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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. AlGaN-Cladding-Free m-Plane InGaN/GaN Laser Diodes with p-Type AlGaN Etch Stop Layers

    NASA Astrophysics Data System (ADS)

    Farrell, Robert M.; Haeger, Daniel A.; Hsu, Po Shan; Hardy, Matthew T.; Kelchner, Kathryn M.; Fujito, Kenji; Feezell, Daniel F.; Mishra, Umesh K.; DenBaars, Steven P.; Speck, James S.; Nakamura, Shuji

    2011-09-01

    We present a new method of improving the accuracy and reproducibility of dry etching processes for ridge waveguide InGaN/GaN laser diodes (LDs). A GaN:Al0.09Ga0.91N etch rate selectivity of 11:1 was demonstrated for an m-plane LD with a 40 nm p-Al0.09Ga0.91N etch stop layer (ESL) surrounded by Al-free cladding layers, establishing the effectiveness of AlGaN-based ESLs for controlling etch depth in ridge waveguide InGaN/GaN LDs. These results demonstrate the potential for integrating AlGaN ESLs into commercial device designs where accurate control of the etch depth of the ridge waveguide is necessary for stable, kink-free operation at high output powers.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Improved color rendering of phosphor-converted white light-emitting diodes with dual-blue active layers and n-type AlGaN layer.

    PubMed

    Yan, Qi-Rong; Zhang, Yong; Li, Shu-Ti; Yan, Qi-Ang; Shi, Pei-Pei; Niu, Qiao-Li; He, Miao; Li, Guo-Ping; Li, Jun-Rui

    2012-05-01

    An InGaN/GaN blue light-emitting diode (LED) structure and an InGaN/GaN blue-violet LED structure were grown sequentially on the same sapphire substrate by metal-organic chemical vapor deposition. It was found that the insertion of an n-type AlGaN layer below the dual blue-emitting active layers showed better spectral stability at the different driving current relative to the traditional p-type AlGaN electron-blocking layer. In addition, color rendering index of a Y3Al5O12:Ce3+ phosphor-converted white LED based on a dual blue-emitting chip with n-type AlGaN reached 91 at 20 mA, and Commission Internationale de L'Eclairage coordinates almost remained at the same point from 5 to 60 mA.

  8. 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.

  9. From Schottky to Ohmic graphene contacts to AlGaN/GaN heterostructures: Role of the AlGaN layer microstructure

    SciTech Connect

    Fisichella, G.; Greco, G.; Roccaforte, F.; Giannazzo, F.

    2014-08-11

    The electrical behaviour of graphene (Gr) contacts to Al{sub x}Ga{sub 1−x}N/GaN heterostructures has been investigated, focusing, in particular, on the impact of the AlGaN microstructure on the current transport at Gr/AlGaN interface. Two Al{sub 0.25}Ga{sub 0.75}N/GaN heterostructures with very different quality in terms of surface roughness and defectivity, as evaluated by atomic force microscopy (AFM) and transmission electron microscopy, were compared in this study, i.e., a uniform and defect-free sample and a sample with a high density of typical V-defects, which locally cause a reduction of the AlGaN thickness. Nanoscale resolution current voltage (I-V) measurements by an Au coated conductive AFM tip were carried out at several positions both on the bare and Gr-coated AlGaN surfaces. Rectifying contacts were found onto both bare AlGaN surfaces, but with a more inhomogeneous and lower Schottky barrier height (Φ{sub B} ≈ 0.6 eV) for AlGaN with V-defects, with respect to the case of the uniform AlGaN (Φ{sub B} ≈ 0.9 eV). Instead, very different electrical behaviours were observed in the presence of the Gr interlayer between the Au tip and AlGaN, i.e., a Schottky contact with reduced barrier height (Φ{sub B} ≈ 0.4 eV) for the uniform AlGaN and an Ohmic contact for the AlGaN with V-defects. Interestingly, excellent lateral uniformity of the local I-V characteristics was found in both cases and can be ascribed to an averaging effect of the Gr electrode over the AlGaN interfacial inhomogeneities. Due to the locally reduced AlGaN layer thickness, V defect act as preferential current paths from Gr to the 2DEG and can account for the peculiar Ohmic behaviour of Gr contacts on defective AlGaN.

  10. Reduction in leakage current in AlGaN/GaN HEMT with three Al-containing step-graded AlGaN buffer layers on silicon

    NASA Astrophysics Data System (ADS)

    Yu, Xinxin; Ni, Jinyu; Li, Zhonghui; Zhou, Jianjun; Kong, Cen

    2014-05-01

    AlGaN/GaN high-electron-mobility transistor (HEMT) structures with two and three Al-containing step-graded AlGaN buffer layers (BLs) were grown on silicon (111) substrates by metal organic chemical vapor deposition. Considerable tensile stress was observed in the GaN grown with only two 0.8 µm AlGaN BLs, while a large in-plane compression in GaN grown with three 2.3 µm AlGaN BLs. The reverse gate leakage current in the HEMT with three AlGaN BLs was approximately 0.1 µA/mm, which was more than one order of magnitude smaller than that for the HEMT with two AlGaN BLs. A three-terminal off-state breakdown voltage of 265 V and a vertical gate-to-substrate breakdown voltage of 510 V were obtained in the HEMT with three AlGaN BLs. Detailed analysis was performed on the basis of the structural properties of AlGaN/GaN heterostructures.

  11. 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.

  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. Influence of thermal stress on the relative permittivity of the AlGaN barrier layer in an AlGaN/GaN heterostructure Schottky contacts

    NASA Astrophysics Data System (ADS)

    Lü, Yuan-Jie; Lin, Zhao-Jun; Zhang, Yu; Meng, Ling-Guo; Cao, Zhi-Fang; Luan, Chong-Biao; Chen, Hong; Wang, Zhan-Guo

    2011-09-01

    Ni Schottky contacts on AlGaN/GaN heterostructures were fabricated. Some samples were thermally treated in a furnace with N2 ambience at 600 °C for different times (0.5 h, 4.5 h, 10.5 h, 18 h, 33 h, 48 h, and 72 h), the others were thermally treated for 0.5 h at different temperatures (500 °C, 600 °C, 700 °C, and 800 °C). With the measured current—voltage (I—V) and capacitance—voltage (C—V) curves and by self-consistently solving Schrodinger's and Poisson's equations, we found that the relative permittivity of the AlGaN barrier layer was related to the piezoelectric and the spontaneous polarization of the AlGaN barrier layer. The relative permittivity was in proportion to the strain of the AlGaN barrier layer. The relative permittivity and the strain reduced with the increased thermal stress time until the AlGaN barrier totally relaxed (after 18 h at 600 °C in the current study), and then the relative permittivity was almost a constant with the increased thermal stress time. When the sample was treated at 800 °C for 0.5 h, the relative permittivity was less than the constant due to the huge diffusion of the contact metal atoms. Considering the relation between the relative permittivity of the AlGaN barrier layer and the converse piezoelectric effect, the conclusion can be made that a moderate thermal stress can restrain the converse piezoelectric effect and can improve the stability of AlGaN/GaN heterostructure devices.

  14. 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.

  15. Defects reduction in a-plane AlGaN epi-layers grown on r-plane sapphire substrates by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Zhao, Jianguo; Zhang, Xiong; Dai, Qian; Wang, Nan; Wu, Zili; Wang, Shuchang; Cui, Yiping

    2017-01-01

    Nonpolar a-plane AlGaN epi-layers were grown on a semi-polar r-plane sapphire substrate with an innovative two-way pulsed-flows metal organic chemical vapor deposition growth technology. A root-mean-square value of 1.79 nm was achieved, and the relative light transmittance of the a-plane AlGaN epi-layer was enhanced by 36.9%. These results reveal that the innovative growth method is able to improve the surface morphology and reduce the defect density in nonpolar a-plane Al x Ga1- x N epi-layers, particularly those with an Al composition greater than 0.5, which are key materials for the fabrication of nonpolar AlGaN-based high light emission efficiency deep-ultraviolet light-emitting diodes.

  16. Dislocation blocking by AlGaN hot electron injecting layer in the epitaxial growth of GaN terahertz Gunn diode

    NASA Astrophysics Data System (ADS)

    Li, Liang; Yang, Lin'an; Zhang, Jincheng; Hao, Yue

    2013-09-01

    This paper reports an efficient method to improve the crystal quality of GaN Gunn diode with AlGaN hot electron injecting layer (HEI). An evident reduction of screw dislocation and edge dislocation densities is achieved by the strain management and the enhanced lateral growth in high temperature grown AlGaN HEI layer. Compared with the top hot electron injecting layer (THEI) structure, the bottom hot electron injecting layer (BHEI) structure enhances the crystal quality of transit region due to the growth sequence modulation of HEI layer. A high Hall mobility of 2934 cm2/Vs at 77 K, a nearly flat downtrend of Hall mobility at the temperature ranging from 300 to 573 K, a low intensity of ratio of yellow luminescence band to band edge emission, a narrow band edge emission line-width, and a smooth surface morphology are observed for the BHEI structural epitaxy of Gunn diode, which indicates that AlGaN BHEI structure is a promising candidate for fabrication of GaN Gunn diodes in terahertz regime.

  17. 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.

  18. Application of spectral ellipsometry to in situ diagnostics of atomic layer deposition of dielectrics on silicon and AlGaN

    NASA Astrophysics Data System (ADS)

    Clemente, Iosif E.; Miakonkikh, Andrey V.

    2016-12-01

    Atomic layer deposition (ALD) of Al2O3 on Si and AlGaN substrates was studied in situ by means of spectral ellipsometry. Method was used for optimization of process of atomic layer deposition. Optical model takes into account all layers of transparent structure typical for gallium nitride devices Al2O3/AlGaN/AlN/GaN. Developed model is able to measure in situ temperature of wafer before the process and its change during the deposition which is critical for development of new process and understanding of chemical reactions. Difference in temperature between chuck and sample were calculated. Spectral ellipsometry was used to determine initial nucleation lag of film growth which is different on silicon and AlGaN surface and chemical transient during the first steps of deposition. Removal of native oxide in AlGaN structures could play key role in observed effects of passivation GaN transistor structures by alumina.

  19. 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.

  20. 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.

  1. Growth and Implementation of Carbon-Doped AlGaN Layers for Enhancement-Mode HEMTs on 200 mm Si Substrates

    NASA Astrophysics Data System (ADS)

    Su, Jie; Posthuma, Niels; Wellekens, Dirk; Saripalli, Yoga N.; Decoutere, Stefaan; Arif, Ronald; Papasouliotis, George D.

    2016-12-01

    We are reporting the growth of AlGaN based enhancement-mode high electron mobility transistors (HEMTs) on 200 mm silicon (111) substrates using a single wafer metalorganic chemical vapor deposition reactor. It is found that TMAl pre-dosing conditions are critical in controlling the structural quality, surface morphology, and wafer bow of the HEMT stack. Optimal structural quality and pit-free surface are demonstrated for AlGaN HEMTs with pre-dosing temperature at 750°C. Intrinsically, carbon-doped AlGaN, is used as the current blocking layer in the HEMT structures. The lateral buffer breakdown and device breakdown characteristics, reach 400 V at a leakage current of 1 μA/mm measured at 150°C. The fabricated HEMT devices, with a Mg doped p-GaN gate layer, are operating in enhancement mode reaching a positive threshold voltage of 2-2.5 V, a low on-resistance of 10.5 Ω mm with a high drain saturation current of 0.35 A/mm, and a low forward bias gate leakage current of 0.5 × 10-6 A/mm ( V gs = 7 V). Tight distribution of device parameters across the 200 mm wafers and over repeat process runs is observed.

  2. 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.

  3. Programming power reduction in confined phase change memory cells with titanium dioxide clad layer

    NASA Astrophysics Data System (ADS)

    Chen, Liangliang; Zhang, Zhonghua; Song, Sannian; Song, Zhitang; Zheng, Qianqian; Zhang, Xin; Zhang, Juan; Zheng, Wanting; Shao, Hehong; Zhu, Xiuwei; Yu, Wenlei

    2017-01-01

    A confined structure phase change memory (PCM) cell has been fabricated based on the focused-ion beam technique. Furthermore, the titanium dioxide clad layer was proposed for promoting the temperature rise in the Ge0.61Sb2Te layer that causes the reduction in the reset voltage and current compared to the phase change memory cell without clad layer. Theoretical thermal simulation and calculation for the reset process are conducted to analyze the thermal effect of the titanium dioxide heating layer. The improved performance of the PCM cell with dioxide clad layer can be attributed to the fact that the buffer layer not only acted as heating layer but also efficiently reduced the cell dissipated power.

  4. 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.

  5. 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.

  6. Influence of high-temperature AlN intermediate layer on the optical properties of MOCVD grown AlGaN films

    NASA Astrophysics Data System (ADS)

    Xie, Deng; Qiu, Zhi Ren; Liu, Yao; Talwar, Devki N.; Wan, Lingyu; Zhang, Xiong; Mei, Ting; Ferguson, Ian T.; Feng, Zhe Chuan

    2017-02-01

    By combining spectroscopic ellipsometry (SE) and optical transmission (OT) characterization methods we have systematically investigated the influence of AlN intermediate layer and AlN transition layer on the optical properties of AlGaN epilayers grown on sapphire by metalorganic chemical vapor deposition (MOCVD) method. Most dielectric functions of III-nitrides obtained by different research groups show significant band-tail absorption—which is not anticipated for such a direct band gap material. The dielectric functions are studied for a series of AlGaN/AlN/Al2O3 structures, with a four-layer model taking into account both high temperature grown AlN layer and low temperature grown AlN layer. The results obtained by fitting the optical parameters to experimental data show that the band-tail absorption should originate from the transition layer. AlGaN film without high temperature AlN epilayer exhibited a redshift of band gap around 0.24 eV.

  7. 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.

  8. 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.

  9. High f T and f max AlGaN/GaN HFETs achieved by using thin and high-Al-composition AlGaN barrier layers and Cat-CVD SiN passivation

    NASA Astrophysics Data System (ADS)

    Higashiwaki, M.; Onojima, N.; Matsui, T.; Mimura, T.

    2006-05-01

    We fabricated sub-0.1 m-gate Al0.4Ga0.6N/GaN heterostructure field-effect transistors (HFETs) with AlGaN barrier thicknesses of 4-10 nm. The devices were passivated with 2 nm-thick SiN layers formed by catalytic chemical vapor deposition (Cat-CVD). The Cat-CVD SiN passivation greatly increased electron density, and the effect became more significant with decreasing AlGaN barrier thickness. The HFETs had maximum drain current densities of 1.1-1.5 A/mm and peak extrinsic transconductances of 305-438 mS/mm. Peak current-gain cutoff frequency of 163 GHz and maximum oscillation frequency of 192 GHz were obtained for the devices with 8 nm-thick AlGaN barriers.

  10. 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.

  11. 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.

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

    SciTech Connect

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

    2016-01-14

    Nanoscopic potential fluctuations of Si-doped AlGaN epitaxial layers with the AlN molar fraction varying from 0.42 to 0.95 and Si-doped Al{sub 0.61}Ga{sub 0.39}N epitaxial layers with Si concentrations of 3.0–37 × 10{sup 17 }cm{sup −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 Al{sub 0.61}Ga{sub 0.39}N 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 V{sub Al} did not contribute to the linewidth broadening, unlike the case of the V{sub Al} clusters.

  13. Propagation characteristics of surface plasmon polariton modes in graphene layer with nonlinear magnetic cladding

    NASA Astrophysics Data System (ADS)

    Bhagyaraj, C.; Ajith, R.; Vincent, Mathew

    2017-03-01

    We study the dispersion characteristics of surface plasmon polariton modes guided through a graphene monolayer bounded with a nonlinear magnetic cladding and linear substrate. Nonlinear cladding with permeability μ ={μ }{{l}}+{μ }{{nl}}| {\\boldsymbol{H}}{| }2 provides an extra hand for controlling guided mode behavior externally. The presence of graphene layer enhances nonlinearity in the waveguide configuration thereby changing position of the self-focused peak of field components in the nonlinear medium. Also the propagation length of the fundamental mode strongly depends on the chemical potential of graphene layer. An appreciable increase in propagation length with increase in input power is observed. Phase constant and propagation length of the fundamental mode are calculated as a function of input mode power and graphene layer chemical potential over midinfrared frequencies.

  14. Study of optical waveguide sensor using metamaterial as buffer layer with non-linear cladding and substrate

    NASA Astrophysics Data System (ADS)

    Kumar, Santosh; Kumari, Anamika; Raghuwanshi, Sanjeev K.

    2015-05-01

    In this paper, dispersion equation of optical waveguide using metamaterial as buffer layer with non-linear cladding and substrate is pointed. The sensitivity of TE in metamaterial optical waveguide sensor is computed mathematically. The impacts of buffer layer with non-linear cladding and substrate on metamaterial optical waveguide sensor are also tried out. The effects of various parameters on sensitivity of sensor are obtained through MATLAB. It is expected that metamaterial as buffer layer with non-linear cladding and substrate profile has a huge application in leaky fibre sensor, gas sensor and chemical sensor for oil and under grounds mining industries.

  15. 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.

  16. 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.

  17. 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.

  18. Zinc-blende (Cubic) GaN and AlGaN Layers, Structures and Bulk Crystals by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Novikov, Sergei V.; Zainal, Norzaini; Akimov, Andrey V.; Staddon, Chris R.; Foxon, C. Thomas; Kent, Anthony J.

    2010-11-01

    We have studied the growth of zinc-blende GaN and AlGaN layers, structures and bulk crystals by molecular beam epitaxy (MBE). We have developed a process for growth by MBE of free-standing cubic GaN layers. Undoped thick cubic GaN films were grown on semi-insulating GaAs (001) substrates by a modified plasma-assisted molecular beam epitaxy (PA-MBE) method and were removed from the GaAs substrate after the growth. The resulting free-standing GaN wafers with thicknesses in the 30-100 μm range may be used as substrates for further epitaxy of cubic GaN-based structures and devices. We have developed procedures to cleave the wafers into 10×10 mm2 square substrates and to polish them to produce epi-ready surfaces. The first GaN/InGaN LEDs on our zinc-blende GaN substrates have been demonstrated by our collaborators at Sharp Laboratories of Europe.

  19. Tunable Dipole Surface Plasmon Resonances of Silver Nanoparticles by Cladding Dielectric Layers

    PubMed Central

    Liu, Xiaotong; Li, Dabing; Sun, Xiaojuan; Li, Zhiming; Song, Hang; Jiang, Hong; Chen, Yiren

    2015-01-01

    The tunability of surface plasmon resonance can enable the highest degree of localised surface plasmon enhancement to be achieved, based on the emitting or absorbing wavelength. In this article, tunable dipole surface plasmon resonances of Ag nanoparticles (NPs) are realized by modification of the SiO2 dielectric layer thicknesses. SiO2 layers both beneath and over the Ag NPs affected the resonance wavelengths of local surface plasmons (LSPs). By adjusting the SiO2 thickness beneath the Ag NPs from 5 nm to 20 nm, the dipole surface plasmon resonances shifted from 470 nm to 410 nm. Meanwhile, after sandwiching the Ag NPs by growing SiO2 before NPs fabrication and then overcoating the NPs with various SiO2 thicknesses from 5 nm to 20 nm, the dipole surface plasmon resonances changed from 450 nm to 490 nm. The SiO2 cladding dielectric layer can tune the Ag NP surface charge, leading to a change in the effective permittivity of the surrounding medium, and thus to a blueshift or redshift of the resonance wavelength. Also, the quadrupole plasmon resonances were suppressed by the SiO2 cladding layer because the dielectric SiO2 can suppress level splitting of surface plasmon resonances caused by the Ag NP coupling effect. PMID:26218501

  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. 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.

  2. Stress Analysis and Structural Optimization of a Three-Layer Composite Cladding Tube Under Thermo-Mechanical Loads

    SciTech Connect

    S.-S. Zhou; X.-L. Gao; G. W. Griffith

    2012-07-01

    A general solution for the stress and strain fields in a three-layer composite tube subjected to internal and external pressures and temperature changes is first derived using thermo-elasticity. The material in each layer is treated as orthotropic, and the composite tube is regarded to be in a generalized plane strain state. A three-layer ZRY4-SiCf/SiCSiC composite cladding tube under a combined pressure and thermal loading is then analyzed and optimized by applying the general solution. The effects of temperature changes, applied pressures, and layer thickness on the mechanical behavior of the tube are quantitatively studied. The von Mises failure criterion for isotropic materials and the Tsai-Wu's failure theory for composites are used, respectively, to predict the failure behavior of the monolithic ZRY4 (i.e., Zircaloy-4) inner layer and SiC outer layer and the composite SiCf/SiC core layer of the three-layer tube. The numerical results reveal that the maximum radial and circumferential stresses in each layer always occur on the bonding surfaces. By adjusting the thickness of each layer, the effective stress in the three-layer cladding tube under the prescribed thermal-mechanical loading can be changed, thereby making it possible to optimally design the cladding tube.

  3. Surface photovoltage studies of p-type AlGaN layers after reactive-ion etching

    NASA Astrophysics Data System (ADS)

    McNamara, J. D.; Phumisithikul, K. L.; Baski, A. A.; Marini, J.; Shahedipour-Sandvik, F.; Das, S.; Reshchikov, M. A.

    2016-10-01

    The surface photovoltage (SPV) technique was used to study the surface and electrical properties of Mg-doped, p-type AlxGa1-xN (0.06 < x < 0.17) layers. SPV measurements reveal significant deviation from previous SPV studies on p-GaN:Mg thin films and from the predictions of a thermionic model for the SPV behavior. In particular, the SPV of the p-AlGaN:Mg layers exhibited slower-than-expected transients under ultraviolet illumination and delayed restoration to the initial dark value. The slow transients and delayed restorations can be attributed to a defective surface region which interferes with normal thermionic processes. The top 45 nm of the p-AlGaN:Mg layer was etched using a reactive-ion etch which caused the SPV behavior to be substantially different. From this study, it can be concluded that a defective, near-surface region is inhibiting the change in positive surface charge by allowing tunneling or hopping conductivity of holes from the bulk to the surface, or by the trapping of electrons traveling to the surface by a high concentration of defects in the near-surface region. Etching removes the defective layer and reveals a region of presumably higher quality, as evidenced by substantial changes in the SPV behavior.

  4. On the origin of the electron blocking effect by an n-type AlGaN electron blocking layer

    SciTech Connect

    Zhang, Zi-Hui; Ji, Yun; Liu, Wei; Tiam Tan, Swee; Kyaw, Zabu; Ju, Zhengang; Zhang, Xueliang; Hasanov, Namig; Lu, Shunpeng; Zhang, Yiping; Zhu, Binbin; Wei Sun, Xiao E-mail: volkan@stanfordalumni.org; Volkan Demir, Hilmi E-mail: volkan@stanfordalumni.org

    2014-02-17

    In this work, the origin of electron blocking effect of n-type Al{sub 0.25}Ga{sub 0.75}N electron blocking layer (EBL) for c+ InGaN/GaN light-emitting diodes has been investigated through dual-wavelength emission method. It is found that the strong polarization induced electric field within the n-EBL reduces the thermal velocity and correspondingly the mean free path of the hot electrons. As a result, the electron capture efficiency of the multiple quantum wells is enhanced, which significantly reduces the electron overflow from the active region and increases the radiative recombination rate with holes.

  5. Elimination of AlGaN epilayer cracking by spatially patterned AlN mask

    NASA Astrophysics Data System (ADS)

    Sarzyński, Marcin; Kryśko, Marcin; Targowski, Grzegorz; Czernecki, Robert; Sarzyńska, Agnieszka; Libura, Adam; Krupczyński, Wiktor; Perlin, Piotr; Leszczyński, Michał

    2006-03-01

    The inherent problem in III-nitride technology is the cracking of AlGaN layers that results from lattice mismatch between AlGaN and GaN. In case of thin substrates (30-90μm), such as, bulk GaN grown by the high-pressure/high-temperature method, the bowing of AlGaN /GaN strained structures becomes an additional problem. To eliminate cracking and bowing, AlGaN layers were grown on GaN substrates with an AlN mask patterned to form 3-15μm wide windows. In the 3μm window, the AlGaN layer was not cracked, although its thickness and Al composition exceeded critical values for growth on nonpatterned substrates. Dislocation density in the windows was of 5×106/cm2.

  6. AlN and AlGaN layers grown on Si(111) substrate by mixed-source hydride vapor phase epitaxy method

    NASA Astrophysics Data System (ADS)

    Jeon, Hunsoo; Jeon, Injun; Lee, Gang Seok; Bae, Sung Geun; Ahn, Hyung Soo; Yang, Min; Yi, Sam Nyung; Yu, Young Moon; Honda, Yoshio; Sawaki, Nobuhiko; Kim, Suck-Whan

    2017-01-01

    High Al-composition AlGaN and AlN epilayers were grown directly on Si(111) substrate by a hydride vapor phase epitaxy (HVPE) method with a melted mixed source in a graphite boat set in a source zone with high temperatures of T = 700 and 800 °C, respectively. The presence of the Ga material in the mixed source of Ga and Al promoted the growth of AlN and AlGaN epilayers in the growth zone. When the temperature in the source zone was 800 °C, the crystalline quality of the AlN and AlGaN epilayers increased as the ratio of Ga to Al increased, and the optimum mix ratio of Ga to Al for the growth of AlN epilayers was approximately 0.35-0.42, obtained from a numerical fitting analysis of the X-ray diffraction (XRD) data for these epilayers. It appears that they can be grown directly by our melted-mixed-source HVPE method in a high-temperature source zone.

  7. 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.

  8. Investigation of silver and iodine transport through silicon carbide layers prepared for nuclear fuel element cladding

    NASA Astrophysics Data System (ADS)

    Friedland, E.; van der Berg, N. G.; Malherbe, J. B.; Hancke, J. J.; Barry, J.; Wendler, E.; Wesch, W.

    2011-03-01

    Transport of silver and iodine through polycrystalline SiC layers produced by PBMR (Pty) Ltd. for cladding of TRISO fuel kernels was investigated using Rutherford backscattering analysis and electron microscopy. Fluences of 2 × 10 16 Ag + cm -2 and 1 × 10 16 I + cm -2 were implanted at room temperature, 350 °C and 600 °C with an energy of 360 keV, producing an atomic density of approximately 1.5% at the projected ranges of about 100 nm. The broadening of the implantation profiles and the loss of diffusors through the front surface during vacuum annealing at temperatures up to 1400 °C was determined. The results for room temperature implantations point to completely different transport mechanisms for silver and iodine in highly disordered silicon carbide. However, similar results are obtained for high temperature implantations, although iodine transport is much stronger influenced by lattice defects than is the case for silver. For both diffusors transport in well annealed samples can be described by Fickian grain boundary diffusion with no abnormal loss through the surface as would be expected from the presence of nano-pores and/or micro-cracks. At 1100 °C diffusion coefficients for silver and iodine are below our detection limit of 10 -21 m 2 s -1, while they increase into the 10 -20 m 2 s -1 range at 1300 °C.

  9. Completely transparent ohmic electrode on p-type AlGaN for UV LEDs with core-shell Cu@alloy nanosilk network (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Cai, Duanjun; Wang, Huachun; Huang, Youyang; Wu, Chenping; Chen, Xiaohong; Gao, Na; Wei, Tongbo T.; Wang, Junxi; Li, Shuping; Kang, Junyong

    2016-09-01

    Metal nanowire networks hold a great promise, which have been supposed the only alternative to ITO as transparent electrodes for their excellent performance in touch screen, LED and solar cell. It is well known that the difficulty in making transparent ohmic electrode to p-type high-Al-content AlGaN conducting layer has highly constrained the further development of UV LEDs. On the IWN-2014, we reported the ohmic contact to n, p-GaN with direct graphene 3D-coated Cu nanosilk network and the fabrication of complete blue LED. On the ICNS-2015, we reported the ohmic contact to n-type AlGaN conducting layer with Cu@alloy nanosilk network. Here, we further demonstrate the latest results that a novel technique is proposed for fabricating transparent ohmic electrode to high-Al-content AlGaN p-type conducting layer in UV LEDs using Cu@alloy core-shell nanosilk network. The superfine copper nanowires (16 nm) was synthesized for coating various metals such as Ni, Zn, V or Ti with different work functions. The transmittance showed a high transparency (> 90%) over a broad wavelength range from 200 to 3000 nm. By thermal annealing, ohmic contact was achieved on p-type Al0.5Ga0.5N layer with Cu@Ni nanosilk network, showing clearly linear I-V curve. By skipping the p-type GaN cladding layer, complete UV LED chip was fabricated and successfully lit with bright emission at 276 nm.

  10. Plasma-assisted molecular beam epitaxy of Al(Ga)N layers and quantum well structures for optically pumped mid-UV lasers on c-Al2O3

    NASA Astrophysics Data System (ADS)

    Ivanov, S. V.; Nechaev, D. V.; Sitnikova, A. A.; Ratnikov, V. V.; Yagovkina, M. A.; Rzheutskii, N. V.; Lutsenko, E. V.; Jmerik, V. N.

    2014-06-01

    This paper reports on novel approaches developed for plasma-assisted molecular beam epitaxy of Al-rich AlGaN epilayers and quantum well heterostructures on c-sapphire, which allowed us to fabricate low-threshold optically-pumped separate confinement heterostructure lasers emitting in the mid-UV spectral range (258-290 nm) with the threshold power density below 600 kW cm-2. The optimum buffer structure has been developed which provides lowering the near-surface threading dislocation density down to 1.5 × 108 and 3 × 109 cm-2 for screw and edge types, respectively, and improving the surface morphology (rms < 0.7 nm at the area of 3 × 3 μm-2). It comprises the high-temperature (780 °C) migration enhanced epitaxy growth of a (30-70) nm thick AlN nucleation layer on c-Al2O3, followed by a 2 μm thick AlN buffer grown under the metal-rich conditions in the Al-flux modulation mode and containing several (up to 6) ultra-thin (˜3 nm) GaN interlayers grown at N-rich conditions. Proper strain engineering in AlGaN single quantum well heterostructure grown atop of the AlN buffer layer enables one to preserve dominant TE polarization of both spontaneous and stimulated emission even at shortest obtained wavelength (258 nm). The threshold power density of stimulated emission as low as 150 kW cm-2 at 289 nm for a single quantum well laser structure has been demonstrated.

  11. Statistical nanoscale study of localised radiative transitions in GaN/AlGaN quantum wells and AlGaN epitaxial layers

    NASA Astrophysics Data System (ADS)

    Rigutti, L.; Mancini, L.; Lefebvre, W.; Houard, J.; Hernàndez-Maldonado, D.; Di Russo, E.; Giraud, E.; Butté, R.; Carlin, J.-F.; Grandjean, N.; Blavette, D.; Vurpillot, F.

    2016-09-01

    Compositional disorder has important consequences on the optical properties of III-nitride ternary alloys. In AlGaN epilayers and AlGaN-based quantum heterostructures, the potential fluctuations induced by such disorder lead to the localisation of carriers at low temperature, which affects their transition energies. Using the correlations between micro-photoluminescence, scanning transmission electron microscopy and atom probe tomography we have analysed the optical behaviour of Al0.25Ga0.75N epilayers and that of GaN/AlGaN quantum wells, and reconstructed in three dimensions the distribution of chemical species with sub-nanometre spatial resolution. These composition maps served as the basis for the effective mass calculation of electrons and holes involved in radiative transitions. Good statistical predictions were subsequently obtained for the above-mentioned transition and localisation energies by establishing a link with their microstructural properties.

  12. 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.

  13. The structure and corrosion resistance of Ti-Nb layers formed on the surface of CP-titanium by electron beam cladding

    NASA Astrophysics Data System (ADS)

    Polyakov, Igor A.; Kolesnikova, Kseniya A.; Lozhkina, Elena A.; Samoylenko, Vitaliy V.

    2016-11-01

    The structure and corrosion resistance of Ti-Nb layers formed on the surface of CP-titanium plates by electron beam cladding in vacuum has been investigated. It is found that the cladded material is characterized by a defect-free structure. Optical and scanning electron microscopy showed that the martensitic structure is observed in the cladded layers. The concentration of niobium in the layers was 7.7 wt %. Surface alloying of niobium provides a 2.6-fold increase in the corrosion resistance of titanium in boiling 65% solution of nitric acid. The corrosion resistance of Ti-Nb layers in boiling 5% solution of hydrochloric acid is almost 10.6 times higher in comparison with commercially pure titanium.

  14. Influence of AlN thickness on AlGaN epilayer grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Jayasakthi, M.; Juillaguet, S.; Peyre, H.; Konczewicz, L.; Baskar, K.; Contreras, S.

    2016-10-01

    AlGaN/AlN layers were grown by metalorganic chemical vapor deposition (MOCVD) on sapphire substrates. The AlN buffer thickness was varied from 400 nm to 800 nm. The AlGaN layer thickness was 1000 nm. The crystalline quality, thickness and composition of AlGaN were determined using high resolution X-ray diffraction (HRXRD). The threading dislocation density (TDD) was found to decrease with increase of AlN layer thickness. Reciprocal space mapping (RSM) was used to estimate the strain and relaxation between AlGaN and AlN. The optical properties of AlGaN layers were investigated by temperature dependent photoluminescence (PL). PL intensities of AlGaN layers increases with increasing the AlN thickness. The surface morphology of AlGaN was studied by atomic force microscopy (AFM). Root mean square (RMS) roughness values were found to be decreased while increase of AlN thickness.

  15. 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.

  16. 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.

  17. Design of p-type cladding layers for tunnel-injected UV-A light emitting diodes

    SciTech Connect

    Zhang, Yuewei; Krishnamoorthy, Sriram; Akyol, Fatih; Allerman, Andrew A.; Moseley, Michael W.; Armstrong, Andrew M.; Rajan, Siddharth

    2016-11-09

    Here, we discuss the engineering of p-AlGaN cladding layers for achieving efficient tunnel-injected III-Nitride ultraviolet light emitting diodes (UV LEDs) in the UV-A spectral range. We show that the capacitance-voltage measurements can be used to estimate the compensation and doping in the p-AlGaN layers located between the multi-quantum well region and the tunnel junction layer. By increasing the p-type doping concentration to overcome the background compensation, on-wafer external quantum efficiency and wall-plug efficiency of 3.37% and 1.62%, respectively, were achieved for the tunnel-injected UV LEDs emitting at 325 nm. We also show that interband tunneling hole injection can be used to realize UV LEDs without any acceptor doping. The work discussed here provides new understanding of hole doping and transport in AlGaN-based UV LEDs and demonstrates the excellent performance of tunnel-injected LEDs for the UV-A wavelength range.

  18. Design of p-type cladding layers for tunnel-injected UV-A light emitting diodes

    DOE PAGES

    Zhang, Yuewei; Krishnamoorthy, Sriram; Akyol, Fatih; ...

    2016-11-09

    Here, we discuss the engineering of p-AlGaN cladding layers for achieving efficient tunnel-injected III-Nitride ultraviolet light emitting diodes (UV LEDs) in the UV-A spectral range. We show that the capacitance-voltage measurements can be used to estimate the compensation and doping in the p-AlGaN layers located between the multi-quantum well region and the tunnel junction layer. By increasing the p-type doping concentration to overcome the background compensation, on-wafer external quantum efficiency and wall-plug efficiency of 3.37% and 1.62%, respectively, were achieved for the tunnel-injected UV LEDs emitting at 325 nm. We also show that interband tunneling hole injection can be usedmore » to realize UV LEDs without any acceptor doping. The work discussed here provides new understanding of hole doping and transport in AlGaN-based UV LEDs and demonstrates the excellent performance of tunnel-injected LEDs for the UV-A wavelength range.« less

  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. Effect of the addition of Sm2O3 on the microstructure of laser cladding alloy coating layers

    NASA Astrophysics Data System (ADS)

    Zhang, Shi Hong; Li, Ming Xi; Cho, Tong Yul; Yoon, Jae Hong; Fang, Wei; Joo, Yun Kon; Kang, Jin Ho; Lee, Chan Gyu

    2008-06-01

    The effects on the microstructures and phases of coating layers by the addition of micron-sized (m) and nano-sized (n) (m&n) Sm2O3 powders were investigated. The coating materials, which were prepared by means of 2.0 kW CO2 laser cladding, consist of a powder mixture of m Ni-based alloy (NBA) powders comprising 1.5 wt.% m Sm2O3 and 3.0% n Sm2O3 powders. The results indicate that γ-Ni, Cr23C6 and Ni3B are the primary phases of the NBA coatings. The Fe7Sm and Ni3Si phases are highlighted by the addition of m&n Sm2O3 powders. From the substrate, planar crystal layers are first grown in all NBA and m&n Sm2O3/NBA coatings. The dendrite growth then occurs as a result of the addition of the m Sm2O3 powder, and the equiaxed dendrite growth occurs as a result of the addition of the n Sm2O3. With the addition of a rare earth oxide such as Sm2O3 powder, the width of the planar crystal becomes smaller than that of the NBA coating.

  1. 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.

  2. 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.

  3. 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

    2016-05-25

    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.

  4. 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

  5. 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.

  6. High efficiency improvements in AlGaN-based ultraviolet light-emitting diodes with specially designed AlGaN superlattice hole and electron blocking layers

    NASA Astrophysics Data System (ADS)

    Yi, Xinyan; Sun, Huiqing; Sun, Jie; Yang, Xian; Fan, Xuancong; Zhang, Zhuding; Guo, Zhiyou

    2017-04-01

    AlxGa1-xN/Al0.6Ga0.4N graded superlattice hole blocking layers (GSL-HBLs) and AlxGa1-xN/Al0.6Ga0.4N graded superlattice electron blocking layers (GSL-EBLs) are applied to the traditional AlGaN-based ultraviolet light-emitting diodes (UVLEDs). This can obtain much higher internal quantum efficiency (IQE) and output power. In order to reveal the underlying physical mechanism of this unique structure, we have studied it numerically by APSYS simulation programs. We find that GSL-EBLs can obviously increase the electron potential height and reduce the hole potential height, produce less electron leakage and more hole injection, leading to higher carrier contration. GSL-HBLs can obviously reduce the hole leakage, reduce the thermal velocity and correspondingly the mean free path of the hot electrons, and increase the electron injection. This enhanced the electron capture efficiency of the multiple quantum wells, which can also help to reduce electron leakage.

  7. Comparative study of NH 4OH and HCl etching behaviours on AlGaN surfaces

    NASA Astrophysics Data System (ADS)

    Sohal, Rakesh; Dudek, Piotr; Hilt, Oliver

    2010-01-01

    A controlled AlGaN surface preparation method avails to improve the performance of GaN-based HEMT devices. A comparative investigation of chemical treatments by (1:10) NH 4OH:H 2O and (1:10) HCl:H 2O solutions for AlGaN surface preparation by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) is reported. The XPS data clearly reveal that the native oxide on AlGaN was composed of Al 2O 3, Ga 2O 3 and NO compounds. These compounds were etched off partially or completely by both the chemical treatments, namely NH 4OH or HCl solutions, independently. The HCl treatment etches out Al 2O 3 completely from native oxide unlike NH 4OH treatment. The HCl treatment results in larger amount of carbon segregation on AlGaN surfaces, however it removes all oxides' compounds faster than NH 4OH treatment. The AFM results reveal the improvement of surface morphology by both the chemical treatments leading to the surface roughness RMS values of 0.24 nm and 0.21 nm for NH 4OH and HCl treated AlGaN layers, respectively.

  8. 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.

  9. Clad metal joint closure

    SciTech Connect

    Siebert, O.W.

    1985-04-09

    A plasma arc spray overlay of cladding metals is used over joints between clad metal pieces to provide a continuous cladding metal surface. The technique permits applying an overlay of a high melting point cladding metal to a cladding metal surface without excessive heating of the backing metal.

  10. Performance of 128×128 solar-blind AlGaN ultraviolet focal plane arrays

    NASA Astrophysics Data System (ADS)

    Yuan, Yongang; Zhang, Yan; Liu, Dafu; Chu, Kaihui; Wang, Ling; Li, Xiangyang

    2009-07-01

    Ozone layer intensively absorbs 240nm to 285 nm incidence, when the sunshine goes through stratospheric. There is almost no UVC (200nm-280nm) band radiation existing below stratospheric. Because the radiation target presents a strong contrast between atmosphere and background, solar-blind band radiation is very useful. Wide band gap materials, especially III-V nitride materials, have attracted extensive interest. The direct band gap of GaN and A1N is 3.4 and 6.2 eV, respectively. Since they are miscible with each other and form a complete series of AlGaN alloys, AlGaN has direct band gaps from 3.4 to 6.2 eV, corresponding to cutoff wavelengths from 365 to 200 nm. A back-illuminated hybrid FPA has been developed by Shanghai Institute of Technical Physics Chinese Academy of Science. This paper reports the performance of the 128x128 solar-blind AlGaN UV Focal Plane Arrays (FPAs). More and more a CTIA (capacitivetransimpedance) readout circuit architecture has been proven to be well suited for AlGaN detectors arrays. The bared readout circuit was first tested to find out optimal analog reference voltage. Second, this ROIC was tested in a standard 20-pin shielded dewar at 115 K to 330K. Then, a new test system was set up to obtain test UV FPA noise, swing voltage, data valid time, operating speed, dynamic range, UV response etc. The results show that 128x128 back-illuminated AlGaN PIN detector SNR is as high as 74db at the speed of above30 frame per second. Also, some noise test method is mentioned.

  11. 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.

  12. 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.

  13. 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.

  14. Relaxation of compressively-strained AlGaN by inclined threading dislocations

    NASA Astrophysics Data System (ADS)

    Follstaedt, D. M.; Lee, S. R.; Provencio, P. P.; Allerman, A. A.; Floro, J. A.; Crawford, M. H.

    2005-09-01

    Transmission electron microscopy and x-ray diffraction were used to assess the microstructure and strain of AlxGa1-xN(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.

  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. 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.

  17. Design and demonstration of ultra-wide bandgap AlGaN tunnel junctions

    SciTech Connect

    Zhang, Yuewei; Krishnamoorthy, Sriram; Akyol, Fatih; Allerman, Andrew A.; Moseley, Michael W.; Armstrong, Andrew M.; Rajan, Siddharth

    2016-09-19

    Ultra violet light emitting diodes (UV LEDs) face critical limitations in both the injection efficiency and the light extraction efficiency due to the resistive and absorbing p-type contact layers. In this work, we investigate the design and application of polarization engineered tunnel junctions for ultra-wide bandgap AlGaN (Al mole fraction >50%) materials towards highly efficient UV LEDs. We demonstrate that polarization-induced three dimensional charge is beneficial in reducing tunneling barriers especially for high composition AlGaN tunnel junctions. In addition, the design of graded tunnel junction structures could lead to low tunneling resistance below 10–3 Ω cm2 and low voltage consumption below 1 V (at 1 kA/cm2) for high composition AlGaN tunnel junctions. Experimental demonstration of 292 nm emission was achieved through non-equilibrium hole injection into wide bandgap materials with bandgap energy larger than 4.7 eV, and detailed modeling of tunnel junctions shows that they can be engineered to have low resistance and can enable efficient emitters in the UV-C wavelength range.

  18. Design and demonstration of ultra-wide bandgap AlGaN tunnel junctions

    DOE PAGES

    Zhang, Yuewei; Krishnamoorthy, Sriram; Akyol, Fatih; ...

    2016-09-19

    Ultra violet light emitting diodes (UV LEDs) face critical limitations in both the injection efficiency and the light extraction efficiency due to the resistive and absorbing p-type contact layers. In this work, we investigate the design and application of polarization engineered tunnel junctions for ultra-wide bandgap AlGaN (Al mole fraction >50%) materials towards highly efficient UV LEDs. We demonstrate that polarization-induced three dimensional charge is beneficial in reducing tunneling barriers especially for high composition AlGaN tunnel junctions. In addition, the design of graded tunnel junction structures could lead to low tunneling resistance below 10–3 Ω cm2 and low voltage consumptionmore » below 1 V (at 1 kA/cm2) for high composition AlGaN tunnel junctions. Experimental demonstration of 292 nm emission was achieved through non-equilibrium hole injection into wide bandgap materials with bandgap energy larger than 4.7 eV, and detailed modeling of tunnel junctions shows that they can be engineered to have low resistance and can enable efficient emitters in the UV-C wavelength range.« less

  19. Effects of tensile stress induced by silicon nitride passivation on electrical characteristics of AlGaN /GaN heterostructure field-effect transistors

    NASA Astrophysics Data System (ADS)

    Jeon, Chang Min; Lee, Jong-Lam

    2005-04-01

    The effects of tensile stress induced by silicon nitride (Si3N4) passivation on electrical characteristics of AlGaN /GaN heterostructure field-effect transistors (HFETs) were investigated. The biaxial tensile stress applied to the AlGaN layer was increased with the thickness of the Si3N4 passivation layer, leading to the increase of sheet charge density confined at the heterointerface. The stress-induced charge density was 1.75×1011e/cm2 for 80-nm-thick Si3N4 and 6.74×1011e/cm2 for 500-nm-thick Si3N4. The maximum drain current and transconductance of AlGaN /GaN HFET increased from 769 to 858mA/mm and from 146 to 155mS/mm after passivation, respectively.

  20. 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.

  1. Reduction of Liquid Clad Formation Due to Solid State Diffusion in Clad Brazing Sheet

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    Warm forming operations have shown promise in expanding automotive heat exchanger designs by increasing forming limits of clad brazing sheet. The impact of isothermal holds below the clad melting temperature on subsequent brazeability has not previously been studied in detail. The effect of these holds on brazeability, as measured by the clad thickness loss due to solid state diffusion of Si out of the clad layer prior to clad melting, was assessed through parallel DSC and optical microscopy measurements, as well as through the use of a previously developed model. EPMA measurements were also performed to support the other measures. Overall, the same trends were predicted by DSC, microscopy, and the theoretical model; however, the DSC predictions were unable to accurately predict remaining clad thickness prior to melting, even after correcting the data for clad-core interactions. Microscopy measurements showed very good agreement with the model predictions, although there were slight discrepancies at short hold times due to the inability of the model to account for clad loss during heating to the brazing temperature. Further microscopy measurements showed that when the heating rate is set below a critical value, there is a reduction in the clad thickness from the as-received condition.

  2. Compositional inhomogeneities in AlGaN thin films grown by molecular beam epitaxy: Effect on MSM UV photodetectors

    NASA Astrophysics Data System (ADS)

    Pramanik, Pallabi; Sen, Sayantani; Singha, Chirantan; Roy, Abhra Shankar; Das, Alakananda; Sen, Susanta; Bhattacharyya, A.

    2016-10-01

    Ultraviolet (UV) MSM photodetectors (PD) based on AlGaN alloys find many applications, including flame sensing. In this work we investigate the dependence of AlGaN based photodetectors grown by MBE on the kinetics of growth. MSM photodetectors were fabricated in the interdigitated configuration with Ni/Au contacts having 400 μm finger length and 10 μm finger spacing. Bulk Al0.4Ga0.6N films were grown on to sapphire substrates using an AlN buffer layer. A series of PDs were developed using the Al0.4Ga0.6N films grown under different group III/V flux ratios ranging from stoichiometric conditions to much higher than unity. Upon testing, it was observed that the otherwise identical photodetectors show significant decrease in dark current as AlGaN deposition conditions change from stoichiometric to excess group III, due to reduction of unintentional incorporation of oxygen-related point defects. In addition, the intensity and spectral dependence of the photocurrent also change, showing an extended low energy tail for the former and a sharp and prominent excitonic peak for the latter. The optical transmission measurements indicate a variation in Urbach energy with deposition conditions of the AlGaN films, although they have the same absorption edge. While all samples show a single red-shifted photoluminescence peak at room temperature, upon cooling, multiple higher energy peaks appear in the photoluminescence (PL) spectra, indicating that the alloys contain complex compositional inhomogeneities. Two types of alloy fluctuations, determined by the growth conditions, have been identified that modulate the optoelectronic properties of AlGaN by changing the spatial localization of excitons, thereby altering their stability. We identified that growth under stoichiometric conditions leads to compositional inhomogeneities that play a detrimental role in the operation of MSM photodetectors, which reduces the sharpness of the sensitivity edge, while growth under excess metal

  3. 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.

  4. Vertical transport through AlGaN barriers in heterostructures grown by ammonia molecular beam epitaxy and metalorganic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Browne, David A.; Fireman, Micha N.; Mazumder, Baishakhi; Kuritzky, Leah Y.; Wu, Yuh-Renn; Speck, James S.

    2017-02-01

    The results of vertical transport through AlGaN heterobarriers are presented for ammonia molecular beam epitaxy (NH3-MBE) on c-plane GaN on sapphire templates and on m-plane bulk GaN substrates, as well as by metalorganic chemical vapor deposition (MOCVD) on m-plane bulk GaN substrates. Experiments were performed to determine the role of the AlGaN alloy as an effective barrier to vertical transport, which is an essential component of both optoelectronic and power electronic devices. The alloy composition, thickness, and doping levels of the AlGaN layers, as well as substrate orientation, were systematically varied to examine their influence on electron transport. Atom probe tomography (APT) was used to directly determine the alloy composition at the atomic scale to reveal the presence of random alloy fluctuations which provides insight into the nature of the observed transport.

  5. 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.

  6. Performance improvement of AlGaN-based deep-ultraviolet light-emitting diodes via asymmetric step-like AlGaN quantum wells

    NASA Astrophysics Data System (ADS)

    Lu, Lin; Wan, Zhi; Xu, FuJun; Wang, XinQiang; Lv, Chen; Shen, Bo; Jiang, Ming; Chen, QiGong

    2017-04-01

    Characteristics of AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) with light-emitting wavelength around 265 nm via step-like AlGaN quantum wells (QWs) have been investigated. Simulation approach yields a result that, there is significant enhancement of light output power (LOP) for DUV-LEDs with two-layer step-like AlGaN QWs compared to that with conventional one. The location and thickness of AlGaN layer with higher Al-content in the step-like QWs are confirmed to significantly affect the distributions and overlap of electron and hole wavefunctions. The best material characteristic is obtained when the step-like QW is designed as an asymmetric structure, such as Al0.74Ga0.26N (1.8 nm)/Al0.64Ga0.36N (1.2 nm), where AlGaN with higher Al-content layer is set to be located nearer from n-side and be thick as far as possible. The key factors for the performance improvements for this specific design is the enhanced hole transport and mitigated auger recombination.

  7. 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.

  8. Inductively coupled BCl3/Cl2 /Ar plasma etching of Al-rich AlGaN

    DOE PAGES

    Douglas, Erica A.; Sanchez, Carlos A.; Kaplar, Robert J.; ...

    2016-12-01

    Varying atomic ratios in compound semiconductors is well known to have large effects on the etching properties of the material. The use of thin device barrier layers, down to 25 nm, adds to the fabrication complexity by requiring precise control over etch rates and surface morphology. The effects of bias power and gas ratio of BCl3 to Cl2 for inductively coupled plasma etching of high Al content AlGaN were contrasted with AlN in this study for etch rate, selectivity, and surface morphology. Etch rates were greatly affected by both bias power and gas chemistry. Here we detail the effects ofmore » small variations in Al composition for AlGaN and show substantial changes in etch rate with regards to bias power as compared to AlN.« less

  9. Inverted vertical algan deep ultraviolet leds grown on p-SiC substrates by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Nothern, Denis Maurice

    Deep ultraviolet light emitting diodes (UV LEDs) are an important emerging technology for a number of applications such as water/air/surface disinfection, communications, and epoxy curing. However, as of yet, deep UV LEDs grown on sapphire substrates are neither efficient enough nor powerful enough to fully serve these and other potential applications. The majority of UV LEDs reported so far in the literature are grown on sapphire substrates and their design consists of AlGaN quantum wells (QWs) embedded in an AlGaN p-i-n junction with the n-type layer on the sapphire. These devices suffer from a high concentration of threading defects originating from the large lattice mismatch between the sapphire substrate and AlGaN alloys. Other issues include the poor doping efficiency of the n- and particularly the p-AlGaN alloys, the extraction of light through the sapphire substrate, and the heat dissipation through the thermally insulating sapphire substrate. These problems have historically limited the internal quantum efficiency (IQE), injection efficiency (IE), and light extraction efficiency (EE) of devices. As a means of addressing these efficiency and power challenges, I have contributed to the development of a novel inverted vertical deep UV LED design based on AlGaN grown on p-SiC substrates. Starting with a p-SiC substrate that serves as the p-type side of the p-i-n junction largely eliminates the necessity for the notoriously difficult p-type doping of AlGaN alloys, and allows for efficient heat dissipation through the highly thermally conductive SiC substrate. UV light absorption in the SiC substrate can be addressed by first growing p-type doped distributed Bragg reflectors (DBRs) on top of the substrate prior to the deposition of the active region of the device. A number of n-AlGaN films, AlGaN/AlGaN multiple quantum wells, and p-type doped AlGaN DBRs were grown by molecular beam epitaxy (MBE). These were characterized in situ by reflected high energy electron

  10. CONDENSED MATTER: STRUCTURE, THERMAL AND MECHANICAL PROPERTIES: The effect of single AlGaN interlayer on the structural properties of GaN epilayers grown on Si (111) substrates

    NASA Astrophysics Data System (ADS)

    Wu, Yu-Xin; Zhu, Jian-Jun; Zhao, De-Gang; Liu, Zong-Shun; Jiang, De-Sheng; Zhang, Shu-Ming; Wang, Yu-Tian; Wang, Hui; Chen, Gui-Feng; Yang, Hui

    2009-10-01

    High-quality and nearly crack-free GaN epitaxial layer was obtained by inserting a single AlGaN interlayer between GaN epilayer and high-temperature AlN buffer layer on Si (111) substrate by metalorganic chemical vapor deposition. This paper investigates the effect of AlGaN interlayer on the structural properties of the resulting GaN epilayer. It confirms from the optical microscopy and Raman scattering spectroscopy that the AlGaN interlayer has a remarkable effect on introducing relative compressive strain to the top GaN layer and preventing the formation of cracks. X-ray diffraction and transmission electron microscopy analysis reveal that a significant reduction in both screw and edge threading dislocations is achieved in GaN epilayer by the insertion of AlGaN interlayer. The process of threading dislocation reduction in both AlGaN interlayer and GaN epilayer is demonstrated.

  11. 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.

  12. Bendability of aluminiumand steel-clad chromium plates

    NASA Astrophysics Data System (ADS)

    Yoshida, Fusahito; Okada, Tatsuo; Itoh, Misao; Harada, Yasunori; Ohmori, Masanobu

    1998-05-01

    The present paper describes how the cladding of chromium plate with dissimilar metals improves the plastic bendability of the chromium. Three-point bending tests at various temperatures were performed for three types of chromium specimens: a monolithic chromium plate, aluminium- and steel-clad chromium plate. The aluminium-clad chromium plate was bent at 343 K up to a bent angle of 90 degrees without failure, even when the chromium layer was located outside of the plate (tension side), while the monolithic chromium plate could be bent exclusively at temperatures above 403 K. When the chromium layer was located inside of the steel-clad chromium plate (compression side), the plate was successfully bent at 307 K. The FE stress analysis of bending proved that the cladding of chromium plates with proper metals of different kinds is effective to reduce the tensile stress in chromium induced during bending and also the residual stress existing after bending operation.

  13. 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)

  14. Enhanced output power of GaN-based LEDs with embedded AlGaN pyramidal shells.

    PubMed

    Tu, Shang-Ju; Sheu, Jinn-Kong; Lee, Ming-Lun; Yang, Chih-Ciao; Chang, Kuo-Hua; Yeh, Yu-Hsiang; Huang, Feng-Wen; Lai, Wei-Chih

    2011-06-20

    In this article, the characteristics of GaN-based LEDs grown on Ar-implanted GaN templates to form inverted Al0.27Ga0.83N pyramidal shells beneath an active layer were investigated. GaN-based epitaxial layers grown on the selective Ar-implanted regions had lower growth rates compared with those grown on the implantation-free regions. This resulted in selective growth, and formation of V-shaped concaves in the epitaxial layers. Accordingly, the inverted Al0.27Ga0.83N pyramidal shells were formed after the Al0.27Ga0.83N and GaN layers were subsequently grown on the V-shaped concaves. The experimental results indicate that the light-output power of LEDs with inverted AlGaN pyramidal shells was higher than those of conventional LEDs. With a 20 mA current injection, the output power was enhanced by 10% when the LEDs were embedded with inverted Al0.27Ga0.83N pyramidal shells. The enhancement in output power was primarily due to the light scattering at the Al0.27Ga0.83N/GaN interface, which leads to a higher escape probability for the photons, that is, light-extraction efficiency. Based on the ray tracing simulation, the output power of LEDs grown on Ar-implanted GaN templates can be enhanced by over 20% compared with the LEDs without the embedded AlGaN pyramidal shells, if the AlGaN layers were replaced by Al0.5Ga0.5N layers.

  15. Microstructural Characterization of Cermet Cladding Developed Through Microwave Irradiation

    NASA Astrophysics Data System (ADS)

    Gupta, Dheeraj; Sharma, Apurbba Kumar

    2012-10-01

    In the present work, cladding of hardfacing WC10Co2Ni powder on austenitic stainless steel has been developed through a novel processing technique. The clads were developed using microwave hybrid heating. The clad of average thickness ~2 mm has been developed through the exposure of microwave radiation at frequency 2.45 GHz and power 900 W for the duration of 360 s. The developed clads were characterized using field emission scanning electron microscope, X-ray elemental analysis, X-ray diffraction, and measurement of Vicker's microhardness. The microstructure study of the clad showed good metallurgical bonding with substrate and revealed that clads are free from any visible interface cracking. Clads were formed with partial dilution of a thin layer of the substrate. The cermet microstructure mainly consists of relatively soft metallic matrix phase and uniformly distributed hard carbide phase with skeleton-like structure. The developed clads exhibit an average microhardness of 1064 ± 99 Hv. The porosity of developed clad has been significantly less at approximately 0.89%.

  16. 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.

  17. 35CrMo steel surface by laser cladding Fe-based WC composite coating performance analysis

    NASA Astrophysics Data System (ADS)

    Zhou, Houming; Zhang, Haomin; Qin, Hengfeng

    2014-12-01

    The laser cladding technique in 35CrMo steel substrate prepared with different dosage under WC iron-based alloy cladding.Research the effects of different cladding WC addition on surface morphology, microstructure, microhardness and wear properties. The results show that 5% and 10% WC added amount of the surface quality of the cladding layer is preferably 15 % and 25 % of the volume of the WC surface of the cladding layer with varying degrees of cracks and pores, WC adding cladding layer can significantly improve the hardness. Through analysis we draw the conculation that,with 10% WC addition of iron-based alloy cladding the microhardness is 4.2 times the substrate , the relative wear resistance increased 4.1 than the substrate , enabling optimum cladding friction and wear properties.

  18. The effect of surface cleaning on quantum efficiency in AlGaN photocathode

    NASA Astrophysics Data System (ADS)

    Hao, Guanghui; Zhang, Yijun; Jin, Muchun; Feng, Cheng; Chen, Xinlong; Chang, Benkang

    2015-01-01

    To improve the quantum efficiency of AlGaN photocathode, various surfaces cleaning techniques for the removal of alumina and carbon from AlGaN photocathode surface were investigated. The atomic compositions of AlGaN photocathode structure and surface were measured by the X-ray photoelectron spectroscopy and Ar+ ion sputtering. It is found that the boiling KOH solution and the mixture of sulfuric acid and hydrogen peroxide, coupled with the thermal cleaning at 850 °C can effectively remove the alumina and carbon from the AlGaN photocathode surface. The quantum efficiency of AlGaN photocathode is improved to 35.1% at 240 nm, an increase of 50% over the AlGaN photocathode chemically cleaned by only the mixed solution of sulfuric acid and hydrogen peroxide and thermally cleaned at 710 °C.

  19. 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.

  20. Hollow core anti-resonant fiber with split cladding.

    PubMed

    Huang, Xiaosheng; Qi, Wenliang; Ho, Daryl; Yong, Ken-Tye; Luan, Feng; Yoo, Seongwoo

    2016-04-04

    An improved design for hollow core anti-resonant fibers (HAFs) is presented. A split cladding structure is introduced to reduce the fabrication distortion within design tolerance. We use numerical simulations to compare the Kagome fibers (KFs) and the proposed split cladding fibers (SCFs) over two normalized transmission bands. It reveals that SCFs are able to maintain the desired round shape of silica cladding walls, hence improving the confinement loss (CL) compared to the KF and is comparable to that of the nested antiresonant nodeless fiber (NANF) with the same core size. In addition, the SCF allows stacking multiple layers of cladding rings to control the CL. The influences of the number of cladding layers and the cladding gap width on the CL of the SCFs have been studied. SCF with three cladding rings is fabricated by the stack-and-draw technique. A measured attenuation spectrum matches well with the calculation prediction. The measured near field mode patterns also prove the feasibility of our fiber design.

  1. 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.

  2. 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.

  3. Properties of multilayer coatings produced by coaxial laser cladding

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    This article contains results of the study of multilayer coatings produced by laser cladding on the substrate steel 34HMA using iron based powder PR-10R6M5 as the filler material. The coatings were produced with consistent application of the tracks with fixed overlapping. The dependencies between the characteristics of tracks and the technological mode of deposition were revealed. Properties of coatings were determined for various overlapping of tracks and directions of the cladding layers.

  4. Large-energy, wavelength-tunable, all-fiber passively Q-switched Er:Yb-codoped double-clad fiber laser with mono-layer chemical vapor deposition graphene.

    PubMed

    Wu, Duanduan; Xiong, Fengfu; Zhang, Cankun; Chen, Shanshan; Xu, Huiying; Cai, Zhiping; Cai, Weiwei; Che, Kaijun; Luo, Zhengqian

    2014-07-01

    We demonstrate a large-energy, wavelength-tunable, all-fiber passively Q-switched Er:Yb-codoped laser using a mono-layer chemical vapor deposition (CVD) graphene saturable absorber (SA). By exploiting the large laser gain of Er:Yb double-clad fiber and optimizing the coupling ratio of the output coupler, not only can the mono-layer CVD graphene SA be protected from oversaturation and thermal damage, but also a large pulse energy up to 1.05 μJ (corresponding to the average output power of 25.6 mW) is thus achieved. Using a tunable fiber Fabry-Perot filter, stable Q-switched pulses can operate with a tunable range from 1530.97 to 1546.92 nm, covering a wavelength range of ∼16  nm. The Q-switching states at the different lasing wavelengths have been observed and recorded. The Q-switched repetition rate and the pulse duration (with the minimum one of 2.6 μs) have been characterized as well. This is, to the best of our knowledge, the largest pulse energy from an all-fiber graphene Q-switched laser.

  5. 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.

  6. 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.

  7. Inductively coupled BCl3/Cl2 /Ar plasma etching of Al-rich AlGaN

    SciTech Connect

    Douglas, Erica A.; Sanchez, Carlos A.; Kaplar, Robert J.; Allerman, Andrew A.; Baca, Albert G.

    2016-12-01

    Varying atomic ratios in compound semiconductors is well known to have large effects on the etching properties of the material. The use of thin device barrier layers, down to 25 nm, adds to the fabrication complexity by requiring precise control over etch rates and surface morphology. The effects of bias power and gas ratio of BCl3 to Cl2 for inductively coupled plasma etching of high Al content AlGaN were contrasted with AlN in this study for etch rate, selectivity, and surface morphology. Etch rates were greatly affected by both bias power and gas chemistry. Here we detail the effects of small variations in Al composition for AlGaN and show substantial changes in etch rate with regards to bias power as compared to AlN.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Neutron-induced helium implantation in GCFR cladding

    SciTech Connect

    Yamada, H.; Poeppel, R. B.; Sevy, R. H.

    1980-10-01

    The neutron-induced implantation of helium atoms on the exterior surfaces of the cladding of a prototypic gas-cooled fast reactor (GCFR) has been investigated analytically. A flux of recoil helium particles as high as 4.2 x 10/sup 10/ He/cm/sup 2/.s at the cladding surface has been calculated at the peak power location in the core of a 300-MWe GCFR. The calculated profile of the helium implantation rates indicates that although some helium is implanted as deep as 20 ..mu..m, more than 99% of helium particles are implanted in the first 2-..mu..m-deep layer below the cladding surface. Therefore, the implanted helium particles should mainly affect surface properties of the GCFR cladding.

  14. 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.

  15. 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.

  16. AlGaN channel field effect transistors with graded heterostructure ohmic contacts

    NASA Astrophysics Data System (ADS)

    Bajaj, Sanyam; Akyol, Fatih; Krishnamoorthy, Sriram; Zhang, Yuewei; Rajan, Siddharth

    2016-09-01

    We report on ultra-wide bandgap (UWBG) Al0.75Ga0.25N channel metal-insulator-semiconductor field-effect transistors (MISFETs) with heterostructure engineered low-resistance ohmic contacts. The low intrinsic electron affinity of AlN (0.6 eV) leads to large Schottky barriers at the metal-AlGaN interface, resulting in highly resistive ohmic contacts. In this work, we use a reverse compositional graded n++ AlGaN contact layer to achieve upward electron affinity grading, leading to a low specific contact resistance (ρsp) of 1.9 × 10-6 Ω cm2 to n-Al0.75Ga0.25N channels (bandgap ˜5.3 eV) with non-alloyed contacts. We also demonstrate UWBG Al0.75Ga0.25N channel MISFET device operation employing the compositional graded n++ ohmic contact layer and 20 nm atomic layer deposited Al2O3 as the gate-dielectric.

  17. 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}.

  18. Semi-polar (11-22) AlGaN on overgrown GaN on micro-rod templates: Simultaneous management of crystal quality improvement and cracking issue

    NASA Astrophysics Data System (ADS)

    Li, Z.; Jiu, L.; Gong, Y.; Wang, L.; Zhang, Y.; Bai, J.; Wang, T.

    2017-02-01

    Thick and crack-free semi-polar (11-22) AlGaN layers with various high Al compositions have been achieved by means of growth on the top of nearly but not yet fully coalesced GaN overgrown on micro-rod templates. The range of the Al composition of up to 55.7% was achieved, corresponding to an emission wavelength of up to 270 nm characterised by photoluminescence at room temperature. X-ray diffraction (XRD) measurements show greatly improved crystal quality as a result of lateral overgrowth compared to the AlGaN counterparts on standard planar substrates. The full width at half maximums of the XRD rocking curves measured along the [1-100]/[11-2-3] directions (the two typical orientations for characterizing the crystal quality of (11-22) AlGaN) are 0.2923°/0.2006° for 37.8% Al and 0.3825°/0.2064° for 55.7% Al, respectively, which have never been achieved previously. Our calculation based on reciprocal space mapping measurements has demonstrated significant strain relaxation in the AlGaN as a result of utilising the non-coalesced GaN underneath, contributing to the elimination of any cracks. The results presented have demonstrated that our overgrowth technique can effectively manage strain and improve crystal quality simultaneously.

  19. High-quality Ga-rich AlGaN grown on trapezoidal patterned GaN template using super-short period AlN/GaN superlattices for rapid coalescence

    NASA Astrophysics Data System (ADS)

    Xiao, Ming; Zhang, Jincheng; Hao, Yue

    2017-04-01

    High quality crack-free Ga-rich Al26.1Ga73.9N film was grown on trapezoidal patterned GaN template (TPGT) by low-pressure metalorganic chemical vapor deposition. The super-short period AlN/GaN superlattices structure was used to grow AlGaN material instead of the direct growth method. We obtained large lateral to vertical growth rate ratio larger than 4.79. The growth rate of GaN layer was proved to be the decisive factor of the lateral to vertical growth rate ratio. Moreover, for AlGaN growth, we found that that the TPGT is more beneficial to suppression of crack and relaxation of biaxial tensile strain than planar GaN template. The obtained results demonstrate that, comparing with AlGaN grown on planar GaN template, the threading dislocation density in AlGaN grown on TPGT was reduced from 2×109 cm-2 to 2×108 cm-2.

  20. Conical reflection of light during free-space coupling into a symmetrical metal-cladding waveguide.

    PubMed

    Zheng, Yuanlin; Cao, Zhuangqi; Chen, Xianfeng

    2013-09-01

    Novel conical reflection of light by a thick three-layered metal-clad optical waveguide is observed. A symmetrical metal-cladding optical waveguide is used, which exhibits extraordinary conical reflection during free-space coupling of light to the waveguide. The phenomenon is attributed to the leakage of excited ultrahigh-order guided modes and their inter- and intramode coupling interaction.

  1. Refractive index sensitivity enhancement of optical fiber cladding mode by depositing nanofilm via ALD technology.

    PubMed

    Zhao, Ying; Pang, Fufei; Dong, Yanhua; Wen, Jianxiang; Chen, Zhenyi; Wang, Tingyun

    2013-11-04

    The atomic layer deposition (ALD) technology is introduced to enhance the sensitivity of optical fiber cladding mode to surrounding refractive index (SRI) variation. The highly uniform Al2O nanofilm was deposited around the double cladding fiber (DCF) which presents cladding mode resonant feature. With the high refractive index coating, the cladding mode resonant spectrum was tuned. And the sensitivity enhancement for SRI sensor was demonstrated. Through adjusting the deposition cycles, a maximum sensitivity of 723 nm/RIU was demonstrated in the DCF with 2500 deposition cycles at the SRI of 1.34. Based on the analysis of cladding modes reorganization, the cladding modes transition of the coated DCF was investigated theoretically. With the high performance nanofilm coating, the proposed SRI sensor is expected to have wide applications in chemical sensors and biosensors.

  2. Observations on the behavior of surface flaws in the presence of cladding

    SciTech Connect

    Iskander, S.K.; Nanstad, R.K.

    1988-01-01

    A small crack near the inner surface of clad nuclear reactor pressure vessels (RPV) is an important consideration in the safety assessment of the structural integrity of the vessel. Four-point bend tests on large plate specimens, six clad and two unclad, were performed to determine the effect, if any, of stainless steel cladding upon the propagation of small surface cracks subjected to stress states similar to those produced by pressurized thermal shock conditions. Results of tests at temperature 10 and 60/degree/C below the nil-ductility-transition temperature (NDT) have shown that (1) a tough surface layer composed of cladding and/or heat-affected zone has arrested running flaws in clad plates under conditions where unclad plates have ruptured, and (2) the residual load-bearing capacity of clad plates with large subclad flaws significantly exceeded that of an unclad plate. 6 refs., 7 figs., 2 tabs.

  3. 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.

  4. Optical Measurement of Forming Limit and Formability of Cu/Al Clad Metals

    NASA Astrophysics Data System (ADS)

    Sun, Tao; Liang, Jin; Guo, Xiang; Ren, Maodong; Wang, Lizhong

    2015-04-01

    A digital image deformation measurement and analysis control system (XJTUDIC 8.0) was employed to measure the forming limit strain for Cu/Al clad metals produced via explosive welding technique. A contrast test between the digital image correlation (DIC) method and the conventional grid method was also implemented using the SPCC sheet metal forming limit test. The effect of heat treatment and contact status on forming limit was discussed based on the forming limit strain of Cu/Al clad metals. The interfacial and fracture structures were analyzed using scanning electron microscopy. The fracture site was predicted by finite element method. Results demonstrate that the forming limit curve of Cu/Al clad metals through DIC is more likely to reflect the formability of SPCC accurately. The forming limit of the clad with Al in the inner layer is higher than that of the clad with Cu in the inner layer. The formability of the annealed clads is superior to that of the non-annealed clads. The local interface failure induces the microcracks in Cu/Al clad metals during the forming process, which could be the main failure mode. With the finite element method, the fracture location of Cu/Al clad metals caused by uniaxial tensile during the forming limit test using DIC method is predicted accurately.

  5. 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.

  6. 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.

  7. Effect of doping swelling polymer cladding with phthalocyanine dye in plastic optical fiber humidity sensors

    NASA Astrophysics Data System (ADS)

    Morisawa, Masayuki; Yokomori, Haruyuki

    2011-05-01

    We have developed and tested plastic optical fiber (POF)-type humidity sensors, which consist of a dye-doped swelling polymer cladding. POF-type humidity sensors consist of a hydroxyethyl cellulose or polyvinylpyrrolidone (PVP) cladding layer that surrounds a poly(methyl methacrylate) core. The operation of these sensors is based on the change in refractive index caused by swelling of the cladding layer. To improve the sensitivity of the humidity sensor, we have investigated the effect of doping the cladding polymer with phthalocyanine dye. The results indicate that the POF-type humidity sensor using PVP is three times more sensitive for relative humidities above 80% when the dyedoped swelling-polymer cladding is used.

  8. 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.

  9. 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.

  10. 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.

  11. Molecular beam epitaxy growth of Al-rich AlGaN nanowires for deep ultraviolet optoelectronics

    NASA Astrophysics Data System (ADS)

    Zhao, S.; Woo, S. Y.; Sadaf, S. M.; Wu, Y.; Pofelski, A.; Laleyan, D. A.; Rashid, R. T.; Wang, Y.; Botton, G. A.; Mi, Z.

    2016-08-01

    Self-organized AlGaN nanowires by molecular beam epitaxy have attracted significant attention for deep ultraviolet optoelectronics. However, due to the strong compositional modulations under conventional nitrogen rich growth conditions, emission wavelengths less than 250 nm have remained inaccessible. Here we show that Al-rich AlGaN nanowires with much improved compositional uniformity can be achieved in a new growth paradigm, wherein a precise control on the optical bandgap of ternary AlGaN nanowires can be achieved by varying the substrate temperature. AlGaN nanowire LEDs, with emission wavelengths spanning from 236 to 280 nm, are also demonstrated.

  12. 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.

  13. 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.

  14. Study of the Linewidths of Excitonic Luminescence Transitions in AlGaN Alloys

    NASA Astrophysics Data System (ADS)

    Bajaj, K. K.; Coli, Giuliano; Li, J.; Lin, Jingyu; Jiang, H. X.

    2001-03-01

    We have investigated the linewidth of excitonic photoluminescence transitions at 10 K and as a function of Al concentration in AlGaN alloys grown by low-pressure metal organic chemical vapor deposition on (0001) oriented sapphire substrates, with low-temperature GaN buffer layers. Al composition ranged from 0 to 35 percent. By means of a lineshape analysis of the excitonic transition we identify the contribution of the compositional disorder in the alloy to the excitonic linewidth and find that the values of the excitonic linewidths in our samples are considerably smaller than those reported recently[1]. These values of the excitonic linewidths, as expected, increase as a function of Al concentration and agree very well with those calculated by a model presented by Lee and Bajaj[2]. [1] G. Steude, B.K. Meyer, A. Göldner, A. Hoffmann, F. Bertram, J.Christen, H. Amano and I. Akasaki, Appl. Phys. Lett 74, 2456 (1999) [2] S. M. Lee and K. K. Bajaj, J. Appl. Phys. 73, 1788 (1993)

  15. An experimental study of the effect of stainless steel cladding on the structural integrity of flawed steel plates in bending

    SciTech Connect

    Iskander, S.K.; Nanstad, R.K.; Robinson, G.C.; Oland, C.B.

    1989-01-01

    A small crack near the inner surface of clad nuclear reactor pressure vessels is an important consideration in the safety assessment of the structural integrity of the vessel. Experimental results from tests on large clad and unclad plate specimens with surface flaws have shown that (1) a tough surface layer composed of cladding and/or heat-affected zone has arrested running flaws in clad plates under conditions where unclad plates have ruptured, and (2) the residual load-bearing capacity of clad plates with large subclad flaws significantly exceeded that of an unclad plate. The fracture surfaces of unclad plates suggest that the flaw evolves through alternately tunneling then breaking to the surface. In the case of clad plates, it is hypothesized that the tough, strong surface layer inhibits the tunneled flaw from propagating to the surface.

  16. 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.

  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. Modification of Al-Si alloy surface layer using Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Radziszewska, Agnieszka E.; Kąc, Sławomir Z.

    2007-02-01

    The paper describes the laser cladding of hypereutectic Al-Si alloy with chromium. An impulse Nd:YAG laser was employed for laser cladding process. The article presents the changes of microstructure, chemical composition, microhardness of the obtained clad layers, which were depended on the effect of the laser processing parameters and the thickness of chromium coatings. The laser cladding produced the very fine microstructure and higher hardness of clad layers.

  19. 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.

  20. 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.

  1. Polarization-induced electrical conductivity in ultra-wide band gap AlGaN alloys

    NASA Astrophysics Data System (ADS)

    Armstrong, Andrew M.; Allerman, Andrew A.

    2016-11-01

    Unintentionally doped (UID) AlGaN epilayers graded over Al compositions of 80%-90% and 80%-100% were grown by metal organic vapor phase epitaxy and were electrically characterized using contactless sheet resistance (Rsh) and capacitance-voltage (C-V) measurements. Strong electrical conductivity in the UID graded AlGaN epilayers resulted from polarization-induced doping and was verified by the low resistivity of 0.04 Ω cm for the AlGaN epilayer graded over 80%-100% Al mole fraction. A free electron concentration (n) of 4.8 × 1017 cm-3 was measured by C-V for Al compositions of 80%-100%. Average electron mobility ( μ ¯ ) was calculated from Rsh and n data for three ranges of Al composition grading, and it was found that UID AlGaN graded from 88%-96% had μ ¯ = 509 cm2/V s. The combination of very large band gap energy, high μ ¯ , and high n for UID graded AlGaN epilayers make them attractive as a building block for high voltage power electronic devices such as Schottky diodes and field effect transistors.

  2. Hydrogen permeation in FeCrAl alloys for LWR cladding application

    DOE PAGES

    Hu, Xunxiang; Terrani, Kurt A.; Wirth, Brian D.; ...

    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

  3. 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.

  4. Underwater cladding with laser beam and plasma arc welding

    SciTech Connect

    White, R.A.; Fusaro, R.; Jones, M.G.; Solomon, H.D.; Milian-Rodriguez, R.R.

    1997-01-01

    Two welding processes, plasma arc (transferred arc) (PTA) and laser beam, were investigated to apply cladding to austenitic stainless steels and Inconel 600. These processes have long been used to apply cladding layers , but the novel feature being reported here is that these cladding layers were applied underwater, with a water pressure equivalent to 24 m (80 ft). Being able to apply the cladding underwater is very important for many applications, including the construction of off-shore oil platforms and the repair of nuclear reactors. In the latter case, being able to weld underwater eliminates the need for draining the reactor and removing the fuel. Welding underwater in reactors presents numerous challenges, but the ability to weld without having to drain the reactor and remove the fuel provides a huge cost savings. Welding underwater in reactors must be done remotely, but because of the radioactive corrosion products and neutron activation of the steels, remote welding would also be required even if the reactor is drained and the fuel removed. In fact, without the shielding of the water, the remote welding required if the reactor is drained might be even more difficult than that required with underwater welds. Furthermore, as shall be shown, the underwater welds that the authors have made were of high quality and exhibit compressive rather than tensile residual stresses.

  5. Botulinum toxin detection using AlGaN /GaN high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Wang, Yu-Lin; Chu, B. H.; Chen, K. H.; Chang, C. Y.; Lele, T. P.; Tseng, Y.; Pearton, S. J.; Ramage, J.; Hooten, D.; Dabiran, A.; Chow, P. P.; Ren, F.

    2008-12-01

    Antibody-functionalized, Au-gated AlGaN /GaN high electron mobility transistors (HEMTs) were used to detect botulinum toxin. The antibody was anchored to the gate area through immobilized thioglycolic acid. The AlGaN /GaN HEMT drain-source current showed a rapid response of less than 5s when the target toxin in a buffer was added to the antibody-immobilized surface. We could detect a range of concentrations from 1to10ng/ml. These results clearly demonstrate the promise of field-deployable electronic biological sensors based on AlGaN /GaN HEMTs for botulinum toxin detection.

  6. 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]).

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Low threshold for optical damage in AlGaN epilayers and heterostructures

    SciTech Connect

    Saxena, Tanuj; Tamulaitis, Gintautas; Shatalov, Max; Yang, Jinwei; Gaska, Remis; Shur, Michael S.

    2013-11-28

    Laser pulses with duration much shorter than the effective carrier lifetime cause permanent photoluminescence (PL) quenching and enhancement of PL decay rate in bare-faceted and capped AlGaN epilayers and multiple quantum wells at pulse energies about an order of magnitude lower than those causing the surface to melt and degrade. In contrast, GaN epilayers exhibit no photomodification in the same excitation intensity range. PL spectra and decay kinetics show that lattice heating is not responsible for the observed changes in AlGaN, which result from the formation of nonradiative recombination centers via recombination-enhanced defect reactions occurring at high nonequilibrium carrier densities.

  13. Effects of commercial cladding on the fracture behavior of pressure vessel steel plates

    SciTech Connect

    Iskander, S.K.; Alexander, D.J.; Bolt, S.E.; Cook, K.V.; Corwin, W.R.; Oland, B.C.; Nanstad, R.K.; Robinson, G.C.

    1987-01-01

    The objective of this program is to determine the effect, if any, of stainless steel cladding upon the propagation of small surface cracks subjected to stress states similar to those produced by thermal shock conditions. Preliminary results from testing at temperatures 10/sup 0/ and 60/sup 0/C below NDT have shown that (1) a tough surface layer (cladding and/or HAZ) has arrested running flaws under conditions where unclad plates have ruptured, and (2) the residual load-bearing capacity of clad plates with large subclad flaws significantly exceeded that of an unclad plate.

  14. 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

  15. 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

    2016-09-01

    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.

  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. 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)

  18. Improved Synthesis of Carbon Clad Silica Stationary Phases

    PubMed Central

    Ahmad, Imad A. Haidar; Carr, Peter W.

    2014-01-01

    Previously we described a novel method for clading elemental carbon onto the surface of catalytically activated silica by a chemical vapor deposition (CVD) method using hexane as the carbon source and its use as a substitute for carbon clad zirconia.1,2 In that method, we showed that very close to exactly one uniform monolayer of Al (III) was deposited on the silica by a process analogous to precipitation from homogeneous solution in order to preclude pore blockage. The purpose of the Al(III) monolayer layer is to activate the surface for subsequent CVD of carbon. In this work, we present an improved procedure for preparing the carbon clad silica (denoted CCSi) phases along with a new column packing process. The new method yields CCSi phases having better efficiency, peak symmetry and higher retentivity compared to carbon clad zirconia. The enhancements were achieved by modifying the original procedure in three ways: first. the kinetics of the deposition of Al(III) were more stringently controlled, second the CVD chamber was flushed with a mixture of hydrogen and nitrogen gas during the carbon cladding process to minimize generation of polar sites by oxygen incorporation, and third the fine particles generated during the CVD process were exhaustively removed by flotation in an appropriate solvent. PMID:24228897

  19. 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.

  20. 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.

  1. 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).

  2. Cladding of the carbon fiber on the steel base using electron beam in the air atmosphere

    NASA Astrophysics Data System (ADS)

    Losinskaya, A.; Lozhkina, E.; Bardin, A.; Stepanova, N.

    2016-11-01

    The formation of the high-carbon layers on the low-carbon steel (0.18 % C) using the method of electron-beam partial melting of the carbon fibers is considered. A 1.4 MeV electron beam extracted into air was used. The features of the cladded layers formation using different binders for a reliable fixation of the cladding material are studied. It is revealed that the best results are obtained using the phenol-formaldehyde glue as the binder. A 3 mm thickness layers with 2.2 % C are shown to be formed.

  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. Novel design of hollow-core multi clad fiber for long haul optical communication system

    NASA Astrophysics Data System (ADS)

    Palodiya, Vikram; Raghuwanshi, Sanjeev K.

    2016-09-01

    We have described a dispersion characteristics of hollow-core multi-clad index profiles, which include a hollow core. The designs satisfy the most important requirements for applications in long haul communication. This design fiber shows zero dispersion at 1550 nm can be obtained for the fundamental air core mode over a wide wavelength range by introducing the partial reflector layer around the core, optimizing expanded core size and silica cladding thickness. Also analyze dispersion compensating properties of these fibers. This unique structure of the fundamental air core mode is presented by the introduction of partial reflector cladding around the core. The potential applications of hollow-core multi clad fibers in long-haul optical communication system.

  5. Material and design engineering of (Al)GaN for high-performance avalanche photodiodes and intersubband applications

    NASA Astrophysics Data System (ADS)

    Razeghi, M.; Bayram, C.

    2009-05-01

    Numerous applications in scientific, medical, and military areas demand robust, compact, sensitive, and fast ultraviolet (UV) detection. Our (Al)GaN photodiodes pose high avalanche gain and single-photon detection efficiency that can measure up to these requirements. Inherit advantage of back-illumination in our devices offers an easier integration and layout packaging via flip-chip hybridization for UV focal plane arrays that may find uses from space applications to hostile-agent detection. Thanks to the recent (Al)GaN material optimization, III-Nitrides, known to have fast carrier dynamics and short relaxation times, are employed in (Al)GaN based superlattices that absorb in near-infrared regime. In this work, we explain the origins of our high performance UV APDs, and employ our (Al)GaN material knowledge for intersubband applications. We also discuss the extension of this material engineering into the far infrared, and even the terahertz (THz) region.

  6. Molecular beam epitaxial growth and characterization of Al(Ga)N nanowire deep ultraviolet light emitting diodes and lasers

    NASA Astrophysics Data System (ADS)

    Mi, Z.; Zhao, S.; Woo, S. Y.; Bugnet, M.; Djavid, M.; Liu, X.; Kang, J.; Kong, X.; Ji, W.; Guo, H.; Liu, Z.; Botton, G. A.

    2016-09-01

    We report on the detailed molecular beam epitaxial growth and characterization of Al(Ga)N nanowire heterostructures on Si and their applications for deep ultraviolet light emitting diodes and lasers. The nanowires are formed under nitrogen-rich conditions without using any metal catalyst. Compared to conventional epilayers, Mg-dopant incorporation is significantly enhanced in nearly strain- and defect-free Al(Ga)N nanowire structures, leading to efficient p-type conduction. The resulting Al(Ga)N nanowire LEDs exhibit excellent performance, including a turn-on voltage of ∼5.5 V for an AlN nanowire LED operating at 207 nm. The design, fabrication, and performance of an electrically injected AlGaN nanowire laser operating in the UV-B band is also presented.

  7. The Property Research on High-entropy Alloy AlxFeCoNiCuCr Coating by Laser Cladding

    NASA Astrophysics Data System (ADS)

    Ye, Xiaoyang; Ma, Mingxing; Cao, Yangxiaolu; Liu, Wenjin; Ye, Xiaohui; Gu, Yu

    High-entropy alloys have been found to have novel microstructures and unique properties. The main method of manufacturing is vacuum arc remelting. As in situ cladding laser cladding has capability of achieving a controllable dilution ratio, fabricating highentropy alloy by laser cladding is of great significance and potential for extensive use. In this study, a novel AlxFeCoNiCuCr high-entropy alloy system was manufactured as the thin layer of the substrate by laser cladding; also high temperature hardness, abrasion performance, corrosion nature of the AlxFeCoNiCuCr high-entropy alloy were tested under the different ratio of aluminum. This study shows higher aluminum clad exhibit higher hardness, better abrasion resistance and corrosion resistance.

  8. 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).

  9. 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.

  10. 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.

  11. Secondary ion mass spectrometry of irradiated nuclear fuel and cladding

    NASA Astrophysics Data System (ADS)

    Portier, S.; Brémier, S.; Walker, C. T.

    2007-06-01

    The principles and operating modes of secondary ion mass spectrometry (SIMS) are first described after which the different methods of quantification are summarised. Some current applications of SIMS in nuclear fuel and cladding research are then reviewed after briefly considering the modifications that are needed to allow a SIMS instrument to be used for the analysis of highly radioactive materials. Amongst the applications reported are the investigation of the behaviour of fission gas xenon and the volatile fission products tellurium, iodine and caesium in UO2 nuclear fuel, measurement of the radial distribution of Pu isotopes in mixed oxide (MOX) fuel and of the radial distribution of Gd isotopes in (U,Gd)O2 fuel, and determination of the distribution of Li and B in the external oxide layer on Zircaloy cladding. It is evident from the large amount of new information gained that SIMS is a powerful complementary technique to electron probe microanalysis (EPMA) in these fields of study.

  12. Modelling of capacitance and threshold voltage for ultrathin normally-off AlGaN /GaN MOSHEMT

    NASA Astrophysics Data System (ADS)

    Swain, R.; Jena, K.; Lenka, T. R.

    2017-01-01

    A compact quantitative model based on oxide semiconductor interface density of states (DOS) is proposed for Al0.25Ga0.75N/GaN metal oxide semiconductor high electron mobility transistor (MOSHEMT). Mathematical expressions for surface potential, sheet charge concentration, gate capacitance and threshold voltage have been derived. The gate capacitance behaviour is studied in terms of capacitance-voltage (CV) characteristics. Similarly, the predicted threshold voltage ( V T) is analysed by varying barrier thickness and oxide thickness. The positive V T obtained for a very thin 3 nm AlGaN barrier layer enables the enhancement mode operation of the MOSHEMT. These devices, along with depletion mode devices, are basic constituents of cascode configuration in power electronic circuits. The expressions developed are used in conventional long-channel HEMT drain current equation and evaluated to obtain different DC characteristics. The obtained results are compared with experimental data taken from literature which show good agreement and hence endorse the proposed model.

  13. 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.

  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. Status of AlGaN based focal plane arrays for UV solar blind detection

    NASA Astrophysics Data System (ADS)

    Reverchon, Jean-Luc; Mazzeo, Giovanni; Dussaigne, Amélie; Duboz, Jean-Yves

    2005-10-01

    The fast development of nitrides has given the opportunity to investigate AlGaN as a material for ultraviolet solar blind detection in competition with technologies based on photocathodes, MCP intensifiers, back thinned CCD or hybrid CMOS focal plane arrays. All of the them must be associated to UV blocking filters. These new detectors present both an intrinsic spectral selectivity and an extremely low dark current at room temperature. First we will present the ultimate properties of the AlGaN based devices. These spectral properties are analysed in regards to the sharp cut off required for solar blind detection around 280nm, and we will quantify how the stringent difficulties to achieve solar blind filters can be reduced. We also investigated the electrical capabilities of Schottky diodes or Metal-Semiconductor-Metal (MSM) technologies to detect extremely low UV signal. We will especially present results from a linear array based on a CCD readout multiplexor.

  16. 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.

  17. Theoretical study of electrolyte gate AlGaN /GaN field effect transistors

    NASA Astrophysics Data System (ADS)

    Bayer, M.; Uhl, C.; Vogl, P.

    2005-02-01

    We predict the sensitivity of solution gate AlGaN /GaN field effect transistors to pH values of the electrolyte and to charged adsorbates at the semiconductor-electrolyte interface. Invoking the site-binding model for the chemical reactions at the oxidic semiconductor-electrolyte interface and taking into account the large polarization fields within the nitride heterostructure, the spatial charge and potential distribution have been calculated self-consistently both in the semiconductor and the electrolyte. In addition, the source-drain current is calculated and its sensitivity to the electrolyte's pH value is studied systematically. Comparison with experiment shows good agreement. A significantly enhanced resolution is predicted for AlGaN /GaN structures of N-face polarity.

  18. 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.

  19. 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

  20. The role of surface kinetics on composition and quality of AlGaN

    NASA Astrophysics Data System (ADS)

    Bryan, Isaac; Bryan, Zachary; Mita, Seiji; Rice, Anthony; Hussey, Lindsay; Shelton, Christopher; Tweedie, James; Maria, Jon-Paul; Collazo, Ramón; Sitar, Zlatko

    2016-10-01

    Metal-polar, Al-rich AlGaN films were grown on both single crystalline AlN and sapphire substrates. The role of surface morphology and surface kinetics on AlGaN composition is presented. With the reduced dislocation density of the films grown on AlN substrates, atomically smooth bilayer stepped surfaces are achieved with RMS roughness of less than 50 pm for a 5×5 μm2 AFM scan area. By controlling the surface supersaturation through adjusting the growth rate, a transition from 2D nucleation to step flow was observed. The critical misorientation angle for step-bunching in nominal Al0.70Ga0.30N grown with a growth rate of 600 nm/h on AlN substrates was found to be 0.4°. The composition of bilayer stepped AlGaN was strongly dependent on substrate misorientation angle, where a compositional variation by a factor of two for a change in misorientation angle from 0.05 to 0.40° was observed; this is explained by the different surface diffusion lengths of Ga and Al. Step-bunching resulted in strong compositional inhomogeneity as observed by photoluminescence and scanning transmission electron microscopy studies.

  1. Interfacial characteristics and properties of a low-clad-ratio AA4045/AA3003 cladding billet fabricated by semi-continuous casting

    NASA Astrophysics Data System (ADS)

    Han, Xing; Zhang, Hai-tao; Shao, Bo; Li, Lei; Qin, Ke; Cui, Jian-zhong

    2016-09-01

    A low-clad-ratio AA4045/AA3003 cladding billet was fabricated using a semi-continuous casting process and was subsequently extruded indirectly into a cladding pipe. The temperature distribution near the interface was measured. The microstructures, elemental distribution, Vickers hardness around the bonding interface, and the interfacial shear strength were examined. The results showed that the interface temperature rebounded when AA4045 melt contacted the supporting layer. The two alloys bonded well, with few defects, via the diffusion of Si and Mn in the temperature range from 569°C to 632°C. The mean shear strength of the bonding interface was 82.3 MPa, which was greater than that of AA3003 (75.8 MPa), indicating that the two alloys bonded with each other metallurgically via elemental interdiffusion. Moreover, no relative slip occurred between the two alloys during the extrusion process.

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

    SciTech Connect

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

    1995-12-31

    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 are 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 3.3-inch OD x 2.5-inch ID tubes, and (at a ratio of 37.6) to 2-inch OD x 1.5-inch ID tubes. In all, ten castings were produced, and 12 billets were extruded to tubes. For the most part, thicknesses of the cladding and tube wall are rather uniform around the circumference and from end to end of the tubes. Hardness and tensile Properties of annealed 2-inch tubes are uniform from end to 6nd 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 hear-strength test and a twist test. In the latter test, rings 0.125 inch 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 just 2.7 percent of the bond-line length. Cost estimates OCCUPY for commercial production of 2-inch 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).

  3. 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).

  4. Microstructure and properties of laser-clad high-temperature wear-resistant alloys

    NASA Astrophysics Data System (ADS)

    Yang, Yongqiang

    1999-02-01

    A 2-kW CO 2 laser with a powder feeder was used to produce alloy coatings with high temperature-wear resistance on the surface of steel substrates. To analyze the microstructure and microchemical composition of the laser-clad layers, a scanning electron microscope (SEM) equipped with an energy dispersive X-ray microanalysis system was employed. X-ray diffraction techniques were applied to characterize the phases formed during the cladding process. The results show that the microstructure of the cladding alloy consists mainly of many dispersed particles (W 2C, (W,Ti)C 1- x, WC), a lamellar eutectic carbide M 12C, and an (f.c.c) matrix. Hardness tested at room and high temperature showed that the laser-clad zone has a moderate room temperature hardness and relatively higher elevated temperature hardness. The application of the laser-clad layer to a hot tool was very successful, and its operational life span was prolonged 1 to 4 times.

  5. The effect of stainless steel overlay cladding on corrosion fatigue crack propagation in pressure vessel steel in PWR primary coolant

    SciTech Connect

    Bramwell, I.L.; Tice, D.R.; Worswick, D.; Heys, G.B.

    1995-12-31

    The growth of sub-critical cracks in pressure boundary materials in light water reactors is assessed using codified procedures, but the presence of the overlay-welded stainless steel cladding on the pressure vessel is not normally taken into consideration because of the difficulty in demonstrating clad integrity for the lifetime of the plant. In order to investigate any possible effect of the cladding layer on crack propagation, tests have been performed using two types of specimen. The first was sputter ion plated with a thin layer of austenitic stainless steel to simulate the electrochemical and oxide effects due to the cladding, whilst the second used an overlay clad specimen to investigate the behavior of a crack propagating from the austenitic into the ferritic material. Testing was carried out under cyclic loading conditions in well controlled simulated PWR primary water. At 288 C, the presence of stainless steel in contact with the low alloy steel did not enhance crack propagation in PWR primary coolant compared to unclad or unplated specimens. There was limited evidence that at 288 C under certain loading conditions, in both air and PWR water, there may be an effect of the cladding which reduces crack growth rates, at least for a short distance of crack propagation into the low alloy steel. Crack growth rates in the ferritic steel at 130 C were higher for both the plated and clad specimens than found in previous tests under similar conditions on the unclad material. However, the crack growth rates were bounded by current ASME 11 Appendix A recommendations for defects exposed to water and at low R ratio. There was no evidence of environmental enhancement of crack propagation in the stainless steel in clad specimens. The results indicate that the current approach of ignoring the cladding for assessment purposes is conservative at plant operating temperature.

  6. 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?

  7. 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?

  8. 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.

  9. 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).

  10. 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.

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

    DOE PAGES

    Crawford, Mary H.; Allerman, Andrew A.; Armstrong, Andrew M.; ...

    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.

  12. 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.

  13. Room-temperature deep-ultraviolet lasing at 241.5 nm of AlGaN multiple-quantum-well laser

    NASA Astrophysics Data System (ADS)

    Takano, Takayoshi; Narita, Yoshinobu; Horiuchi, Akihiko; Kawanishi, Hideo

    2004-05-01

    Room-temperature deep-ultraviolet lasing of AlxGa1-xN multiple-quantum-well lasers with an Al composition x of 0.66 was achieved at 241.5 nm under pulsed optical pumping. The threshold pumping power was approximately 1200 kW/cm2 at room temperature. The shortest lasing wavelength was 231.8 nm at 20 K. The laser structure was grown on a high-quality AlN layer, which was grown on a 4H-SiC substrate by inserting an AlN/GaN multibuffer-layer structure between the substrate and the AlN layer. Temperature dependence of lasing wavelength was also estimated to be 0.01 and 0.03 nm/K in the temperature region from 20 to 150 K and from 160 K to room temperature, respectively. The laser cavity was made of a cleaved facet of AlGaN epitaxial layers and a SiC substrate. For this purpose, it was necessary to polish the wafer to a thickness of less than 100 μm. The optimal wafer thickness for cleaving in our experiments was 60-70 μm.

  14. High quantum efficiency ultraviolet/blue AlGaN /InGaN photocathodes grown by molecular-beam epitaxy

    NASA Astrophysics Data System (ADS)

    Leopold, D. J.; Buckley, J. H.; Rebillot, P.

    2005-08-01

    Enormous technological breakthroughs have been made in optoelectronic devices through the use of advanced heteroepitaxial-semiconductor crystal-growth techniques. This technology is being extended toward enhanced ultraviolet/blue single-photon detection through the design and fabrication of atomically tailored heteroepitaxial GaAlN /GaInN photocathode device structures. The AlGaN /InGaN system is ideal because the band gap can be tailored over an energy range from 0.8 to 6.2 eV and epitaxial thin-film layers can be grown directly on optically transparent sapphire substrates. Although a single p-type GaN layer activated with cesium can produce reasonably high quantum efficiency in the ultraviolet wave band, a more complex design is necessary to achieve high levels extending into the blue region. In the present work, band-gap engineering concepts have been utilized to design heterostructure photocathodes. The increased level of sophistication offered by this approach has been exploited in an attempt to precisely control photoelectron transport to the photocathode surface. Thin heterostructure layers designed for transmission-mode detection were fabricated by molecular-beam epitaxy. A quantum efficiency of 40% at 250 nm was achieved using a thin, compositionally graded GaN /InGaN layer, epitaxially grown on a sapphire substrate. Further improvements are anticipated through continued optimization, defect reduction, and more complex photocathode designs.

  15. 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.

  16. 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.

  17. The influence of cladding on fission gas release from irradiated U-Mo monolithic fuel

    NASA Astrophysics Data System (ADS)

    Burkes, Douglas E.; Casella, Amanda J.; Casella, Andrew M.

    2017-04-01

    The monolithic uranium-molybdenum (U-Mo) alloy has been proposed as a fuel design capable of converting the world's highest power research reactors from use of high enriched uranium to low enriched uranium. However, a zirconium (Zr) diffusion barrier must be used to eliminate interactions that form between the U-Mo monolith and aluminum alloy 6061 (AA6061) cladding during fabrication and are enhanced during irradiation. One aspect of fuel development and qualification is to demonstrate an appropriate understanding of the extent of fission product release from the fuel under anticipated service environments. An exothermic reaction has previously been observed between the AA6061 cladding and Zr diffusion layer. In this paper, two fuel segments with different irradiation history were subjected to specified thermal profiles under a controlled atmosphere using a thermogravimetric/differential thermal analyzer coupled with a mass spectrometer inside a hot cell. Samples from each segment were tested with cladding and without cladding to investigate the effect, if any, that the exothermic reaction has on fission gas release mechanisms. Measurements revealed there is an instantaneous effect of the cladding/Zr exothermic reaction, but not necessarily a cumulative effect above approximately 973 K (700 °C). The mechanisms responsible for fission gas release events are discussed.

  18. 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.

  19. 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

  20. Lasing and Longitudinal Cavity Modes in Photo-Pumped Deep Ultraviolet AlGaN Heterostructures

    DTIC Science & Technology

    2013-04-29

    found else- where.19 Laser cavities were obtained by cleaving along the m-facet of the AlN wafer . For the 1.5 mm long cavity, the cleaving was done with... lasers . The authors would like to thank Paul Rozvadovsky of HexaTech for wafer thinning, which made cleaving of short cavities possible. 1S. Nakamura...NC 27709-2211 15. SUBJECT TERMS AlGaN lasers , optical pumping, longitudinal cavity modes Jinqiao Xie, Seiji Mita, Zachary Bryan, Wei Guo, Lindsay

  1. Photogalvanic effects for interband absorption in AlGaN /GaN superlattices

    NASA Astrophysics Data System (ADS)

    Cho, K. S.; Chen, Y. F.; Tang, Y. Q.; Shen, B.

    2007-01-01

    The linear and circular photogalvanic effects (CPGEs), induced by ultraviolet (325nm) radiation, have been observed in the (0001)-oriented Al0.15Ga0.85N/GaN superlattices. The CPGE current changes sign upon reversing the radiation helicity, and it is up to two orders of magnitude larger than that obtained by far-infrared radiation. This result suggests the existence of a sizeable Rashba spin splitting in AlGaN /GaN superlattices. It also provides a possibility for the generation of spin orientation-induced current at room temperature.

  2. 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

  3. Corrosion Behavior of Copper-Clad Steel Bars with Unclad Two-End Faces for Grounding Grids in the Red Clay Soil

    NASA Astrophysics Data System (ADS)

    Shao, Yupei; Mu, Miaomiao; Zhang, Bing; Nie, Kaibin; Liao, Qiangqiang

    2017-02-01

    Iron-aluminum oxides in the red soil have a significant impact on the corrosion behavior of the metal for grounding grids. Effects of iron-aluminum oxides on the corrosion behavior of the cross section of copper-clad steel in the red soil have been investigated using electrochemical impedance spectroscopy and Tafel polarization. All the data indicate that the iron-aluminum oxides can promote the corrosion of copper-clad steel in the red soil. The corrosivity of the red soil greatly increases after iron-aluminum oxides are added into the soil. Iron-aluminum oxides promote galvanic corrosion of copper-clad steel and increase the corrosion degree of the center steel layer. The iron-aluminum oxides stimulate corrosion process of copper-clad steel acting as a cathodic depolarizing agent. XRD results further validate that the corrosion products of the copper-clad steel bar mainly consist of Fe3O4 and Cu2O.

  4. 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

  5. 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.

  6. Enhanced photoluminescence efficiency in AlGaN quantum wells with gradient-composition AlGaN barriers

    NASA Astrophysics Data System (ADS)

    Shevchenko, E. A.; Nechaev, D. V.; Jmerik, V. N.; Kaibyshev, V. Kh; Ivanov, S. V.; Toropov, A. A.

    2016-08-01

    We present photoluminescence studies of AIxGa1-xN/AlyGa1-yN (y = x+0.3) quantum well (QW) heterostructures with graded AI content in barrier layers, emitting in the range 285-315 nm. The best-established internal quantum efficiency of the QW emission is as high as 81% at 300 K, owing to enhanced activation energy of charge carriers and exciton binding energy in the QW heterostructure with optimized design.

  7. 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

    2015-09-03

    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.

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

    DOE PAGES

    Keiser, Dennis D.; Jue, Jan-Fong; Miller, Brandon; ...

    2015-09-03

    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 inmore » 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.« less

  9. Efficient operation of double-clad Yb3+-doped fiber lasers with a novel circular cladding geometry.

    PubMed

    Martínez-Rios, A; Starodumov, A N; Po, H; Wang, Y; Demidov, A A; Li, X

    2003-09-15

    A highly efficient double-clad Yb3+-doped fiber laser with a novel cladding geometry is described. A round double-clad fiber with a small D-shaped hole for breaking a circular symmetry in a cladding combines the advantages of ease of manufacture and handling round fibers with efficient absorption of pump light. Fiber lasers with a double-D cladding shape and a D-hole cladding are compared. We report what are to our knowledge the highest slope efficiencies of 73% and 69%, respectively, pumping at 915 nm. Output powers in excess of 13 W are demonstrated.

  10. 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

  11. Fabrication of a tantalum-clad tungsten target for LANSCE

    NASA Astrophysics Data System (ADS)

    Nelson, A. T.; O'Toole, J. A.; Valicenti, R. A.; Maloy, S. A.

    2012-12-01

    Development of a solid state bonding technique suitable to clad tungsten targets with tantalum was completed to improve operation of the Los Alamos Neutron Science Centers spallation target. Significant deterioration of conventional bare tungsten targets has historically resulted in transfer of tungsten into the cooling system through corrosion resulting in increased radioactivity outside the target and reduction of delivered neutron flux. The fabrication method chosen to join the tantalum cladding to the tungsten was hot isostatic pressing (HIP) given the geometry constraints of a cylindrical assembly and previous success demonstrated at KENS. Nominal HIP parameters of 1500 °C, 200 MPa, and 3 h were selected based upon previous work. Development of the process included significant surface engineering controls and characterization given tantalums propensity for oxide and carbide formation at high temperatures. In addition to rigorous acid cleaning implemented at each step of the fabrication process, a three layer tantalum foil gettering system was devised such that any free oxygen and carbon impurities contained in the argon gas within the HIP vessel was mitigated to the extent possible before coming into contact with the tantalum cladding. The result of the numerous controls and refined techniques was negligible coarsening of the native Ta2O5 surface oxide, no measureable oxygen diffusion into the tantalum bulk, and no detectable carburization despite use of argon containing up to 5 ppm oxygen and up to 40 ppm total CO, CO2, or organic contaminants. Post bond characterization of the interface revealed continuous bonding with a few microns of species interdiffusion.

  12. Development of ultraviolet electroabsorption modulators and light emitting diodes based on AlGaN alloys

    NASA Astrophysics Data System (ADS)

    Kao, Chen-Kai

    The research in this dissertation addressed the development of ultraviolet (UV) electroabsorption modulators and ultraviolet light emitting diodes (UV-LEDs), covering the spectral range from 360 to 265 nm. The materials system for both types of devices is the AlGaN alloys, either in bulk or quantum well (QW) form, grown by plasma-assisted molecular beam epitaxy (MBE). Potential applications of these devices either individually or in combination include UV non-line-of-sight free-space-optical communications, UV sensing and spectroscopic systems, Q-switched pulsed lasers, water/air purification and various medical applications. Optical modulators based on cubic III-V semiconductors have been the subject of extensive research over the past several years. Such devices are typically based on the quantum-confined Stark effect to modify the absorption spectrum of multiple-quantum-well active regions. On the other hand, in wurtzite III-Nitride semiconductors, strong electric fields are already present in the quantum wells due to intrinsic and piezoelectric polarizations; as a result, an even greater change in absorption is achievable, especially if the internal fields are compensated by the external bias so that the net field in the quantum wells is reduced. A number of UV electroabsorption modulators based on Schottky barriers on bulk GaN and GaN /AlGaN multiple quantum wells (MQWs) were designed, fabricated and characterized. Record modulation ratio of 30 % was obtained from bulk GaN Schottky barrier modulators at the excitonic resonant energy of 3.45 eV (360 nm) upon the application of 12 V reverse bias. Similarly, record modulation ratio of 43% was obtained from GaN / AlGaN MQWs Schottky barrier modulators at the excitonic resonant energy of 3.48 eV (356 nm) upon the application of 17 V reverse bias. The external quantum efficiency (EQE) of AlGaN based deep UV LEDS is relatively low (˜1% at 270 nm). This is generally attributed to the poor internal quantum efficiency

  13. 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

  14. Engineering the carrier dynamics of InGaN nanowire white light-emitting diodes by distributed p-AlGaN electron blocking layers.

    PubMed

    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

    2015-01-16

    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.

  15. 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.

  16. High-temperature carrier density and mobility enhancements in AlGaN/GaN HEMT using AlN spacer layer

    NASA Astrophysics Data System (ADS)

    Ko, Tsung-Shine; Lin, Der-Yuh; Lin, Chia-Feng; Chang, Che-Wei; Zhang, Jin-Cheng; Tu, Shang-Ju

    2017-04-01

    In this paper, we experimentally studied the effect of AlN spacer layer on optical and electrical properties of AlGaN/GaN high electric mobility transistors (HEMTs) grown by metal organic chemical vapor deposition method. For AlGaN layer in HEMT structure, the Al composition of the sample was determined using x-ray diffraction and photoluminescence. Electrolyte electro-reflectance (EER) measurement not only confirmed the aluminum composition of AlGaN layer, but also determined the electric field strength on the AlGaN layer through the Franz-Keldysh oscillation phenomenon. This result indicated that the electric field on the AlGaN layer could be improved from 430 to 621 kV/cm when AlN spacer layer was inserted in HEMT structure, which increased the concentration of two dimensional electron gas (2DEG) and improve the mobility. The temperature dependent Hall results show that both the mobility and the carrier concentration of 2DEG would decrease abruptly causing HEMT loss of function due to phonon scattering and carrier thermal escape when temperature increases above a specific value. Meanwhile, our study also demonstrates using AlN spacer layer could be beneficial to allow the mobility and carrier density of 2DEG sustaining at high temperature region.

  17. Surface protection of light metals by one-step laser cladding with oxide ceramics

    NASA Astrophysics Data System (ADS)

    Nowotny, S.; Richter, A.; Tangermann, K.

    1999-06-01

    Today, intricate problems of surface treatment can be solved through precision cladding using advanced laser technology. Metallic and carbide coatings have been produced with high-power lasers for years, and current investigations show that laser cladding is also a promising technique for the production of dense and precisely localized ceramic layers. In the present work, powders based on Al2O3 and ZrO2 were used to clad aluminum and titanium light alloys. The compact layers are up to 1 mm thick and show a nonporous cast structure as well as a homogeneous network of vertical cracks. The high adhesive strength is due to several chemical and mechanical bonding mechanisms and can exceed that of plasmasprayed coatings. Compared to thermal spray techniques, the material deposition is strictly focused onto small functional areas of the workpiece. Thus, being a precision technique, laser cladding is not recommended for large-area coatings. Examples of applications are turbine components and filigree parts of pump casings.

  18. 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.

  19. Laser powder technology for cladding and welding

    NASA Astrophysics Data System (ADS)

    Arnold, J.; Volz, R.

    1999-06-01

    Laser powder technology offers several advantages compared to conventional cladding and welding techniques and is attracting increasing industrial interest. The laser materials processing group of the German Aerospace Center at Stuttgart, Germany, is currently developing these new methods for application in industrial process engineering. Key areas of the work include the design and implementation of a modular working head that can be universally used for laser welding and surface treatment, the development of powder nozzles for cladding and welding, and the construction of new systems for special applications (e.g., for inner cladding). Some of these developments are described, as well as some important examples that highlight the potential of welding and surface treatment using laser powder techniques.

  20. 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.

  1. Phosphate-core silica-clad Er/Yb-doped optical fiber and cladding pumped laser.

    PubMed

    Egorova, O N; Semjonov, S L; Velmiskin, V V; Yatsenko, Yu P; Sverchkov, S E; Galagan, B I; Denker, B I; Dianov, E M

    2014-04-07

    We present a composite optical fiber with a Er/Yb co-doped phosphate-glass core in a silica glass cladding as well as cladding pumped laser. The fabrication process, optical properties, and lasing parameters are described. The slope efficiency under 980 nm cladding pumping reached 39% with respect to the absorbed pump power and 28% with respect to the coupled pump power. Due to high doping level of the phosphate core optimal length was several times shorter than that of silica core fibers.

  2. 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.

  3. 78 FR 7451 - Clad Steel Plate From Japan; Determination

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-01

    ... COMMISSION Clad Steel Plate From Japan; Determination On the basis of the record \\1\\ developed in the subject... order on clad steel plate from Japan would be likely to lead to continuation or recurrence of material... contained in USITC Publication 4370 (January 2013), entitled Clad Steel Plate from Japan: Investigation...

  4. 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.

  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. Structure Formation and Properties of Weld Overlay Produced by Laser Cladding under the Influence of Nanoparticles of High-melting Compounds

    NASA Astrophysics Data System (ADS)

    Murzakov, M.; Petrovskiy, V.; Birukov, V.; Dzhumaev, P.; Polski, V.; Markushov, Y.; Bykovskiy, D.

    Researches of flat samples using laser cladding technology were carried out. Nickel-based powders with the addition of nanopowders of tantalum carbide and tungsten carbide with water-based hydroxyethylcellulose as the binder, were used for slip cladding. Powders are fused on under local argon protection. The experiments were carried out to determine minimal base metal penetration depth, microhardness distribution over cross section of substrate and deposited layers, enrichment level of cladding metal with base components depending on power density and deposition rate. Metallographic studies of obtained overlays were conducted using a high-precision analytical equipment.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. Prism coupling into clad uniform optical waveguides

    SciTech Connect

    Revelli, J.F.; Sarid, D.

    1980-07-01

    The theory of prism coupling into multilayered dielectric slab waveguides is presented. In addition to including the possibility of high index cladding, the present theory also extends the region of validity of previously reported work to cover the regime of ''strong coupling''. The limiting conditions for validity of the present theory are that both ..cap alpha../sub m//k and ..cap alpha../sub m/ +- p/k be much smaller than either unity or vertical-bar..beta../sub m/-..beta../sub m/ +- pvertical-bar, where m is the mode under consideration, ..cap alpha../sub m/ is the leakage of that mode, and vertical-bar..beta../sub m/-..beta../sub m/ +- pvertical-bar is the separation of the effective indices of adjacent modes. A numerical example is presented in which the coupling efficiency into a uniform or slab waveguide with ..delta..n=0.002 is calculated for various cladding thicknesses with a cladding index of 2.5. The introduction of cladding is found to reduce coupling efficiency in this example due to increased phase mismatch between the incident and ''ideal'' beams.

  12. CLAD/BCLAD Examinations. Test Specifications.

    ERIC Educational Resources Information Center

    California Commission on Teacher Credentialing, Sacramento.

    This draft handbook provides descriptions and summaries of the six tests that California elementary and secondary teachers must pass to earn the Crosscultural, Language, and Academic Development (CLAD) or Bilingual, Crosscultural, Language, and Academic Development (BCLAD) certificates. The six tests include: (1) "Language Structure and…

  13. 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.

  14. Growth and characterization of AlGaN films on patterned sapphire substrates

    NASA Astrophysics Data System (ADS)

    Kwak, Y. S.; Lee, D. S.; Kim, K. H.; Kim, W. H.; Moon, S. W.

    2011-12-01

    A GaN film and two AlGaN films with Al compositions of 5% and 10% have been grown on the patterned sapphire substrates (PSSs) by metal organic chemical vapor deposition (MOCVD). Optical properties and crystalline qualities of the films have been investigated. The GaN film and the Al0.05Ga0.95N film are almost entirely coalesced except for some point defects. However, the Al0.1Ga0.9N film contains large pits encircled by small pits adjacent to them. The large pits are distributed in the same manner with the PSS arrangement. Dislocations and inversion domain boundaries were also observed in the Al0.1Ga0.9N film.

  15. Deep-ultraviolet polychromatic emission from three-dimensionally structured AlGaN quantum wells

    NASA Astrophysics Data System (ADS)

    Kataoka, Ken; Funato, Mitsuru; Kawakami, Yoichi

    2017-03-01

    Three-dimensional (3D) AlGaN/AlN quantum wells (QWs) were fabricated on trench-patterned AlN templates using a regrowth technique based on metalorganic vapor phase epitaxy. The 3D structures are composed of planar (0001) facets, \\{ 1\\bar{1}01\\} facets, and misoriented (0001) planes with bunched steps. Cathodoluminescence spectroscopy revealed double-peaked deep-ultraviolet (DUV) emissions: the shorter-wavelength emission was attributed to the (0001) facets, whereas the longer-wavelength emission arose from bunched step structures located around the bottom corner of the AlN trench, a region in which the AlGaN QWs possessed a relatively high Ga concentration and a thick well width compared with planar (0001) QWs.

  16. 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.

  17. Boronization of nickel and nickel clad materials for potential use in polymer electrolyte membrane fuel cells

    SciTech Connect

    Weil, K. Scott; Kim, Jin Yong Y.; Xia, Gordon; Coleman, J. E.; Yang, Z Gary

    2006-12-20

    A new low-cost, nickel clad bipolar plate concept is currently being developed for use in polymer electrolyte membrane fuel cells. Reported in this paper are the details of a powder-pack boronization process that would be used to establish a passivation layer on the electrolyte exposed surfaces of the bipolar plate in the final stage of manufacture. Results from energy dispersive X-ray analysis, X-ray diffraction, and scanning electron microscopy indicate that under moderate boronization conditions a homogeneous Ni3B layer grows on the exposed surfaces of the nickel clad material, the thickness of which depends on the time and temperature of boronization according to a Wagner-type scale growth relationship. At higher temperatures and longer reaction times, a Ni2B overlayer forms on top of the Ni3B during boronization.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. Thermochemical Compatibility and Oxidation Resistance of Advanced LWR Fuel Cladding

    SciTech Connect

    Besmann, T. M.; Yamamoto, Y.; Unocic, K. A.

    2016-06-21

    We assessed the thermochemical compatibility of potential replacement cladding materials for zirconium alloys in light water reactors. Considered were FeCrAl steel (similar to Kanthal APMT), Nb-1%Zr (similar to PWC-11), and a hybrid SiC-composite with a metallic barrier layer. The niobium alloy was also seen as requiring an oxidation protective layer, and a diffusion silicide was investigated. Metallic barrier layers for the SiC-composite reviewed included a FeCrAl alloy, Nb-1%Zr, and chromium. Thermochemical calculations were performed to determine oxidation behavior of the materials in steam, and for hybrid SiC-composites possible interactions between the metallic layer and SiC. Additionally, experimental exposures of SiC-alloy reaction couples at 673K, 1073K, and 1273K for 168 h in an inert atmosphere were made and microanalysis performed. Whereas all materials were determined to oxidize under higher oxygen partial pressures in the steam environment, these varied by material with expected protective oxides forming. Finally, the computed and experimental results indicate the formation of liquid phase eutectic in the FeCrAl-SiC system at the higher temperatures.

  5. Thermochemical Compatibility and Oxidation Resistance of Advanced LWR Fuel Cladding

    DOE PAGES

    Besmann, T. M.; Yamamoto, Y.; Unocic, K. A.

    2016-06-21

    We assessed the thermochemical compatibility of potential replacement cladding materials for zirconium alloys in light water reactors. Considered were FeCrAl steel (similar to Kanthal APMT), Nb-1%Zr (similar to PWC-11), and a hybrid SiC-composite with a metallic barrier layer. The niobium alloy was also seen as requiring an oxidation protective layer, and a diffusion silicide was investigated. Metallic barrier layers for the SiC-composite reviewed included a FeCrAl alloy, Nb-1%Zr, and chromium. Thermochemical calculations were performed to determine oxidation behavior of the materials in steam, and for hybrid SiC-composites possible interactions between the metallic layer and SiC. Additionally, experimental exposures of SiC-alloymore » reaction couples at 673K, 1073K, and 1273K for 168 h in an inert atmosphere were made and microanalysis performed. Whereas all materials were determined to oxidize under higher oxygen partial pressures in the steam environment, these varied by material with expected protective oxides forming. Finally, the computed and experimental results indicate the formation of liquid phase eutectic in the FeCrAl-SiC system at the higher temperatures.« less

  6. Creation of heterogeneous materials by laser cladding of heterogeneous powder compositions on the base of steel and nickel

    NASA Astrophysics Data System (ADS)

    Drozdov, V. O.; Malikov, A. G.; Orishich, A. M.; Cherepanov, A. N.

    2016-11-01

    The paper presents the experimental investigation of the creation of complex composition corrosion-resistant coatings with low abrasive wear which are used in oil industry, by the method of laser cladding additive technology. Availability of the additive laser cladding of the complex composition corrosion-resistant coatings with a strengthening phase is shown. Optimal conditions for the cladding layers creation regarding the laser radiation parameters and radiation direction are found. The changes in micro-hardness, micro-structure and structure-phase components are established against the strengthening phase content in the upper clad layer. Different content of the strengthening phase in the upper layer from 10% to 30% does not change the micro-hardness of the upper layer and is on the average 700 HV. The laser irradiation of the powder mixture containing the strengthening phase results in the partial rupture of the WC strengthening phase. Hence the chemical interaction of the tungsten-cobalt powder mixture and stainless steel occurs and results in complex carbide formation.

  7. Deep UV AlGaN light emitting diodes grown by gas source molecular beam epitaxy on sapphire and AlGaN/sapphire substrates

    NASA Astrophysics Data System (ADS)

    Nikishin, S.; Borisov, B.; Kuryatkov, V.; Usikov, A.; Dmitriev, V.; Holtz, M.

    2006-02-01

    We report the electrical and optical properties of deep ultraviolet light emitting diodes (LEDs) based on digital alloy structures (DAS) of AlN/Al 0.08Ga 0.92N grown by gas source molecular beam epitaxy with ammonia on sapphire substrates and AlGaN/sapphire templates. AlGaN/sapphire templates were grown by recently developed stress controlled hydride vapor phase epitaxy (HVPE). For DAS with effective bandgap of 5.1 eV we obtain room temperature electron concentrations up to 1x10 19 cm -3 and hole concentrations of 1x10 18 cm -3. Based on these results we prepared double heterostructure (DHS) LEDs operating in the range of 250 to 290 nm. The emission wavelengths were controlled through the effective bandgap of the active region. The possible ways for increase of LED's efficiency are discussed. We observed significant improvement in the room temperature luminescence efficiency (by factor of 100) of AlGaN quantum wells when a transition growth mode is induced by reduced flux of ammonia. We found that active layer grown on HVPE AlGaN/sapphire substrates have higher luminescence efficiency (by factor of 3) than DAS grown on sapphire.

  8. Improving the Thermal Shock Resistance of Thermal Barrier Coatings Through Formation of an In Situ YSZ/Al2O3 Composite via Laser Cladding

    NASA Astrophysics Data System (ADS)

    Soleimanipour, Zohre; Baghshahi, Saeid; Shoja-razavi, Reza

    2017-03-01

    In the present study, laser cladding of alumina on the top surface of YSZ thermal barrier coatings (TBC) was conducted via Nd:YAG pulsed laser. The thermal shock behavior of the TBC before and after laser cladding was modified by heating at 1000 °C for 15 min and quenching in cold water. Phase analysis, microstructural evaluation and elemental analysis were performed using x-ray diffractometry, scanning electron microscopy (SEM), and energy-dispersive spectroscopy. The results of thermal shock tests indicated that the failure in the conventional YSZ (not laser clad) and the laser clad coatings happened after 200 and 270 cycles, respectively. The SEM images of the samples showed that delamination and spallation occurred in both coatings as the main mechanism of failure. Formation of TGO was also observed in the fractured cross section of the samples, which is also a main reason for degradation. Thermal shock resistance in the laser clad coatings improved about 35% after cladding. The improvement is due to the presence of continuous network cracks perpendicular to the surface in the clad layer and also the thermal stability and high melting point of alumina in Al2O3/ZrO2 composite.

  9. 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.

  10. 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

  11. 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

    2016-06-01

    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.

  12. Enhancing the light extraction efficiency of AlGaN deep ultraviolet light emitting diodes by using nanowire structures

    SciTech Connect

    Djavid, Mehrdad; Mi, Zetian

    2016-02-01

    The performance of conventional AlGaN deep ultraviolet light emitting diodes has been limited by the extremely low light extraction efficiency (<10%), due to the unique transverse magnetic (TM) polarized light emission. Here, we show that, by exploiting the lateral side emission, the extraction efficiency of TM polarized light can be significantly enhanced in AlGaN nanowire structures. Using the three-dimensional finite-difference time domain simulation, we demonstrate that the nanowire structures can be designed to inhibit the emission of guided modes and redirect trapped light into radiated modes. A light extraction efficiency of more than 70% can, in principle, be achieved by carefully optimizing the nanowire size, nanowire spacing, and p-GaN thickness.

  13. Short-period intrinsic Stark GaN /AlGaN superlattice as a Bloch oscillator

    NASA Astrophysics Data System (ADS)

    Litvinov, V. I.; Manasson, A.; Pavlidis, D.

    2004-07-01

    We discuss the properties of AlGaN /GaN superlattice (SL) related to the feasibility of a terahertz-range oscillator. The distortion of the conduction-band profile by the polarization fields has been taken into account. We have calculated the conduction-band offset between the pseudomorphic AlGaN barrier and the GaN quantum well, the first miniband width and energy dispersion, as functions of Al content in the barrier. As the short-period SL miniband energy dispersion contains contributions from next to nearest neighbors, it causes anharmonic electron oscillations at the multiples of the fundamental Bloch frequency. The Al content and SL period that favor high-frequency oscillations have been determined.

  14. Electrical detection of kidney injury molecule-1 with AlGaN /GaN high electron mobility transistors

    NASA Astrophysics Data System (ADS)

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

    2007-11-01

    AlGaN /GaN high electron mobility transistors (HEMTs) were used to detect kidney injury molecule-1 (KIM-1), an important biomarker for early kidney injury detection. The gate region consisted of 5nm gold deposited onto the AlGaN surface. The gold was conjugated to highly specific KIM-1 antibodies through a self-assembled monolayer of thioglycolic acid. The HEMT source-drain current showed a clear dependence on the KIM-1 concentration in phosphate-buffered saline solution. The limit of detection was 1ng/ml using a 20×50μm2 gate sensing area. This approach shows potential for both preclinical and clinical kidney injury diagnosis with accurate, rapid, noninvasive, and high throughput capabilities.

  15. Reversible switching of quantum cascade laser-modes using a pH-responsive polymeric cladding as transducer.

    PubMed

    Basnar, Bernhard; Schartner, Stephan; Austerer, Maximilian; Andrews, Aaron Maxwell; Roch, Tomas; Schrenk, Werner; Strasser, Gottfried

    2008-06-09

    We present a novel approach for the reversible switching of the emission wavelength of a quantum cascade laser (QCL) using a halochromic cladding. An air-waveguide laser ridge is coated with a thin layer of polyacrylic acid. This cladding introduces losses corresponding to the absorption spectrum of the polymer. By changing the state of the polymer, the absorption spectrum and losses change, inducing a shift of 7 cm(-1) in the emission wavelength. This change is induced by exposure to acidic or alkaline vapors under ambient conditions and is fully reversible. Such lasers can be used as multi-color light source and as sensor for atmospheric pH.

  16. 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.

  17. Magnetically controllable silicon microring with ferrofluid cladding.

    PubMed

    El Amili, A; Souza, M C M M; Vallini, F; Frateschi, N C; Fainman, Y

    2016-12-01

    We experimentally investigate the application of magnetic fluids (MFs) on integrated silicon photonics. Using a ferrofluid-clad silicon microring resonator, we demonstrate active control of resonances by applying an external magnetic field. Relatively high loaded quality factors on the order of 6000 are achieved, despite the optical losses introduced by the magnetic nanoparticles. We demonstrate resonance shifts of 185 pm in response to a 110 Oe strong magnetic field, corresponding to an overall refractive index change of -3.2×10-3 for the cladding MF. The combination of MFs and integrated photonics could potentially lead to the development of magnetically controllable optical devices and ultra-compact cost-effective magnetic field sensors.

  18. Copper-Nickel Cladding on Stainless Steel

    DTIC Science & Technology

    2005-07-01

    steel,. Monel (65Ni/35Cu) alloy consumables should be used as they can tolerate more iron dilution from the steel than the 70-30 copper-nickel alloy ...Cooper Alloys , 400 , K-500 Stainless Steel - Tyles 302, 304, 321, 347 N ickel 200 Silver Braze Alloys Nickel-Chromium Alloy 600 Nickel-Aluminum Bronze 70...cladding of austenitic stainless steels may also offer some ballistic, non-magnetic, and electromagnetic signature advantages over current hull alloys and

  19. 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.

  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. Cladded single crystal fibers for high power fiber lasers

    NASA Astrophysics Data System (ADS)

    Kim, W.; Shaw, B.; Bayya, S.; Askins, C.; Peele, J.; Rhonehouse, D.; Meyers, J.; Thapa, R.; Gibson, D.; Sanghera, J.

    2016-09-01

    We report on the recent progress in the development of cladded single crystal fibers for high power single frequency lasers. Various rare earth doped single crystal YAG fibers with diameters down to 17 μm with length > 1 m have been successfully drawn using a state-of-the-art Laser Heated Pedestal Growth system. Single and double cladding on rare earth doped YAG fibers have been developed using glasses where optical and physical properties were precisely matched to doped YAG core single crystal fiber. The double clad Yb:YAG fiber structures have dimensions analogous to large mode area (LMA) silica fiber. We also report successful fabrications of all crystalline core/clad fibers where thermal and optical properties are superior over glass cladded YAG fibers. Various fabrication methods, optical characterization and gain measurements on these cladded YAG fibers are reported.

  2. 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.

  3. 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.

  4. Clad fiber capacitor and method of making same

    DOEpatents

    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.

  5. 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)

  6. Interfacial design and structure of protein/polymer films on oxidized AlGaN surfaces

    NASA Astrophysics Data System (ADS)

    Gupta, Samit K.; Wu, Hao-Hsuan; Kwak, Kwang J.; Casal, Patricia; Nicholson, Theodore R., III; Wen, Xuejin; Anisha, R.; Bhushan, Bharat; Berger, Paul R.; Lu, Wu; Brillson, Leonard J.; Lee, Stephen Craig

    2011-01-01

    Protein detection using biologically or immunologically modified field-effect transistors (bio/immunoFETs) depends on the nanoscale structure of the polymer/protein film at sensor interfaces (Bhushan 2010 Springer Handbook of Nanotechnology 3rd edn (Heidelberg: Springer); Gupta et al 2010 The effect of interface modification on bioFET sensitivity, submitted). AlGaN-based HFETs (heterojunction FETs) are attractive platforms for many protein sensing applications due to their electrical stability in high osmolarity aqueous environments and favourable current drive capabilities. However, interfacial polymer/protein films on AlGaN, though critical to HFET protein sensor function, have not yet been fully characterized. These interfacial films are typically comprised of protein-polymer films, in which analyte-specific receptors are tethered to the sensing surface with a heterobifunctional linker molecule (often a silane molecule). Here we provide insight into the structure and tribology of silane interfaces composed of one of two different silane monomers deposited on oxidized AlGaN, and other metal oxide surfaces. We demonstrate distinct morphologies and wear properties for the interfacial films, attributable to the specific chemistries of the silane monomers used in the films. For each specific silane monomer, film morphologies and wear are broadly consistent on multiple oxide surfaces. Differences in interfacial film morphology also drive improvements in sensitivity of the underlying HFET (coincident with, though not necessarily caused by, differences in interfacial film thickness). We present a testable model of the hypothetical differential interfacial depth distribution of protein analytes on FET sensor interfaces with distinct morphologies. Empirical validation of this model may rationalize the actual behaviour of planar immunoFETs, which has been shown to be contrary to expectations of bio/immunoFET behaviour prevalent in the literature for the last 20 years

  7. Quantitative study of the effect of cladding thickness on modal confinement loss in photonic waveguides.

    PubMed

    Jiang, Shidong; Lai, Jun

    2016-10-31

    There has been increasing interest in making photonic devices more and more compact in the integrated photonics industry, and one of the important questions for manufacturers and design engineers is how to quantify the effect of the finite cladding thickness on the modal confinement loss of photonic waveguides. This requires at least six to seven digits of accuracy for the computation of propagation constant β since the modal confinement loss is proportional to the imaginary part of β that is six to seven orders of magnitude smaller than its real part by the industrial standard. In this paper, we present an accurate and efficient method to compute the propagation constant of the electromagnetic modes of photonic waveguides with an arbitrary number of (nonsmooth) inclusions in a layered media. The method combines a well-conditioned boundary integral equation formulation for photonic waveguides which requires the discretization of the material interface only, and efficient Sommerfeld integral representations to treat the effect of the layered medium. Our scheme is capable of calculating the propagation loss of the electromagnetic modes with high fidelity, even for waveguides with corners embedded in a cladding material of finite thickness. The numerical results, with a more than 10-digit accuracy, show quantitatively that the modal confinement loss of the rectangular waveguide increases exponentially fast as the cladding thickness decreases.

  8. Microstructure and wear behavior of Cu-Mo-Si coatings by laser cladding

    NASA Astrophysics Data System (ADS)

    Peilei, Zhang; Xiaopeng, Liu; Yunlong, Lu; Hua, Yan; Zhishui, Yu; Chonggui, Li; Qinghua, Lu

    2014-08-01

    Three Cu-Mo-Si coatings were synthesized on steel using laser cladding. The coatings have dense microstructure with composite phases including metal silicates and Cu-based solid solution. Different alloy compositions reduce different phases generated in the coatings. Phases appeared in three coatings were Cu + MoSi2 + Mo5Si3 + Cu3Si (Coatings 1 and 2), Cu + Mo3Si + Mo5Si3 + Cu3Si (Coating 3), respectively. The microhardness of coatings is in the range of 600 to 900 HV. The amount of Mo5Si3 phase decides the hardness of Cu-Mo-Si coatings in laser processing. The proof is that the highest hardness which is about 900 HV occurs in the clad layer of Coating 1. The thickness of clad layer of three coatings is about 0.7 mm (Coating 1), 0.8 mm (Coating 2) and 1.0 mm (Coating 3), respectively. The average friction coefficient for Coatings 1-3 is 0.40, 0.56 and 0.60, respectively. Wear rate values of 2.9 × 10-6 g/N m (Coating 1), 3.1 × 10-6 g/N m (Coating 2) and 3.5 × 10-6 g/N m (Coating 3) are calculated, respectively. The amount and kind of metal silicates have a huge influence on the wear resistance of coatings.

  9. Hollow core anti-resonant fibres with split cladding

    NASA Astrophysics Data System (ADS)

    Huang, Xiaosheng; Qi, Wenliang; Ho, Daryl; Luan, Feng; Yong, Ken-Tye; Yoo, Seongwoo

    2016-03-01

    A split cladding fibers (SCF) is proposed as an additional design to the anti-resonant type fiber. The introduced split cladding helps to reduce the fabrication distortion. We use numerical simulations to compare the Kagome fibers (KFs) and the proposed split cladding fibers (SCFs) over two normalized transmission bands. It reveals that SCFs are able to maintain the desired round shape of silica cladding walls, hence improving the confinement loss (CL) compared to the KF. Fabrication of the SCF is demonstrated by the stack-and-draw technique. The near filed mode patterns are measured to prove the feasibility of this fiber design.

  10. 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.

  11. 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.

  12. Investigation of Ni-Cr-Si-Fe-B coatings produced by the electron beam cladding technique

    NASA Astrophysics Data System (ADS)

    Zimogliadova, T. A.; Drobyaz, E. A.; Golkovskii, M. G.; Bataev, V. A.; Durakov, V. G.; Cherkasova, N. Yu

    2016-11-01

    This paper presents the results of structural investigations and results of tribological and microhardness tests of the coating obtained by electron beam cladding of a Ni-Cr-Si-Fe-B self-fluxing alloy on low-carbon steel. After electron beam treatment high-quality dense layer with a thickness of 1.2-1.8 mm was obtained. The structure of the coating consisted of dendrite crystals based on y-Ni-solid solution and eutectic with complex composition. Microhardness of the coating achieves 370 HV. Wear-resistance of the coating obtained by electron-beam cladding technique was 1.6-fold higher than that of low-carbon carburized steel.

  13. Cladding doped defect-core large mode area W-type photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Boruah, Jiten; Kalra, Yogita; Sinha, Ravindra K.

    2016-09-01

    Propagation characteristics of a cladding doped defect-core large mode area W-type photonic crystal fiber have been investigated by using finite element method. In the proposed structure the central air hole has been removed to form the defect core and the second layer of cladding rings around the central core have been selectively doped with different concentration of fluorine to tune the refractive index of the doped silica rods. The bend loss, dispersion, effect of bending on dispersion, and nonlinear coefficient of the proposed photonic crystal fiber design has been numerically investigated. The proposed W-type photonic crystal fiber has low bend loss, low dispersion, large-mode-area with low value of nonlinear coefficient at wavelength of 1.55μm. The structure can be utilized for telecommunication applications, for applications in high power fiber lasers, amplifiers and sensors.

  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. 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.

  16. 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.

  17. Rheological evaluation of pretreated cladding removal waste

    SciTech Connect

    McCarthy, D.; Chan, M.K.C.; Lokken, R.O.

    1986-01-01

    Cladding removal waste (CRW) contains concentrations of transuranic (TRU) elements in the 80 to 350 nCi/g range. This waste will require pretreatment before it can be disposed of as glass or grout at Hanford. The CRW will be pretreated with a rare earth strike and solids removal by centrifugation to segregate the TRU fraction from the non-TRU fraction of the waste. The centrifuge centrate will be neutralized with sodium hydroxide. This neutralized cladding removal waste (NCRW) is expected to be suitable for grouting. The TRU solids removed by centrifugation will be vitrified. The goal of the Rheological Evaluation of Pretreated Cladding Removal Waste Program was to evaluate those rheological and transport properties critical to assuring successful handling of the NCRW and TRU solids streams and to demonstrate transfers in a semi-prototypic pumping environment. This goal was achieved by a combination of laboratory and pilot-scale evaluations. The results obtained during these evaluations were correlated with classical rheological models and scaled-up to predict the performance that is likely to occur in the full-scale system. The Program used simulated NCRW and TRU solid slurries. Rockwell Hanford Operations (Rockwell) provided 150 gallons of simulated CRW and 5 gallons of simulated TRU solid slurry. The simulated CRW was neutralized by Pacific Northwest Laboratory (PNL). The physical and rheological properties of the NCRW and TRU solid slurries were evaluated in the laboratory. The properties displayed by NCRW allowed it to be classified as a pseudoplastic or yield-pseudoplastic non-Newtonian fluid. The TRU solids slurry contained very few solids. This slurry exhibited the properties associated with a pseudoplastic non-Newtonian fluid.

  18. Improving the tribocorrosion resistance of Ti6Al4V surface by laser surface cladding with TiNiZrO2 composite coating

    NASA Astrophysics Data System (ADS)

    Obadele, Babatunde Abiodun; Andrews, Anthony; Mathew, Mathew T.; Olubambi, Peter Apata; Pityana, Sisa

    2015-08-01

    Ti6Al4V alloy was laser cladded with titanium, nickel and zirconia powders in different ratio using a 2 kW CW ytterbium laser system (YLS). The microstructures of the cladded layers were examined using field emission scanning electron microscopy (FESEM) equipped with energy dispersive X-ray spectroscopy (EDS) and X-ray diffractometry (XRD). Corrosion and tribocorrosion tests were performed on the cladded surface in 1 M H2SO4 solution. The microstructure revealed the transformation from a dense dendritic structure in TiNi coating to a flower-like structure observed in TiNiZrO2 cladded layers. There was a significant increase in surface microindentation hardness values of the cladded layers due to the present of hard phase ZrO2 particles. The results obtained show that addition of ZrO2 improves the corrosion resistance property of TiNi coating but decrease the tribocorrosion resistance property. The surface hardening effect induced by ZrO2 addition, combination of high hardness of Ti2Ni phase could be responsible for the mechanical degradation and chemical wear under sliding conditions.

  19. Optimization on the luminous efficiency in AlGaN-based ultraviolet light-emitting diodes by amendment of a superlattice hole reservoir layer

    NASA Astrophysics Data System (ADS)

    Yang, Xian; Sun, Huiqing; Fan, Xuancong; Zhang, Zhuding; Sun, Jie; Yi, Xinyan; Guo, Zhiyou

    2017-01-01

    The application of a p-type superlattice hole reservoir layer in the traditional ultraviolet light-emitting diodes (UVLED) can obtain better Internal quantum efficiency (IQE) and output power, ease the problem about efficient carrier movement in high Al-content AlGaN material. Through computation and analysis by using the APSYS simulation software, the change of position of the hole reservoir layer can influence the luminous efficiency. The design of a superlattice hole reservoir layer between electron blocking layer (EBL) and p-type AlGaN layer can obviously reduce the hole potential height and increase the electron potential height, produce more hole injection and less electron leak, leading to higher carrier concentration, so as to realize the further increased for carrier recombination rate.

  20. 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.

  1. 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.

  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 PAGES

    Pint, B. A.; Terrani, K. A.; Yamamoto, Y.; ...

    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. 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.

  7. Hydrogen uptake in Zircaloy-2 reactor fuel claddings studied with elastic recoil detection

    NASA Astrophysics Data System (ADS)

    Rajasekhara, S.; Doyle, B. L.; Enos, D. G.; Clark, B. G.

    2013-04-01

    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 × 10-11 cm2/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.

  8. 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.

  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. 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

  11. Online monitoring of thermo-cycles and its correlation with microstructure in laser cladding of nickel based super alloy

    NASA Astrophysics Data System (ADS)

    Muvvala, Gopinath; Patra Karmakar, Debapriya; Nath, Ashish Kumar

    2017-01-01

    Laser cladding, basically a weld deposition technique, is finding applications in many areas including surface coatings, refurbishment of worn out components and generation of functionally graded components owing to its various advantages over conventional methods like TIG, PTA etc. One of the essential requirements to adopt this technique in industrial manufacturing is to fulfil the increasing demand on product quality which could be controlled through online process monitoring and correlating the signals with the mechanical and metallurgical properties. Rapid thermo-cycle i.e. the fast heating and cooling rates involved in this process affect above properties of the deposited layer to a great extent. Therefore, the current study aims to monitor the thermo-cycles online, understand its variation with process parameters and its effect on different quality aspects of the clad layer, like microstructure, elemental segregations and mechanical properties. The effect of process parameters on clad track geometry is also studied which helps in their judicious selection to deposit a predefined thickness of coating. In this study Inconel 718, a nickel based super alloy is used as a clad material and AISI 304 austenitic steel as a substrate material. The thermo-cycles during the cladding process were recorded using a single spot monochromatic pyrometer. The heating and cooling rates were estimated from the recorded thermo-cycles and its effects on microstructures were characterised using SEM and XRD analyses. Slow thermo-cycles resulted in severe elemental segregations favouring Laves phase formation and increased γ matrix size which is found to be detrimental to the mechanical properties. Slow cooling also resulted in termination of epitaxial growth, forming equiaxed grains near the surface, which is not preferred for single crystal growth. Heat treatment is carried out and the effect of slow cooling and the increased γ matrix size on dissolution of segregated elements in

  12. Scanning Optics Enabled Possibilities and Challenges in Laser Cladding

    NASA Astrophysics Data System (ADS)

    Pekkarinen, Joonas

    Laser cladding using a scanned beam is quite a similar process than laser cladding using static optics (e.g. lens or mirror optics). The main difference comes from the manipulation of the laser beam. In laser cladding with scanning optics the laser beam is manipulated with a scanner so that the laser's area of influence can be shaped numerically. This increases cladding process flexibility. Scanning optics enable laser beam modification considerably versatile way than normal static optics can. This is due to possibility of numerical adjustment of scanning amplitude, laser power and scanning frequency. By modifying these parameters clad beads geometry can by modified quite freely. However scanned laser beam in surface modification process creates some restricting factors to the process. Mainly limitations for the process parameter values come from the dual characteristics of the energy input. This paper treats usability of scanning optics in laser cladding process in general level. In this paper is discussed how scanned beam can be used to increase the flexibility but also maters that limit the usage of scanned beam in cladding process. Process possibilities and limitations are presented in trough experimental data and examples.

  13. Analysis and prediction of single laser tracks geometrical characteristics in coaxial laser cladding process

    NASA Astrophysics Data System (ADS)

    El Cheikh, Hussam; Courant, Bruno; Branchu, Samuel; Hascoët, Jean-Yves; Guillén, Ronald

    2012-03-01

    Direct Laser Fabrication is a promising new manufacturing technology coming from laser cladding process. From a coaxial nozzle, powder is fed through a laser beam on a substrate. The powder melting and solidification processes lead to the fabrication of a part layer by layer. In this work 316L stainless steel powder is used to form laser tracks on a low carbon steel substrate. The layer geometry is an important process characteristic to control the final part of fabrication. This paper presents analytical relationships between the laser tracks geometrical characteristics (width, height, area, penetration depth) and the processing parameters (laser power P, scanning speed V and powder mass flow Qm). Three values of each processing parameters are fixed and so 27 different experiments have been made and analyzed. The validity of these results is discussed studying the correlation coefficient R, the graphical analysis of the residuals and the uncertainty evaluations. Two kinds of models are studied to predict the form and the geometrical characteristics of the single laser tracks cross sections. The first one is an analytical model in which the distribution of the powder in the feed jet is supposed to govern the laser clad geometry. Three distributions are proposed: Gaussian, uniform and polynomial. In the second model the general form of the clad cross section is supposed to be a disk due to the surface tension forces. Analytical relationships are established between the radius and the center of the disk in one hand and the process parameters in the other hand. This way we show that we can reproduce the laser track geometry in all the area experimentally explored.

  14. 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.

  15. 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.

  16. 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.

  17. Coulomb correlation effects and density dependence of radiative recombination rates in polar AlGaN quantum wells

    NASA Astrophysics Data System (ADS)

    Rupper, Greg; Rudin, Sergey; Bertazzi, Francesco; Garrett, Gregory; Wraback, Michael

    2013-03-01

    AlGaN narrow quantum wells are important elements of deep-ultraviolet light emitting devices. The electron-hole radiative recombination rates are important characteristics of these nanostructures. In this work we evaluated their dependence on carrier density and lattice temperature and compared our theoretical results with the experimentally determined radiative lifetimes in the c-plane grown AlGaN quantum wells. The bands were determined in the k .p approximation for a strained c-plane wurtzite quantum well and polarization fields were included in the model. In order to account for Coulomb correlations at relatively high densities of photo-excited electron-hole plasma and arbitrary temperature, we employed real-time Green's function formalism with self-energies evaluated in the self-consistent T-matrix approximation. The luminescence spectrum was obtained from the susceptibility by summing over scattering in-plane directions and polarization states. The recombination coefficient was obtained from the integrated photo-luminescence. The density dependence of the radiative recombination rate shows effects of strong screening of the polarization electric field at high photo-excitation density.

  18. 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.

  19. Process for producing clad superconductive materials

    DOEpatents

    Cass, Richard B.; Ott, Kevin C.; Peterson, Dean E.

    1992-01-01

    A process for fabricating superconducting composite wire by the steps of placing a superconductive precursor admixture capable of undergoing a self propagating combustion in stoichiometric amounts sufficient to form a superconductive product within a metal tube, sealing one end of said tube, igniting said superconductive precursor admixture whereby said superconductive precursor admixture endburns along the length of the admixture, and cross-section reducing said tube at a rate substantially equal to the rate of burning of said superconductive precursor admixture and at a point substantially planar with the burnfront of the superconductive precursor mixture, whereby a clad superconductive product is formed in situ, the product characterized as superconductive without a subsequent sintering stage, is disclosed.

  20. Laser cladding of bioactive glass coatings.

    PubMed

    Comesaña, R; Quintero, F; Lusquiños, F; Pascual, M J; Boutinguiza, M; Durán, A; Pou, J

    2010-03-01

    Laser cladding by powder injection has been used to produce bioactive glass coatings on titanium alloy (Ti6Al4V) substrates. Bioactive glass compositions alternative to 45S5 Bioglass were demonstrated to exhibit a gradual wetting angle-temperature evolution and therefore a more homogeneous deposition of the coating over the substrate was achieved. Among the different compositions studied, the S520 bioactive glass showed smoother wetting angle-temperature behavior and was successfully used as precursor material to produce bioactive coatings. Coatings processed using a Nd:YAG laser presented calcium silicate crystallization at the surface, with a uniform composition along the coating cross-section, and no significant dilution of the titanium alloy was observed. These coatings maintain similar bioactivity to that of the precursor material as demonstrated by immersion in simulated body fluid.

  1. 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.

  2. Silver-clad Bi-2223 processing

    NASA Astrophysics Data System (ADS)

    Lay, K. W.; Arendt, R. H.; Tkaczyk, J. E.; Garbauskas, M. F.

    1992-04-01

    One of the most promising techniques for the production of long lengths of high Tc Superconductors utilizes themechanical deformation and subsequent heat treatment of silver-clad bismuth cuprates. Some recent experiments on Bi 1.7Pb0.3Sr2Ca2+x Cu3+xOy, with x=0.2, 0.4, and 0.75, processed by packing powder ina silver tube followed by swaging, drawing, and rolling are described. The effect of the initial powder composition, both cation ratios and phase composition, on the critical current of the composite tapes are explored. Different final deformation methods and heat treatment schedules also are discussed. A set of guidelines for the production of high Jc 2223 tapes is given.

  3. 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.

  4. 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.

  5. Linear inner cladding fiber amplifier suppressing mode instability

    NASA Astrophysics Data System (ADS)

    Li, Zebiao; Huang, Zhihua; Lin, Honghuan; Xu, Shanhui; Yang, Zhongmin; Wang, Jianjun; Jing, Feng

    2016-11-01

    We use a semi-analytical model considering pump power saturation in high power fiber laser systems of multi-kW-class to calculate mode instability threshold. A novel designed fiber, linear inner-cladding fiber, can mitigate mode instability effect by decreasing nonlinear coupling coefficient and smoothing heat profile along the fiber. We investigate strong pump absorption of linear inner-cladding fiber, leading to shorter fiber length. With 915 nm pumping, linear inner-cladding fiber can reach 10 kW output power without mode instability in theory.

  6. 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).

  7. 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.

  8. Optical and mechanical properties of hollow-core fibers with cobweb cladding structure

    NASA Astrophysics Data System (ADS)

    Chen, Mingyang; Yu, Rongjin; Tian, Zhenguo; Bai, Xiangzhong

    2006-02-01

    This paper explores the possibility of realizing a hollow-core optical fiber, whose cladding is composed of cylindrical alternating layers of air and high-index material with supporting structure. The optical properties and the design criteria of the proposed fiber are evaluated by the compact two-dimensional (2D) finite-difference time-domain (FDTD) method. In particular, the influence of the number and width of supporting strips on the leakage loss of the fiber is investigated. Furthermore, the mechanical performances of the fiber are estimated by finite-element method, confirming that hollow-core fibers with a reasonable size and number of supporting strips are reliable.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. High Resolution Temperature Estimation During Laser Cladding of Stainless Steel

    NASA Astrophysics Data System (ADS)

    Devesse, Wim; De Baere, Dieter; Hinderdael, Michaël; Guillaume, Patrick

    Laser cladding is a technique that is used for the coating, repair and production of metallic parts. Material is added to the surface of the part by injecting a flow of powder into a melt pool that is created with a high power laser beam. When the beam scans the surface of the substrate, strong local heating and cooling results. A good knowledge of the temperature distribution history during the laser cladding process is vital to predict and optimize the material properties of the final part. This paper presents a contactless temperature measurement system with high temporal and spatial resolution based on a hyperspectral line camera. High temperature measurements were made during laser cladding of AISI 316L stainless steel. A good correlation is shown between the temperature measurements and microscope images taken after creation of the clad.

  15. 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.

  16. Jet slurry erosion performance of composite clad and its characterization

    NASA Astrophysics Data System (ADS)

    B, Lohit R.; Horakeri, Gururaj S.; Bhovi, Prabakhar M.

    2016-09-01

    In the present work, development of composite cladding consists of Cr23C6 (chromium carbide) as reinforcement particles 20 wt. % in Ni-based matrix 80 wt. % on austenitic stainless steel through exposure of microwave radiation has been carried out. The jet slurry erosion test was performed on microwave composite clad. The functional performance of composite clad has been evaluated for different parametric conditions like varying impingement velocity and impact angle. The increasing weight loss trend was observed with time for the first 30 min. after that the individual trend decreased; at high impingement velocity and maximum impact angle. SEM micrographs of eroded clad samples at various impact angle and impingement velocity were discussed. The maximum weight loss occurred at 90° angle and velocity of 60 m/s, and minimum at 30° angle and velocity of 20 m/s.

  17. Young's modulus anisotropy in reactor pressure vessel cladding

    NASA Astrophysics Data System (ADS)

    Vandermeulen, W.; Mertens, M.; Scibetta, M.

    2012-02-01

    In a previous study it was shown that the anisotropy of Young's modulus in the stainless steel cladding of a reactor pressure vessel could be attributed to the solidification texture of the cladding. Further it was found that annealing the samples to remove the delta phase caused a modulus change but only in some directions. Since the texture was only estimated from X-ray diffraction patterns the moduli, calculated for some principal directions, differed considerably from the measured ones. In the present study, executed on a practically identical cladding, the texture was determined by actual texture measurements. It was found to be close to a fibre texture with <0 0 1> perpendicular to the cladding plane and the values calculated from it agreed much better with the experimental ones. The annealing effect found in the previous study was shown to be due to surface recrystallization induced by milling damage.

  18. 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.

  19. 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.

  20. 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.

  1. Cladding-pumped erbium-doped multicore fiber amplifier.

    PubMed

    Abedin, K S; Taunay, T F; Fishteyn, M; DiGiovanni, D J; Supradeepa, V R; Fini, J M; Yan, M F; Zhu, B; Monberg, E M; Dimarcello, F V

    2012-08-27

    A cladding pumped multicore erbium-doped fiber amplifier for simultaneous amplification of 6 channels is demonstrated. Peak gain over 32 dB has been obtained at a wavelength of 1560 nm and the bandwidth measured at 20-dB gain was about 35 nm. Numerical modeling of cladding pumped multicore erbium-doped amplifier was also performed to study the properties of the amplifier. The results of experiment and simulation are found to be in good agreement.

  2. Review of cladding-coolant interactions during LWR accident transients

    SciTech Connect

    Hobson, D.O.

    1980-01-01

    Some of the coolant-cladding interactions that can take place during the design basis loss-of-coolant accident and the Three Mile Island loss-of-coolant accident are analyzed. The physical manifestations of the interactions are quite similar, but the time sequences involved can cause very different end results. These results are described and a listing is given of the main research programs that are involved in coolant-cladding interaction research.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. Fuel clad chemical interactions in fast reactor MOX fuels

    NASA Astrophysics Data System (ADS)

    Viswanathan, R.

    2014-01-01

    Clad corrosion being one of the factors limiting the life of a mixed-oxide fast reactor fuel element pin at high burn-up, some aspects known about the key elements (oxygen, cesium, tellurium, iodine) in the clad-attack are discussed and many Fuel-Clad-Chemical-Interaction (FCCI) models available in the literature are also discussed. Based on its relatively superior predictive ability, the HEDL (Hanford Engineering Development Laboratory) relation is recommended: d/μm = ({0.507 ṡ [B/(at.% fission)] ṡ (T/K-705) ṡ [(O/M)i-1.935]} + 20.5) for (O/M)i ⩽ 1.98. A new model is proposed for (O/M)i ⩾ 1.98: d/μm = [B/(at.% fission)] ṡ (T/K-800)0.5 ṡ [(O/M)i-1.94] ṡ [P/(W cm-1)]0.5. Here, d is the maximum depth of clad attack, B is the burn-up, T is the clad inner surface temperature, (O/M)i is the initial oxygen-to-(uranium + plutonium) ratio, and P is the linear power rating. For fuels with [n(Pu)/n(M = U + Pu)] > 0.25, multiplication factors f are recommended to consider the potential increase in the depth of clad-attack.

  8. 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.

  9. 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.

  10. Erratic Dislocations Within Funnel Defects in AlN Templates for AlGaN Epitaxial Layer Growth

    DTIC Science & Technology

    2009-05-21

    optoelectronic devices that operate in the UV region of the electromagnetic spectrum due to their direct tunable band gaps in this energy range1...funnel. A similar process has been observed for V-pits in InGaN /GaN multi quantum wells (MQWs), where it should be noted that the deformation in...the MQW structure leads to localization of charge carriers17, 18. In the case of the MPEG 8 sample shown in Figs. 1 and 2, the material filling

  11. Cladding-filled graphene in a photonic crystal fiber as a saturable absorber and its first application for ultrafast all-fiber laser

    NASA Astrophysics Data System (ADS)

    Zhao, Junqing; Ruan, Shuangchen; Yan, Peiguang; Zhang, Han; Yu, Yongqin; Wei, Huifeng; Luo, Jie

    2013-10-01

    We demonstrate a saturable absorber (SA) based on cladding-filled graphene in a specially designed and manufactured photonic crystal fiber (PCF) for the first time. The saturation absorption property is achieved through the evanescent coupling between the guided light and the cladding-filled graphene layers. To boost the mutual interaction, the PCF is designed to contain five large air holes in the cladding and small-core region. Employing this graphene-PCF SA device, we construct an erbium-doped all-fiber laser oscillator and achieve mode-locked operation. This device can pave the way for high power and all-fiber applications of photonics with graphene with some unique advantages, such as single-mode operation, nonlinearity enhancement, high-power tolerance, environmental robustness, all-fiber configuration, and easy fabrication.

  12. Comparison of fiber lasers based on distributed side-coupled cladding-pumped fibers and double-cladding fibers.

    PubMed

    Huang, Zhihe; Cao, Jianqiu; Guo, Shaofeng; Chen, Jinbao; Xu, Xiaojun

    2014-04-01

    We compare both analytically and numerically the distributed side-coupled cladding-pumped (DSCCP) fiber lasers and double cladding fiber (DCF) lasers. We show that, through optimization of the coupling and absorbing coefficients, the optical-to-optical efficiency of DSCCP fiber lasers can be made as high as that of DCF lasers. At the same time, DSCCP fiber lasers are better than the DCF lasers in terms of thermal management.

  13. In-situ measurement of the effect of LiOH on the stability of fuel cladding oxide film in simulated PWR primary water environment

    SciTech Connect

    Saario, T.; Taehtinen, S.; Piippo, J.; Kukkonen, J.J.V.

    1995-12-31

    Development of new improved fuel cladding materials is a long process, partly because of the lack of fast and reliable in-situ techniques for investigations of cladding degradation in high temperature water environments. This paper describes results gained with the Contact Electric Resistance (CER) technique on the electric resistance of oxides growing on zirconium based fuel cladding materials. LiOH decreased the electric resistance of the oxides when about 70 ppm was injected in PWR water at 300 C. When PWR water contains boric acid and LiOH from the beginning of the exposure the fuel cladding material is covered by a hydroxide layer that protects the amorphous oxide layer and later hinders the increase of the resistance of the crystalline oxide layer. The dependency of electric resistance of the oxides on LiOH concentration is shown to correlate inversely with the effect of LiOH on weight gain. The kinetics of the breakdown process of electric resistance indicate that a phase transformation rather than a diffusion limited process is the mechanism of degradation. The growth rate of the electric resistance of the oxide in the early stage of oxide formation is shown to correlate well with the in-reactor weight gain of similar alloys. In-situ monitoring of the electric resistance of the oxide during growth is shown to give the same ranking order as long term in-reactor weight gain tests, but in a fraction of the testing time needed for weight gain tests.

  14. 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

    2015-09-25

    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.

  15. Processing of pure Ti by rapid prototyping based on laser cladding

    NASA Astrophysics Data System (ADS)

    Arias-González, F.; del Val, J.; Comesaña, R.; Lusquiños, F.; Quintero, F.; Riveiro, A.; Boutinguiza, M.; Pou, J.

    2013-11-01

    Rapid prototyping based on laser cladding is an additive manufacturing (AM) process based on the overlapping of cladding tracks to produce functional components. Powder or wire are fed into a melting pool created using laser radiation as a heat source and the relative movement between the beam and the work piece makes possible to generate pieces layer-by-layer. This technique can be applied for any material which can be melted and the components can be manufactured directly according to a computer aided design (CAD) model. Additive manufacturing is particularly interesting to produce titanium components because, in this case, the loss of material produced by subtractive manufacturing methods is highly costly. Moreover, titanium and its alloys are widely used in biomedical, aircraft, chemical and marine industries due to their biocompatibility, excellent corrosion resistance and superior strength-to-weight ratio. In this research work, a near-infrared laser delivering a maximum power of 500W is used to produce pure titanium thin parts. Dimensions and surface morphology are characterized using Optical Microscopy (OM) and Scanning Electron Microscopy (SEM), the hardness by nanoindentation and the composition by X-Ray Diffraction (XRD) and Energy Dispersive X-Ray Spectroscopy (EDS). The aim of this work is to establish the conditions under which satisfactory properties are obtained and to understand the relationship between microstructure/properties and deposition parameters.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  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. 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.

  2. Prediction of inhomogeneous texture in clad sheet metals by hot roll bond method

    NASA Astrophysics Data System (ADS)

    Choi, Shi-Hoon; Kwon, Jae Wook; Oh, Kyu Hwan

    1996-06-01

    A finite element analysis was applied to analyze the evolution of an inhomogeneity of rolling texture in hot rolled clad metal with Taylor-Bishop-Hill model and Renourd-Winterberger method. The shear texture has been developed in the surface layer of the aluminum and plane strain texture has been developed in the center layer. The calculated texture variations through thickness direction could simulate experimental texture using deformation gradient from FEM. The ratio of shear strain to rolling strain, x, which represents the degree of rotation about transverse direction could give the degree of development of shear texture. The larger value of x gives the larger crystal rotation about transverse direction and subsequently the development of shear texture. The calculated (111) pole figures were in good agreement with experimentally measured pole figures.

  3. Optical monitoring of high power direct diode laser cladding

    NASA Astrophysics Data System (ADS)

    Liu, Shuang; Farahmand, Parisa; Kovacevic, Radovan

    2014-12-01

    Laser cladding is one of the most advanced surface modification techniques which can be used to build and repair high-value components. High power direct diode laser (HPDDL) offers unique quality and cost advantages over other lasers (CO2, Nd:YAG). Especially its rectangular laser beam with top-hat intensity distribution makes HPDDL an ideal tool for large area cladding. In order to utilize this technique successfully, the development of on-line monitoring and process control is necessary. In this study, an optical monitoring system consisting of a high-speed CCD camera, a pyrometer, and an infrared camera was used to analyze the mass- and heat-transfer in the cladding process. The particle transport in flight was viewed by a high-speed CCD camera; the interaction between powder flow and laser beam was observed by an infrared camera; and the thermal behavior of the molten pool was recorded by the pyrometer and the infrared camera. The effects of the processing parameters on the laser attenuation, particle heating and clad properties were investigated based on the obtained signals. The optical monitoring method improved the understanding about mutual interrelated phenomena in the cladding process.

  4. 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.

  5. Sub-milliwatt AlGaN nanowire tunnel junction deep ultraviolet light emitting diodes on silicon operating at 242 nm

    NASA Astrophysics Data System (ADS)

    Zhao, S.; Sadaf, S. M.; Vanka, S.; Wang, Y.; Rashid, R.; Mi, Z.

    2016-11-01

    We report AlGaN nanowire light emitting diodes (LEDs) operating in the ultraviolet-C band. The LED structures are grown by molecular beam epitaxy on Si substrate. It is found that with the use of the n+-GaN/Al/p+-AlGaN tunnel junction (TJ), the device resistance is reduced by one order of magnitude, and the light output power is increased by two orders of magnitude, compared to AlGaN nanowire LEDs without TJ. For unpackaged TJ ultraviolet LEDs emitting at 242 nm, a maximum output power of 0.37 mW is measured, with a peak external quantum efficiency up to 0.012%.

  6. Optical polarization control of photo-pumped stimulated emissions at 238 nm from AlGaN multiple-quantum-well laser structures on AlN substrates

    NASA Astrophysics Data System (ADS)

    Lachab, Mohamed; Sun, WenHong; Jain, Rakesh; Dobrinsky, Alex; Gaevski, Mikhail; Rumyantsev, Sergey; Shur, Michael; Shatalov, Max

    2017-01-01

    We demonstrate the capability to control the optical polarization of room-temperature stimulated emissions (SEs) at 238-239 nm from optically pumped AlGaN multiple-quantum-well (MQW) heterostructures on bulk AlN. The results of structural and optical characterizations provided evidence that altering the strain state in the pseudomorphically grown MQW laser structures enabled the switching of the polarization direction of the SE from predominantly transverse electric (TE) at 238 nm to predominantly transverse magnetic (TM) at 239 nm. The SE observed at 238 nm represents the shortest peak wavelength with TE polarization yet reported for AlGaN materials grown on any type of substrate.

  7. 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%.

  8. 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

  9. 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.

  10. Fuel/cladding compatibility in irradiated metallic fuel pins at elevated temperatures

    SciTech Connect

    Tsai, Hanchung.

    1990-04-01

    Over fifty fuel/cladding compatibility tests on irradiated metallic fuel specimens have been conducted in an in-cell facility at elevated temperatures. At temperatures below 700--725{degree}C, no fuel/cladding interaction was noted in tests up to 7 h. Liquid-phase cladding penetration occurred in some of the tests at temperatures greater than 725--750{degree}C. The effective rates of liquid- phase cladding penetration of six different fuel/cladding combinations during 1-h testing are reported. After the initial liquefaction at the fuel/cladding interface, which may be affected by the solid-state diffusional interaction during the steady-state irradiation, the rate of further cladding penetration stays constant or decreases with time. There was no runaway cladding penetration in the latter part of a heating cycle.

  11. 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.

  12. Influence Of The Laser Cladding Strategies On The Mechanical Properties Of Inconel 718

    NASA Astrophysics Data System (ADS)

    Lamikiz, A.; Tabernero, I.; Ukar, E.; López de Lacalle, L. N.; Delgado, J.

    2011-01-01

    This work presents different experimental results of the mechanical properties of Inconel® 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® 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.

  13. 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

  14. 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.

  15. Complete Non-Radioactive Operability Tests for Cladding Hull Chlorination

    SciTech Connect

    Collins, Emory D; Johnson, Jared A.; Hylton, Tom D.; Brunson, Ronald Ray; Hunt, Rodney Dale; DelCul, Guillermo Daniel; Bradley, Eric Craig; Spencer, Barry B.

    2016-04-01

    Non-radioactive operability tests were made to test the metal chlorination reactor and condenser and their accessories using batch chlorinations of non-radioactive cladding samples and to identify optimum operating practices and components that need further modifications prior to installation of the equipment into the hot cell for tests on actual used nuclear fuel (UNF) cladding. The operability tests included (1) modifications to provide the desired heating and reactor temperature profile; and (2) three batch chlorination tests using, respectively, 100, 250, and 500 g of cladding. During the batch chlorinations, metal corrosion of the equipment was assessed, pressurization of the gas inlet was examined and the best method for maintaining solid salt product transfer through the condenser was determined. Also, additional accessing equipment for collection of residual ash and positioning of the unit within the hot cell were identified, designed, and are being fabricated.

  16. In situ synthesis of hydroxyapatite coating by laser cladding.

    PubMed

    Wang, D G; Chen, C Z; Ma, J; Zhang, G

    2008-10-15

    HA bioceramic coatings were synthesized on titanium substrate by laser cladding using cheap calcium carbonate and calcium hydrogen phosphate. The thermodynamic condition for synthesizing HA was calculated by software Matlab 5.0, the microstructure and phase analysis of laser clad HA bioceramic coatings were studied by electron probe microanalyser (EPMA), X-ray diffractometer (XRD) and transmission electron microscopy (TEM). The theoretical results show that the Gibbs free enthalpy for the synthesis of HA phase is satisfied, and the presence of HA phase in the clad coatings was then further verified by XRD and the selected area diffraction patterns. When the laser power is 600W and the scanning speed is 3.5mm/s, the compact HA bioceramic coatings were obtained, which have cellular dendritic structure and consist of the phases of HA, alpha-Ca(2)P(2)O(7), CaO and CaTiO(3).

  17. Clad Nd:YAG fibers for laser applications

    SciTech Connect

    Digonnet, M.J.F.; Shaw, H.J.; Gaeta, C.J.; O'meara, D.

    1987-05-01

    The implementation of an extrusion method to clad Nd:YAG single crystal fibers with index-matched glasses (Delta-n = 0.048) is reported. A propagation-loss coefficient of 0.08 dB/cm was measured for the fundamental mode of a 41-micron-diameter glass-clad fiber laser, an improvement of about one order of magnitude over unclad fibers. Guided clad fiber lasers operated at 1.064 microns with thresholds as low as 0.3-0.5 mW and up to 65-mW CW output power are also reported. The origins of and means of reducing the residual loss are discussed. 14 references.

  18. 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.

  19. Process for Making Optical Fibers from Core and Cladding Glass Rods.

    DTIC Science & Technology

    1996-08-12

    77,577 PATENT APPLICATION Inventor’s Name: Sanghera et al. ORIGINAL 2 3 PROCESS FOR MAKING OPTICAL FIBERS FROM CORE AND CLADDING GLASS 4 RODS S...core and cladding glass rods and to the fibers 10 made by the process. More particularly, the invention relates to 11 separately melting core and...cladding glass rods and combining the 12 melts proximate a fiber drawing orifice so that the core glass is 13 surrounded by the cladding glass and

  20. 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)

  1. Evaluation of stainless steel cladding for use in current design LWRs. Final report

    SciTech Connect

    Strasser, A.; Santucci, J.; Lindquist, K.; Yario, W.; Stern, G.; Goldstein, L.; Joseph, L.

    1982-12-01

    The design of stainless steel-clad LWR fuel and its performance at steady-state, transient, and accident conditions were reviewed. The objective was to evaluate the potential benefits and disadvantages of substituting stainless steel-clad fuel for the currently used Zircaloy-clad fuel. For a large, modern PWR, the technology and the fuel-cycle costs of stainless steel- and Zircaloy-clad fuels were compared.

  2. 46 CFR 111.60-23 - Metal-clad (Type MC) cable.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Metal-clad (Type MC) cable. 111.60-23 Section 111.60-23...-GENERAL REQUIREMENTS Wiring Materials and Methods § 111.60-23 Metal-clad (Type MC) cable. (a) Metal-clad (Type MC) cable permitted on board a vessel must be continuous corrugated metal-clad cable. (b)...

  3. 46 CFR 111.60-23 - Metal-clad (Type MC) cable.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 4 2014-10-01 2014-10-01 false Metal-clad (Type MC) cable. 111.60-23 Section 111.60-23...-GENERAL REQUIREMENTS Wiring Materials and Methods § 111.60-23 Metal-clad (Type MC) cable. (a) Metal-clad (Type MC) cable permitted on board a vessel must be continuous corrugated metal-clad cable. (b)...

  4. 46 CFR 111.60-23 - Metal-clad (Type MC) cable.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 4 2011-10-01 2011-10-01 false Metal-clad (Type MC) cable. 111.60-23 Section 111.60-23...-GENERAL REQUIREMENTS Wiring Materials and Methods § 111.60-23 Metal-clad (Type MC) cable. (a) Metal-clad (Type MC) cable permitted on board a vessel must be continuous corrugated metal-clad cable. (b)...

  5. 46 CFR 111.60-23 - Metal-clad (Type MC) cable.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 4 2013-10-01 2013-10-01 false Metal-clad (Type MC) cable. 111.60-23 Section 111.60-23...-GENERAL REQUIREMENTS Wiring Materials and Methods § 111.60-23 Metal-clad (Type MC) cable. (a) Metal-clad (Type MC) cable permitted on board a vessel must be continuous corrugated metal-clad cable. (b)...

  6. 46 CFR 111.60-23 - Metal-clad (Type MC) cable.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 4 2012-10-01 2012-10-01 false Metal-clad (Type MC) cable. 111.60-23 Section 111.60-23...-GENERAL REQUIREMENTS Wiring Materials and Methods § 111.60-23 Metal-clad (Type MC) cable. (a) Metal-clad (Type MC) cable permitted on board a vessel must be continuous corrugated metal-clad cable. (b)...

  7. Polariton Bose–Einstein condensate at room temperature in an Al(Ga)N nanowire–dielectric microcavity with a spatial potential trap

    PubMed Central

    Das, Ayan; Bhattacharya, Pallab; Heo, Junseok; Banerjee, Animesh; Guo, Wei

    2013-01-01

    A spatial potential trap is formed in a 6.0-μm Al(Ga)N nanowire by varying the Al composition along its length during epitaxial growth. The polariton emission characteristics of a dielectric microcavity with the single nanowire embedded in-plane have been studied at room temperature. Excitation is provided at the Al(Ga)N end of the nanowire, and polariton emission is observed from the lowest bandgap GaN region within the potential trap. Comparison of the results with those measured in an identical microcavity with a uniform GaN nanowire and having an identical exciton–photon detuning suggests evaporative cooling of the polaritons as they are transported into the trap in the Al(Ga)N nanowire. Measurement of the spectral characteristics of the polariton emission, their momentum distribution, first-order spatial coherence, and time-resolved measurements of polariton cooling provides strong evidence of the formation of a near-equilibrium Bose–Einstein condensate in the GaN region of the nanowire at room temperature. In contrast, the condensate formed in the uniform GaN nanowire–dielectric microcavity without the spatial potential trap is only in self-equilibrium. PMID:23382183

  8. An AlGaN Core-Shell Tunnel Junction Nanowire Light-Emitting Diode Operating in the Ultraviolet-C Band.

    PubMed

    Sadaf, S M; Zhao, S; Wu, Y; Ra, Y-H; Liu, X; Vanka, S; Mi, Z

    2017-02-08

    To date, semiconductor light emitting diodes (LEDs) operating in the deep ultraviolet (UV) spectral range exhibit very low efficiency due to the presence of large densities of defects and extremely inefficient p-type conduction of conventional AlGaN quantum well heterostructures. We have demonstrated that such critical issues can be potentially addressed by using nearly defect-free AlGaN tunnel junction core-shell nanowire heterostructures. The core-shell nanowire arrays exhibit high photoluminescence efficiency (∼80%) in the UV-C band at room temperature. With the incorporation of an epitaxial Al tunnel junction, the p-(Al)GaN contact-free nanowire deep UV LEDs showed nearly one order of magnitude reduction in the device resistance, compared to the conventional nanowire p-i-n device. The unpackaged Al tunnel junction deep UV LEDs exhibit an output power >8 mW and a peak external quantum efficiency ∼0.4%, which are nearly one to two orders of magnitude higher than previously reported AlGaN nanowire devices. Detailed studies further suggest that the maximum achievable efficiency is limited by electron overflow and poor light extraction efficiency due to the TM polarized emission.

  9. Results of NDE Technique Evaluation of Clad Hydrides

    SciTech Connect

    Kunerth, Dennis C.

    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

  10. 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.

  11. Method and system for edge cladding of laser gain media

    DOEpatents

    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.

  12. Characterization of Hydrogen Content in ZIRCALOY-4 Nuclear Fuel Cladding

    NASA Astrophysics Data System (ADS)

    Pfeif, E. A.; Lasseigne, A. N.; Krzywosz, K.; Mader, E. V.; Mishra, B.; Olson, D. L.

    2010-02-01

    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.

  13. 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.

  14. 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.

  15. Spatial mode-selective waveguide with hyperbolic cladding

    NASA Astrophysics Data System (ADS)

    Tang, Y.; Xi, Z.; Xu, M.; Bäumer, S.; Adam, A. J. L.; Urbach, H. P.

    2016-09-01

    Hyperbolic Meta-Materials~(HMMs) are anisotropic materials with permittivity tensor that has both positive and negative eigenvalues. Here we report that by using a type II HMM as cladding material, a waveguide which only supports higher order modes can be achieved, while the lower order modes become leaky and are absorbed in the HMM cladding. This counter intuitive property can lead to novel application in optical communication and photonic integrated circuit. The loss in our HMM-Insulator-HMM~(HIH) waveguide is smaller than that of similar guided mode in a Metal-Insulator-Metal~(MIM) waveguide.

  16. 78 FR 9676 - Clad Steel Plate From Japan: Continuation of Antidumping Duty Order

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-11

    ... International Trade Administration Clad Steel Plate From Japan: Continuation of Antidumping Duty Order AGENCY... International Trade Commission (ITC) that revocation of the antidumping duty order on clad steel plate from... sunset review of the antidumping duty order on clad steel plate from Japan pursuant to section 751(c)...

  17. A compact optofluidic cytometer with integrated liquid-core/PDMS-cladding waveguides.

    PubMed

    Fei, Peng; Chen, Zitian; Men, Yongfan; Li, Ang; Shen, Yiran; Huang, Yanyi

    2012-10-07

    We developed a simple method to construct liquid-core/PDMS-cladding optical waveguides through pressurized filling of dead-ended micro-channels with optical fluids. The waveguides are in the same layer as microfluidic channels which greatly simplifies device fabrication. With proper contrast between the refractive index of the core and cladding, the transmission loss of the waveguides is less than 5 dB cm(-1). We also developed a method to create flat and optically clear surfaces on the sides of PDMS devices in order to couple light between free-space and the waveguides embedded inside the chip. With these newly developed techniques, we make a compact flow cytometer and demonstrate the fluorescence counting of single cells at a rate of up to ~50 cell s(-1) and total sample requirement of a few microlitres. This method of making liquid-core optical waveguides and flat surfaces has great potential to be integrated into many PDMS-based microsystems.

  18. 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.

  19. 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.

  20. A new single-mode LMA optical fiber based on an anti-resonance in the cladding

    NASA Astrophysics Data System (ADS)

    Sharabi, Avidan; Sheintop, Uzziel; Goldin, Shlomo

    2016-03-01

    A novel single-mode large-mode-area (LMA) optical fiber is proposed. The primary part of the cladding is a thin layer with high refractive index. The layer possesses a periodic array of holes (or intrusions) which are either drawn in the propagation direction or drilled in the radial direction. When the holes (or intrusions) are drawn in the propagation direction, the periodicity of their array is in the azimuthal direction. The core may be hollow. The light confinement is achieved via a transmission anti-resonance. Namely, the array of holes allows coupling between an optical mode inside the primary cladding layer and the light both in the core and in the outer space. The light then sees two channels to penetrate the cladding: direct transmission and holes-assisted transmission. A distractive interference between these channels is achieved at an appropriate combination of fiber parameters. The fiber can be designed to hold nearly anyone of TE/TMnm modes. Computer simulations of the fiber were performed using COMSOL. The open boundary was simulated using a perfectly matched layer and the attenuation constants of different modes were determined via the imaginary parts of their propagation constants. As an example, a fiber holding a single TE01 mode inside a core of 100 μm diameter for the vacuum wavelength 1.55 μm was designed. The attenuation constant of the TE01 mode was found to be 5.8 ṡ 10-6 [dB/cm] while the other modes had attenuation of at least 4 orders of magnitude larger. Required fabrication tolerances were calculated and the fabrication of fibers of lengths 10 - 1000 m was found to be feasible. The bandwidth of the fiber was found to be in the range of 5 - 35 nm, depending on its length. Possible applications include high-power CW and pulsed lasers and amplifiers, sensors and others.

  1. 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.

  2. Using wire shaping techniques and holographic optics to optimize deposition characteristics in wire-based laser cladding

    NASA Astrophysics Data System (ADS)

    Goffin, N. J.; Higginson, R. L.; Tyrer, J. R.

    2016-12-01

    In laser cladding, the potential benefits of wire feeding are considerable. Typical problems with the use of powder, such as gas entrapment, sub-100% material density and low deposition rate are all avoided with the use of wire. However, the use of a powder-based source material is the industry standard, with wire-based deposition generally regarded as an academic curiosity. This is because, although wire-based methods have been shown to be capable of superior quality results, the wire-based process is more difficult to control. In this work, the potential for wire shaping techniques, combined with existing holographic optical element knowledge, is investigated in order to further improve the processing characteristics. Experiments with pre-placed wire showed the ability of shaped wire to provide uniformity of wire melting compared with standard round wire, giving reduced power density requirements and superior control of clad track dilution. When feeding with flat wire, the resulting clad tracks showed a greater level of quality consistency and became less sensitive to alterations in processing conditions. In addition, a 22% increase in deposition rate was achieved. Stacking of multiple layers demonstrated the ability to create fully dense, three-dimensional structures, with directional metallurgical grain growth and uniform chemical structure.

  3. Using wire shaping techniques and holographic optics to optimize deposition characteristics in wire-based laser cladding.

    PubMed

    Goffin, N J; Higginson, R L; Tyrer, J R

    2016-12-01

    In laser cladding, the potential benefits of wire feeding are considerable. Typical problems with the use of powder, such as gas entrapment, sub-100% material density and low deposition rate are all avoided with the use of wire. However, the use of a powder-based source material is the industry standard, with wire-based deposition generally regarded as an academic curiosity. This is because, although wire-based methods have been shown to be capable of superior quality results, the wire-based process is more difficult to control. In this work, the potential for wire shaping techniques, combined with existing holographic optical element knowledge, is investigated in order to further improve the processing characteristics. Experiments with pre-placed wire showed the ability of shaped wire to provide uniformity of wire melting compared with standard round wire, giving reduced power density requirements and superior control of clad track dilution. When feeding with flat wire, the resulting clad tracks showed a greater level of quality consistency and became less sensitive to alterations in processing conditions. In addition, a 22% increase in deposition rate was achieved. Stacking of multiple layers demonstrated the ability to create fully dense, three-dimensional structures, with directional metallurgical grain growth and uniform chemical structure.

  4. Using wire shaping techniques and holographic optics to optimize deposition characteristics in wire-based laser cladding

    PubMed Central

    Higginson, R. L.; Tyrer, J. R.

    2016-01-01

    In laser cladding, the potential benefits of wire feeding are considerable. Typical problems with the use of powder, such as gas entrapment, sub-100% material density and low deposition rate are all avoided with the use of wire. However, the use of a powder-based source material is the industry standard, with wire-based deposition generally regarded as an academic curiosity. This is because, although wire-based methods have been shown to be capable of superior quality results, the wire-based process is more difficult to control. In this work, the potential for wire shaping techniques, combined with existing holographic optical element knowledge, is investigated in order to further improve the processing characteristics. Experiments with pre-placed wire showed the ability of shaped wire to provide uniformity of wire melting compared with standard round wire, giving reduced power density requirements and superior control of clad track dilution. When feeding with flat wire, the resulting clad tracks showed a greater level of quality consistency and became less sensitive to alterations in processing conditions. In addition, a 22% increase in deposition rate was achieved. Stacking of multiple layers demonstrated the ability to create fully dense, three-dimensional structures, with directional metallurgical grain growth and uniform chemical structure. PMID:28119550

  5. 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.

  6. 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.

  7. 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.

  8. Orientation-Dependent Displacement Sensor Using an Inner Cladding Fiber Bragg Grating.

    PubMed

    Yang, Tingting; Qiao, Xueguang; Rong, Qiangzhou; Bao, Weijia

    2016-09-11

    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.

  9. 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.

  10. A Multi-Scale Modeling of Laser Cladding Process (Preprint)

    DTIC Science & Technology

    2006-04-01

    possibilities to alter a component at its surface. Despite immense potentials and advancements, the process model of microstructure evolution and its coupling...with macro parameter of laser cladding process has not been fully developed. To address this issue, a process model of microstructure evolution has

  11. Cladding burst behavior of Fe-based alloys under LOCA

    DOE PAGES

    Terrani, Kurt A.; Dryepondt, Sebastien N.; Pint, Bruce A.; ...

    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

  12. 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

  13. Performance of titanium stabilized D9 cladding and ducts

    SciTech Connect

    Makenas, B J

    1986-04-01

    A series of mixed oxide UO/sub 2/-PuO/sub 2/ Liquid Metal Reactor (LMR) Fuel assemblies using D9 alloy cladding and/or ducts have been irradiated to high exposure in the Fast Flux Test Facility (FFTF) with very encouraging results. D9 is a titanium modified variant of 316 stainless steel. The highest burnup attained for 316 stainless steel clad driver fuel pins in FFTF has been achieved in an assembly with a cold worked D9 duct while assemblies which simultaneously utilize both D9 ducts and D9 clad pins have achieved burnups as high as 155 MWd/kgM with a corresponding fast fluence of 25 x 10/sup 22/ n/cm/sup 2/. The cold worked D9 ducts demonstrated less length increase and less dilation than their Cold Worked 316 SS counterparts. The D9 pins also showed less length and diameter increase than comparable 316 SS pins with less evidence of deformation due to interference between the pin bundle and the duct. Corrosion behavior at the inner and outer surface of the D9 cladding has proved to be very similar to that of 316 stainless steel.

  14. 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.

  15. Comments on ""Contact Diffusion Interaction of Materials with Cladding''

    NASA Technical Reports Server (NTRS)

    Morris, J. F.

    1972-01-01

    A Russian paper by A. A. Babad-Zakhryapina contributes much to the understanding of fuel, clad interactions, and thus to nuclear thermionic technology. In that publication the basic diffusion expression is a simple one. A more general but complicated equation for this mass transport results from the present work. With appropriate assumptions, however, the new relation reduces to Babad-Zakhryapina's version.

  16. Experimental evidences for reducing Mg activation energy in high Al-content AlGaN alloy by MgGa δ doping in (AlN)m/(GaN)n superlattice.

    PubMed

    Wang, Xiao; Wang, Wei; Wang, Jingli; Wu, Hao; Liu, Chang

    2017-03-14

    P-type doping in high Al-content AlGaN alloys is a main challenge for realizing AlGaN-based deep ultraviolet optoelectronics devices. According to the first-principles calculations, Mg activation energy may be reduced so that a high hole concentration can be obtained by introducing nanoscale (AlN)5/(GaN)1 superlattice (SL) in Al0.83Ga0.17N disorder alloy. In this work, experimental evidences were achieved by analyzing Mg doped high Al-content AlGaN alloys and Mg doped AlGaN SLs as well as MgGa δ doped AlGaN SLs. Mg acceptor activation energy was significantly reduced from 0.378 to 0.331 eV by using MgGa δ doping in SLs instead of traditional doping in alloys. This new process was confirmed to be able to realize high p-type doping in high Al-content AlGaN.

  17. Experimental evidences for reducing Mg activation energy in high Al-content AlGaN alloy by MgGa δ doping in (AlN)m/(GaN)n superlattice

    NASA Astrophysics Data System (ADS)

    Wang, Xiao; Wang, Wei; Wang, Jingli; Wu, Hao; Liu, Chang

    2017-03-01

    P-type doping in high Al-content AlGaN alloys is a main challenge for realizing AlGaN-based deep ultraviolet optoelectronics devices. According to the first-principles calculations, Mg activation energy may be reduced so that a high hole concentration can be obtained by introducing nanoscale (AlN)5/(GaN)1 superlattice (SL) in Al0.83Ga0.17N disorder alloy. In this work, experimental evidences were achieved by analyzing Mg doped high Al-content AlGaN alloys and Mg doped AlGaN SLs as well as MgGa δ doped AlGaN SLs. Mg acceptor activation energy was significantly reduced from 0.378 to 0.331 eV by using MgGa δ doping in SLs instead of traditional doping in alloys. This new process was confirmed to be able to realize high p-type doping in high Al-content AlGaN.

  18. 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

  19. Experimental evidences for reducing Mg activation energy in high Al-content AlGaN alloy by MgGa δ doping in (AlN)m/(GaN)n superlattice

    PubMed Central

    Wang, Xiao; Wang, Wei; Wang, Jingli; Wu, Hao; Liu, Chang

    2017-01-01

    P-type doping in high Al-content AlGaN alloys is a main challenge for realizing AlGaN-based deep ultraviolet optoelectronics devices. According to the first-principles calculations, Mg activation energy may be reduced so that a high hole concentration can be obtained by introducing nanoscale (AlN)5/(GaN)1 superlattice (SL) in Al0.83Ga0.17N disorder alloy. In this work, experimental evidences were achieved by analyzing Mg doped high Al-content AlGaN alloys and Mg doped AlGaN SLs as well as MgGa δ doped AlGaN SLs. Mg acceptor activation energy was significantly reduced from 0.378 to 0.331 eV by using MgGa δ doping in SLs instead of traditional doping in alloys. This new process was confirmed to be able to realize high p-type doping in high Al-content AlGaN. PMID:28290480

  20. 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

    2016-03-03

    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.

  1. Air-clad fibers: pump absorption assisted by chaotic wave dynamics?

    PubMed

    Mortensen, Niels A

    2007-07-09

    Wave chaos is a concept which has already proved its practical usefulness in design of double-clad fibers for cladding-pumped fiber lasers and fiber amplifiers. In general, classically chaotic geometries will favor strong pump absorption and we address the extent of chaotic wave dynamics in typical air-clad geometries. While air-clad structures supporting sup-wavelength convex air-glass interfaces (viewed from the high-index side) will promote chaotic dynamics we find guidance of regular whispering-gallery modes in air-clad structures resembling an overall cylindrical symmetry. Highly symmetric air-clad structures may thus suppress the pump-absorption efficiency eta below the ergodic scaling law etainfinity Ac/Acl, where Ac and Acl are the areas of the rare-earth doped core and the cladding, respectively.

  2. Pulsed high-power AlGaN-cladding-free blue laser diodes on semipolar (202xAF1xAF) GaN substrates

    NASA Astrophysics Data System (ADS)

    Pourhashemi, A.; Farrell, R. M.; Hardy, M. T.; Hsu, P. S.; Kelchner, K. M.; Speck, J. S.; DenBaars, S. P.; Nakamura, S.

    2013-10-01

    We demonstrate high-power AlGaN-cladding-free blue laser diodes (LDs) on semipolar (202¯1¯) GaN substrates with peak output powers and external quantum efficiencies (EQEs) that are comparable to state-of-the-art commercial c-plane devices. Ridge waveguide LDs were fabricated on (202¯1¯) GaN substrates using InGaN waveguiding layers and GaN cladding layers. The devices lased at 454 nm at room temperature. We measured an output power of 2.15 W, an EQE of 39%, and a differential quantum efficiency of 49% from a single facet with a pulsed drive current (current density) of 2.02 A (28.1 kA/cm2).

  3. Wavelength-dependent polarization absorber based on multi-cladding fiber with gold coating

    NASA Astrophysics Data System (ADS)

    Weng, Sijun; Pei, Li; Liu, Chao; Wang, Jianshuai; Li, Jing; Ning, Tigang

    2016-12-01

    The wavelength-dependent polarization absorber based on multi-cladding fiber (MCF) with surface plasmon resonance (SPR) is proposed and demonstrated. In order to obtain the SPR effect both in the x- and y- polarized direction, the MCF is polished in two sides. The numerical simulations show that the polarization absorber with the wavelengths of 980/1550 nm and 1310/1550 nm can be obtained by adjusting the parameters of dielectric layer. Each wavelength only transmits a single polarization in the wavelength-dependent polarization absorber, and the loss of unwanted polarized mode is more than 95 dB/cm. In addition, when the length of fiber is only 550 μm, the bandwidths of polarization absorber are 29 nm at 980 nm and 413 nm at 1550 nm, respectively; meanwhile, the bandwidth of 1310/1550 nm polarization absorber reaches 102 nm and 302 nm, respectively.

  4. 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.

  5. Capabilities to improve corrosion resistance of fuel claddings by using powerful laser and plasma sources

    NASA Astrophysics Data System (ADS)

    Borisov, V. M.; Trofimov, V. N.; Sapozhkov, A. Yu.; Kuzmenko, V. A.; Mikhaylov, V. B.; Cherkovets, V. Ye.; Yakushkin, A. A.; Yakushin, V. L.; Dzhumayev, P. S.

    2016-12-01

    The treatment conditions of fuel claddings of the E110 alloy by using powerful UV or IR laser radiation, which lead to the increase in the corrosion resistance at the high-temperature ( T = 1100°C) oxidation simulating a loss-of-coolant accident, are determined. The possibility of the complete suppression of corrosion under these conditions by using pulsed laser deposition of a Cr layer is demonstrated. The behavior of protective coatings of Al, Al2O3, and Cr planted on steel EP823 by pulsed laser deposition, which is planned to be used in the BREST-OD-300, is studied. The methods of the almost complete suppression of corrosion in liquid lead to the temperature of 720°C are shown.

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. AlGaN Nanostructures with Extremely High Room-Temperature Internal Quantum Efficiency of Emission Below 300 nm

    NASA Astrophysics Data System (ADS)

    Toropov, A. A.; Shevchenko, E. A.; Shubina, T. V.; Jmerik, V. N.; Nechaev, D. V.; Evropeytsev, E. A.; Kaibyshev, V. Kh.; Pozina, G.; Rouvimov, S.; Ivanov, S. V.

    2016-11-01

    We present theoretical optimization of the design of a quantum well (QW) heterostructure based on AlGaN alloys, aimed at achievement of the maximum possible internal quantum efficiency of emission in the mid-ultraviolet spectral range below 300 nm at room temperature. A sample with optimized parameters was fabricated by plasma-assisted molecular beam epitaxy using the submonolayer digital alloying technique for QW formation. High-angle annular dark-field scanning transmission electron microscopy confirmed strong compositional disordering of the thus-fabricated QW, which presumably facilitates lateral localization of charge carriers in the QW plane. Stress evolution in the heterostructure was monitored in real time during growth using a multibeam optical stress sensor intended for measurements of substrate curvature. Time-resolved photoluminescence spectroscopy confirmed that radiative recombination in the fabricated sample dominated in the whole temperature range up to 300 K. This leads to record weak temperature-induced quenching of the QW emission intensity, which at 300 K does not exceed 20% of the low-temperature value.

  12. 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.

  13. 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.

  14. An elegant route to overcome fundamentally-limited light extraction in AlGaN deep-ultraviolet light-emitting diodes: preferential outcoupling of strong in-plane emission (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Kim, Jong Kyu; Lee, Jong Won; Kim, Dong-Yeong; Park, Jun Hyuk; Schubert, E. Fred; Kim, Jungsub; Kim, Yong-Il

    2016-09-01

    AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) are being developed for their numerous applications such as purification of air and water, sterilization in food processing, UV curing, medical-, and defense-related light sources. However, external quantum efficiency (EQE) of AlGaN-based DUV LEDs is very poor (<5% for 250nm) particularly due to low hole concentration and light extraction efficiency (LEE). Conventional LEE-enhancing techniques used for GaInN-based visible LEDs turned out to be ineffective for DUV LEDs due to difference in intrinsic material property between GaInN and AlGaN (Al< 30%). Unlike GaInN visible LEDs, DUV light from a high Al-content AlGaN active region is strongly transverse-magnetic (TM) polarized, that is, the electric field vector is parallel to the (0001) c-axis and shows strong sidewall emission through m- or a-plane due to crystal-field split-off hole band being top most valence band. Therefore, a new LEE-enhancing approach addressing the unique intrinsic property of AlGaN DUV LEDs is strongly desired. In this study, 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 is presented. 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 simultaneously. 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 to maximize the power conversion efficiency.

  15. 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

  16. 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).

  17. 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

  18. 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.

  19. Modeling of MOX Fuel Pellet-Clad Interaction Using ABAQUS

    SciTech Connect

    Ambrosek, Richard G.; Pedersen, Robert C.; Maple, Amanda

    2002-07-01

    Post-irradiation examination (PIE) has indicated an increase in the outer diameter of fuel pins being irradiated in the Advanced Test Reactor (ATR) for the MOX irradiation program. The diameter increase is the largest in the region between fuel pellets. The fuel pellet was modeled using PATRAN and the model was evaluated using ABAQUS, version 6.2. The results from the analysis indicate the non-uniform clad diameter is caused by interaction between the fuel pellet and the clad. The results also demonstrate that the interaction is not uniform over the pellet axial length, with the largest interaction occurring in the region of the pellet-pellet interface. Results were obtained for an axisymmetric model and for a 1/8 pie shaped segment, using the coupled temperature-displacement solution technique. (authors)

  20. 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)

  1. 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.

  2. Interactions of Zircaloy Cladding with Gallium: Final Report

    SciTech Connect

    D.F. Wilson; E.T. Manneschmidt; J.F. King; J.P. Strizak; J.R. DiStefano

    1998-09-01

    The U.S. Department of Energy has established a dual-track approach to the disposition of plutonium arising from the dismantling of nuclear weapons. Both immobilization and reactor-based mixed-oxide (MOX) fuel technologies are being evaluated. The reactor-based MOX fuel option requires assessment of the potential impact of concentrations of gallium (on the order of 1 to 10 ppm), not present in conventional MOX fhel, on cladding material performance. Three previous repmts"3 identified several compatibility issues relating to the presence of gallium in MOX fuel and its possible reaction with fiel cladding. Gallium initially present in weapons-grade (WG) plutonium is largely removed during processing to produce MOX fhel. After blending the plutonium with uranium, only 1 to 10 ppm gallium is expected in the sintered MOX fuel. Gallium present as gallium oxide (G~OJ could be evolved as the suboxide (G~O). Migration of the evolved G~O and diffusion of gallium in the MOX matrix along thermal gradients could lead to locally higher concentrations of G~03. Thus, while an extremely low concentration of gallium in MOX fiel almost ensures a lack of significant interaction of gallium whh Zircaloy fhel cladding, there remains a small probability that corrosion effects will not be negligible. General corrosion in the form of surface alloying resulting from formation of intermetallic compounds between Zircaloy and gallium should be ma& limited and, therefore, superficial because of the expected low ratio of gallium to the surface area or volume of the Zircaloy cladding. Although the expected concentration of gallium is low and there is very limited volubility of gallium in zirconium, especially at temperatures below 700 "C,4 grain boundary penetration and liquid metal embrittlement (LME) are forms of localized corrosion that were also considered. One fuel system darnage mechanism, pellet clad interaction, has led to some failure of the Zircaloy cladding in light-water reactors (LWRS

  3. 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.

  4. SF6/O2 plasma effects on silicon nitride passivation of AlGaN /GaN high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Meyer, David J.; Flemish, Joseph R.; Redwing, Joan M.

    2006-11-01

    The effects of various plasma and wet chemical surface pretreatments on the electrical characteristics of AlGaN /GaN high electron mobility transistors (HEMTs) passivated with plasma-deposited silicon nitride were investigated. The results of pulsed IV measurements show that samples exposed to various SF6/O2 plasma treatments have markedly better rf dispersion characteristics compared to samples that were either untreated or treated in wet buffered oxide etch prior to encapsulation. The improvement in these characteristics correlates with the reduction of carbon on the semiconductor surface as measured with x-ray photoelectron spectroscopy. HEMT channel sheet resistance was also affected by varying silicon nitride deposition parameters.

  5. Experimental observation of isotropic in-plane spin splitting in GaN /AlGaN two-dimensional electron gas

    NASA Astrophysics Data System (ADS)

    Zhao, Hongming; Liu, Baoli; Guo, Liwei; Tan, Changling; Chen, Hong; Chen, Dongmin

    2007-12-01

    The circular photogalvanic effect (CPGE) was used to study the in-plane-orientation dependent spin splitting in the C(0001)-oriented GaN /AlGaN two-dimensional electron gas (2DEG). The CPGE current induced by the interband transition shows an isotropic in-plane spin splitting in this system at room temperature. The spin relaxation time is found to be 14ps using the time resolved Kerr rotation technique, which is another evidence of the spin splitting in this 2DEG system.

  6. Modeling Explosive Cladding of Metallic Liners to Gun Tubes

    DTIC Science & Technology

    2010-01-01

    velocity of the explosive. Using the experimental Dfor the Chapman - Jouguet state and assuming the empirical v2£ is valid at seven volume expansions...process. EQUATION OF STATE The explosives used in this cladding effort have very low energy levels compared to traditional military explosives. A...impact for all the steps modeled. This indicates that a traditional Gurney assumption for final tube velocity is not accurate, as a final asymptotic

  7. Optical Fiber Geometry: Accurate Measurement of Cladding Diameter

    PubMed Central

    Young, Matt; Hale, Paul D.; Mechels, Steven E.

    1993-01-01

    We have developed three instruments for accurate measurement of optieal fiber cladding diameter: a contact micrometer, a scanning confocal microscope, and a white-light interference microscope. Each instrument has an estimated uncertainty (3 standard deviations) of 50 nm or less, but the confocal microscope may display a 20 nm systematic error as well. The micrometer is used to generate Standard Reference Materials that are commercially available. PMID:28053467

  8. Stopping light by an air waveguide with anisotropic metamaterial cladding.

    PubMed

    Jiang, Tian; Zhao, Junming; Feng, Yijun

    2009-01-05

    We present a detailed study of oscillating modes in a slab waveguide with air core and anisotropic metamaterial cladding. It is shown that, under specific dielectric configurations, slow and even stopped electromagnetic wave can be supported by such an air waveguide. We propose a linearly tapped waveguide structure that could lead the propagating light to a complete standstill. Both the theoretical analysis and the proposed waveguide have been validated by full-wave simulation based on finite-difference time-domain method.

  9. 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.

  10. 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.

  11. Liquid crystal claddings for passive temperature stabilization of silicon photonics

    NASA Astrophysics Data System (ADS)

    Ptasinski, Joanna N.; Khoo, Iam-Choon; Fainman, Yeshaiahu

    2014-10-01

    Silicon photonics allows for high density component integration on a single chip and it brings promise for low-loss, high-bandwidth data processing in modern computing systems. Owing to silicon's high positive thermo-optic coefficient, temperature fluctuations tend to degrade the device performance. This work explores passive thermal stabilization of silicon photonic devices using nematic liquid crystal (NLC) claddings, as they possess large negative thermo-optic coefficients in addition to low absorption at the telecommunication wavelengths.

  12. Interactions of Zircaloy cladding with gallium: 1998 midyear status

    SciTech Connect

    Wilson, D.F.; DiStefano, J.R.; Strizak, J.P.; King, J.F.; Manneschmidt, E.T.

    1998-06-01

    A program has been implemented to evaluate the effect of gallium in mixed-oxide (MOX) fuel derived from weapons-grade (WG) plutonium on Zircaloy cladding performance. The objective is to demonstrate that low levels of gallium will not compromise the performance of the MOX fuel system in a light-water reactor. The graded, four-phase experimental program was designed to evaluate the performance of prototypic Zircaloy cladding materials against (1) liquid gallium (Phase 1), (2) various concentrations of Ga{sub 2}O{sub 3} (Phase 2), (3) centrally heated surrogate fuel pellets with expected levels of gallium (Phase 3), and (4) centrally heated prototypic MOX fuel pellets (Phase 4). This status report describes the results of a series of tests for Phases 1 and 2. Three types of tests are being performed: (1) corrosion, (2) liquid metal embrittlement, and (3) corrosion-mechanical. These tests will determine corrosion mechanisms, thresholds for temperature and concentration of gallium that may delineate behavioral regimes, and changes in the mechanical properties of Zircaloy. Initial results have generally been favorable for the use of WG-MOX fuel. The MOX fuel cladding, Zircaloy, does react with gallium to form intermetallic compounds at {ge}300 C; however, this reaction is limited by the mass of gallium and is therefore not expected to be significant with a low level (parts per million) of gallium in the MOX fuel. Although continued migration of gallium into the initially formed intermetallic compound can result in large stresses that may lead to distortion, this was shown to be extremely unlikely because of the low mass of gallium or gallium oxide present and expected clad temperatures below 400 C. Furthermore, no evidence for grain boundary penetration by gallium has been observed.

  13. Interactions of zircaloy cladding with gallium -- 1997 status

    SciTech Connect

    Wilson, D.F.; DiStefano, J.R.; King, J.F.; Manneschmidt, E.T.; Strizak, J.P.

    1997-11-01

    A four phase program has been implemented to evaluate the effect of gallium in mixed oxide (MOX) fuel derived from weapons grade (WG) plutonium on Zircaloy cladding performance. The objective is to demonstrate that low levels of gallium will not compromise the performance of the MOX fuel system in LWR. This graded, four phase experimental program will evaluate the performance of prototypic Zircaloy cladding materials against: (1) liquid gallium (Phase 1), (2) various concentrations of Ga{sub 2}O{sub 3} (Phase 2), (3) centrally heated surrogate fuel pellets with expected levels of gallium (Phase 3), and (4) centrally heated prototypic MOX fuel pellets (Phase 4). This status report describes the results of an initial series of tests for phases 1 and 2. Three types of tests are being performed: (1) corrosion, (2) liquid metal embrittlement (LME), and (3) corrosion mechanical. These tests are designed to determine the corrosion mechanisms, thresholds for temperature and concentration of gallium that may delineate behavioral regimes, and changes in mechanical properties of Zircaloy. Initial results have generally been favorable for the use of WG-MOX fuel. The MOX fuel cladding, Zircaloy, does react with gallium to form intermetallic compounds at {ge} 300 C; however, this reaction is limited by the mass of gallium and is therefore not expected to be significant with a low level (in parts per million) of gallium in the MOX fuel. While continued migration of gallium into the initially formed intermetallic compound results in large stresses that can lead to distortion, this is also highly unlikely because of the low mass of gallium or gallium oxide present and expected clad temperatures below 400 C. Furthermore, no evidence for grain boundary penetration by gallium has been observed.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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)

  19. Behavior of Zircaloy Cladding in the Presence of Gallium

    SciTech Connect

    DiStefano, J.R.; King, J.F.; Manneschmidt, E.T.; Strizak, J.P.; Wilson, D.F.

    1998-09-28

    The U.S. Department of Energy has established a dual-track approach to the disposition of plutonium arising from the dismantling of nuclear weapons. Both immobilization and reactor-based mixed-oxide (MOX) fuel technologies are being evaluated. The reactor-based MOX fuel option requires assessment of the potential impact of concentrations of gallium (on the order of 1 to 10 ppm), not present in conventional MOX fuel, on cladding material performance. An experimental program was designed to evaluate the performance of prototypic Zircaloy cladding materials against (1) liquid gallium, and (2) various concentrations of G~03. Three types of tests were performed: (1) corrosion, (2) liquid metal embrittlement, and (3) corrosion-mechanical. These tests were to determine corrosion mechanisms, thresholds for temperature and concentration of gallium that delineate behavioral regimes, and changes in the mechanical properties of Zircaloy. Results have generally been favorable for the use of weapons-grade (WG) MOX fhel. The Zircaloy cladding does react with gallium to form intermetallic compounds at >3000 C; however, this reaction is limited by the mass of gallium and is therefore not expected to be significant with a low level (parts per million) of gallium in the MOX fuel. Furthermore, no evidence for grain boundary penetration by gallium or liquid metal embrittlement was observed.

  20. Performance enhancement of blue light-emitting diodes with InGaN/GaN multi-quantum wells grown on Si substrates by inserting thin AlGaN interlayers

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    We have grown blue light-emitting diodes (LEDs) having InGaN/GaN multi-quantum wells (MQWs) with thin AlyGa1-yN (0 < y < 0.3) interlayers on Si(111) substrates. It was found by high-resolution transmission electron microscopy observations and three-dimensional atom probe analysis that 1-nm-thick interlayers with an AlN mole fraction of less than y = 0.3 were continuously formed between GaN barriers and InGaN wells, and that the AlN mole fraction up to y = 0.15 could be consistently controlled. The external quantum efficiency of the blue LED was enhanced in the low-current-density region (≤45 A/cm2) but reduced in the high-current-density region by the insertion of the thin Al0.15Ga0.85N interlayers in the MQWs. We also found that reductions in both forward voltage and wavelength shift with current were achieved by inserting the interlayers even though the inserted AlGaN layers had potential higher than that of the GaN barriers. The obtained peak wall-plug efficiency was 83% at room temperature. We suggest that the enhanced electroluminescence (EL) performance was caused by the introduction of polarization-induced hole carriers in the InGaN wells on the side adjacent to the thin AlGaN/InGaN interface and efficient electron carrier transport through multiple wells. This model is supported by temperature-dependent EL properties and band-diagram simulations. We also found that inserting the interlayers brought about a reduction in the Shockley-Read-Hall nonradiative recombination component, corresponding to the shrinkage of V-defects. This is another conceivable reason for the observed performance enhancement.

  1. Robust cladding light stripper for high-power fiber lasers using soft metals.

    PubMed

    Babazadeh, Amin; Nasirabad, Reza Rezaei; Norouzey, Ahmad; Hejaz, Kamran; Poozesh, Reza; Heidariazar, Amir; Golshan, Ali Hamedani; Roohforouz, Ali; Jafari, S Naser Tabatabaei; Lafouti, Majid

    2014-04-20

    In this paper we present a novel method to reliably strip the unwanted cladding light in high-power fiber lasers. Soft metals are utilized to fabricate a high-power cladding light stripper (CLS). The capability of indium (In), aluminum (Al), tin (Sn), and gold (Au) in extracting unwanted cladding light is examined. The experiments show that these metals have the right features for stripping the unwanted light out of the cladding. We also find that the metal-cladding contact area is of great importance because it determines the attenuation and the thermal load on the CLS. These metals are examined in different forms to optimize the contact area to have the highest possible attenuation and avoid localized heating. The results show that sheets of indium are very effective in stripping unwanted cladding light.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. UV photoemission study of heteroepitaxial AlGaN films grown on 6H-SiC

    NASA Astrophysics Data System (ADS)

    Benjamin, M. C.; Bremser, M. D.; Weeks, T. W.; King, S. W.; Davis, R. F.; Nemanich, R. J.

    1996-09-01

    This study presents results of UV photoemission measurements of the surface and interface properties of heteroepitaxial AlGaN on 6H-SiC. Previous results have demonstrated a negative electron affinity of AlN on 6H-SiC. In this study Al xGa 1- xN alloy films were grown by organometallic vapor phase epitaxy (OMVPE) and doped with silicon. The analytical techniques included UPS, Auger electron spectroscopy, and LEED. All analysis took place in an integrated UHV transfer system which included the analysis techniques, a surface processing chamber and a gas source MBE. The OMVPE alloy samples were transported in air to the surface characterization system while the AlN and GaN investigations were prepared in situ. The surface electronic states were characterized by surface normal UV photoemission to determine whether the electron affinity was positive or negative. Two aspects of the photoemission distinguish a surface that exhibits a NEA: (1) the spectrum exhibits a sharp peak in the low kinetic energy region, and (2) the width of the spectrum is hv - Eg. The in situ prepared AlN samples exhibited the characteristics of a NEA while the GaN and Al 0.13Ga 0.87N samples did not. The Al 0.55Ga 0.45N sample shows a low positive electron affinity. Annealing of the sample to > 400°C resulted in the disappearance of the sharp emission features, and this effect was related to contaminant effects on the surface. The results suggest the potential of nitride based cold cathode electron emitters.

  7. 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.

  8. Behavior of an improved Zr fuel cladding with oxidation resistant coating under loss-of-coolant accident conditions

    NASA Astrophysics Data System (ADS)

    Park, Dong Jun; Kim, Hyun Gil; Jung, Yang Il; Park, Jung Hwan; Yang, Jae Ho; Koo, Yang Hyun

    2016-12-01

    This study investigates protective coatings for improving the high temperature oxidation resistance of Zr fuel claddings for light water nuclear reactors. FeCrAl alloy and Cr layers were deposited onto Zr plates and tubes using cold spraying. For the FeCrAl/Zr system, a Mo layer was introduced between the FeCrAl coating and the Zr matrix to prevent inter-diffusion at high temperatures. Both the FeCrAl and Cr coatings improved the oxidation resistance compared to that of the uncoated Zr alloy when exposed to a steam environment at 1200 °C. The ballooning behavior and mechanical properties of the coated cladding samples were studied under simulated loss-of-coolant accident conditions. The coated samples showed higher burst temperatures, lower circumferential strain, and smaller rupture openings compared to the uncoated Zr. Although 4-point bend tests of the coated samples showed a small increase in the maximum load, ring compression tests of a sectioned sample showed increased ductility.

  9. Development of the recovery technology for nickel superalloy blades of the aircraft engine by laser cladding

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    Development of cladding modes was performed with a superalloy nickel based powder on a flat substrate from material identical to compressor and turbine blades. Cross sections were made, and a visual inspection of the shape and the quality of the clad track as well as themetallographic analysis were performed. Microhardness of the deposition zone, chemical composition of the base, cladded metals, and the heat affected zone were determined.

  10. Processing and Characterization of Polycrystalline Yag (Yttrium Aluminum Garnet) Core-Clad Fibers - Postprint

    DTIC Science & Technology

    2015-01-01

    AFRL-RY-WP-TP-2014-0296 PROCESSING AND CHARACTERIZATION OF POLYCRYSTALLINE YAG ( YTTRIUM ALUMINUM GARNET) CORE-CLAD FIBERS -POSTPRINT...April 2013 – 1 April 2014 4. TITLE AND SUBTITLE PROCESSING AND CHARACTERIZATION OF POLYCRYSTALLINE YAG ( YTTRIUM ALUMINUM GARNET) CORE-CLAD FIBERS...of polycrystalline YAG ( Yttrium Aluminum Garnet) core-clad fibers Hyun Jun Kima,b, Geoff E. Faira*, Santeri A

  11. Experimental research of surface roughness and surface texture after laser cladding

    NASA Astrophysics Data System (ADS)

    Przestacki, Damian; Majchrowski, Radomir; Marciniak-Podsadna, Lidia

    2016-12-01

    The objective of the investigation was to identify surface integrity of machined parts after laser cladding. Surface analysis was made by using novel metrology methods: auto correlation and gradient distributions. An Infinite Focus Measurement Machine (IFM) has been used for the surface texture analysis. The study has been performed within a production facility during the prototyping process of new products. There are many methods available for geometric and surface topography measurements: contact and non-contact, micro and nanoscale approaches. An optical method based on the measurement of light reflected or scattered from the surface of an examined object can be used for this purpose. We have tested the application of an advanced 3D scanner for this purpose - optical scanner ATOS II. The scanner ATOS II represents the optical method, i.e. the digital light projection (DLP) method. The system consists of a projector and two digital cameras capable of supplying 1.4 million of measuring points per second. This method enables to scan elements from a few millimeters to a several dozen of meters in size. The roughness analysis is based on 2D measurements, which gave two-dimensional characteristics of the surface. In last decades, the metrology of the surface layer notes dynamical development as a science. During the last decades, many scientists and constructors became convinced that the third dimension should be added to the surface analysis. At present, 3D analysis of the surface geometry is widely accepted. In order to complete the topography analysis of the surface texture after laser cladding, our team worked out original program for 2D and 3D surface analysis. It was called TAS (topography analysis and simulation) and was based on Matlab software. Four modules were developed: the initial data processing module, basic parameters calculating module, data visualization module, and digital filtration module.

  12. Additional heat treatment of non-porous coatings obtained on medium carbon steel substrates by electron beam cladding of a Ti-Mo-C powder composition

    NASA Astrophysics Data System (ADS)

    Mul, D. O.; Drobyaz, E. A.; Zimoglyadova, T. A.; Bataev, V. A.; Lazurenko, D. V.; Shevtsova, L. I.

    2016-04-01

    The structure and microhardness of surface layers, obtained by non-vacuum electron beam cladding of Ti-Mo-C powder mixture on a steel substrate after different types of heat treatment, were investigated. After cladding samples were heat treated in a furnace at 200...500 °C, as well as quenched at 860 ° C and then underwent high-temperature tempering. Heat treatment of cladded coatings induced tempering of martensite and precipitation of cementite particles (Fe3C). Transmission electron microscopy of the samples after heating and holding at 300 ° C revealed precipitation of nanosized cubical TiC particles. The formation of hard nanosized particles led to the surface layer microhardness growth. The highest level of microhardness (which was 1.2...1.5-fold higher in comparison with coating microhardness after heat treatment) was achieved after heating of the claded material at 300 °C and 400 °C Additional quenching of samples at 860 °C did not increase the microhardness level.

  13. Dependence of bending losses on cladding thickness in plastic optical fibers.

    PubMed

    Durana, Gaizka; Zubia, Joseba; Arrue, Jon; Aldabaldetreku, Gotzon; Mateo, Javier

    2003-02-20

    Our main goal is to provide a comprehensive explanation of the existing differences in bending losses arising from having step-index multimode plastic optical fibers with different cladding thickness and under different types of conditions, namely, the variable bend radius R, the number of fiber turns, or the fiber diameter. For this purpose, both experimental and numerical result of bending losses are presented for different cladding thicknesses and conditions. For the measurements, two cladding thicknesses have been considered: one finite and another infinite. A fiber in air has a finite cladding thickness, and rays are reflected at the cladding-air interface, whereas a fiber covered by oil is equivalent to having an infinite cladding, since the very similar refractive index of oil prevents reflections from occurring at the cladding-oil interface. For the sake of comparison, numerical simulations based on ray tracing have been performed for finite-cladding step-index multimode waveguides. The numerical results reinforce the experimental data, and both the experimental measurements and the computational simulations turn out to be very useful to explain the behavior of refracting and tunneling rays along bent multimode waveguides and along finite-cladding fibers.

  14. Analysis of unclad and sub-clad semi-elliptical flaws in pressure vessel steels

    SciTech Connect

    Irizarry-Quinones, H.; Macdonald, B.D.; McAfee, W.J.

    1996-06-01

    This study was conducted to support warm prestressing experiments on unclad and sub-clad flawed beams loaded in pure bending. Two cladding yield strengths were investigated: 0.6 Sy and 0.8 Sy, where Sy is the yield strength of the base metal. Cladding and base metal were assumed to be stress free at the stress relief temperature for the 3D elastic-plastic finite element analysis used to model the experiments. The model results indicated that when cooled from the stress relief temperature, the cladding was put in tension due to its greater coefficient of thermal expansion. When cooled, the cladding exhibited various amounts of tensile yielding. The degree of yielding depended on the amount of cooling and the strength of the cladding relative to that of the base metal. When subjected to tensile bending stress, the sub-clad flaw elastic-plastic stress intensity factor, K{sub I}(J), was at first dominated by crack closing force due to tensile yielding in the cladding. Thus, imposed loads initially caused no increase in K{sub I}(J) near the clad-base interface. However, K{sub I}(J) at the flaw depth was little affected. When the cladding residual stress was overcome, K{sub I}(J) gradually increased until the cladding began to flow. Thereafter, the rate at which K{sub I}(J) increased with load was the same as that of an unclad beam. A plastic zone corrected K{sub I} approximation for the unclad flaw was found by the superposition of standard Newman and Raju solutions with those due to a cladding crack closure force approximated by the Kaya and Erdogan solution. These elastic estimates of the effect of cladding in reducing the crack driving force were quite in keeping with the 3D elastic-plastic finite element solution for the sub-clad flaw. The results were also compared with the analysis of clad beam experiments by Keeney and the conclusions by Miyazaki, et al. A number of sub-clad flaw specimens not subjected to warm prestressing were thought to have suffered degraded

  15. Development of data base with mechanical properties of un- and pre-irradiated VVER cladding

    SciTech Connect

    Asmolov, V.; Yegorova, L.; Kaplar, E.; Lioutov, K.; Smirnov, V.; Prokhorov, V.; Goryachev, A.

    1998-03-01

    Analysis of recent RIA test with PWR and VVER high burnup fuel, performed at CABRI, NSRR, IGR reactors has shown that the data base with mechanical properties of the preirradiated cladding is necessary to interpret the obtained results. During 1997 the corresponding cycle of investigations for VVER clad material was performed by specialists of NSI RRC KI and RIAR in cooperation with NRC (USA), IPSN (France) in two directions: measurements of mechanical properties of Zr-1%Nb preirradiated cladding versus temperature and strain rate; measurements of failure parameters for gas pressurized cladding tubes. Preliminary results of these investigations are presented in this paper.

  16. Special optical fiber for temperature sensing based on cladding-mode resonance.

    PubMed

    Pang, Fufei; Xiang, Wenchao; Guo, Hairun; Chen, Na; Zeng, Xianglong; Chen, Zhenyi; Wang, Tingyun

    2008-08-18

    A fiber-optic temperature sensor by using a multi-cladding special fiber is presented. It works on the basis of leaky mode resonance from fiber core to outer cladding. With the thin-thickness inner cladding, the cladding mode is strongly excited and the resonant spectrum is very sensitive to the refractive index variation of coating material. By coating the special fiber with temperature-sensitive silicone, the temperature response was investigated experimentally from -20 degrees C to 80 degrees C. The results show high temperature sensitivity (240 pm/degrees C at 20 degrees C) and good repeatability.

  17. Orientation-Dependent Displacement Sensor Using an Inner Cladding Fiber Bragg Grating

    PubMed Central

    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

  18. Theoretical analysis of swelling characteristics of cylindrical uranium dioxide fuel pins with a niobium - 1-percent-zirconium clad

    NASA Technical Reports Server (NTRS)

    Saltsman, J. F.

    1973-01-01

    The relations between clad creep strain and fuel volume swelling are shown for cylindrical UO2 fuel pins with a Nb-1Zr clad. These relations were obtained by using the computer code CYGRO-2. These clad-strain - fuel-volume-swelling relations may be used with any fuel-volume-swelling model, provided the fuel volume swelling is isotropic and independent of the clad restraints. The effects of clad temperature (over a range from 118 to 1642 K (2010 to 2960 R)), pin diameter, clad thickness and central hole size in the fuel have been investigated. In all calculations the irradiation time was 500 hours. The burnup rate was varied.

  19. A High Temperature, non-TRISO Fuel and Clad Design with Commercial-Grade Enrichment for the Prismatic Block Very High Temperature Reactor

    SciTech Connect

    James W. Sterbentz

    2005-11-01

    The prismatic block Very High Temperature Reactor (VHTR) is a leading Generation IV reactor concept. This reactor with its relatively low core power density and large graphite mass currently satisfies the fundamental goals of the Generation IV charter. However, modifications can be made to the fuel and clad design, such that (1) VHTR uranium enrichment can be lowered to near commercial-grade pressurized water reactor (PWR) enrichments, (2) fuel burnups are extended, and (3) the thermal safety margin under transient conditions is increased. This paper outlines a possible fuel and clad design concept for use in a VHTR prismatic block core which could lead to substantial improvements in overall VHTR economics and sustainability. The results of depletion calculations here will demonstrate comparable burnup between the new fuel and clad design with only 4-6 wt% enriched uranium and the current higher enriched 10-20 wt% VHTR fuel design. In addition, the new fuel and clad design concept uses high-temperature ceramic fuel and clad materials that have the potential to significantly increase the thermal margin under VHTR transient conditions. The current fuel block design for the VHTR is the hexagonal Fort Saint Vrain (FSV) fuel block with 108 coolant channels, 210 fuel rods, and six burnable poison holes drilled axially in the block. This basic FSV block is also part of the new design concept here. The basic hexagonal block dimensions remain fixed with only the fuel pellet and clad materials and radii changed. Further optimizations of the fuel block are in progress. Currently, the proposed nuclear fuel for the prismatic VHTR is the well-known TRISO-coated particle fuel. The TRISO-coated particle offers a nice spherical, high-integrity pressure vessel containment for the fission gases (SiC layer). However, due to the multiple particle coating layers, the fuel kernel represents only 9.4% of the total particle volume (350 {micro}m kernel diameter particle) and together with

  20. Three-Ply Al/Mg/Al Clad Sheets Fabricated by Twin-Roll Casting and Post-treatments (Homogenization, Warm Rolling, and Annealing)

    NASA Astrophysics Data System (ADS)

    Park, Jaeyeong; Song, Hyejin; Kim, Jung-Su; Sohn, Seok Su; Lee, Sunghak

    2017-01-01

    When thin Al alloy sheets are clad on to twin-roll-cast Mg alloy melt, inherent drawbacks of Mg alloys such as poor formability, corrosion resistance, and surface quality can be effectively complemented. In this study, three-ply Al/Mg/Al clad sheets were fabricated by twin-roll casting and post-treatments. Brittle interfacial layers composed of γ (Mg17Al12) and β (Mg2Al3) phases were inevitably formed, but their proper thickening during the post-treatments led to improvement of interfacial bonding and resultant tensile properties. In particular, warm rolling was an effective way to modify interfacial microstructures and tensile properties by minimizing deformation inhomogeneity and stress concentration.

  1. 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.

  2. AlGaN HEMTs on patterned resistive/conductive SiC templates

    NASA Astrophysics Data System (ADS)

    Prystawko, Pawel; Sarzynski, Marcin; Nowakowska-Siwinska, Anna; Crippa, Danilo; Kruszewski, Piotr; Wojtasiak, Wojciech; Leszczynski, Mike

    2017-04-01

    High performance GaN-based high electron mobility transistors (HEMTs) on SiC require low-miscut ( 0.45°), resistive substrates, which are very expensive. A cost-effective solution is to use resistive SiC template i.e., grow a thick resistive SiC epitaxial layer on cheap, conductive SiC substrate. However, this approach requires much higher miscut (2-8°). In the present work we show a lateral patterning technology capable to locally decrease the high miscut of the resistive SiC template, down to a level acceptable for GaN epitaxy. On such patterned SiC templates we grew smooth AlGaN/GaN structures. The maximum width of flat regions available for device fabrication was nearly 100 μm. In these flat regions AlGaN-based HEMTs were fabricated and characterized.

  3. Impact of wet-oxidized Al2O3/AlGaN interface on AlGaN/GaN 2-DEGs

    NASA Astrophysics Data System (ADS)

    Meer, Mudassar; Majety, Sridhar; Takhar, Kuldeep; Ganguly, Swaroop; Saha, Dipankar

    2017-04-01

    We investigated the impact of wet-oxidation of AlGaN in an AlGaN/GaN heterostructure by selectively probing the metal/AlGaN interface. The two-dimensional electron gas (2-DEG) characteristics show improved mobility with increasing oxidation time and Al2O3 thickness. The change is attributed to an interplay of the interface trap density (D it) and the oxide thickness. D it is found to reduce progressively for thicker gate oxides as determined by selectively probing the Al2O3/AlGaN interface and employing frequency dependent capacitance and conductance spectroscopy on these devices. The energies of the interface traps are found to be in the range of 0.35–0.45 eV below the conduction band edge. The D it is found to reduce from 2 × 1013 cm‑2 eV‑1 for 2.3 nm of Al2O3 to 5 × 1012 cm‑2 eV‑1 for 16 nm of Al2O3. Contrary to the earlier reports of increased 2-DEG electron density, the primary advantage is found to be a reduction in Dit leading to an increased electron mobility from 1730 to 2800 cm2V‑1s‑1.

  4. 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.

  5. 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.

  6. Results of U-xMo (x=7, 10, 12 wt.%) Alloy versus Al-6061 Cladding Diffusion Couple Experiments Performed at 500, 550 and 600 Degrees C

    SciTech Connect

    Emmanuel Perez; Dennis D. Keiser, Jr.; Yongho Sohn

    2013-04-01

    The Reduced Enrichment for Research and Test Reactors (RERTR) program has been developing low enrichment fuel systems encased in Al 6061 for use in research and test reactors. U–Mo alloys in contact with Al and Al alloys can undergo diffusional interactions that can result in the development of interdiffusion zones with complex fine-grained microstructures composed of multiple phases. A monolithic fuel currently being developed by the RERTR program has local regions where the U–Mo fuel plate is in contact with the Al 6061 cladding and, as a result, the program finds information about interdiffusion zone development at high temperatures of interest. In this study, the microstructural development of diffusion couples consisting of U-7wt.%Mo, U-10wt.%Mo, and U-12wt.%Mo vs. Al 6061 (or 6061 aluminum) cladding, annealed at 500, 550, 600 degrees C for 1, 5, 20, 24, or 132 hours, was analyzed by backscatter electron microscopy and x-ray energy dispersive spectroscopy on a scanning electron microscope. Concentration profiles were determined by standardized wavelength dispersive spectroscopy and standardless x-ray energy dispersive spectroscopy. The results of this work shows that the presence of surface layers at the U–Mo/Al 6061 interface can dramatically impact the overall interdiffusion behavior in terms of rate of interaction and uniformity of the developed interdiffusion zones. It further reveals that relatively uniform interaction layers with higher Si concentrations can develop in U–Mo/Al 6061 couples annealed at shorter times and that longer times at temperature result in the development of more non-uniform interaction layers with more areas that are enriched in Al. At longer annealing times and relatively high temperatures, U–Mo/Al 6061 couples can exhibit more interaction compared to U–Mo/pure Al couples. The minor alloying constituents in Al 6061 cladding can result in the development of many complex phases in the interaction layer of U

  7. 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

  8. Effects of GaN/AlGaN/Sputtered AlN nucleation layers on performance of GaN-based ultraviolet light-emitting diodes

    PubMed Central

    Hu, Hongpo; Zhou, Shengjun; Liu, Xingtong; Gao, Yilin; Gui, Chengqun; Liu, Sheng

    2017-01-01

    We report on the demonstration of GaN-based ultraviolet light-emitting diodes (UV LEDs) emitting at 375 nm grown on patterned sapphire substrate (PSS) with in-situ low temperature GaN/AlGaN nucleation layers (NLs) and ex-situ sputtered AlN NL. The threading dislocation (TD) densities in GaN-based UV LEDs with GaN/AlGaN/sputtered AlN NLs were determined by high-resolution X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (TEM), which revealed that the TD density in UV LED with AlGaN NL was the highest, whereas that in UV LED with sputtered AlN NL was the lowest. The light output power (LOP) of UV LED with AlGaN NL was 18.2% higher than that of UV LED with GaN NL owing to a decrease in the absorption of 375 nm UV light in the AlGaN NL with a larger bandgap. Using a sputtered AlN NL instead of the AlGaN NL, the LOP of UV LED was further enhanced by 11.3%, which is attributed to reduced TD density in InGaN/AlInGaN active region. In the sputtered AlN thickness range of 10–25 nm, the LOP of UV LED with 15-nm-thick sputtered AlN NL was the highest, revealing that optimum thickness of the sputtered AlN NL is around 15 nm. PMID:28294166

  9. Effects of GaN/AlGaN/Sputtered AlN nucleation layers on performance of GaN-based ultraviolet light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Hu, Hongpo; Zhou, Shengjun; Liu, Xingtong; Gao, Yilin; Gui, Chengqun; Liu, Sheng

    2017-03-01

    We report on the demonstration of GaN-based ultraviolet light-emitting diodes (UV LEDs) emitting at 375 nm grown on patterned sapphire substrate (PSS) with in-situ low temperature GaN/AlGaN nucleation layers (NLs) and ex-situ sputtered AlN NL. The threading dislocation (TD) densities in GaN-based UV LEDs with GaN/AlGaN/sputtered AlN NLs were determined by high-resolution X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (TEM), which revealed that the TD density in UV LED with AlGaN NL was the highest, whereas that in UV LED with sputtered AlN NL was the lowest. The light output power (LOP) of UV LED with AlGaN NL was 18.2% higher than that of UV LED with GaN NL owing to a decrease in the absorption of 375 nm UV light in the AlGaN NL with a larger bandgap. Using a sputtered AlN NL instead of the AlGaN NL, the LOP of UV LED was further enhanced by 11.3%, which is attributed to reduced TD density in InGaN/AlInGaN active region. In the sputtered AlN thickness range of 10–25 nm, the LOP of UV LED with 15-nm-thick sputtered AlN NL was the highest, revealing that optimum thickness of the sputtered AlN NL is around 15 nm.

  10. Reactivity Initiated Accident Simulation to Inform Transient Testing of Candidate Advanced Cladding

    SciTech Connect

    Brown, Nicholas R; Wysocki, Aaron J; Terrani, Kurt A

    2016-01-01

    Abstract. Advanced cladding materials with potentially enhanced accident tolerance will yield different light water reactor performance and safety characteristics than the present zirconium-based cladding alloys. These differences are due to different cladding material properties and responses to the transient, and to some extent, reactor physics, thermal, and hydraulic characteristics. Some of the differences in reactors physics characteristics will be driven by the fundamental properties (e.g., absorption in iron for an iron-based cladding) and others will be driven by design modifications necessitated by the candidate cladding materials (e.g., a larger fuel pellet to compensate for parasitic absorption). Potential changes in thermal hydraulic limits after transition from the current zirconium-based cladding to the advanced materials will also affect the transient response of the integral fuel. This paper leverages three-dimensional reactor core simulation capabilities to inform on appropriate experimental test conditions for candidate advanced cladding materials in a control rod ejection event. These test conditions are using three-dimensional nodal kinetics simulations of a reactivity initiated accident (RIA) in a representative state-of-the-art pressurized water reactor with both nuclear-grade iron-chromium-aluminum (FeCrAl) and silicon carbide based (SiC-SiC) cladding materials. The effort yields boundary conditions for experimental mechanical tests, specifically peak cladding strain during the power pulse following the rod ejection. The impact of candidate cladding materials on the reactor kinetics behavior of RIA progression versus reference zirconium cladding is predominantly due to differences in: (1) fuel mass/volume/specific power density, (2) spectral effects due to parasitic neutron absorption, (3) control rod worth due to hardened (or softened) spectrum, and (4) initial conditions due to power peaking and neutron transport cross sections in the

  11. Silica Cladding of Ag Nanoparticles for High Stability and Surface-Enhanced Raman Spectroscopy Performance

    NASA Astrophysics Data System (ADS)

    Zhao, Miaomiao; Guo, Hao; Liu, Wenyao; Tang, Jun; Wang, Lei; Zhang, Binzhen; Xue, Chenyang; Liu, Jun; Zhang, Wendong

    2016-09-01

    For high-precision biochemical sensing, surface-enhanced Raman spectroscopy (SERS) has been demonstrated to be a highly sensitive spectroscopic analytical method and Ag is considered to be the best material for SERS performance. Due to the high surface activity of Ag nanoparticles, the high stability of Ag nanostructures, especially in moist environments, is one of the key issues that need to be solved. A method for silica (SiO2) cladding of Ag nanoparticles (NPs) is demonstrated here for high sensitivity and long-term stability when putted in aqueous solution. The chemically inert, transparent, hydrophilic, and bio-compatible SiO2 surface acts as the protection layer for the Ag nanoparticles, which can also enhance the Raman intensity to a certain extent. In our study, the Ag@SiO2 core-shell substrate can detect crystal violet solutions with molar concentrations down to 10-12 M. After 24 h of immersion, the reduction in Raman scattering intensity is about 85 % for sole Ag NP films, compared to 12 % for the Ag coated with a 10-nm SiO2 layer. This thickness was found to be optimum for Ag@SiO2 core-shell substrates with long-term stability and high SERS activity.

  12. Three-dimensional bioactive glass implants fabricated by rapid prototyping based on CO(2) laser cladding.

    PubMed

    Comesaña, R; Lusquiños, F; Del Val, J; López-Álvarez, M; Quintero, F; Riveiro, A; Boutinguiza, M; de Carlos, A; Jones, J R; Hill, R G; Pou, J

    2011-09-01

    Three-dimensional bioactive glass implants were produced by rapid prototyping based on laser cladding without using moulds. CO(2) laser radiation was employed to melt 45S5 and S520 bioactive glass particles and to deposit the material layer by layer following a desired geometry. Controlled thermal input and cooling rate by fine tuning of the processing parameters allowed the production of crack-free fully dense implants. Microstructural characterization revealed chemical composition stability, but crystallization during processing was extensive when 45S5 bioactive glass was used. Improved results were obtained using the S520 bioactive glass, which showed limited surface crystallization due to an expanded sintering window (the difference between the glass transition temperature and crystallization onset temperature). Ion release from the S520 implants in Tris buffer was similar to that of amorphous 45S5 bioactive glass prepared by casting in graphite moulds. Laser processed S520 scaffolds were not cytotoxic in vitro when osteoblast-like MC3T3-E1 cells were cultured with the dissolution products of the glasses; and the MC3T3-E1 cells attached and spread well when cultured on the surface of the materials.

  13. Spontaneously grown GaN and AlGaN nanowires

    NASA Astrophysics Data System (ADS)

    Bertness, K. A.; Roshko, A.; Sanford, N. A.; Barker, J. M.; Davydov, A. V.

    2006-01-01

    We have identified crystal growth conditions in gas-source molecular beam epitaxy (MBE) that lead to spontaneous formation of GaN nanowires with high aspect ratio on Si (1 1 1) substrates. The nanowires were oriented along the GaN c-axis and normal to the substrate surface. Unlike in many other reports of GaN nanowire growth, no metal catalysts were used. Low growth rates at substrate temperatures near 820 °C were combined with high nitrogen flux (partially dissociated with RF plasma excitation) to form well-separated GaN wires with diameters from 50 to 250 nm in diameter and lengths ranging from 2 to 7 μm. The nanowires grew out of an irregular matrix layer containing deep faceted holes. X-ray diffraction indicated that the wires were fully relaxed and aligned to the silicon substrate. The growth morphology was strongly affected by the presence of Al and Be. The changes suggest that surface diffusion is a primary driving force in the growth of GaN nanowires with MBE.

  14. Inductively coupled plasma–reactive ion etching of c- and a-plane AlGaN over the entire Al composition range: Effect of BCl{sub 3} pretreatment in Cl{sub 2}/Ar plasma chemistry

    SciTech Connect

    Shah, Amit P.; Laskar, Masihhur R.; Azizur Rahman, A.; Gokhale, Maheshwar R.; Bhattacharya, Arnab

    2013-11-15

    Inductively coupled plasma (ICP)–reactive ion etching (RIE) patterning is a standard processing step for UV and optical photonic devices based on III-nitride materials. There is little research on ICP-RIE of high Al-content AlGaN alloys and for nonpolar nitride orientations. The authors present a comprehensive study of the ICP-RIE of c- and a-plane AlGaN in Cl{sub 2}/Ar plasma over the entire Al composition range. The authors find that the etch rate decreases in general with increasing Al content, with different behavior for c- and a-plane AlGaN. They also study the effect of BCl{sub 3} deoxidizing plasma pretreatment. An ICP deoxidizing BCl{sub 3} plasma with the addition of argon is more efficient in removal of surface oxides from Al{sub x}Ga{sub 1−x}N than RIE alone. These experiments show that Al{sub x}Ga{sub 1−x}N etching is affected by the higher binding energy of AlN and the higher affinity of oxygen to aluminum compared to gallium, with oxides on a-plane AlGaN more difficult to etch as compared to oxides on c-plane AlGaN, specifically for high Al composition materials. The authors achieve reasonably high etch rate (∼350 nm/min) for high Al-content materials with a smooth surface morphology at a low DC bias of ∼−45 VDC.

  15. Some recent studies on laser cladding and dissimilar welding

    NASA Astrophysics Data System (ADS)

    Kaul, Rakesh; Ganesh, P.; Paul, C. P.; Albert, S. K.; Mudali, U. Kamachi; Nath, A. K.

    2006-01-01

    Indigenous development of high power CO II laser technology and industrial application of lasers represent two important mandates of the laser program, being pursued at Centre for Advanced Technology (CAT), India. The present paper describes some of the important laser material processing studies, involving cladding and dissimilar welding, performed in authors' laboratory. The first case study describes how low heat input characteristics of laser cladding process has been successfully exploited for suppressing dilution in "Colmonoy6" (a nickel-base hardfacing alloy) deposits on austenitic stainless steel components. Crack free hardfaced deposits were obtained by controlling heating and cooling rates associated with laser treatment. The results show significant advantage over Colmonoy 6 deposits made by GTAW, where a 2.5 mm thick region of dilution (with reduced hardness) develops next to substrateiclad interface. The next work involves laser-assisted deposition of graded "Stellite6" (a Co-base hardfacing alloy) with smooth transition in chemical composition and hardness for enhanced resistance against cracking, esp. under thermal cycling conditions. The following two case studies demonstrate significant improvement in corrosion properties of type 304L stainless steel by laser surface alloying, achieved through cladding route. The following case study demonstrates engineering of fusion zone microstructure of end plug dissimilar weld (between alloy D9 and type 3 16M stainless steel) by controlled preferential displacement of focused laser beam, which, in-turn, enhanced its resistance against solidification cracking. Crater appearing at the termination point of laser weld is also eliminated by ramping of laser power towards the end of laser welding. The last case study involves engineering of fusion zone microstructure of dissimilar laser weld between type 304 austenitic stainless steel and stabilized 17%Cr ferritic stainless steel by controlling welding parameters.

  16. A cladding-pumped, tunable holmium doped fiber laser.

    PubMed

    Simakov, Nikita; Hemming, Alexander; Clarkson, W Andrew; Haub, John; Carter, Adrian

    2013-11-18

    We present a tunable, high power cladding-pumped holmium doped fiber laser. The laser generated >15 W CW average power across a wavelength range of 2.043 - 2.171 μm, with a maximum output power of 29.7 W at 2.120 μm. The laser also produced 18.2 W when operating at 2.171 µm. To the best of our knowledge this is the highest power operation of a holmium doped laser at a wavelength >2.15 µm. We discuss the significance of background losses and fiber design for achieving efficient operation in holmium doped fibers.

  17. Widely tunable femtosecond solitonic radiation in photonic crystal fiber cladding

    SciTech Connect

    Peng Jiahui; Sokolov, Alexei V.; Benabid, F.; Light, P. S.; Couny, F.; Biancalana, F.; Roberts, P. J.

    2010-03-15

    We report on a means to generate tunable ultrashort optical pulses. We demonstrate that dispersive waves generated by solitons within the small-core features of a photonic crystal fiber cladding can be used to obtain femtosecond pulses tunable over an octave-wide spectral range. The generation process is highly efficient and occurs at the relatively low laser powers available from a simple Ti:sapphire laser oscillator. The described phenomenon is general and will play an important role in other systems where solitons are known to exist.

  18. Postirradiation examination of the HT9 clad fuel test X425 at 2.9% burnup

    SciTech Connect

    Pahl, R G; Beck, W N; Sanecki, J E

    1987-11-01

    The X425 experiment was the first EBR-II subassembly to be irradiated with U-Pu-Zr metallic fuel clad in the HT9 alloy. This report summarizes our initial postirradiation examination of selected elements from X425 at 2.9% peak burnup. Fuel microstructure, swelling behavior, fission gas release, and fuel/clad chemical interaction are discussed.

  19. Intercode Advanced Fuels and Cladding Comparison Using BISON, FRAPCON, and FEMAXI Fuel Performance Codes

    NASA Astrophysics Data System (ADS)

    Rice, Aaren

    As part of the Department of Energy's Accident Tolerant Fuels (ATF) campaign, new cladding designs and fuel types are being studied in order to help make nuclear energy a safer and more affordable source for power. This study focuses on the implementation and analysis of the SiC cladding and UN, UC, and U3Si2 fuels into three specific nuclear fuel performance codes: BISON, FRAPCON, and FEMAXI. These fuels boast a higher thermal conductivity and uranium density than traditional UO2 fuel which could help lead to longer times in a reactor environment. The SiC cladding has been studied for its reduced production of hydrogen gas during an accident scenario, however the SiC cladding is a known brittle and unyielding material that may fracture during PCMI (Pellet Cladding Mechanical Interaction). This work focuses on steady-state operation with advanced fuel and cladding combinations. By implementing and performing analysis work with these materials, it is possible to better understand some of the mechanical interactions that could be seen as limiting factors. In addition to the analysis of the materials themselves, a further analysis is done on the effects of using a fuel creep model in combination with the SiC cladding. While fuel creep is commonly ignored in the traditional UO2 fuel and Zircaloy cladding systems, fuel creep can be a significant factor in PCMI with SiC.

  20. Pump radiation distribution in multi-element first cladding laser fibres

    SciTech Connect

    Mel'kumov, Mikhail A; Bufetov, Igor' A; Bubnov, M M; Shubin, Aleksei V; Semenov, S L; Dianov, Evgenii M

    2005-11-30

    Pump radiation transfer is studied experimentally in multi-element first cladding laser fibres. A model of this process is proposed, which is in good agreement with experimental results. An all-fibre single-mode cw ytterbium laser based on a three-element first cladding fibre with an output power of 100W is fabricated. (lasers)

  1. Influence of additions of nanoparticles TaC on a microstructure laser cladding

    NASA Astrophysics Data System (ADS)

    Murzakov, M. A.; Petrovskiy, V. N.; Polski, V. I.; Mironov, V. D.; Prokopova, N. M.; Tret'yakov, E. V.

    2015-03-01

    The features of a laser cladding of nickel-based powders with TaC nanopowder additives have been experimentally investigated. The minimum depth of pro-melting of a basis, microhardness distribution over the cross section of the substrate, and the saturation of the metal of the cladding with basis components has been determined in the experiments.

  2. 77 FR 5052 - Clad Steel Plate From Japan; Institution of a Five-Year Review

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-01

    ... COMMISSION Clad Steel Plate From Japan; Institution of a Five-Year Review AGENCY: United States International... whether revocation of the antidumping duty order on clad steel plate from Japan would be likely to lead to... part 207), as most recently amended at 74 FR 2847 (January 16, 2009). \\1\\ No response to this...

  3. Assessment of wear coefficients of nuclear zirconium claddings without and with pre-oxidation

    DOE PAGES

    Qu, Jun; Cooley, Kevin M.; Shaw, Austin H.; ...

    2016-03-16

    In the cores of pressurized water nuclear reactors, water-flow induced vibration is known to cause claddings on the fuel rods to rub against their supporting grids. Such grid-to-rod-fretting (GTRF) may lead to fretting wear-through and the leakage of radioactive species. The surfaces of actual zirconium alloy claddings in a reactor are inevitably oxidized in the high-temperature pressurized water, and some claddings are even pre-oxidized. As a result, the wear process of the surface oxide film is expected to be quite different from the zirconium alloy substrate. In this paper, we attempt to measure the wear coefficients of zirconium claddings withoutmore » and with pre-oxidation rubbing against grid samples using a bench-scale fretting tribometer. Results suggest that the volumetric wear coefficient of the pre-oxidized cladding is 50 to 200 times lower than that of the untreated cladding. In terms of the linear rate of wear depth, the pre-oxidized alloy wears about 15 times more slowly than the untreated cladding. Finally, fitted with the experimentally-determined wear rates, a stage-wise GTRF engineering wear model demonstrates good agreement with in-reactor experience in predicting the trend of cladding lives.« less

  4. An Examination of Collaborative Learning Assessment through Dialogue (CLAD) in Traditional and Hybrid Human Development Courses

    ERIC Educational Resources Information Center

    McCarthy, Wanda C.; Green, Peter J.; Fitch, Trey

    2010-01-01

    This investigation assessed the effectiveness of using Collaborative Learning Assessment through Dialogue (CLAD) (Fitch & Hulgin, 2007) with students in undergraduate human development courses. The key parts of CLAD are student collaboration, active learning, and altering the role of the instructor to a guide who enhances learning opportunities.…

  5. Assessment of wear coefficients of nuclear zirconium claddings without and with pre-oxidation

    SciTech Connect

    Qu, Jun; Cooley, Kevin M.; Shaw, Austin H.; Lu, Roger Y.; Blau, Peter J.

    2016-03-16

    In the cores of pressurized water nuclear reactors, water-flow induced vibration is known to cause claddings on the fuel rods to rub against their supporting grids. Such grid-to-rod-fretting (GTRF) may lead to fretting wear-through and the leakage of radioactive species. The surfaces of actual zirconium alloy claddings in a reactor are inevitably oxidized in the high-temperature pressurized water, and some claddings are even pre-oxidized. As a result, the wear process of the surface oxide film is expected to be quite different from the zirconium alloy substrate. In this paper, we attempt to measure the wear coefficients of zirconium claddings without and with pre-oxidation rubbing against grid samples using a bench-scale fretting tribometer. Results suggest that the volumetric wear coefficient of the pre-oxidized cladding is 50 to 200 times lower than that of the untreated cladding. In terms of the linear rate of wear depth, the pre-oxidized alloy wears about 15 times more slowly than the untreated cladding. Finally, fitted with the experimentally-determined wear rates, a stage-wise GTRF engineering wear model demonstrates good agreement with in-reactor experience in predicting the trend of cladding lives.

  6. Fracture properties of hydrided Zircaloy-4 cladding in recrystallization and stress-relief anneal conditions

    NASA Astrophysics Data System (ADS)

    Hsu, Hsiao-Hung; Tsay, Leu-Wen

    2012-03-01

    In this work, the stress-relieved (SRA) and recrystallized (RXA) Zircaloy-4 cladding specimens were hydrogen-charged to the target concentration of 300 wppm and then manufactured into X-specimens for fracture toughness test. The hydrogen embrittlement susceptibility of Zircaloy-4 cladding specimens in both SRA and RXA conditions were investigated. At the hydrogen concentration level of 300 wppm, J-integral values for RXA cladding were higher than those for SRA cladding at both 25 °C and 300 °C. The formation of brittle zirconium hydrides had a significant impact on the fracture toughness of Zircaloy-4 cladding in both SRA and RXA states, especially at 25 °C. Among all the tests, SRA cladding tested at 25 °C exhibited a great loss of the fracture toughness. The micrographic and fractographic observations further demonstrated that the fracture toughness of Zircaloy-4 cladding would be improved by the coarse grains in RXA cladding, but degraded by zirconium hydrides precipitated along the grain boundary.

  7. Examination of T-111 clad uranium nitride fuel pins irradiated up to 13,000 hours at a clad temperature of 990 C

    NASA Technical Reports Server (NTRS)

    Slaby, J. G.; Siegel, B. L.

    1973-01-01

    The examination of 27 fuel pins irradiated for up to 13,000 hours at 990 C is described. The fuel pin clad was a tantalum alloy with uranium nitride as the nuclear fuel. Two nominal fuel pin diameters were tested with a maximum burnup of 2.34 atom percent. Twenty-two fuel pins were tested for fission gas leaks; thirteen pins leaked. Clad ductility tests indicated clad embrittlement. The embrittlement is attributed to hydrogen from an n,p reaction in the fuel. Fuel swelling was burnup dependent, and the amount of fission gas release was low, generally less than 0.5 percent. No incompatibilities between fuel, liner, and clad were in evidence.

  8. INSTRUMENTS AND METHODS OF INVESTIGATION: Cladding modes of optical fibers: properties and applications

    NASA Astrophysics Data System (ADS)

    Ivanov, Oleg V.; Nikitov, Sergei A.; Gulyaev, Yurii V.

    2006-02-01

    One of the new methods of fiber optics uses cladding modes for controlling propagation of radiation in optical fibers. This paper reviews the results of studies on the propagation, excitation, and interaction of cladding modes in optical fibers. The resonance between core and cladding modes excited by means of fiber Bragg gratings, including tilted ones, is analyzed. Propagation of cladding modes in microstructured fibers is considered. The most frequently used method of exciting cladding modes is described, based on the application of long-period fiber gratings. Examples are presented of long-period gratings used as sensors and gain equalizers for fiber amplifiers, as well as devices for coupling light into and out of optical fibers.

  9. Cyclic furnace oxidation of clad WI-52 systems at 1040 C and 1090 C

    NASA Technical Reports Server (NTRS)

    Gedwill, M. A.

    1972-01-01

    Cyclic furnace oxidation studies were conducted on the cobalt alloy WI-52 clad with Ni-30Cr, Fe-25Cr-4A1, and Ni-20Cr-4A1 foils (0.051 to 0.254 mm thick). Tests as long as 400 hours using 1- and 20-hour cycles showed that the Ni-Cr- and Fe-Cr-A1 claddings were about equally protective at both temperatures. The protective ability of these alloys was influenced by exposure temperature and cladding thickness. At both temperatures, they protected WI-52 about as well as, or better than, a widely used commercial aluminide coating. The Ni-Cr-Al claddings did not protect WI-52 nearly as well. Interdiffusion generally influenced the oxidation behavior of all clad WI-52 systems.

  10. Properties and features of structure formation CuCr-contact alloys in electron beam cladding

    SciTech Connect

    Durakov, Vasiliy G.; Dampilon, Bair V. E-mail: gnusov@rambler.ru; Gnyusov, Sergey F. E-mail: gnusov@rambler.ru

    2014-11-14

    The microstructure and properties of the contact CuCr alloy produced by electron-beam cladding have been investigated. The effect of the electron beam cladding parameters and preheating temperature of the base metal on the structure and the properties of the coatings has been determined. The bimodal structure of the cladding coating has been established. The short circuit currents tests have been carried out according to the Weil-Dobke synthetic circuit simulating procedure developed for vacuum circuit breakers (VCB) test in real electric circuits. Test results have shown that the electron beam cladding (EBC) contact material has better breaking capacity than that of commercially fabricated sintered contact material. The application of the technology of electron beam cladding for production of contact material would significantly improve specific characteristics and reliability of vacuum switching equipment.

  11. The Mechanical Response of Advanced Claddings during Proposed Reactivity Initiated Accident Conditions

    SciTech Connect

    Cinbiz, Mahmut N; Brown, Nicholas R; Terrani, Kurt A; Lowden, Rick R; ERDMAN III, DONALD L

    2017-01-01

    This study investigates the failure mechanisms of advanced nuclear fuel cladding of FeCrAl at high-strain rates, similar to design basis reactivity initiated accidents (RIA). During RIA, the nuclear fuel cladding was subjected to the plane-strain to equibiaxial tension strain states. To achieve those accident conditions, the samples were deformed by the expansion of high strength Inconel alloy tube under pre-specified pressure pulses as occurring RIA. The mechanical response of the advanced claddings was compared to that of hydrided zirconium-based nuclear fuel cladding alloy. The hoop strain evolution during pressure pulses were collected in situ; the permanent diametral strains of both accident tolerant fuel (ATF) claddings and the current nuclear fuel alloys were determined after rupture.

  12. Space-efficient fiber ribbon composed of reduced-cladding single-mode fibers

    NASA Astrophysics Data System (ADS)

    Chang, J. H.; Bae, S. H.; Kim, Hoon; Ouh, C. H.; Jung, C. H.; Cho, H. S.; Chung, Y. C.

    2016-09-01

    We develop a space-efficient single-mode fiber (SMF) having a cladding diameter of only 82 μm. This SMF has the depressed-cladding index profile and its mode-field diameter, cutoff wavelength, and macro bending loss are designed to be similar to those of the conventional step-index SMF. We fabricate this reduced-cladding SMF and measure its optical and mechanical characteristics. The results show that this fiber satisfies major specifications of the ITU-T G.654 recommendations. We also fabricate a fiber ribbon by using twelve of these reduced-cladding SMFs. Compared to a commercial fiber ribbon made of twelve standard SMFs having 125-μm cladding diameter, this fiber ribbon can improve the spatial efficiency by ∼75%.

  13. 77 FR 38825 - Clad Steel Plate From Japan; Scheduling of a Full Five-Year Review Concerning the Antidumping...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-29

    ... COMMISSION Clad Steel Plate From Japan; Scheduling of a Full Five-Year Review Concerning the Antidumping Duty Order on Clad Steel Plate From Japan AGENCY: United States International Trade Commission. ACTION... revocation of the antidumping duty order on clad steel plate from Japan would be likely to lead...

  14. Evaluation of intermediate phases formed on the bonding interface of hot pressed Cu/Al clad materials

    NASA Astrophysics Data System (ADS)

    Lee, Kwang Seok; Lee, Sangmok; Lee, Jong-Sup; Kim, Yong-Bae; Lee, Geun-An; Lee, Sang-Pill; Bae, Dong-Su

    2016-09-01

    The aim of the present study is to identify the properties of intermediate phases formed on the bonding interface of hot pressed Cu/Al clad materials by transmission electron microscopy and nano-indentation analyses. Cu/Al clad materials were fabricated by hot pressing under 200 MPa at 250 °C for 1 h and then heat treated at 400 °C for 1 h. Nano-indentation measurement was conducted to evaluate the nanohardness and modulus of the intermediate phases formed between the Cu/Al interfaces. A 3-tier diffusion layer was observed at the Cu/Al interfaces. Knoop microhardness values at the bonding interface were 7 to 11 times that of the Cu and Al matrix metals. The intermediate phases formed at the bonding interface were Al4Cu9, AlCu, and Al2Cu. A mapping analysis confirmed that the Al and Cu particles moved via mutual diffusion toward the intermediate phases formed at the bonding interface. The nanohardness values of η2-AlCu and γ1-Al4Cu9 were 4 to 7 times that of the Cu and Al matrix metals. Nanohardness and Knoop microhardness measurement curves exhibited similar tendencies. The rigidity values of the respective intermediate phases can be arranged in descending order as follows: γ1-Al4Cu9 > η2-AlCu > θ-Al2Cu.

  15. Simulation with DIONISIO 1.0 of thermal and mechanical pellet-cladding interaction in nuclear fuel rods

    NASA Astrophysics Data System (ADS)

    Soba, Alejandro; Denis, Alicia

    2008-02-01

    The code DIONISIO 1.0 describes most of the main phenomena occurring in a fuel rod throughout its life under normal operation conditions of a nuclear thermal reactor. Starting from the power history, DIONISIO predicts the temperature distribution in the domain, elastic and plastic stress and strain, creep, swelling and densification, release of fission gases, caesium and iodine to the rod free volume, gas mixing, pressure increase, restructuring and grain growth in the UO 2 pellet, irradiation growth of the Zircaloy cladding, oxide layer growth on its surface, hydrogen uptake and the effects of a corrosive atmosphere either internal or external. In particular, the models of thermal conductance of the gap and of pellet-cladding mechanical interaction incorporated to the code constitute two realistic tools. The possibility of gap closure (including partial contact between rough surfaces) and reopening during burnup is allowed. The non-linear differential equations are integrated by the finite element method in two-dimensions assuming cylindrical symmetry. Good results are obtained for the simulation of several irradiation tests.

  16. Nonequilibrium synthesis of NbAl3 and Nb-Al-V alloys by laser cladding. II - Oxidation behavior

    NASA Technical Reports Server (NTRS)

    Haasch, R. T.; Tewari, S. K.; Sircar, S.; Loxton, C. M.; Mazumder, J.

    1992-01-01

    Isothermal oxidation behaviors of NbAl3 alloy synthesized by laser cladding were investigated at temperatures between 800 and 1400 C, and the effect of vanadium microalloying on the oxidation of the laser-clad alloy was examined. The oxidation kinetics of the two alloys were monitored using thermal gravimetric weight gain data, and the bulk and surface chemistries were analyzed using XRD and XPS, respectively. It was found that NbAl3 did not form an exclusive layer of protective Al2O3. The oxidation products at 800 C were found to be a mixture of Nb2O5 and Al2O3. At 1200 C, a mixture of NbAlO4, Nb2O5, and Al2O3 formed; and at 1400 C, a mixture of NbAlO4, Al2O3, NbO2, NbO(2.432), and Nb2O5 formed. The addition of V led to a dramatic increase of the oxidation rate, which may be related to the formation of (Nb, V)2O5 and VO2, which grows in preference to protective Al2O3.

  17. Cladding and Structural Materials for Advanced Nuclear Energy Systems

    SciTech Connect

    Was, G S; Allen, T R; Ila, D; C,; Levi,; Morgan, D; Motta, A; Wang, L; Wirth, B

    2011-06-30

    The goal of this consortium is to address key materials issues in the most promising advanced reactor concepts that have yet to be resolved or that are beyond the existing experience base of dose or burnup. The research program consists of three major thrusts: 1) high-dose radiation stability of advanced fast reactor fuel cladding alloys, 2) irradiation creep at high temperature, and 3) innovative cladding concepts embodying functionally-graded barrier materials. This NERI-Consortium final report represents the collective efforts of a large number of individuals over a period of three and a half years and included 9 PIs, 4 scientists, 3 post-docs and 12 students from the seven participating institutions and 8 partners from 5 national laboratories and 3 industrial institutions (see table). University participants met semi-annually and participants and partners met annually for meetings lasting 2-3 days and designed to disseminate and discuss results, update partners, address outstanding issues and maintain focus and direction toward achieving the objectives of the program. The participants felt that this was a highly successful program to address broader issues that can only be done by the assembly of a range of talent and capabilities at a more substantial funding level than the traditional NERI or NEUP grant. As evidence of the success, this group, collectively, has published 20 articles in archival journals and made 57 presentations at international conferences on the results of this consortium.

  18. Microindentation hardness evaluation of iridium alloy clad vent set cups

    NASA Astrophysics Data System (ADS)

    Ulrich, George B.; DeRoos, Larry F.; Stinnette, Samuel E.

    1993-01-01

    An iridium alloy, DOP-26, is used as cladding for 238PuO2 fuel in radioisotope heat sources for space power systems. Presently, DOP-26 iridium alloy clad vent sets (CVS) are being manufactured at the Oak Ridge Y-12 Plant for potential use in the National Aeronautics and Space Administration's Cassini mission to Saturn. Wrought/ground/stress relieved blanks are warm formed into CVS cups. These cups are then annealed to recrystallize the material for subsequent fabrication/assembly operations as well as for final use. One of the cup manufacturing certification requirements is to test for Vickers microindentation hardness. New microindentation hardness specification limits, 210 to 310 HV, have been established for a test load of 1000 grams-force (gf). The original specification limits, 250 to 350 HV, were for 200 gf testing. The primary reason for switching to a higher test load was to reduce variability in the test data. The DOP-26 alloy exhibits microindentation hardness load dependence, therefore, new limits were needed for 1000 gf testing. The new limits were established by testing material from 15 CVS cups using 200 gf and 1000 gf loads and then statistically analyzing the data. Additional work using a Knoop indenter and a 10 gf load indicated that the DOP-26 alloy grain boundaries have higher hardnesses than the grain interiors.

  19. Microindentation hardness evaluation of iridium alloy clad vent set cups

    SciTech Connect

    Ulrich, G.B.; DeRoos, L.F.; Stinnette, S.E. )

    1993-01-15

    An iridium alloy, DOP-26, is used as cladding for [sup 238]PuO[sub 2] fuel in radioisotope heat sources for space power systems. Presently, DOP-26 iridium alloy clad vent sets (CVS) are being manufactured at the Oak Ridge Y-12 Plant for potential use in the National Aeronautics and Space Administration's Cassini mission to Saturn. Wrought/ground/stress relieved blanks are warm formed into CVS cups. These cups are then annealed to recrystallize the material for subsequent fabrication/assembly operations as well as for final use. One of the cup manufacturing certification requirements is to test for Vickers microindentation hardness. New microindentation hardness specification limits, 210 to 310 HV, have been established for a test load of 1000 grams-force (gf). The original specification limits, 250 to 350 HV, were for 200 gf testing. The primary reason for switching to a higher test load was to reduce variability in the test data. The DOP-26 alloy exhibits microindentation hardness load dependence, therefore, new limits were needed for 1000 gf testing. The new limits were established by testing material from 15 CVS cups using 200 gf and 1000 gf loads and then statistically analyzing the data. Additional work using a Knoop indenter and a 10 gf load indicated that the DOP-26 alloy grain boundaries have higher hardnesses than the grain interiors.

  20. Microindentation hardness evaluation of iridium alloy clad vent set cups

    SciTech Connect

    Ulrich, G.B.; DeRoos, L.F.; Stinnette, S.E.

    1992-05-15

    An iridium alloy, DOP-26, is used as cladding for {sup 238}PuO{sup 2} fuel in radioisotope heat sources for space power systems. Presently, DOP-26 iridium alloy clad vent sets (CVS) are being manufactured at the Oak Ridge Y-12 Plant for potential use in the National Aeronautics and Space Administration`s Cassini mission to Saturn. Wrought/ground/stress relieved blanks are warm formed into CVS cups. These cups are then annealed to recrystallize the material for subsequent fabrication/assembly operations as well as for final use. One of the cup manufacturing certification requirements is to test for Vickers microindentation hardness. New microindentation hardness specification limits, 210 to 310 HV, have been established for a test load of 1000 grams-force (gf). The original specification limits, 250 to 350 HV, were for 200 gf testing. The primary reason for switching to a higher test load was to reduce variability in the test data. The DOP-26 alloy exhibits microindentation hardness load dependence, therefore, new limits were needed for 1000 gf testing. The new limits were established by testing material from 15 CVS cups using 200 gf and 1000 gf loads and then statistically analyzing the data. Additional work using a Knoop indenter and a 10 gf load indicated that the DOP-26 alloy grain boundaries have higher hardnesses than the grain interiors.