Amorphization of embedded Cu nanocrystals by ion irradiation

While bulk crystalline elemental metals cannot be amorphized by ion irradiation in the absence of chemical impurities, the authors demonstrate that finite-size effects enable the amorphization of embedded Cu nanocrystals. The authors form and compare the atomic-scale structure of the polycrystalline, nanocrystalline, and amorphous phases, present an explanation for the extreme sensitivity to irradiation exhibited by nanocrystals, and show that low-temperature annealing is sufficient to return amorphized material to the crystalline form

In situ incorporation of nanostructured antimony in an N-doped carbon matrix for advanced sodium-ion batteries

Herein, a facile one-step and solvent-free pyrolysis method was developed to control the synthesis of nanostructured Sb embedded in an N-doped carbon matrix (Sb@G x N y -T, where T, G x and N y denote the annealing temperature and the mass (g) of glucose and NH 4 Cl used in the process, respectively). By adjusting these parameters, hybrid architectures can be in situ constructed, including hollow Sb embedded in holeless carbon matrixes (Sb@G 0.25 N 0.5 -950) and Sb nanoplates embedded in holey carbon matrixes (Sb@G 0.25 N 0.25 -950). Our findings suggest that the formation of diverse nanostructures closely relate to the sublimation and evaporation of Sb, and the structural remold of liquid Sb by surface tension. Benefitting from the unique structural features, these optimized electrodes show highly reversible sodium storage with high specific capacities and good cycling stability. More importantly, this strategy can be further extended to other material systems, such as Sn- and SnO 2 nanodots embedded in a holey carbon matrix. This work presents a new scalable methodology to confine/remold nanostructured materials in a carbon matrix which allows for the future design of functional materials with tunable composition and architecture

Fate of ZnO nanoparticles in soils and cowpea (Vigna unguiculata)

The increasing use of zinc oxide nanoparticles (ZnO-NPs) in various commercial products is prompting detailed investigation regarding the fate of these materials in the environment. There is, however, a lack of information comparing the transformation of ZnO-NPs with soluble Zn2+ in both soils and plants. Synchrotron-based techniques were used to examine the uptake and transformation of Zn in various tissues of cowpea (Vigna unguiculata (L.) Walp.) exposed to ZnO-NPs or ZnCI2 following growth in either solution or soil culture. In solution culture, soluble Zn (ZnCI2) was more toxic than the ZnO-NPs, although there was substantial accumulation of ZnO-NPs on the root surface. When grown in soil, however, there was no significant difference in plant growth and accumulation or speciation of Zn between soluble Zn and ZnO-NP treatments, indicating that the added ZnO-NPs underwent rapid dissolution following their entry into the soil. This was confirmed by an incubation experiment with two soils, in which ZnO-NPs could not be detected after incubation for 1 h. The speciation of Zn was similar in shoot tissues for both soluble Zn and ZnO-NPs treatments and no upward translocation of ZnO-NPs from roots to shoots was observed in either solution or soil culture. Under the current experimental conditions, the similarity in uptake and toxicity of Zn from ZnO-NPs and soluble Zn in soils indicates that the ZnO-NPs used in this study did not constitute nanospecific risks

Characteristics of x-ray attenuation in electrospun bismuth oxide/polylactic acid nanofibre mats

The characteristics of the X-ray attenuation in electrospun nano(n)- and micro(m)-Bi2O3/polylactic acid (PLA) nanofibre mats with different Bi2O3 loadings were compared as a function of energy using mammography (i.e. tube voltages of 22–49 kV) and X-ray absorption spectroscopy (XAS) (7–20 keV). Results indicate that X-ray attenuation by electrospun n-Bi2O3/PLA nanofibre mats is distinctly higher than that of m-Bi2O3/PLA nanofibre mats at all energies investigated. In addition, with increasing filler loading (n-Bi2O3 or m-Bi2O3), the porosity of the nanofibre mats decreased, thus increasing the X-ray attenuation, except for the sample containing 38 wt% Bi2O3 (the highest loading in the present study). The latter showed higher porosity, with some beads formed, thus resulting in a sudden decrease in the X-ray attenuation

FORMATION AND CHARACTERISATION OF NANOCRYSTALLINE COPPER IN AMORPHOUS SILICA

Samples were prepared by high-energy implantation of Cu ions into a SiO_2 (5μm)/Si (substrate) matrix. Cu ions were implanted to a nominal dose of 1×10^16 - 3×10^17 /cm^2 at a sequential beam energy of 5000 - 800 keV and at a current density of ~5 μA/cm2. Implantation was carried out at LN2 temperature in a vacuum of < 10^-7 Torr. Nucleation and growth was induced by subsequential anneals in 5%H_2+95%N_2 (forming gas) for one hour at 500, 800, and 1100C. Determination of the nanocrystal structure and morphology within the silica film was accomplished by correlating results from X-Ray Diffraction (XRD), Rutherford Backscattering Spectroscopy (RBS), Transmission Electron Microscopy (TEM) and Extended X-ray Absorption Fine Structure (EXAFS). Results show that a mean dose of 1×10^16 /cm2 tends to form a significant fraction of Cu-O bonds at all annealing temperatures, except 1100C at which most Cu evaporates from the SiO_2 film. Oxides are also apparent in the as-implanted and 500C annealed sample of dose 3×10^16 /cm2. All higher anneals and doses readily formed Cu nanocrystals. In particular a dose of 3×10^17 /cm^2 showed similar EXAFS to that of a bulk Cu standard largely independent of temperature, while 1×10^17 cm^2 exhibited a crystalline size growth with increasing temperature. TEM displayed the nanocrystal size distribution, while XRD and in particular EXAFS data verified a mean nanocrystal size growth with dose as well as annealing temperature. The latter exemplified by an increase in co-ordination number. Further, EXAFS showed the bond length remained constant for all samples, except 1×10^16 /cm2 possibly due to oxides, at all annealing temperatures. The bond length was found to be distinctively longer than that for a bulk Cu standard

Den norske modellen: bruken av ikke statlige aktører i norsk utenrikspolitikk : et mulig svar på utenrikspolitiske utfordringer for Norge etter den kalde krigen norske modellen: bruken av ikke statlige aktører i norsk utenrikspolitikk

Bucher-Johannesen, Bernt Den norske modellen: bruken av ikke statlige aktører i norsk utenrikspolitikk. Et mulig svar på utenrikspolitiske utfordringer for Norge etter den kalde krigen Denne oppgave tar for seg den såkalte "norske modellen" i norsk utenrikspolitikk. Den norsk modellen (DNM) knytter seg til bruken av ulike typer av ikke-statlige aktører i utenrikspolitikken. Foki for oppgaven har i tid vært perioden etter den kalde krigen(1989-19989 og i rom det utenrikspolitiske. Jeg har arbeidet utfra to problemstillinger, hva kan forklare bruken av en slik modell og hvilke utenrikspolitiske implikasjoner har den. Den først nevnt problemstillingen har utgjort hoveddelen av oppgaven. Jeg har forsøkt å belyse problemstillingene utfra tre tradisjonelle analyse nivåer i studie av staters utenrikspolitikk. Det tre nivåene blir diskutert i teorikapittelet og er: det internasjonale, det statlige og det individuelle. Innen hvert nivå har jeg operert med flere kritiske faktorer. For det internasjonale har det vært bortfallet av den kalde krigen og fordypningen av den gjensidige avhengigheten mellom statene. På det statlige nivå har betydningen av demokratisering og korporativisering av utenrikspolitikken blitt studert. Og endelig, på det individuelle nivå har jeg studert sentrale beslutningstakere og mulige konstellasjoner de inngår i. I empirikapittelet har jeg en omfattende gjennomgang av modellens ulike bestandeler. Det gjelder for det første det overordene arbeidsfellesskapet mellom det private humanitære organisasjonene og Utenriksdepartementet. Det gjelder for det andre de tre innsatsfeltene som er ulik uttrykk for dette arbeidsfellesskapet. Og de er: Beredskapsordningene Norwegian Emergency Prepardness System (NOREPS) og Norsk ressursbank for demokratibygging (NORDEM), de mange norske initiativ for fred og konfliktløsning på 1990-tallet og til siste den sterkt voksende norske humanitære bistanden. Dette arbeidet er ikke gjort tidligere og kan dermed sees på som et pionerarbeid. I analysen viste det seg at innenfor det tre nivåene var det særlig følgende forhold som kunne belyse problemstillingene. Det gjelder for det første at DNM kan sees på som en "linkage politics", et forsøk fra Norges side å kompensere for den utenrikspolitisk marginalisering landet er blitt til del etter slutten på den kalde krigen og ved selv å sette seg utenfor intergrasjonsprosessene i Europa. DNM kan videre forstås som et uttrykk for en endring av staten Norge som utenrikspolitisk aktør. Staten kan ikke lenger opptre som monopolist på det utenrikspolitiske marked, til det er konkurransen blitt for hard. Og endelig kan DNM forstås som uttrykk for klare interesser hos sentrale enkelt individer i den utenrikspolitiske ledelsen og i de større humanitære organisasjonene i Norge. I dette siste er Jan Egeland sentral sammen med representanter for de fem store blant de humanitære organisasjonene. Et uttrykk for at modellen er blitt en sentral del av norsk utenrikspolitikk er de to kampanjene mot anti-personell miner og mot håndvåpen. To kampanjer som har gått veien fra ideell politikk til å bli sentrale deler av offisiell norsk utenrikspolitikk, seneste uttrykt av utenriksminister Knut Vollebæk i Norges innlegg til FN 53 generalforsamling høsten 1998 (http://odin.dep.no/ud/taler/1998/u980921.html). Disse to kampanjene er ikke en del av denne oppgaven, men burde tjene som et meget godt utgangspunkt for en annen studie av DNM. Oppfordringen er herved sendt

Felles forskningsarena 2014. Vitenskapelig publisering i perioden 2010-2013 ved Haukeland universitetssykehus og Det medisinsk-odontologiske fakultet, Universitetet i Bergen

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Local and extended atomic structure of strained polycrystalline In(1-x)Al(x)Sb alloys

© 2020 Elsevier Ltd In(1-x)Al(x)Sb films were deposited on amorphous SiO2 by magnetron sputtering with four different In/Al concentration ratios and the local and extended atomic structure were investigated through extended x-ray absorption fine structure (EXAFS) spectroscopy and grazing incidence x-ray diffraction (GIXRD) analyses, respectively. GIXRD showed the deposited films are strained polycrystalline, however, preserving the cubic symmetry of zinc blende structure due to homogeneous compression. EXAFS analysis of In and Sb atoms in strained In(1-x)Al(x)Sb films provided information about the interatomic distance distributions of the first three nearest-neighbor (NN) shells. For the first NN, the average cation-anion distances presented only the alloying effect, resembling the unstrained ternary alloy with a relaxation parameter of ε=0.77±0.01 and ε=0.79±0.01 for the dilute limit InSb:Al and AlSb:In, respectively, and with the extra structural modifications due to the strain factor appearing in higher coordination shells only. In the second NN shell distance it was observed that the strain effect is more pronounced in In–Al than In–In interatomic distance, which is, within uncertainty, independent of strain, evidencing an anisotropy in the process of accommodating the strain in the mixed sublattice, which is favored by bond bending over bond stretching, similarly to unstrained III-V ternary alloys. On the other hand, anion-anion distances exhibited a bimodal distribution, showing a tendency to retain the values of unstrained pure compounds. The third NN shell mean distances vary linearly with concentration. Moreover, the core effect in(1-x)Al(x)Sb alloys was described via EXAFS demonstrating that elastic continuous medium theory is not adequate to describe this system. Using x-ray absorption near edge structure, it was observed that In K-edge position is constant with In/Al ratio in(1-x)Al(x)Sb alloys, whereas Sb K-edge position changed, evidencing its relation with the local atomic arrangement