube/cladding connection. Secondly, the cladding itself may have been damaged during maintenance procedures requiring removal of the elements or repositioning of the leadout tubes.

  6. Metallography of pitted aluminum-clad, depleted uranium fuel

    SciTech Connect

    Nelson, D.Z.; Howell, J.P.

    1994-12-01

    The storage of aluminum-clad fuel and target materials in the L-Disassembly Basin at the Savannah River Site for more than 5 years has resulted in extensive pitting corrosion of these materials. In many cases the pitting corrosion of the aluminum clad has penetrated in the uranium metal core, resulting in the release of plutonium, uranium, cesium-137, and other fission product activity to the basin water. In an effort to characterize the extent of corrosion of the Mark 31A target slugs, two unirradiated slug assemblies were removed from basin storage and sent to the Savannah River Technology Center for evaluation. This paper presents the results of the metallography and photographic documentation of this evaluation. The metallography confirmed that pitting depths varied, with the deepest pit found to be about 0.12 inches (3.05 nun). Less than 2% of the aluminum cladding was found to be breached resulting in less than 5% of the uranium surface area being affected by corrosion. The overall integrity of the target slug remained intact.

  7. Oxidation of Zircaloy Fuel Cladding in Water-Cooled Nuclear Reactors

    SciTech Connect

    Macdonald, Digby; Urquidi-Macdonald, Mirna; Chen, Yingzi; Ai, Jiahe; Park, Pilyeon; Kim, Han-Sang

    2006-12-12

    Our work involved the continued development of the theory of passivity and passivity breakdown, in the form of the Point Defect Model, with emphasis on zirconium and zirconium alloys in reactor coolant environments, the measurement of critically-important parameters, and the development of a code that can be used by reactor operators to actively manage the accumulation of corrosion damage to the fuel cladding and other components in the heat transport circuits in both BWRs and PWRs. In addition, the modified boiling crevice model has been further developed to describe the accumulation of solutes in porous deposits (CRUD) on fuel under boiling (BWRs) and nucleate boiling (PWRs) conditions, in order to accurately describe the environment that is contact with the Zircaloy cladding. In the current report, we have derived expressions for the total steady-state current density and the partial anodic and cathodic current densities to establish a deterministic basis for describing Zircaloy oxidation. The models are “deterministic” because the relevant natural laws are satisfied explicitly, most importantly the conversation of mass and charge and the equivalence of mass and charge (Faraday’s law). Cathodic reactions (oxygen reduction and hydrogen evolution) are also included in the models, because there is evidence that they control the rate of the overall passive film formation process. Under open circuit conditions, the cathodic reactions, which must occur at the same rate as the zirconium oxidation reaction, are instrumental in determining the corrosion potential and hence the thickness of the barrier and outer layers of the passive film. Controlled hydrodynamic methods have been used to measure important parameters in the modified Point Defect Model (PDM), which is now being used to describe the growth and breakdown of the passive film on zirconium and on Zircaloy fuel sheathing in BWRs and PWRs coolant environments. The modified PDMs recognize the existence of a

  8. Analysis of transmission characteristics of doubly clad fibers with an inner cladding made of uniaxial crystal materials

    NASA Astrophysics Data System (ADS)

    Xiaoping, Zhang; Zhihong, Tan

    2002-04-01

    A doubly clad optical fiber with an inner cladding made of a uniaxial crystal material whose optical axis is parallel to the fiber axis was proposed, and exact characteristic equations of vector modes were derived. The influence of the ratio ( kcl) of the extraordinary to the ordinary ray indexes upon the waveguide dispersion was examined in detail. In view of the impossibility to deduce the expression of waveguide dispersion directly due to the complexity of the characteristic equations, a feasible approach to calculate waveguide dispersion was established. The calculated results indicate that the values of waveguide dispersion can be effectively changed through variation of kcl without changing the geometrical and optical parameters ( S and R). The influences of kcl, S and R on the propagation and cutoff characteristics of the low order modes are also analyzed.

  9. Final report on accident tolerant fuel performance analysis of APMT-Steel Clad/UO₂ fuel and APMT-Steel Clad/UN-U₃Si₅ fuel concepts

    SciTech Connect

    Unal, Cetin; Galloway, Jack D.

    2014-09-12

    In FY2014 our group completed and documented analysis of new Accident Tolerant Fuel (ATF) concepts using BISON. We have modeled the viability of moving from Zircaloy to stainless steel cladding in traditional light water reactors (LWRs). We have explored the reactivity penalty of this change using the MCNP-based burnup code Monteburns, while attempting to minimize this penalty by increasing the fuel pellet radius and decreasing the cladding thickness. Fuel performance simulations using BISON have also been performed to quantify changes to structural integrity resulting from thinner stainless steel claddings. We account for thermal and irradiation creep, fission gas swelling, thermal swelling and fuel relocation in the models for both Zircaloy and stainless steel claddings. Additional models that account for the lower oxidation stainless steel APMT are also invoked where available. Irradiation data for HT9 is used as a fallback in the absence of appropriate models. In this study the isotopic vectors within each natural element are varied to assess potential reactivity gains if advanced enrichment capabilities were levied towards cladding technologies. Recommendations on cladding thicknesses for a robust cladding as well as the constitutive components of a less penalizing composition are provided. In the first section (section 1-3), we present results accepted for publication in the 2014 TOPFUEL conference regarding the APMT/UO₂ ATF concept (J. Galloway & C. Unal, Accident Tolerant and Neutronically Favorable LWR Cladding, Proceedings of WRFPM 2014, Sendai, Japan, Paper No.1000050). Next we discuss our preliminary findings from the thermo-mechanical analysis of UN-U₃Si₅ fuel with APMT clad. In this analysis we used models developed from limited data that need to be updated when the irradiation data from ATF-1 test is available. Initial results indicate a swelling rate less than 1.5% is needed to prevent excessive clad stress.

  10. Interface control technologies for high-power GaN transistors: Self-stopping etching of p-GaN layers utilizing electrochemical reactions

    NASA Astrophysics Data System (ADS)

    Sato, Taketomo; Kumazaki, Yusuke; Edamoto, Masaaki; Akazawa, Masamichi; Hashizume, Tamotsu

    2016-02-01

    The selective and low-damaged etching of p-type GaN or AlGaN layer is inevitable process for AlGaN/GaN high-power transistors. We have investigated an electrochemical etching of p-GaN layer grown on AlGaN/GaN heterostructures, consisting of an anodic oxidation of p-GaN surface and a subsequent dissolution of the resulting oxide. The p-GaN layer was electrochemically etched by following the pattern of the SiO2 film that acted as an etching mask. Etching depth was linearly controlled by cycle number of triangular waveform at a rate of 25 nm/cycle. The AFM, TEM and μ-AES results showed that the top p-GaN layer was completely removed after 5 cycles applied, and the etching reaction was automatically sopped on the AlGaN surface. I-V and C-V measurements revealed that no significant damages were induced in the AlGaN/GaN heterostructures.

  11. Design and optimization of terahertz directional coupler based on hybrid-cladding hollow waveguide with low confinement loss

    NASA Astrophysics Data System (ADS)

    Yu, Ying-Ying; Li, Xu-You; Sun, Bo; He, Kun-Peng

    2015-06-01

    We propose a design and optimization for directional coupling in terahertz hybrid-cladding hollow waveguide. It is composed of two square hollow waveguides which touch each other and are surrounded by a metallic layer. By employing the finite element method, the coupling performance and loss property are numerically investigated. Numerical results indicate that this directional coupler with hybrid-cladding can realize ultra-narrow-band coupling; it provides a low confinement loss performance: the confinement loss can reach as low as 6.27 × 10-5 cm-1. Moreover, the further analyses of configuration and performance show that confinement loss and frequency range shift for the low-confinement-loss frequency regime can be realized and optimized by appropriately tuning the thickness values of the metallic and dielectric layer. In addition, through the further analysis of coupling performance, the possibilities of realizing ultra-narrow-band couplings in different frequency ranges are demonstrated. It is a powerful candidate for high precision optical fiber sensing, and communication in terahertz splitting fields. Project supported by the Specific Scientific and Technological Cooperation between China and Russia (Grant No. 2010DFR80140) and the National Natural Science Foundation of China (Grant No. 51309059).

  12. Study of oxide and α-Zr(O) growth kinetics from high temperature steam oxidation of Zircaloy-4 cladding

    NASA Astrophysics Data System (ADS)

    Sawarn, Tapan K.; Banerjee, Suparna; Samanta, Akanksha; Rath, B. N.; Kumar, Sunil

    2015-12-01

    Oxidation kinetics of Zircaloy-4 cladding of fuel pins of Indian pressurized heavy water reactors (IPHWRs) under a simulated loss of coolant accident (LOCA) condition was investigated. The kinetic rate constants for the oxide and oxygen stabilized α-Zr phase growth were established from the isothermal metal-steam reaction at high temperatures (900-1200 °C) with soaking periods in the range of 60-900 s. Oxide and α-Zr(O) layer thickness were measured to derive the respective growth rates. The observed rates obeyed a parabolic law and Arrhenius expressions of rate constants were established. Percentage equivalent clad reacted (%ECR) was calculated using Baker-Just equation. Hydrogen estimation was carried out on the oxidized samples using inert gas fusion technique. The hydrogen pick up was found to be in the range 10-30 ppm. The measured values of oxide and α-Zr(O) layer thickness were compared with the results obtained using OXYCON, an indigenously developed model. The model predicts the oxide growth reasonably well but under predicts the α-Zr(O) growth significantly at thickness values higher than 80 μm.

  13. Surface-plasmon-enhanced deep-UV light emitting diodes based on AlGaN multi-quantum wells

    PubMed Central

    Gao, Na; Huang, Kai; Li, Jinchai; Li, Shuping; Yang, Xu; Kang, Junyong

    2012-01-01

    We report the development of complete structural AlGaN-based deep-ultraviolet light-emitting diodes with an aluminum thin layer for increasing light extraction efficiency. A 217% enhancement in peak photoluminescence intensity at 294 nm is observed. Cathodoluminescence measurement demonstrates that the internal quantum efficiency of the deep-UV LEDs coated with Al layer is not enhanced. The emission enhancement of deep-UV LEDs is attributed to the higher LEE by the surface plasmon-transverse magnetic wave coupling. When the proportion of the TM wave to the Al layer increases with the Al content in the AlxGa1-xN multiple quantum wells, i.e., the band edge emission energy, the enhancement ratio of the Al-coated deep-UV LEDs increases. PMID:23150780

  14. The Deformation of Clad Aluminum Sheet Produced By Direct Chill Casting

    NASA Astrophysics Data System (ADS)

    Lloyd, David J.; Gallerneault, Mark; Wagstaff, Robert B.

    2010-08-01

    The tensile and bending response of AA3003/AA6111 sheet produced by direct chill casting has been investigated. It is shown that the interface strength of the clad sheet has a minimum value of 175 MPa, and failure does not occur in the interface. The yield strength of the clad sheet obeys the rule of mixtures, and up to a cladding thickness of 100 μm—which was the thickest investigated—the work hardening behavior and tensile response are essentially unaffected by the presence of the cladding. The bending response of the sheet is improved greatly by the presence of ductile cladding, which was the case for prestrained and aged sheet. Under bending, failure is initiated in the lower bendability core and then eventually propagates through the more ductile cladding, which yields the final bend failure.

  15. An improved method for stripping cladding light in high power fiber lasers

    NASA Astrophysics Data System (ADS)

    Li, Tenglong; Wu, Juan; Sun, Yinghong; Wang, Yanshan; Ma, Yi

    2015-02-01

    In order to ensure the high power all-fiber laser reliability and excellent beam quality, it is necessary to strip the unwanted cladding light. The common method for stripping cladding light is to recoat the double cladding fiber with a high index gel, but localized heating and low thermal conductivity of the recoating gel are the prime factors limiting the power-handling capability of the cladding power stripper(CPS). An improved fabrication technique to manufacture the CPS is presented. Light stripping section of the fiber is fused with a transparent quartz tube, by applying different amount of etchant along the quartz tube, frosted surface is created and uniformly removal of the cladding light is achieved. The quartz tube is joined to water-cooled thermal enclosure tightly without the gel to avoid heat aggregation. The power-handling capability of the device is tested under 200W of cladding light, and attenuation of 20 dB is achieved.

  16. Method and etchant to join Ag-clad BSSCO superconducting tape

    DOEpatents

    Balachandran, U.; Iyer, A.N.; Huang, J.Y.

    1999-03-16

    A method of removing a silver cladding from high temperature superconducting material clad in silver (HTS) is disclosed. The silver clad HTS is contacted with an aqueous solution of HNO{sub 3} followed by an aqueous solution of NH{sub 4}OH and H{sub 2}O{sub 2} for a time sufficient to remove the silver cladding from the superconducting material without adversely affecting the superconducting properties of the superconducting material. A portion of the silver cladding may be masked with a material chemically impervious to HNO{sub 3} and to a combination of NH{sub 4}OH and H{sub 2}O{sub 2} to preserve the Ag coating. A silver clad superconductor is disclosed, made in accordance with the method discussed. 3 figs.

  17. Method and etchant to join ag-clad BSSCO superconducting tape

    DOEpatents

    Balachandran, Uthamalingam; Iyer, Anand N.; Huang, Jiann Yuan

    1999-01-01

    A method of removing a silver cladding from high temperature superconducting material clad in silver (HTS) is disclosed. The silver clad HTS is contacted with an aqueous solution of HNO.sub.3 followed by an aqueous solution of NH.sub.4 OH and H.sub.2 O.sub.2 for a time sufficient to remove the silver cladding from the superconducting material without adversely affecting the superconducting properties of the superconducting material. A portion of the silver cladding may be masked with a material chemically impervious to HNO.sub.3 and to a combination of NH.sub.4 OH and H.sub.2 O.sub.2 to preserve the Ag coating. A silver clad superconductor is disclosed, made in accordance with the method discussed.

  18. Analysis and optimization of process parameters in Al-SiCp laser cladding

    NASA Astrophysics Data System (ADS)

    Riquelme, Ainhoa; Rodrigo, Pilar; Escalera-Rodríguez, María Dolores; Rams, Joaquín

    2016-03-01

    The laser cladding process parameters have great effect on the clad geometry and on dilution in the single and multi-pass aluminum matrix composite reinforced with SiC particles (Al/SiCp) coatings on ZE41 magnesium alloys deposited using a high-power diode laser (HPLD). The influence of the laser power (500-700 W), scan speed (3-17 mm/s) and laser beam focal position (focus, positive and negative defocus) on the shape factor, cladding-bead geometry, cladding-bead microstructure (including the presence of pores and cracks), and hardness has been evaluated. The correlation of these process parameters and their influence on the properties and ultimately, on the feasibility of the cladding process, is demonstrated. The importance of focal position is demonstrated. The different energy distribution of the laser beam cross section in focus plane or in positive and negative defocus plane affect on the cladding-bead properties.

  19. Thermodynamic Stability and Redistribution of Charges in Ternary AlGaN, InGaN, and InAlN Alloys

    SciTech Connect

    Deibuk, V.G.; Voznyi, A.V.

    2005-06-15

    A model of the delta lattice parameter is used to study the thermodynamics of AlGaN, InGaN, and InAlN alloys. The phase diagrams obtained indicate that Al{sub x}Ga{sub 1-x}N is stable in the entire range of x, whereas the miscibility gap corresponds to 0.2 < x < 0.69 for In{sub x}Ga{sub 1-x}N and to 0.16 < x < 0.7 for In{sub x}Al{sub 1-x}N at 1000 K. Biaxial stresses lower the critical temperature and narrow the miscibility gap. The charge-density distribution is analyzed using the pseudopotential method to obtain an approximation of 32-atom supercells. The results of the analysis show that the stability of these alloys is controlled by the competition between the destabilizing contribution of strains related to the mismatch between the lattice constants and a stabilizing charge exchange between various chemical bonds. Biaxial stress reduces the charge redistribution caused by strains and thus increases the stability of an alloy.

  20. Low-ohmic-contact-resistance V-based electrode for n-type AlGaN with high AlN molar fraction

    NASA Astrophysics Data System (ADS)

    Mori, Kazuki; Takeda, Kunihiro; Kusafuka, Toshiki; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi

    2016-05-01

    We investigated a V-based electrode for the realization of low ohmic-contact resistivity in n-type AlGaN with a high AlN molar fraction characterized by the circular transmission line model. The contact resistivity of n-type Al0.62Ga0.38N prepared using the V/Al/Ni/Au electrode reached 1.13 × 10‑6 Ω cm2. Using this electrode, we also demonstrated the fabrication of UV light-emitting diodes (LEDs) with an emission wavelength of approximately 300 nm. An operating voltage of LED prepared using a V/Al/Ni/Au electrode was 1.6 V lower at 100 mA current injection than that prepared using a Ti/Al/Ti/Au electrode, with a specific contact resistance of approximately 2.36 × 10‑4 Ω cm2 for n-type Al0.62Ga0.38N.