An alternative to the expensive and time-consuming processing of bulk thermoelectric microgenerators (TEGs) could be the structuring of TEGs by means of screen-printing technology. In comparison with ...conventional TEGs made from alloys, an oxide-based semiconducting TEG could have many advantages, such as non-toxicity, thermal stability and oxidation resistance at high temperatures. Two types of thermoelectric microgenerators (TEGs) made by screen-printing on alumina substrates, one from a Ca3Co4O9 (Ca349) p-type leg and the other from a (ZnO)5In2O3 (Z5I) n-type leg, are presented. The overall performance of the devices was determined by measuring the electrical conductivity and the Seebeck coefficient of the Ca3Co4O9- and (ZnO)5In2O3-based thick-film thermopiles in the temperature range from room temperature to 500°C. Their microstructural properties, such as grain morphology, density, phase composition and interface with the substrate, were also investigated, with the goal being to determine the optimum firing conditions for the best TEG properties. Our study defines a promising fabrication method for oxide-based thermoelectric devices and identifies the main challenges associated with microgenerator fabrication.
In this work, we investigated the influence of Al doping on the structure of the (ZnO)5In2O3 homologous phase and the thermoelectric characteristics of (ZnO)5(In1−xAlx)2O3 ceramics for x=0, 0.01, ...0.03, 0.05, 0.1, and 0.2, prepared using a classic ceramic procedure and sintering at 1500°C for 2 hours. The Al substituted for In on both the primary sites in the Zn5(In1−xAlx)2O8 homologous phase, the octahedral sites in the basal‐plane inversion boundaries and the trigonal bi‐pyramidal sites in the zig‐zag inversion boundaries, which resulted in a uniformly increased shrinkage of the unit cell with the additions of Al. The a and c parameters were reduced for x=0.2 by a maximum 0.8%. All the samples had similar microstructures, so the differences in the TE characteristics mainly resulted from the effects of the substitution of Al for In, decreasing the charge‐carrier concentration and affecting their mobility. Slightly improved TE characteristics were only observed for Al additions with x=0.01‐0.05, while larger additions of Al only resulted in a reduced electrical conductivity and decreased ZT values in comparison to the un‐doped composition.
New sources of supplementary cementitious materials (SCMs) are needed to meet the future demand. A potential new source of SCM is spent pot lining, a residue from aluminum production. The present ...work showed that the refined aluminosilicate part of spent pot lining (SPL) has a moderate chemical reactivity in a cementitious system measured in the R3 calorimetry test, comparable to commercially used coal fly ash. The reaction of SPL led to the consumption of Ca(OH)2 in a cement paste beyond 7 days after mixing. At 28 and 90 days a significant contribution to strength development was therefore observed, reaching a relative strength, which is similar to composite cements with coal fly ash. At early age a retardation of the cement hydration is caused by the SPL, which should most likely be associated with the presence of trace amounts of NH3. The spent pot lining is also investigated as silica source for autoclaved aerated concrete blocks. The replacement of quartz by spent pot lining did not show an adverse effect on the strength-density relation of the lightweight blocks up to 50 wt% quartz substitution. Overall, spent pot lining can be used in small replacement volumes (30 wt%) as SCM or as replacement of quartz (50 wt%) in autoclaved aerated concrete blocks.
The (ZnO)kIn2O3 system is interesting for applications in the fields of thermoelectrics and opto-electronics. In this study we resolve the complex homologous phase evolution with increasing ...temperature in polycrystalline ceramics for k=5, 11 and 18 and its influence on the microstructural development and thermoelectric properties. The phase formation at temperatures above 1000°C is influenced by the local ZnO-to-In2O3 ratio in the starting-powder mixture. While the Zn5In2O8 equilibrium phase for k=5 is formed directly after sintering at 1200°C, the formation of the k=11 and k=18 equilibrium phases proceeds at higher temperatures by diffusion between the initially formed phases, the lower k Zn5In2O8/Zn7In2O10 and the higher k ZnkIn2Ok+3 (9<k<∞). Such phase formation affects the sintering and grain growth, and consequently, with the degree of structural and compositional homogeneity, also the thermoelectric characteristics of the (ZnO)kIn2O3 ceramics.
Abstract
In this work, we investigated the influence of Al doping on the structure of the (ZnO)
5
In
2
O
3
homologous phase and the thermoelectric characteristics of (ZnO)
5
(In
1−
x
Al
x
)
2
O
3
...ceramics for
x
=0, 0.01, 0.03, 0.05, 0.1, and 0.2, prepared using a classic ceramic procedure and sintering at 1500°C for 2 hours. The Al substituted for In on both the primary sites in the Zn
5
(In
1−
x
Al
x
)
2
O
8
homologous phase, the octahedral sites in the basal‐plane inversion boundaries and the trigonal bi‐pyramidal sites in the zig‐zag inversion boundaries, which resulted in a uniformly increased shrinkage of the unit cell with the additions of Al. The
a
and
c
parameters were reduced for
x
=0.2 by a maximum 0.8%. All the samples had similar microstructures, so the differences in the
TE
characteristics mainly resulted from the effects of the substitution of Al for In, decreasing the charge‐carrier concentration and affecting their mobility. Slightly improved
TE
characteristics were only observed for Al additions with
x
=0.01‐0.05, while larger additions of Al only resulted in a reduced electrical conductivity and decreased
ZT
values in comparison to the un‐doped composition.
Review of: Skupnost znanja in inovacij EIT Urbana mobilnost –prijetnejše in bolj trajnostno bivanje v evropskih mestih z uporabo inovativnih rešitev. EIT Urban Mobility (2021) EIT urban mobility ...strategic agenda 2021–2027. Barcelona. Reviewed by: Anja Ilenič, Alenka Mauko Pranjić, Darko Kokot, Ana Mladenovič, Mateja Košir.
In this work, we investigated the influence of Al doping on the structure of the (ZnO)(5)In2O3 homologous phase and the thermoelectric characteristics of (ZnO)(5)(In1-xAlx)(2)O-3 ceramics for x=0, ...0.01, 0.03, 0.05, 0.1, and 0.2, prepared using a classic ceramic procedure and sintering at 1500 degrees C for 2 hours. The Al substituted for In on both the primary sites in the Zn-5(In1-xAlx)(2)O-8 homologous phase, the octahedral sites in the basal-plane inversion boundaries and the trigonal bi-pyramidal sites in the zig-zag inversion boundaries, which resulted in a uniformly increased shrinkage of the unit cell with the additions of Al. The a and c parameters were reduced for x=0.2 by a maximum 0.8%. All the samples had similar microstructures, so the differences in the TE characteristics mainly resulted from the effects of the substitution of Al for In, decreasing the charge-carrier concentration and affecting their mobility. Slightly improved TE characteristics were only observed for Al additions with x=0.01-0.05, while larger additions of Al only resulted in a reduced electrical conductivity and decreased ZT values in comparison to the un-doped composition.
Review of: The EIT Urban Mobility Knowledge and Innovation Community: More pleasant and sustainable living in European cities through innovative mobility solutions. EIT Urban Mobility (2021) EIT ...urban mobility strategic agenda 2021–2027. Barcelona. Reviewed by: Anja Ilenič, Alenka Mauko Pranjić, Darko Kokot, Ana Mladenovič, Mateja Košir.
Colour of interior surfaces has to be considered in order to provide optimal visual and non-visual performance. Colour selection is often related to the occupant's colour preferences. First part of ...the presented study was a questionnaire-based cross-sectional study among the employees of the University of Ljubljana conducted in December 2019 in order to identify possible association between personal determinants, room typology, preferred colour of indoor surfaces and general colour preferences. Based on the findings from the survey results, a simulation study on a generic cellular office was executed in order to evaluate the implications of occupant's wall colour preference on the resulting non-visual luminous environment under the climate of Ljubljana. Results showed a strong association between the general colour preference and wall colour preference. Significant differences between gender and age groups were identified. The respondents preferred white, orange and blue coloured walls, the latter two, as deduced from the simulations, may have a substantial negative or positive impact on the spatial distribution and duration of appropriate non-visual exposure in the indoor environment. The results of the presented study highlight the importance of considering the potential impact of indoor surface colour selection when evaluating the quality of the indoor luminous environment.
PDF
