1,721,182 research outputs found
Co-Cr-Fe-Mn-Ni Oxide as a Highly Efficient Thermoelectric High-Entropy Alloy
Full text linkAmong the existing materials for heat conversion, high-entropy alloys are of great interest due to the tunability of their functional properties. Here, we aim to produce single-phase high-entropy oxides composed of Co-Cr-Fe-Mn-Ni-O through spark plasma sintering (SPS), testing their thermoelectric (TE) properties. This material was successfully obtained before via a different technique, which requires a very long processing time. Hence, the main target of this work is to apply spark plasma sintering, a much faster and scalable process. The samples were sintered in the temperature range of 1200–1300 °C. Two main phases were formed: rock salt-structured Fm3̅m and spinel-structured Fd3̅m. Comparable transport properties were achieved via the new approach: the highest value of the Seebeck coefficient reached −112.6 μV/K at room temperature, compared to −150 μV/K reported before; electrical properties at high temperatures are close to the properties of the single-phase material (σ = 0.2148 S/cm, σ ≈ 0.2009 S/cm reported before). These results indicate that SPS can be successfully applied to produce highly efficient TE high-entropy alloys in a fast and scalable way. Further optimization is needed for the production of single-phase materials, which are expected to exhibit an even better TE functionality.Validerad;2023;Nivå 2;2023-05-10 (joosat);Funder: Swedish Foundations Consolidator Fellowship;Licens fulltext: CC BY License</p
3D-printed zeolite 13X-Strontium chloride units as ammonia carriers
Full text linkThe selective catalytic reduction (SCR) system in automobiles using urea solution as a source of NH3 suffers from solid deposit problems in pipelines and poor efficiency during engine startup. Although direct use of high pressure NH3 is restricted due to safety concerns, which can be overcome by using solid sorbents as NH3 carrier. Strontium chloride (SrCl2) is considered the best sorbent due to its high sorption capacity; however, challenges are associated with the processing of stable engineering structures due to extraordinary volume expansion during the NH3 sorption. This study reports the fabrication of a novel structure consisting of a zeolite cage enclosing the SrCl2 pellet (SPZC) through extrusion-based 3D printing (Direct Ink Writing). The printed SPZC structure demonstrated steady sorption of NH3 for 10 consecutive cycles without significant uptake capacity and structural integrity loss. Furthermore, the structure exhibited improved sorption and desorption kinetics than pure SrCl2. The synergistic effect of zeolite as physisorbent and SrCl2 as chemisorbent in the novel composite structure enabled the low-pressure (0.4 bar) NH3 sorption, compared to pure SrCl2, which absorbed NH3 at pressures above 0.4 bar. Regeneration of SPZC composite sorbent under evacuation showed that 87.5% percent of NH3 was desorbed at 20 °C. Thus, the results demonstrate that the rationally designed novel SPZC structure offers safe and efficient storage of NH3 in the SCR system and other applications
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A comparative study of 5A and 13X zeolites doped by Eu3+ ion-exchange in water or ethanol
Full text linkCommercial zeolites are crystalline aluminosilicate materials with high surface area and porosity which can be
used in several applications. This study aims at adding luminescent functionality to the zeolite network, either
enabling optical monitoring of the capturing process or towards the development of efficient light-emitting
materials. Two representative commercial zeolites were chosen: 5A and 13X, adding europium (Eu3+) by an
ion-exchange process. The effects of different solvents (water and ethanol) and thermal treatments on the
structural and optical properties of the doped zeolites were investigated. The results demonstrate that 13X zeolites
have superior Eu uptake and luminescent properties compared to 5A. XRD analysis suggests that Eu exchange
can stress and disorder the network, which is recovered by annealing up to 600 ◦C. Instead, a higher
temperature of 800 ◦C induces the collapsing of the porosity, with partial amorphization and significant
reduction of the surface area of the material. The optical analysis showed that the PL intensities for 13X samples
can be 60 times higher than those obtained for 5A samples. Moreover, ethanol emerged as a superior solvent to
water, avoiding the presence of -OH vibrational energies detrimental to the luminescence of rare earth ions
Characterization of high-entropy alloys: study of the addition of aluminum to the high entropy system HfMoTaTi+Al
No full textHigh Entropy Alloys (HEA) are alloy systems that are formed with five or more principal elements of alloy or have an entropy of mixture higher than 1.5R. Although at first it may seem like if it is extrapolated from binary and ternary diagrams these supposed high entropy alloys may generate very complex microstructures with multiple phases, segregations and intermetallic compounds, making them very difficult to analyze and understand, however, due to the thermodynamics involved in a system with multiple components, HEAs tend to have simple crystal structure like body-centered cubic (BCC) and face-centered cubic (FCC).
Because of the first ideas that multiple elements alloys tend to have complicated microstructures and non-interesting properties, this field of study wasn’t explored until the year 2004 when Jian-Wei Yeh and Brian Candor started investigating them. After the first studies, showing to the world that these new alloys presented interesting properties, publications related to High Entropy Alloys started increasing worldwide as it can be seen in Figure 1.
As the investigation effort related to HEAs is increasing, the more it is becoming clear that HEA systems exhibit excellent characteristics such as high strength and hardness, excellent wear resistance, high-temperature strength, good structural stability, good corrosion and oxidation resistance over conventional alloys
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Characterization of high-entropy alloys: study of the addition of aluminum to the high entropy system HfMoTaTi+Al
No full textHigh Entropy Alloys (HEA) are alloy systems that are formed with five or more principal elements of alloy or have an entropy of mixture higher than 1.5R. Although at first it may seem like if it is extrapolated from binary and ternary diagrams these supposed high entropy alloys may generate very complex microstructures with multiple phases, segregations and intermetallic compounds, making them very difficult to analyze and understand, however, due to the thermodynamics involved in a system with multiple components, HEAs tend to have simple crystal structure like body-centered cubic (BCC) and face-centered cubic (FCC).
Because of the first ideas that multiple elements alloys tend to have complicated microstructures and non-interesting properties, this field of study wasn’t explored until the year 2004 when Jian-Wei Yeh and Brian Candor started investigating them. After the first studies, showing to the world that these new alloys presented interesting properties, publications related to High Entropy Alloys started increasing worldwide as it can be seen in Figure 1.
As the investigation effort related to HEAs is increasing, the more it is becoming clear that HEA systems exhibit excellent characteristics such as high strength and hardness, excellent wear resistance, high-temperature strength, good structural stability, good corrosion and oxidation resistance over conventional alloys
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Characterization of high-entropy alloys: study of the addition of aluminum to the high entropy system HfMoTaTi+Al
Full text linkHigh Entropy Alloys (HEA) are alloy systems that are formed with five or more principal elements of alloy or have an entropy of mixture higher than 1.5R. Although at first it may seem like if it is extrapolated from binary and ternary diagrams these supposed high entropy alloys may generate very complex microstructures with multiple phases, segregations and intermetallic compounds, making them very difficult to analyze and understand, however, due to the thermodynamics involved in a system with multiple components, HEAs tend to have simple crystal structure like body-centered cubic (BCC) and face-centered cubic (FCC).
Because of the first ideas that multiple elements alloys tend to have complicated microstructures and non-interesting properties, this field of study wasn’t explored until the year 2004 when Jian-Wei Yeh and Brian Candor started investigating them. After the first studies, showing to the world that these new alloys presented interesting properties, publications related to High Entropy Alloys started increasing worldwide as it can be seen in Figure 1.
As the investigation effort related to HEAs is increasing, the more it is becoming clear that HEA systems exhibit excellent characteristics such as high strength and hardness, excellent wear resistance, high-temperature strength, good structural stability, good corrosion and oxidation resistance over conventional alloys
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