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- Zhang, Hanzhu, 1991-
(författare)
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High-entropy boron-carbide and its composites
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- High-entropy alloy (HEA) is a multicomponent alloy material that contains five or more principal elements in equi- or near equi-atomic ratios. The entropy stabilisation leads to the formation of a crystalline solid solution accommodating the principal elements. The HEA solid solution has characteristic features such as lattice distortion, sluggish diffusion and cocktail effect that contribute to the superior properties of HEA including high strength, high hardness, excellent thermal and chemical stability, etc. The concept of HEA has been extended to ceramic materials to process high-entropy ceramic (HEC) that consists of multiple ceramic compounds such as metallic oxides, nitrides or carbides. The HECs have shown entropy stabilisation and formed single-phase ceramic solid solutions. However, the formation mechanism of high-entropic phase in HECs remains unclear and unpredictable. Generally, in order to maximise the probability of forming a high-entropy solid solution in a ceramic system, ceramic compounds with least difference in the crystal structure, preferably with only one anionic constituent element, are favoured when designing HECs, which limits the potential of discovering and developing new HECs. In this project, a multicomponent ceramic system containing six ultra-high temperature ceramics (UHTCs), B4C, HfC, Mo2C, TaC, TiC and SiC, was used to investigate the formation of high-entropy ceramics, UHTC composites, as well as the microstructure evolution, properties and high temperature applications. A ceramic composite composed of SiC and a high-entropy boron-carbide with hexagonal crystal structure was successfully processed from the carbide system in spite of the difference in the crystal structures of precursors (face-centred cubic, hexagonal and rhombohedral). The hexagonal HEC solid solution exhibited a unique AlB2 structure with alternating layers of metal and non-metal C/B atoms according to the experimental and simulation investigations. The HEC/SiC composite showed superior mechanical properties such as ultra-high hardness, excellent wear and oxidation resistance. The addition of B4C was discovered to be the key factor in the formation of the hexagonal high-entropy boron-carbide solid solution, while the final phase composition was tailored by utilising precursors of different particle size. Additionally, SiC as the reinforcement component in the HEC/SiC composite was used to tailor the microstructure, phase evolution and mechanical properties of the high-entropy boron-carbide composite. Higher content of SiC resulted in enhanced mechanical properties such as hardness and fracture toughness, as well as promoted the formation of the hexagonal high-entropy boron-carbide solid solution. To extend the investigation on the high-entropy boron-carbide composite to application, B4C, HfC, Mo2C, TaC and TiC were consolidated into a target for magnetron sputtering. The target was used to deposit oxidation-resistant high-entropy coatings using magnetron sputtering on carbon-carbon composites. The coatings showed superior mechanical performance and high temperature oxidation resistance at 2000 °C on carbon-carbon composite, suggesting potential applications of high-entropy boron-carbide ceramics as a protective coating material against oxidation at elevated temperature. This work pointed out the possibilities of synthesising high-performance HECs with superior properties from components with vast elemental and structure diversity, and thereby advanced the design criteria of HECs and provided more potential research directions for the new high-performance ceramic materials.
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- Cui, Yong, et al.
(författare)
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Accurate photovoltaic measurement of organic cells for indoor applications
- 2021
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Ingår i: Joule. - : CELL PRESS. - 2542-4351. ; 5:5, s. 1016-1023
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Photovoltaic (PV) cells offer a convenient energy source to drive micropower electronic devices for indoor applications. However, it is challenging to measure the power conversion efficiency (PCE) of PV cells under indoor lighting and the PV community lacks a feasible and accurate measurement protocol. Here, we start with the fundamental parameters which determine the PCE, and carefully design a series of experiments to examine the origins which might cause measurement errors for organic PV measurements under indoor lighting. We demonstrate the critical importance of: 1, temporal stability and spatial homogeneity of the light sources, 2, calibration of the spectral irradiance and illuminations of the light sources, 3, the area of the cells (1 cm2 or large cells are preferred), 4, the aperture of the mask (an aperture slightly smaller than the cell area is preferred), and 5, stray lights from the measurement environment. Based on these careful investigations, we suggest a feasible measurement method, by which accurate measurement of the indoor PV efficiency is made possible. Our study will promote the healthy development of indoor PV technology for practical applications.
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- Li, Xin, et al.
(författare)
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Innovation of International Logistics Talent Training Mode in Applied Undergraduate Colleges and Universities Based on the ‘Belt and Road’
- 2023
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Ingår i: Advances in Artificial Systems for Medicine and Education VI. - Cham : Springer Nature. ; , s. 624-633
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Under the tide of world multi polarization and economic globalization, the internationalization of higher education has become the general trend. Implementing the ‘going out’ strategy and cultivating international logistics talents are the internal needs of Application-oriented Undergraduate Colleges and universities to adapt to the development trend of higher education, and also the internal needs of Application-oriented Undergraduate Colleges and universities to improve the level of running a school. At present, in terms of international logistics talent training, there are some problems in the undergraduate of application-oriented universities, such as the lack of international logistics talent training platform and funds, the lack of international teaching staff, and the imperfect teaching system of international logistics talent training. In view of these problems, this topic introduces the guiding ideology of the ‘the Belt and Road’ and builds an application-oriented undergraduate university, which can explore the cultivation of international logistics talents from the aspects of the construction of an international logistics talent training platform, giving full play to its own characteristics and advantages, improving the curriculum, teaching and evaluation system, and promoting the internationalization of professional construction, so as to continuously improve the cultivation level of international logistics talents.
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- Liu, Qingyun, 1993-, et al.
(författare)
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High throughput decoding approach for luminescencekinetics-based optical encoding of lanthanide upconversion nanoparticles
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Lanthanide upconversion nanoparticles (UCNPs) are increasingly explored to develop high-security-level anti-counterfeiting and multiplexing applications, due to the availability of ample encoding dimensions. Among other applications, upconversion luminescence(UCL) kinetics-based optical encoding is particularly attractive as it provides an almost unlimited encoding capacity due to the ease of manipulating the UCL kinetics by chemical engineering. However, current decoding methods limit its applications because of a typically low throughput and high cost of the system. In this Letter, we propose a novel decoding approach for UCL kinetics-based optical encoding, which utilizes a pulsed excitation source with adjustable pulse duration and a low time-resolution and large-area detector. We develop a theoretical fitting model and show how fingerprint time constants of the UCNPs (the encoding identities) can be extracted from the correlation between the averaged UCL intensity and the pulse duration. Our new approach provides a high-throughput and cost-effective solution to decode UCL kinetics.
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- Neuhoff, Karsten, et al.
(författare)
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Inclusion of Consumption of carbon intensive materials in emissions trading – An option for carbon pricing post-2020
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A project led jointly by Climate Strategies and DIW Berlin has been exploring whether inclusion of domestic sales of selected energy intensive commodities (e.g. steel) in domestic emission trading schemes is an effective and feasible approach towards restoring the carbon price signal in these sectors, without damaging competitiveness. It has been delivered by a multidisciplinary, international team of researchers from a number of institutions, representing various fields (EU law and institutions, climate policy and economics, energy market and infrastructure policy and economics).
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