Imperial College London

DrNaNi

Faculty of EngineeringDepartment of Materials

Honorary Lecturer
 
 
 
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Contact

 

n.ni

 
 
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Location

 

LM04Royal School of MinesSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

41 results found

Grovenor CRM, Ni N, Yardley SS, Hughes G, Lozano-Perez S, Sykes JMet al., 2012, 3D visualisation of crack distributions in oxidised zirconium alloys by FIB-slicing, Pages: 24-29, ISSN: 0272-9172

Zirconium alloys have been used as fuel cladding and structural fuel assembly components in nuclear reactors since the 1950s, and show a characteristic variation in oxidation rate and layered crack morphology during aqueous corrosion. It is common to associate the first phenomenon with the appearance of the second. We have used 3D serial sectioning to study the morphology and distribution of cracks in corroded ZIRLO samples at different stages of oxidation, and have shown that cracks nucleate and grow at all stages of the oxidation process not just at the kinetic transition. We have used this data to analyse the nucleation of cracks with reference to the shape of the oxide/metal interface and the distribution of second phase precipitates. © 2012 Materials Research Society.

Conference paper

Ni N, Lozano-Perez S, Sykes J, Grovenor Cet al., 2012, Multi-scale characterisation of oxide on zirconium alloys, MATERIALS AT HIGH TEMPERATURES, Vol: 29, Pages: 166-170, ISSN: 0960-3409

Journal article

Grovenor CRM, Ni N, Hudson D, Yardley SS, Moore KL, Smith GDW, Lozano-Perez S, Sykes JMet al., 2012, Mechanisms of Oxidation of Fuel Cladding Alloys Revealed by High Resolution APT, TEM and SIMS Analysis, MRS Proceedings, Vol: 1383, ISSN: 0272-9172

<jats:title>ABSTRACT</jats:title><jats:p>Aqueous corrosion of zirconium alloys has become the major factor limiting prolonged fuel campaigns in nuclear plant. Studies using SEM, TEM and electrochemical impedance measurements have been interpreted as showing a dense inner-most oxide layer, and an increased thickness of the layer has been correlated to a better corrosion resistance. Many authors have reported that an ‘intermediate layer’ at the metal oxide interface has a complex structure or/and stochiometry different to that of both the bulk oxide and bulk metal, sometimes claimed to be a suboxide phase. Diffraction evidence has suggested the presence of both cubic ZrO and rhombohedral Zr<jats:sub>3</jats:sub>O phases, and compositional analysis has revealed similar variations in local oxygen stoichiometry.</jats:p><jats:p>We have carried out a systematic investigation of the structure and chemistry of the metal/oxide interface in samples of commercial ZIRLO corroded for times up to 180 days. We have developed new experimental techniques for the study of these interfaces both by Electron Energy Loss Spectroscopy (EELS) analysis in the Transmission Electron Microscope (TEM) and by Atom Probe Tomography (APT), and exactly the same samples have been investigated by both techniques. Our results show the development of a clearly defined suboxide layer of stoichiometry close to ZrO, and the subsequent disappearance of this layer at the first of the characteristic ‘breakaway’ transitions in the oxidation kinetics. We can correlate this behaviour with changes in the structure of the oxide layer, and particularly the development of interconnected porosity that links the corroding interface with the aqueous environment. Using high resolution SIMS analysis of isotopically spiked samples we demonstrate the penetration of the oxidising species through these porous outer oxide layers.</jats:p>

Journal article

Hanisch C, Ni N, Kulkarni A, Zaporojtchenko V, Strunskus T, Faupel Fet al., 2011, Fast electrical response to volatile organic compounds of 2D Au nanoparticle layers embedded into polymers, JOURNAL OF MATERIALS SCIENCE, Vol: 46, Pages: 438-445, ISSN: 0022-2461

Journal article

Ni N, Lozano-Perez S, Sykes J, Grovenor Cet al., 2011, Quantitative EELS analysis of zirconium alloy metal/oxide interfaces, ULTRAMICROSCOPY, Vol: 111, Pages: 123-130, ISSN: 0304-3991

Journal article

Lozano-Perez S, Ni N, Kruska K, Grovenor C, Terachi T, Yamada Tet al., 2011, Characterizing environmental degradation in PWRs by 3D FIB sequential sectioning, 15th International Conference on Environmental Degradation of Materials in Nuclear Power Systems-Water Reactors, Publisher: JOHN WILEY & SONS, Pages: 993-1004

Conference paper

Ni N, Lozano-Perez S, Jenkins ML, English C, Smith GDW, Sykes JM, Grovenor CRMet al., 2010, Porosity in oxides on zirconium fuel cladding alloys, and its importance in controlling oxidation rates, SCRIPTA MATERIALIA, Vol: 62, Pages: 564-567, ISSN: 1359-6462

Journal article

Ni N, Lozano-Perez S, Sykes JM, Grovenor CRMet al., 2010, Transmission EELS Quantification Study of Oxygen Content at Zirconium Alloy Metal/Oxide Interface, Microscopy and Microanalysis, Vol: 16, Pages: 1614-1615

Journal article

Faupel F, Zaporojtchenko V, Strunskus T, Greve H, Schuermann U, Takele H, Hanisch C, Chakravadhanula VSK, Ni N, Gerber A, Quandt E, Podschun Ret al., 2008, Functional Polymer Nanocomposites, POLYMERS & POLYMER COMPOSITES, Vol: 16, Pages: 471-481, ISSN: 0967-3911

Journal article

Fan ZY, Wang YR, Ni N, Bu HSet al., 2003, Melting behavior and morphology of freeze-dried ultra-high molar mass polyethylene, JOURNAL OF MACROMOLECULAR SCIENCE-PHYSICS, Vol: B42, Pages: 127-137, ISSN: 0022-2348

Journal article

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