Tchouateu Kamwa Rolande Aurelie, Sylvain Tome, Chongouang Judicaёl, E. Idriss, A. Spieß, Markus N. A. Fetzer, K. Elie, C. Janiak, Marie-Annie Etoh
This work proposes the poly(phospho-ferro-siloxo) binder resulting from the phosphoric acid activation of pozzolana (PZ) as a friendly stabilizing agent for compressed earth bricks (CEBs). Different proportions of pozzolana were incorporated into the clay soil (5, 10, 15 and 20 wt%). The CEBs were cured at room temperature and at 70 °C. Powder X-ray diffraction (PXRD), Fourier transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) spectroscopy, water absorption as well as mechanical strength tests were used to characterize the 28 days aged CEBs. The compressive strength of CEBs varies from 9.2 to 20.6 MPa and 10.2 to 42.8 MPa at room temperature and 70 °C, respectively. Water absorption ranges from 6 to 11% at 25 °C and 8 to 12% at 70 °C. This work showed that ground pozzolana can be used similarly as calcined laterites and clays for efficient geopolymerization stabilization of compressed earth bricks.
{"title":"Stabilization of Compressed Earth Blocks (CEB) by Pozzolana Based Phosphate Geopolymer: Physico-Mechanical, Structural and Microstructural Investigations","authors":"Tchouateu Kamwa Rolande Aurelie, Sylvain Tome, Chongouang Judicaёl, E. Idriss, A. Spieß, Markus N. A. Fetzer, K. Elie, C. Janiak, Marie-Annie Etoh","doi":"10.2139/ssrn.3855724","DOIUrl":"https://doi.org/10.2139/ssrn.3855724","url":null,"abstract":"This work proposes the poly(phospho-ferro-siloxo) binder resulting from the phosphoric acid activation of pozzolana (PZ) as a friendly stabilizing agent for compressed earth bricks (CEBs). Different proportions of pozzolana were incorporated into the clay soil (5, 10, 15 and 20 wt%). The CEBs were cured at room temperature and at 70 °C. Powder X-ray diffraction (PXRD), Fourier transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) spectroscopy, water absorption as well as mechanical strength tests were used to characterize the 28 days aged CEBs. The compressive strength of CEBs varies from 9.2 to 20.6 MPa and 10.2 to 42.8 MPa at room temperature and 70 °C, respectively. Water absorption ranges from 6 to 11% at 25 °C and 8 to 12% at 70 °C. This work showed that ground pozzolana can be used similarly as calcined laterites and clays for efficient geopolymerization stabilization of compressed earth bricks.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73239972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Dimanov, A. El Sabbagh, J. Raphanel, T. Le, M. Bornert, S. Hallais, A. Tanguy
Mechanical testing in situ scanning electron microscopy (SEM) has become a current technique for multiscale micromechanical investigation of polycrystalline materials, because direct observation of deformation microstructures allows identification of strain heterogeneities and related mechanisms. Yet, most of the studies are based on the inherited post mortem microstructures, thus precluding to unravel the local loading history, to understand the development of localization patterns, the potential interactions of concomitant mechanisms and to quantify their respective contributions to the overall strain. We therefore developed a novel experimental setup for thermomechanical testing in situ SEM, especially suited for full strain field measurements based on digital image correlation (DIC) from the sample scale, to the scales of the aggregate and the single grain. We present results obtained during simple compression, at controlled displacement rate and at temperatures up to 400°C, for polycrystalline aluminum presenting randomly oriented coarse grains (ca. 300 μm in size). According to the different scales of interest, specific surface marking patterns were realized by electron microlithography. Kinematic analysis by digital image correlation (DIC) allowed to retrieve full surface strain fields. The latter evidenced that the overall viscoplastic response was dominated by crystal slip plasticity. Increasing temperature favored the activation of non-octahedral slip, but also substantial and continuous contribution of grain boundary sliding (GBS). We suggest the latter mechanism as necessary to accommodate local plastic incompatibilities between neighboring grains.
{"title":"Deformation of Aluminum in Situ Sem and Full Field Measurements by Digital Image Correlation: Evidence of Concomitant Crystal Slip and Grain Boundary Sliding","authors":"A. Dimanov, A. El Sabbagh, J. Raphanel, T. Le, M. Bornert, S. Hallais, A. Tanguy","doi":"10.2139/ssrn.3922862","DOIUrl":"https://doi.org/10.2139/ssrn.3922862","url":null,"abstract":"Mechanical testing in situ scanning electron microscopy (SEM) has become a current technique for multiscale micromechanical investigation of polycrystalline materials, because direct observation of deformation microstructures allows identification of strain heterogeneities and related mechanisms. Yet, most of the studies are based on the inherited post mortem microstructures, thus precluding to unravel the local loading history, to understand the development of localization patterns, the potential interactions of concomitant mechanisms and to quantify their respective contributions to the overall strain. We therefore developed a novel experimental setup for thermomechanical testing in situ SEM, especially suited for full strain field measurements based on digital image correlation (DIC) from the sample scale, to the scales of the aggregate and the single grain. We present results obtained during simple compression, at controlled displacement rate and at temperatures up to 400°C, for polycrystalline aluminum presenting randomly oriented coarse grains (ca. 300 μm in size). According to the different scales of interest, specific surface marking patterns were realized by electron microlithography. Kinematic analysis by digital image correlation (DIC) allowed to retrieve full surface strain fields. The latter evidenced that the overall viscoplastic response was dominated by crystal slip plasticity. Increasing temperature favored the activation of non-octahedral slip, but also substantial and continuous contribution of grain boundary sliding (GBS). We suggest the latter mechanism as necessary to accommodate local plastic incompatibilities between neighboring grains.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"41 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85112375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. Madden, S. Briggs, Diana Perales, T. Boyle, K. Hattar, J. Krogstad
Radiation enhanced diffusion often contributes significantly to the evolution of microstructures subject to radiation but can be challenging to predict in complex nonmetallic material systems. Here, microstructural evolution in the presence of ion radiation was leveraged to explore the underlying transport phenomenon. Specifically, in situ ion irradiation of nanoparticles reveal rapid densification at room temperature for nanoparticles of cerium oxide (CeO2) and yttria stabilized zirconia (YSZ) but not for magnesium oxide (MgO) or silicon carbide (SiC). This is attributed to rapid diffusion of radiation induced interstitial defects to the high density of free surfaces in the nanoparticle agglomerates. When these observations are combined with image processing and application of a simple two-sphere sintering model, radiation enhanced diffusivity values can be calculated. In situ irradiation of YSZ nanoparticles over a broader temperature range, 50 K to 1073 K, clearly revealed a transition between three distinct rate limiting regimes: (i) low temperature, sink-limited kinetics, (ii) intermediate temperature, recombination-limited kinetics, and (iii) at high-temperature the densification is consistent with thermally activated diffusion kinetics. The high spatial and temporal resolution provided by the in situ methodology is critical to confidently distinguishing these regimes in nonmetallic oxides. While only four nonmetallic nanoparticle systems are presented here (YSZ, CeO2, SiC, and MgO), application of this methodology to the readily accessible, diverse catalog of nanoparticle chemistries and morphologies will allow for rapid exploration of radiation-enhanced diffusion behavior in a broader range of complex nonmetallic systems without the need for tracers.
{"title":"Measuring Radiation Enhanced Diffusion Through in situ Ion Radiation Induced Sintering of Oxide Nanoparticles","authors":"N. Madden, S. Briggs, Diana Perales, T. Boyle, K. Hattar, J. Krogstad","doi":"10.2139/ssrn.3951050","DOIUrl":"https://doi.org/10.2139/ssrn.3951050","url":null,"abstract":"Radiation enhanced diffusion often contributes significantly to the evolution of microstructures subject to radiation but can be challenging to predict in complex nonmetallic material systems. Here, microstructural evolution in the presence of ion radiation was leveraged to explore the underlying transport phenomenon. Specifically, in situ ion irradiation of nanoparticles reveal rapid densification at room temperature for nanoparticles of cerium oxide (CeO2) and yttria stabilized zirconia (YSZ) but not for magnesium oxide (MgO) or silicon carbide (SiC). This is attributed to rapid diffusion of radiation induced interstitial defects to the high density of free surfaces in the nanoparticle agglomerates. When these observations are combined with image processing and application of a simple two-sphere sintering model, radiation enhanced diffusivity values can be calculated. In situ irradiation of YSZ nanoparticles over a broader temperature range, 50 K to 1073 K, clearly revealed a transition between three distinct rate limiting regimes: (i) low temperature, sink-limited kinetics, (ii) intermediate temperature, recombination-limited kinetics, and (iii) at high-temperature the densification is consistent with thermally activated diffusion kinetics. The high spatial and temporal resolution provided by the in situ methodology is critical to confidently distinguishing these regimes in nonmetallic oxides. While only four nonmetallic nanoparticle systems are presented here (YSZ, CeO2, SiC, and MgO), application of this methodology to the readily accessible, diverse catalog of nanoparticle chemistries and morphologies will allow for rapid exploration of radiation-enhanced diffusion behavior in a broader range of complex nonmetallic systems without the need for tracers.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"47 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79451513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Junliang Liu, G. He, A. Callow, Kexue Li, K. Moore, H. Nordin, Michael Moody, S. Lozano-Perez, C. Grovenor
Zr–2.5Nb alloy are used as pressure tubes in Canadian Deuterium Uranium (CANDU) nuclear reactors, and the typical starting microstructure consists of α-Zr grains elongated in both transverse and longitudinal directions and thin layers of partly decomposed β-Zr lying between the α-Zr grains. In this study, we have used state-of-the-art microscopy techniques to characterise the long-term thermally decomposed β phase in these alloys, and the oxide scale formed on them in a reactor coolant loop with the aim of understanding the mechanisms underpinning the thermal decomposition behaviour at service temperatures and exploring the role of the decomposed β-Zr phase in controlling the microstructure and microchemistry of the zirconium oxide, and hence its influence on the general corrosion resistance of the alloy. We observe that these β-Zr layers are heavily decomposed even after the short stress stage at 400°C at the end of the manufacturing cycle, with a closely packed array of β-Nb precipitates forming in an α-Zr matrix. We have shown that the oxidation of these bands is significantly slower than the surrounding α-Zr matrix and that zirconium oxide grains are re-nucleated under each band. We conclude that it is the combination of the Nb-rich remnants of the original β-Zr layers arising from the hot extrusion and drawing stages and this new dense oxide that offers a significant barrier to the oxidation front (and also to the penetration of hydrogenic species), so the characteristic layered microstructure arising from the original manufacturing process is very important in determining the overall oxidation behaviour.
{"title":"The Role of Β-Zr in Zr-2.5nb Alloys During Aqueous Corrosion: A Multi-Technique Study","authors":"Junliang Liu, G. He, A. Callow, Kexue Li, K. Moore, H. Nordin, Michael Moody, S. Lozano-Perez, C. Grovenor","doi":"10.2139/ssrn.3779737","DOIUrl":"https://doi.org/10.2139/ssrn.3779737","url":null,"abstract":"Zr–2.5Nb alloy are used as pressure tubes in Canadian Deuterium Uranium (CANDU) nuclear reactors, and the typical starting microstructure consists of α-Zr grains elongated in both transverse and longitudinal directions and thin layers of partly decomposed β-Zr lying between the α-Zr grains. In this study, we have used state-of-the-art microscopy techniques to characterise the long-term thermally decomposed β phase in these alloys, and the oxide scale formed on them in a reactor coolant loop with the aim of understanding the mechanisms underpinning the thermal decomposition behaviour at service temperatures and exploring the role of the decomposed β-Zr phase in controlling the microstructure and microchemistry of the zirconium oxide, and hence its influence on the general corrosion resistance of the alloy. We observe that these β-Zr layers are heavily decomposed even after the short stress stage at 400°C at the end of the manufacturing cycle, with a closely packed array of β-Nb precipitates forming in an α-Zr matrix. We have shown that the oxidation of these bands is significantly slower than the surrounding α-Zr matrix and that zirconium oxide grains are re-nucleated under each band. We conclude that it is the combination of the Nb-rich remnants of the original β-Zr layers arising from the hot extrusion and drawing stages and this new dense oxide that offers a significant barrier to the oxidation front (and also to the penetration of hydrogenic species), so the characteristic layered microstructure arising from the original manufacturing process is very important in determining the overall oxidation behaviour.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"34 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88390470","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Siwat Siraoranroj, N. Kaewtrakulchai, M. Fuji, A. Eiad-ua
High performance nanoporous carbons (MLC) were directly prepared from mulberry leaves (Morus alba L.) residues by the hydrothermal-carbonization with chemical reagent combined the microwave-assisted treatment. The as-purified MLC was successfully applied for the adsorption of methyl orange, which is one of crucial waste-water pollutants left from an industrial sector. The MLC sample obtained from the hydrothermal process (200 °C, 12 h) using an activation of 15 wt% NaOH (700 °C, 2 h), and combined with microwave treatment at 700 W for 6 min, specifically exhibited micropores and mesopores in the MLC morphological structure. Accordingly, the highest SBET was approximately 791.79 m2/g with the total pore volume of 0.495 cm3/g. Moreover, the adsorption performance test of MLC was conducted by the shaking unit using 100 ppm methyl orange concentration. The MLC showed the highest methyl orange-adsorption uptake of 99% at 30 °C under an ambient pressure (1 atm). The development of mulberry leaves (Morus alba L.) residues into MLC exhibited a great attention for dyes adsorption with a rapid adsorption kinetic, and excellent adsorption capacity, which are a promising-characteristics for practical waste-water adsorption experiments.
{"title":"Nanoporous Carbon From Mulberry Leaves Residues via Microwave Assisted Hydrothermal-Carbonization for Methyl Orange Adsorption: Kinetic, Equilibrium and Thermodynamic Studies","authors":"Siwat Siraoranroj, N. Kaewtrakulchai, M. Fuji, A. Eiad-ua","doi":"10.2139/ssrn.3906849","DOIUrl":"https://doi.org/10.2139/ssrn.3906849","url":null,"abstract":"High performance nanoporous carbons (MLC) were directly prepared from mulberry leaves (Morus alba L.) residues by the hydrothermal-carbonization with chemical reagent combined the microwave-assisted treatment. The as-purified MLC was successfully applied for the adsorption of methyl orange, which is one of crucial waste-water pollutants left from an industrial sector. The MLC sample obtained from the hydrothermal process (200 °C, 12 h) using an activation of 15 wt% NaOH (700 °C, 2 h), and combined with microwave treatment at 700 W for 6 min, specifically exhibited micropores and mesopores in the MLC morphological structure. Accordingly, the highest SBET was approximately 791.79 m2/g with the total pore volume of 0.495 cm3/g. Moreover, the adsorption performance test of MLC was conducted by the shaking unit using 100 ppm methyl orange concentration. The MLC showed the highest methyl orange-adsorption uptake of 99% at 30 °C under an ambient pressure (1 atm). The development of mulberry leaves (Morus alba L.) residues into MLC exhibited a great attention for dyes adsorption with a rapid adsorption kinetic, and excellent adsorption capacity, which are a promising-characteristics for practical waste-water adsorption experiments.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"70 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90655643","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The microband (MB) formation mechanisms in an austenitic Fe-30Mn-6.5Al-0.3C (wt.%) low-density steel tensile deformed at -196°C were investigated by combined electron channeling contrast imaging (ECCI) and electron backscatter diffraction (EBSD). The grain orientation dependences of the MB structure, MB morphology, and MB alignment were quantitatively evaluated in grains oriented with the two main texture components, namely, <111>//tensile axis (TA) and <001>//TA. The interplay between the deformation structure and MB formation was analyzed. Our analysis indicates that the underlying deformation structure controls the MB formation mechanism and, at the current deformation conditions, also determines the crystallographic character of MBs. Most of the evaluated MBs have a crystallographic character (deviation angle <5° from {111} slip plane traces). Specifically, 77% of the MBs in the grains oriented close to <111>//TA directions and all the MBs evaluated in grains oriented close to <001>//TA directions have a crystallographic character. They are associated with a planar strain localization phenomenon occurring along highly-stressed crystallographic slip planes. Non-crystallographic MBs (deviation angle >5° from {111} slip plane traces) only occur in the grains oriented close to <111>//TA directions. They are associated with the splitting of pre-existing dense-dislocation walls (DDWs). At high strain levels, we foresee the activation of a GB-assisted MB formation mechanism associated with twin-GB interactions.
{"title":"Study of Microbands in a Fe-30mn-6.5al-0.3c Low-Density Steel Deformed at Cryogenic Temperature","authors":"I. Gutierrez-Urrutia, A. Shibata, K. Tsuzaki","doi":"10.2139/ssrn.3947689","DOIUrl":"https://doi.org/10.2139/ssrn.3947689","url":null,"abstract":"The microband (MB) formation mechanisms in an austenitic Fe-30Mn-6.5Al-0.3C (wt.%) low-density steel tensile deformed at -196°C were investigated by combined electron channeling contrast imaging (ECCI) and electron backscatter diffraction (EBSD). The grain orientation dependences of the MB structure, MB morphology, and MB alignment were quantitatively evaluated in grains oriented with the two main texture components, namely, <111>//tensile axis (TA) and <001>//TA. The interplay between the deformation structure and MB formation was analyzed. Our analysis indicates that the underlying deformation structure controls the MB formation mechanism and, at the current deformation conditions, also determines the crystallographic character of MBs. Most of the evaluated MBs have a crystallographic character (deviation angle <5° from {111} slip plane traces). Specifically, 77% of the MBs in the grains oriented close to <111>//TA directions and all the MBs evaluated in grains oriented close to <001>//TA directions have a crystallographic character. They are associated with a planar strain localization phenomenon occurring along highly-stressed crystallographic slip planes. Non-crystallographic MBs (deviation angle >5° from {111} slip plane traces) only occur in the grains oriented close to <111>//TA directions. They are associated with the splitting of pre-existing dense-dislocation walls (DDWs). At high strain levels, we foresee the activation of a GB-assisted MB formation mechanism associated with twin-GB interactions.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"1012 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77174468","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. Gong, Z.J. Zhang, Z. Qu, J. Hou, H.J. Yang, X. Shao, Z. Zhang
The high-cycle fatigue (HCF) behaviors of wrought Al alloys are vitally important for their industrial application. To optimize the fatigue property of the wrought Al alloy, the effects of aging conditions on the fatigue properties of 7N01, 7075 and 2024 Al alloys were studied. The results show that the overaged samples have the lowest tensile strength among the three aging states, but their fatigue strength is the highest. Further investigations on the dislocation morphologies indicates that the dislocations are easy to accumulate and annihilate at the second phase boundaries for the overaged state, which reduces the fatigue damage degree at the grain boundaries. Besides, the discontinuous distribution of the grain boundary precipitates and the increased width of the precipitate-free zone also contributed to the improved fatigue property of the overaged state. Those results should be significantly important for the optimization of their fatigue properties and the industrial application of wrought Al alloys.
{"title":"Effect of Aging State on Fatigue Property of Wrought Aluminum Alloys","authors":"B. Gong, Z.J. Zhang, Z. Qu, J. Hou, H.J. Yang, X. Shao, Z. Zhang","doi":"10.2139/ssrn.3919744","DOIUrl":"https://doi.org/10.2139/ssrn.3919744","url":null,"abstract":"The high-cycle fatigue (HCF) behaviors of wrought Al alloys are vitally important for their industrial application. To optimize the fatigue property of the wrought Al alloy, the effects of aging conditions on the fatigue properties of 7N01, 7075 and 2024 Al alloys were studied. The results show that the overaged samples have the lowest tensile strength among the three aging states, but their fatigue strength is the highest. Further investigations on the dislocation morphologies indicates that the dislocations are easy to accumulate and annihilate at the second phase boundaries for the overaged state, which reduces the fatigue damage degree at the grain boundaries. Besides, the discontinuous distribution of the grain boundary precipitates and the increased width of the precipitate-free zone also contributed to the improved fatigue property of the overaged state. Those results should be significantly important for the optimization of their fatigue properties and the industrial application of wrought Al alloys.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"46 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79918412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pengfei Dang, Yumei Zhou, Lei Ding, J. Pang, Lei Zhang, X. Ding, Jun Sun, T. Lookman, D. Xue
Large-scale applications of elastocaloric cooling demand bulk materials showing both large adiabatic temperature change (∆Tad) and low-fatigue characteristics at room temperature. Here we synthesize a bulk Ti49.2Ni40.8Cu10 polycrystalline alloy microstructurally featured by nanocrystalinity and epitaxially related Ti(Ni,Cu) 2 nanoprecipitates through cold-rolling and aging treatment. It exhibits a large ∆Tad of 13.8 K and a high coefficient of performance value of 13 at room temperature. Moreover, the degradation of ∆Tad is only 0.3 K after 450 tensile cycles. The results indicate that the alloy offers a good balance of multiple objectives, holding promise for solid-state refrigeration applications. We attribute the favorable properties to the enhanced reversibility of martensitic transformation during stress cycling, aided by the internal epitaxy-generated stress at the interface between the Ti(Ni,Cu)2 nanoprecipitates and matrix, together with grain refinement.
{"title":"Low-Fatigue and Large Room-Temperature Elastocaloric Effect in a Bulk Ti 49.2Ni 40.8Cu 10 Alloy","authors":"Pengfei Dang, Yumei Zhou, Lei Ding, J. Pang, Lei Zhang, X. Ding, Jun Sun, T. Lookman, D. Xue","doi":"10.2139/ssrn.3927821","DOIUrl":"https://doi.org/10.2139/ssrn.3927821","url":null,"abstract":"Large-scale applications of elastocaloric cooling demand bulk materials showing both large adiabatic temperature change (∆Tad) and low-fatigue characteristics at room temperature. Here we synthesize a bulk Ti49.2Ni40.8Cu10 polycrystalline alloy microstructurally featured by nanocrystalinity and epitaxially related Ti(Ni,Cu) 2 nanoprecipitates through cold-rolling and aging treatment. It exhibits a large ∆Tad of 13.8 K and a high coefficient of performance value of 13 at room temperature. Moreover, the degradation of ∆Tad is only 0.3 K after 450 tensile cycles. The results indicate that the alloy offers a good balance of multiple objectives, holding promise for solid-state refrigeration applications. We attribute the favorable properties to the enhanced reversibility of martensitic transformation during stress cycling, aided by the internal epitaxy-generated stress at the interface between the Ti(Ni,Cu)2 nanoprecipitates and matrix, together with grain refinement.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83361771","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. Garmroudi, M. Parzer, A. Riss, N. Reumann, B. Hinterleitner, K. Tobita, Y. Katsura, K. Kimura, T. Mori, E. Bauer
Full-Heusler compounds with the composition Fe2V1-XTaxAl1-YSiy have recently shown to exhibit some of thehighest power factors reported so far for bulk materials due to the band convergence and band gap opening causedby the V/Ta substitution. Therefore, the solubility limit of Ta and Si regarding the stability of the L21 phase isinvestigated in this study. The crystal structure and microstructure of a large number of samples is probed by X-raydiffraction as well as scanning electron microscopy and energy dispersive X-ray analysis. The results show that the Al/Si substitution significantly hampers the solubility of Ta within the Heusler structure. Furthermore, Fe2V0.9Ta0.1Al and Fe2V0.95Ta0.05Al0.9Si0.1 reveal nanoscale impurity precipitates in the microstructure, together with diffuse contrasts that indicate a non-equilibrium metastable state. For that reason, different annealing conditions, varying the temperature and time, have been applied to the latter and the effect on the microstructure and thermoelectric properties is investigated. It is found that additional annealing leads to further phase segregation and grain growth of the impurity precipitates, which due to their metallic-like nature have a detrimental effect on the Seebeck coefficient. They can however effectively reduce the lattice thermal conductivity if the average grain size remains below the phonon mean free path. The thermoelectric efficiency in terms of the dimensionless gure of merit ZT is increased up to ZT = 0.3 - 0.34 at 300K which is beyond the values previously reported for Fe2VAl-based bulk materials.
{"title":"Solubility Limit and Annealing Effects on the Microstructure & Thermoelectricproperties of Fe 2V 1-XTa xAl 1-YSi y Heusler Compounds","authors":"F. Garmroudi, M. Parzer, A. Riss, N. Reumann, B. Hinterleitner, K. Tobita, Y. Katsura, K. Kimura, T. Mori, E. Bauer","doi":"10.2139/ssrn.3762208","DOIUrl":"https://doi.org/10.2139/ssrn.3762208","url":null,"abstract":"Full-Heusler compounds with the composition Fe<sub>2</sub>V<sub>1-X</sub>Ta<sub>x</sub>Al<sub>1-Y</sub>Si<sub>y</sub> have recently shown to exhibit some of thehighest power factors reported so far for bulk materials due to the band convergence and band gap opening causedby the V/Ta substitution. Therefore, the solubility limit of Ta and Si regarding the stability of the L2<sub>1</sub> phase isinvestigated in this study. The crystal structure and microstructure of a large number of samples is probed by X-raydiffraction as well as scanning electron microscopy and energy dispersive X-ray analysis. The results show that the Al/Si substitution significantly hampers the solubility of Ta within the Heusler structure. Furthermore, Fe<sub>2</sub>V<sub>0.9</sub>Ta<sub>0.1</sub>Al and Fe<sub>2</sub>V<sub>0.95</sub>Ta<sub>0.05</sub>Al<sub>0.9</sub>Si<sub>0.1</sub> reveal nanoscale impurity precipitates in the microstructure, together with diffuse contrasts that indicate a non-equilibrium metastable state. For that reason, different annealing conditions, varying the temperature and time, have been applied to the latter and the effect on the microstructure and thermoelectric properties is investigated. It is found that additional annealing leads to further phase segregation and grain growth of the impurity precipitates, which due to their metallic-like nature have a detrimental effect on the Seebeck coefficient. They can however effectively reduce the lattice thermal conductivity if the average grain size remains below the phonon mean free path. The thermoelectric efficiency in terms of the dimensionless gure of merit <i>ZT</i> is increased up to <i>ZT</i> = 0.3 - 0.34 at 300K which is beyond the values previously reported for Fe2VAl-based bulk materials.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"103 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90309739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Walde, Cheng-Yao Huang, Chia-Lung Tsai, Wen-Hsuang Hsieh, Yi-Keng Fu, S. Hagedorn, Cheng-Yao Huang, T. Lu, M. Weyers, Chia-Yen Huang
AlGaN-based UVC light-emitting diodes (LED) were fabricated on high-quality AlN templates with an engineerable in-plane lattice constant. The controllability of the in-plane strain originated from the vacancy formation in Si-doped AlN (AlN:Si) and their interaction with edge dislocations. The strain state of the AlN:Si top interface could be well depicted by a dislocation-tilt model depending on the buffer strain state, threading dislocation density (TDD), and regrown AlN:Si thickness. The validity of the model was verified by cross-sectional TEM analysis. With a gradually widened lattice constant of regrown AlN:Si layer, strain-induced defects of subsequently grown n-AlGaN was suppressed. Therefore, growing a current spreading layer which possesses a moderate Al content (<65%), decent thickness (>1.5 μm), and a low TDD (<1.0×10 9 cm -2 ) simultaneously becomes possible. Additionally, the idea of an optimal edge TDD ) in the AlN buffer was revealed for growing high-quality n-AlGaN layers with a targeted thickness. After a deliberate strain-TDD engineering for AlN:Si and n-AlGaN, high-power UVC LEDs (P>200 mW) with a low forward voltage (V f =5.7 volt) were demonstrated at I=1.35 A. The low forward voltage under high current injection density was attributed to the success in preparation of a low series resistance and high-quality n-AlGaN current spreading layer.
在高质量的AlN模板上制备了基于algan的UVC发光二极管(LED)，具有可工程的平面内晶格常数。面内应变的可控性源于Si掺杂AlN (AlN:Si)中空位的形成及其与边缘位错的相互作用。根据缓冲应变状态、螺纹位错密度(TDD)和再生AlN:Si厚度，位错-倾斜模型可以很好地描述AlN:Si顶部界面的应变状态。通过横断面透射电镜分析验证了模型的有效性。随着再生AlN:Si层晶格常数逐渐变宽，随后生长的n-AlGaN的应变诱导缺陷被抑制。因此，在I=1.35 a时生长出了Al含量适中(1.5 μm)、TDD低(200 mW)、正向电压低(V f =5.7伏)的电流展布层。高电流注入密度下的低正向电压归因于成功制备了低串联电阻和高质量的n-AlGaN电流扩散层。
{"title":"High-Quality A1GaN Epitaxy on Lattice-Engineerable AlN Template for High-Power UVC Light-Emitting Diodes","authors":"S. Walde, Cheng-Yao Huang, Chia-Lung Tsai, Wen-Hsuang Hsieh, Yi-Keng Fu, S. Hagedorn, Cheng-Yao Huang, T. Lu, M. Weyers, Chia-Yen Huang","doi":"10.2139/ssrn.3946395","DOIUrl":"https://doi.org/10.2139/ssrn.3946395","url":null,"abstract":"AlGaN-based UVC light-emitting diodes (LED) were fabricated on high-quality AlN templates with an engineerable in-plane lattice constant. The controllability of the in-plane strain originated from the vacancy formation in Si-doped AlN (AlN:Si) and their interaction with edge dislocations. The strain state of the AlN:Si top interface could be well depicted by a dislocation-tilt model depending on the buffer strain state, threading dislocation density (TDD), and regrown AlN:Si thickness. The validity of the model was verified by cross-sectional TEM analysis. With a gradually widened lattice constant of regrown AlN:Si layer, strain-induced defects of subsequently grown n-AlGaN was suppressed. Therefore, growing a current spreading layer which possesses a moderate Al content (<65%), decent thickness (>1.5 μm), and a low TDD (<1.0×10 9 cm -2 ) simultaneously becomes possible. Additionally, the idea of an optimal edge TDD ) in the AlN buffer was revealed for growing high-quality n-AlGaN layers with a targeted thickness. After a deliberate strain-TDD engineering for AlN:Si and n-AlGaN, high-power UVC LEDs (P>200 mW) with a low forward voltage (V f =5.7 volt) were demonstrated at I=1.35 A. The low forward voltage under high current injection density was attributed to the success in preparation of a low series resistance and high-quality n-AlGaN current spreading layer.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88398814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：