| 1. |
- Abbondanza, Giuseppe, et al.
(författare)
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Anisotropic strain variations during the confined growth of Au nanowires
- 2023
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 122:12
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Tidskriftsartikel (refereegranskat)abstract
- The electrochemical growth of Au nanowires in a template of nanoporous anodic aluminum oxide was investigated in situ by means of grazing-incidence transmission small- and wide-angle x-ray scattering (GTSAXS and GTWAXS), x-ray fluorescence (XRF), and two-dimensional surface optical reflectance. The XRF and the overall intensity of the GTWAXS patterns as a function of time were used to monitor the progress of the electrodeposition. Furthermore, we extracted powder diffraction patterns in the direction of growth and in the direction of confinement to follow the evolution of the direction-dependent strain. Quite rapidly after the beginning of the electrodeposition, the strain became tensile in the vertical direction and compressive in the horizontal direction, which showed that the lattice deformation of the nanostructures can be artificially varied by an appropriate choice of the deposition time. By alternating sequences of electrodeposition with sequences of rest, we observed fluctuations of the lattice parameter in the direction of growth, attributed to stress caused by electromigration. Furthermore, the porous domain size calculated from the GTSAXS patterns was used to monitor how homogeneously the pores were filled.
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| 2. |
- Abbondanza, Giuseppe, 1991, et al.
(författare)
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Au-Pd Barcode Nanowires with Tailored Lattice Parameters and Segment Lengths for Catalytic Applications
- 2024
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Ingår i: ACS Applied Nano Materials. - 2574-0970. ; 7:4, s. 3861-3874
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we present a systematic investigation of the controlled fabrication of Au-Pd barcode nanowires within nanoporous anodic aluminum oxide (NP-AAO) templates. By using a combination of in situ X-ray diffraction (XRD), focused ion beam scanning electron microscopy (FIB-SEM), and transmission electron microscopy (TEM), we elucidate the influence of template preparation methods on the resulting nanowire properties. The template treatment, involving either pore widening or barrier layer thinning, significantly impacts nanowire growth. Through the analysis of the XRD data, we observe sequential deposition of Au and Pd segments with lattice parameter variations and strain effects. Particularly, the lattice parameters of Au and Pd segments display intricate temporal dependencies, influenced by interfacial effects and strain caused by growth under confinement. FIB-SEM imaging reveals uniform and reproducible nanowire lengths in the template treated with pore widening. Furthermore, TEM analysis confirms the presence of distinct Au and Pd segments, while scanning TEM-energy-dispersive X-ray spectroscopy revealed minor evidence of interdiffusion between the first and the second electrodeposited segments. Our findings emphasize the potential of the electrodeposition process within nanoporous templates for producing barcode nanowires with precise segmental properties. The combination of in situ XRD and electron microscopy offers valuable insights into the growth dynamics and structural characteristics of the fabricated Au-Pd barcode nanowires. This controlled fabrication strategy opens doors to tailoring nanowire properties for diverse applications, particularly in catalysis.
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| 3. |
- Abbondanza, Giuseppe, 1991, et al.
(författare)
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Hydride formation and dynamic phase changes during template-assisted Pd electrodeposition
- 2023
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Ingår i: Nanotechnology. - 1361-6528 .- 0957-4484. ; 34:50
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the structural evolution of electrochemically fabricated Pd nanowires in situ by means of grazing-incidence transmission small- and wide-angle x-ray scattering (GTSAXS and GTWAXS), x-ray fluorescence (XRF) and two-dimensional surface optical reflectance (2D-SOR). This shows how electrodeposition and the hydrogen evolution reaction (HER) compete and interact during Pd electrodepositon. During the bottom-up growth of the nanowires, we show that beta-phase Pd hydride is formed. Suspending the electrodeposition then leads to a phase transition from beta-phase Pd hydride to alpha-phase Pd. Additionally, we find that grain coalescence later hinders the incorporation of hydrogen in the Pd unit cell. GTSAXS and 2D-SOR provide complementary information on the volume fraction of the pores occupied by Pd, while XRF was used to monitor the amount of Pd electrodeposited.
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| 4. |
- Abbondanza, Giuseppe
(författare)
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Ordered arrays of low-dimensional Au and Pd : synthesis and in situ observations
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Electrodeposition of metals in templates of nano-porous anodic aluminum oxide (NP-AAO) is a versatile way of fabricating ordered arrays of metal nanowires. Thanks to the self-arranged long-range hexagonal order of the pores, electrodeposition in NP-AAO is an easily scalable bottom-up synthesis route and an attractive alternative to traditional top-down fabrication methods such as electron beam lithography.Since NP-AAO is a non-conductive medium and since it is potentially soluble in non-neutral pH solutions, the electrodeposition of metals in NP-AAO represents a challenge. These aspects are discussed in this thesis, aiming to establish a reproducible and reliable protocol for the electrodeposition of Au and Pd.By using ex situ x-ray diffraction, it has been found that the growth of Au and Pd in the confined environment of nano-pores leads (i) to a deformation of the crystalline structure, as the lattice constant is smaller along the nanowire radius and larger along the nanowire axis, compared to the bulk lattice constant, and (ii) to a crystallite size anisotropy: it is limited by the pore radius in the horizontal direction and it is larger in the direction of growth.The electrochemical growth of Au and Pd nanowires was followed in situ by x-ray scattering methods. In the case of Au nanowires, the time-resolved measurements revealed that the anisotropy of the lattice parameter progresses as a function of time, which suggests that the strain state of the nanomaterials can be artificially selected. This findings might be beneficial in the strain-engineering of Au nanoelectrode arrays for electrocatalysis. In the case of Pd nanowires, the measurements revealed strain variations, as well as phase transitions attributed to the existence of alpha- and beta-phase Pd hydride in the NP-AAO template, due to the exposure of Pd to hydrogen evolved at the working electrode. These findings suggest that Pd in NP-AAO has potential applications in the design of hydrogen storage devices.
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| 5. |
- Abbondanza, Giuseppe, et al.
(författare)
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Quantitative powder diffraction using a (2 + 3) surface diffractometer and an area detector
- 2021
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Ingår i: Journal of Applied Crystallography. - 1600-5767. ; 54:4, s. 1140-1152
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Tidskriftsartikel (refereegranskat)abstract
- X-ray diffractometers primarily designed for surface X-ray diffraction are often used to measure the diffraction from powders, textured materials and fiber-texture samples in 2θ scans. Unlike in high-energy powder diffraction, only a fraction of the powder rings is typically measured, and the data consist of many detector images across the 2θ range. Such diffractometers typically scan in directions not possible on a conventional laboratory diffractometer, which gives enhanced control of the scattering vector relative to the sample orientation. There are, however, very few examples where the measured intensity is directly used, such as for profile/Rietveld refinement, as is common with other powder diffraction data. Although the underlying physics is known, converting the data is time consuming and the appropriate corrections are dispersed across several publications, often not with powder diffraction in mind. This paper presents the angle calculations and correction factors required to calculate meaningful intensities for 2θ scans with a (2 + 3)-type diffractometer and an area detector. Some of the limitations with respect to texture, refraction and instrumental resolution are also discussed, as is the kind of information that one can hope to obtain.
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| 6. |
- Abbondanza, Giuseppe, et al.
(författare)
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Templated electrodeposition as a scalable and surfactant-free approach to the synthesis of Au nanoparticles with tunable aspect ratios
- 2022
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Ingår i: Nanoscale Advances. - : Royal Society of Chemistry. - 2516-0230. ; 4:11, s. 2452-2467
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Tidskriftsartikel (refereegranskat)abstract
- A high-throughput method for the fabrication of ordered arrays of Au nanoparticles is presented. It is based on pulsed electrodeposition into porous anodic alumina templates. In contrast to many synthesis routes, it is cyanide-free, prior separation of the alumina template from the aluminium substrate is not required, and the use of contaminating surfactants/capping agents often found in colloidal synthesis is avoided. The aspect ratio of the nanoparticles can also be tuned by selecting an appropriate electrodeposition time. We show how to fabricate arrays of nanoparticles, both with branched bases and with hemispherical bases. Furthermore, we compare the different morphologies produced with electron microscopies and grazing-incidence synchrotron X-ray diffraction. We find the nanoparticles are polycrystalline in nature and are compressively strained perpendicular to the direction of growth, and expansively strained along the direction of growth. We discuss how this can produce dislocations and twinning defects that could be beneficial for catalysis.
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| 7. |
- Bertuccio, Giuseppe, et al.
(författare)
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Ultra Low Noise Epitaxial 4H-SiC X-Ray Detectors
- 2009
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Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 615-617, s. 845-848
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Tidskriftsartikel (refereegranskat)abstract
- The design and the experimental results of some prototypes of SiC X-ray detectors are presented. The devices have been manufactured on top of 2 inch 4H-SiC wafer with 115 μm thick undoped high purity epitaxial layer, which constitutes the detection’s active volume. Pad and pixel detectors based on Ni-Schottky junctions have been tested. The residual doping of the epi-layer was found tobe extremely low, 3.7 x 1013 cm-3, allowing to achieve the highest detection efficiency and the lower specific capacitance of the detectors. At 22 °C and in operating bias condition, the reverse current densities of the detector’s Schottky junctions have been measured to be between J = 0.3 pA/cm2 and J = 4 pA/cm2; these values are more than two orders of magnitude lower than those of state of the art silicon detectors. With such low leakage currents, the equivalent electronic noise of SiC pixel detectors is as low as 0.5 electrons r.m.s at room temperature, which represents a new state of the art in the scenario of semiconductor radiation detectors.
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| 8. |
- Haratian, Saber, et al.
(författare)
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Ex‐situ synchrotron X‐ray diffraction study of CO2 corrosion‐induced surface scales developed in low‐alloy steel with different initial microstructure
- 2023
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Ingår i: Corrosion Science. - 0010-938X. ; 222
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Tidskriftsartikel (refereegranskat)abstract
- The CO2 corrosion-induced scale developed in the surface region of the low-grade carbon steel is thoroughly investigated to understand the corrosion mechanisms involved during exposure to CO2-saturated aqueous environments. In this work, in addition to the electron microscopy and lab-source X-ray diffraction (XRD) methods, ex-situ depth-resolved phase identification of the corrosion scales developed on steel with different initial microstructures is performed using synchrotron grazing incidence XRD at different incidence angles. The CO2 corrosion mechanism is discussed considering the observed distribution of the corrosion products formed at a different depth relative to the time of electrochemical exposure of the steels.
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| 9. |
- Harlow, Gary S., et al.
(författare)
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HAT : a high-energy surface X-ray diffraction analysis toolkit
- 2023
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Ingår i: Journal of Applied Crystallography. - 0021-8898. ; 56, s. 312-321
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Tidskriftsartikel (refereegranskat)abstract
- This work introduces the high-energy surface X-ray diffraction analysis toolkit (HAT), an open-source cross-platform software package written in Python to allow the extraction and processing of high-energy surface X-ray diffraction (HESXRD) data sets. Thousands of large-area detector images are collected in a single HESXRD scan, corresponding to billions of pixels and hence reciprocal space positions. HAT is an optimized reciprocal space binner that implements a graphical user interface to allow the easy and interactive exploration of HESXRD data sets. Regions of reciprocal space can be selected with movable and resizable masks in multiple views and are projected onto different axes to allow the creation of reciprocal space maps and the extraction of crystal truncation rods. Current and future versions of HAT can be downloaded and used free of charge.
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| 10. |
- Larsson, Alfred, et al.
(författare)
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Electrochemical Fabrication and Characterization of Palladium Nanowires in Nanoporous Alumina Templates
- 2020
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 167:12
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Tidskriftsartikel (refereegranskat)abstract
- A method for the electrochemical synthesis of palladium nanowires, using porous alumina templates with diameters of 25 nm and 40 nm, is presented. Through an electrochemical barrier layer thinning step, pulsed electrodeposition can take place directly into the anodized aluminum; without need for extra removal, pore opening, and metal contact coating steps. A digital oscilloscope is used to record and integrate the current, allowing the efficiency of the electrodeposition to be calculated. We discuss how using a large 'off period' allows for the replenishment of the depleted diffusion layer. The nanowires are characterized by using a focused ion beam (FIB) to create cross-sections which can be accessed with a scanning electron microscope (SEM). With grazing-incidence X-ray diffraction (GI-XRD) we find that the nanowires have a slight compressive strain in the direction that they are confined by the pores (0.58 % and 0.51 % for the 25 nm and 40 nm pores respectively). Knowing the strain state of the nanowires inside the template is of importance for the use of templated nanowires in devices. Further characterization is made using high-resolution transmission electron microscopy (HR-TEM) and energy dispersive X-ray spectroscopy (EDS), after removal from the alumina templates.
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