| 1. |
- Zhang, Pimin, 1990-, et al.
(författare)
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Effects of surface finish on the initial oxidation of HVAF-sprayed NiCoCrAlY coatings
- 2019
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Ingår i: Surface & Coatings Technology. - Elsevier : Elsevier BV. - 0257-8972 .- 1879-3347. ; 364, s. 43-56
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Tidskriftsartikel (refereegranskat)abstract
- Oxide scale formed on HVAF-sprayed NiCoCrAlY coatings and the effect of surface treatment were investigated by a multi-approach study combining photo-stimulated luminescence, microstructural observation and mass gain. The initial oxidationbehaviour of as-sprayed, polished and shot-peened coatings at 1000 °C is studied. Both polished and shot-peened coatings exhibited superior performance due to rapid formation of α-Al2O3 fully covering the coating and suppressing the growth of transient alumina, assisted by a high density of α-Al2O3 nuclei on surface treatment induced defects. Moreover, the fast development of a two-layer alumina scale consisting of an inward-grown inner α-Al2O3 layer and an outer layer transformed from outward-grown transient alumina resulted in a higher oxide growth rate of the as-sprayed coating.
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| 2. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Direct experimental evidence for unusual effects of hydrogen on the electronic and vibrational properties of GaNxP1−x alloys : a proof for a general property of dilute nitrides
- 2004
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 70:24, s. 245215-245219
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Tidskriftsartikel (refereegranskat)abstract
- Direct experimental evidence for dramatic effects of hydrogen incorporation on the electronic structure and lattice properties of GaNxP1−x alloys is presented. By employing photoluminescence excitation spectroscopy, postgrowth hydrogenation is shown to reopen the band gap of the GaNP alloys and to efficiently reduce the N-induced coupling between the conduction band states. By Raman spectroscopy, these effects are shown to be accompanied by hydrogen-induced breaking of the Ga-P bond in the alloy, evident from disappearance of the corresponding vibrational mode. According to the performed Raman and x-ray diffraction measurements, the hydrogenation is also found to cause a strong expansion of the GaNP lattice, which changes the sign of strain from tensile in the as-grown GaNP epilayers to compressive in the posthydrogenated structures, due to the formation of complexes between N and H.
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| 3. |
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| 4. |
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| 5. |
- Ail, Ujwala, 1980-, et al.
(författare)
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Optimization of Non-Pyrolyzed Lignin Electrodes for Sustainable Batteries
- 2023
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Ingår i: ADVANCED SUSTAINABLE SYSTEMS. - : WILEY-V C H VERLAG GMBH. - 2366-7486. ; 7:2
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Tidskriftsartikel (refereegranskat)abstract
- Lignin, a byproduct from the pulp industry, is one of the redox active biopolymers being investigated as a component in the electrodes for sustainable energy storage applications. Due to its insulating nature, it needs to be combined with a conductor such as carbon or conducting polymer for efficient charge storage. Here, the lignin/carbon composite electrodes manufactured via mechanical milling (ball milling) are reported. The composite formation, correlation between performance and morphology is studied by comparison with manual mixing and jet milling. Superior charge storage capacity with approximate to 70% of the total contribution from the Faradaic process involving the redox functionality of lignin is observed in a mechanically milled composite. In comparison, manual mix shows only approximate to 30% from the lignin storage participation while the rest is due to the electric double layer at the carbon-electrolyte interface. The significant participation of lignin in the ball milled composite is attributed to the homogeneous, intimate mixing of the carbon and the lignin leading the electronic carrier transported in the carbon phase to reach most of the redox group of lignin. A maximum capacity of 49 mAh g(-1) is obtained at charge/discharge rate of 0.25 A g(-1) for the sample milled for 60 min.
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| 6. |
- Bian, Qingzhen, 1988-, et al.
(författare)
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Vibronic coherence contributes to photocurrent generation in organic semiconductor heterojunction diodes
- 2020
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Ingår i: Nature Communications. - : NATURE PUBLISHING GROUP. - 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Charge separation dynamics after the absorption of a photon is a fundamental process relevant both for photosynthetic reaction centers and artificial solar conversion devices. It has been proposed that quantum coherence plays a role in the formation of charge carriers in organic photovoltaics, but experimental proofs have been lacking. Here we report experimental evidence of coherence in the charge separation process in organic donor/acceptor heterojunctions, in the form of low frequency oscillatory signature in the kinetics of the transient absorption and nonlinear two-dimensional photocurrent spectroscopy. The coherence plays a decisive role in the initial 200 femtoseconds as we observe distinct experimental signatures of coherent photocurrent generation. This coherent process breaks the energy barrier limitation for charge formation, thus competing with excitation energy transfer. The physics may inspire the design of new photovoltaic materials with high device performance, which explore the quantum effects in the next-generation optoelectronic applications.
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| 7. |
- Buyanova, Irina A, 1960-, et al.
(författare)
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GaNAs-based nanowires for near-infrared optoelectronics
- 2018
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Ingår i: Novel compound semiconductor nanowires. - Singapore : Pan Stanford Publishing. - 9781315340722 - 9781315364407 ; , s. 133-159
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This chapter analyses the impacts of alloying with nitrogen on structural properties and recombination processes in GaNAs nanowires (NW). It discusses possible innovative applications of these structures in advanced nano-emitters, where the incorporation of nitrogen induces the formation of self-assembled quantum dot-like states embedded in the NWs. The structural properties of these NWs were investigated by transmission electron microcopy. An important material parameter that affects performance of the NW-based devices is carrier lifetime. The non-radiative lifetime is largely affected by the material quality both in bulk and within near-surface regions. The contribution of the surface-related recombination is known to be especially severe in GaAs-based NW structures due to a large surface-to-volume ratio and the presence of surface states participating in the non-radiative recombination processes. The revealed optical properties of the GaNAs-based NW structures may be attractive for future optoelectronic applications in advanced nano-sized light emitters which could be integrated with silicon technology.
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| 8. |
- Buyanova, Irina A, 1960-, et al.
(författare)
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Novel GaNP nanowires for advanced optoelectronics and photonics
- 2018
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Ingår i: Novel compound semiconductor nanowires. - Singapore : Pan Stanford Publishing. - 9781315340722 - 9781315364407 ; , s. 107-132
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This chapter discusses structural and optical properties of novel GaNP nanowires (NW), as well as their potential for future applications in optoelectronics and photonics. It reviews efforts devoted to the optimization of GaNP-based NWs for future applications in light-emitting devices and discusses the impacts of structural polymorphism on the radiative efficiency and band structure of the material. The chapter shows that GaNP NWs can be utilized as a source of linearly polarized light with the polarization direction that is not determined by dielectric mismatch between the NW and its surrounding. GaNP alloys are novel III–V semiconductors, which have a great potential for applications in amber-red light-emitting diodes and also as an active material in innovative intermediate the band solar cells. NWs grown under the non-optimized conditions usually suffer from various point and structural defects, which degrade the radiative efficiency.
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| 9. |
- Buyanova, Irina A, 1960-, et al.
(författare)
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Novel GaNP Nanowires for Advanced Optoelectronics and Photonics
- 2018
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Ingår i: Novel Compound Semiconductor Nanowires: Materials, Devices, and Applications. - : Pan Stanford Publishing. - 9789814745765 - 9781315364407 ; , s. 107-132
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 10. |
- Buyanova, Irina A, 1960-, et al.
(författare)
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Photon upconversion promoted by defects in low-dimensional semiconductor nanostructures
- 2018
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Ingår i: Defects in Advanced Electronic Materials and Novel Low Dimensional Structures. - UK : Elsevier. - 9780081020531 - 9780081020548 ; , s. 189-210
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Bokkapitel (refereegranskat)abstract
- The ability to convert several low-energy photons into a single higher-energy photon is of significant importance in diverse fields ranging from imaging and biological labeling to optoelectronics and photovoltaics. The possibility to realize this phenomenon on the nanoscale can provide an additional degree of freedom in engineering electronic properties of materials and would allow deliberate manipulation and optimization of the upconversion processes. The purpose of this chapter is to provide a review of physical mechanisms that govern the photon upconversion in semiconductor nanostructures. Taking into account a large number of comprehensive reviews on this topic, our main focus is on photon upconversion mediated by defects, which is far less explored so far but provides a viable and attractive alternative for achieving efficient photon upconversion without involving doping.
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