Pub Date : 2019-10-02DOI: 10.1080/15567265.2019.1675830
G. Rojo, S. Ghanbari, J. Darabi
ABSTRACT This paper presents the fabrication, testing, and modeling of an array of composite copper-carbon nanotubes (Cu-CNT) micropillars as a wick structure for potential application in passive phase-change cooling systems. This novel wick structure has a larger spacing at the base of the micropillars to provide a higher liquid permeability and mushroom-like structures on the top surface of the micropillars with a smaller spacing to provide a greater capillary pressure. The composite Cu-CNT micropillars were fabricated by an electrochemical deposition method on a patterned copper template. Cauliflower-like nanostructures were then grown on the top surface of the micropillars using chronoamperometry technique to improve the capillary pressure and thermal performance of the wick structure. After successful fabrication of the micropillars, a series of tests were conducted to quantify the thermal performance of the wick structures. The results demonstrate superior thermal and corrosion performances for composite Cu-CNT micropillars compared to those of copper micropillars. Additionally, a thermal resistance network analysis was conducted to model the thermal performance of the fabricated mushroom-shaped micropillar array. Model predictions were compared with the experimental results and good agreement was observed.
{"title":"Fabrication and Thermal Characterization of Composite Cu-CNT Micropillars for Capillary-driven Phase-Change Cooling Devices","authors":"G. Rojo, S. Ghanbari, J. Darabi","doi":"10.1080/15567265.2019.1675830","DOIUrl":"https://doi.org/10.1080/15567265.2019.1675830","url":null,"abstract":"ABSTRACT This paper presents the fabrication, testing, and modeling of an array of composite copper-carbon nanotubes (Cu-CNT) micropillars as a wick structure for potential application in passive phase-change cooling systems. This novel wick structure has a larger spacing at the base of the micropillars to provide a higher liquid permeability and mushroom-like structures on the top surface of the micropillars with a smaller spacing to provide a greater capillary pressure. The composite Cu-CNT micropillars were fabricated by an electrochemical deposition method on a patterned copper template. Cauliflower-like nanostructures were then grown on the top surface of the micropillars using chronoamperometry technique to improve the capillary pressure and thermal performance of the wick structure. After successful fabrication of the micropillars, a series of tests were conducted to quantify the thermal performance of the wick structures. The results demonstrate superior thermal and corrosion performances for composite Cu-CNT micropillars compared to those of copper micropillars. Additionally, a thermal resistance network analysis was conducted to model the thermal performance of the fabricated mushroom-shaped micropillar array. Model predictions were compared with the experimental results and good agreement was observed.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"23 1","pages":"317 - 333"},"PeriodicalIF":4.1,"publicationDate":"2019-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/15567265.2019.1675830","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44633943","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ABSTRACT Dew-harvesting technology radiatively cools a condenser below the dewpoint to achieve condensation of the water vapor from the atmosphere. Due to its passive nature, this technology has attracted broad interest, in particular in the context of the worldwide drinking-water scarcity. However, the fundamental limit of its performance has not yet been clarified. Moreover, the existing applications have been limited to humid areas. Here, we point out the upper bound of the performance of this technology by carefully considering various parameters such as the ambient temperature (Tambient), the relative humidity (RH), and the convection coefficient (h). Moreover, we highlight the potential of a condenser consisting of a selective emitter, which is capable of condensing water vapor under significantly more arid conditions as compared with the use of a blackbody emitter. For example, a near-ideal emitter could achieve a dew-harvesting mass flux () of 13 gm−2hr−1 even at Tambient = 20°C with RH = 40%, under which condition the blackbody emitter cannot harvest any dew. We provide a numerical design of such a selective emitter, consisting of six layers, optimized for dew-harvesting purposes.
{"title":"Fundamental Limits of the Dew-Harvesting Technology","authors":"Minghao Dong, Zheng Zhang, Yu Shi, Xiaodong Zhao, S. Fan, Zhen Chen","doi":"10.1080/15567265.2020.1722300","DOIUrl":"https://doi.org/10.1080/15567265.2020.1722300","url":null,"abstract":"ABSTRACT Dew-harvesting technology radiatively cools a condenser below the dewpoint to achieve condensation of the water vapor from the atmosphere. Due to its passive nature, this technology has attracted broad interest, in particular in the context of the worldwide drinking-water scarcity. However, the fundamental limit of its performance has not yet been clarified. Moreover, the existing applications have been limited to humid areas. Here, we point out the upper bound of the performance of this technology by carefully considering various parameters such as the ambient temperature (Tambient), the relative humidity (RH), and the convection coefficient (h). Moreover, we highlight the potential of a condenser consisting of a selective emitter, which is capable of condensing water vapor under significantly more arid conditions as compared with the use of a blackbody emitter. For example, a near-ideal emitter could achieve a dew-harvesting mass flux () of 13 gm−2hr−1 even at Tambient = 20°C with RH = 40%, under which condition the blackbody emitter cannot harvest any dew. We provide a numerical design of such a selective emitter, consisting of six layers, optimized for dew-harvesting purposes.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"24 1","pages":"43 - 52"},"PeriodicalIF":4.1,"publicationDate":"2019-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/15567265.2020.1722300","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49618412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-08-30DOI: 10.1080/15567265.2019.1660439
P. Pendyala, H. Kim, H. Grewal, Uikyu Chae, Sungwook Yang, Il-Joo Cho, Simon Song, E. Yoon
ABSTRACT Superhydrophobic textured surfaces are known to maintain a nonwetted state unless external stimuli are applied since they can withstand high wetting pressure. Herein, we report a new category of tunable, one-dimensional (1D) Cassie-to-Wenzel wetting transitions during evaporation, even on superhydrophobic surfaces. The transition initiates at the periphery of the evaporating drop, and the wetting transition propagates toward the center of the drop. The transitions are observed for surfaces with wetting pressures as high as ~ 7,568 Pa, which is much higher than the Laplace pressure, i.e., ~200 Pa. In situ high-contrast fluorescence microscopy images of the evaporating drop show that the transition is induced by preferential depinning of the air-water interface and subsequent formation of air bubbles in the cavities near the three-phase contact line. The evaporation-induced internal flow enhances the pressure within the water droplet and subsequently causes a Cassie-to-Wenzel wetting transition.
{"title":"Internal-Flow-Mediated, Tunable One-dimensional Cassie-to-Wenzel Wetting Transition on Superhydrophobic Microcavity Surfaces during Evaporation","authors":"P. Pendyala, H. Kim, H. Grewal, Uikyu Chae, Sungwook Yang, Il-Joo Cho, Simon Song, E. Yoon","doi":"10.1080/15567265.2019.1660439","DOIUrl":"https://doi.org/10.1080/15567265.2019.1660439","url":null,"abstract":"ABSTRACT Superhydrophobic textured surfaces are known to maintain a nonwetted state unless external stimuli are applied since they can withstand high wetting pressure. Herein, we report a new category of tunable, one-dimensional (1D) Cassie-to-Wenzel wetting transitions during evaporation, even on superhydrophobic surfaces. The transition initiates at the periphery of the evaporating drop, and the wetting transition propagates toward the center of the drop. The transitions are observed for surfaces with wetting pressures as high as ~ 7,568 Pa, which is much higher than the Laplace pressure, i.e., ~200 Pa. In situ high-contrast fluorescence microscopy images of the evaporating drop show that the transition is induced by preferential depinning of the air-water interface and subsequent formation of air bubbles in the cavities near the three-phase contact line. The evaporation-induced internal flow enhances the pressure within the water droplet and subsequently causes a Cassie-to-Wenzel wetting transition.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"23 1","pages":"275 - 288"},"PeriodicalIF":4.1,"publicationDate":"2019-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/15567265.2019.1660439","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44450375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-25DOI: 10.1080/15567265.2019.1633712
M. Alipour, Z. Dursunkaya
ABSTRACT Condensation on a fin top terminating with a groove involves several simultaneous phenomena including vapor–liquid boundaries whose shapes are unknown a priori, fluid flow due to capillary and disjoining pressure gradients, and condensation over thin films. This problem occurs in grooved heat pipes, where the condensation is predominantly present on fin tops due to the thinner liquid film – having a lower thermal resistance compared to inside the groove where the fluid is substantially thicker. Majority of the studies in the literature assume an approximate profile for the liquid film surface and apply an integral balance for conservation laws, accounting for the effect of the capillary pressure only. In addition, this approximate profile is matched with the liquid profile inside the groove, which serves as a boundary condition. Although intuitive, validity of the matching is not straightforward, and its limitations have never been discussed in the literature, despite the presence of experimental findings to the contrary. In the current study, the effect of disjoining pressure and matching conditions with the groove is investigated using a comprehensive model. The results suggest that for small temperature differences and small slopes, the effect of disjoining pressure is non-negligible, and beyond limiting values of edge angles, the effect of disjoining pressure precludes solutions where the fin top film matches the groove in a smooth transition.
{"title":"Limitations of Matching Condensing Film Profile on a Micro Fin with the Groove: Critical Effect of Disjoining Pressure","authors":"M. Alipour, Z. Dursunkaya","doi":"10.1080/15567265.2019.1633712","DOIUrl":"https://doi.org/10.1080/15567265.2019.1633712","url":null,"abstract":"ABSTRACT Condensation on a fin top terminating with a groove involves several simultaneous phenomena including vapor–liquid boundaries whose shapes are unknown a priori, fluid flow due to capillary and disjoining pressure gradients, and condensation over thin films. This problem occurs in grooved heat pipes, where the condensation is predominantly present on fin tops due to the thinner liquid film – having a lower thermal resistance compared to inside the groove where the fluid is substantially thicker. Majority of the studies in the literature assume an approximate profile for the liquid film surface and apply an integral balance for conservation laws, accounting for the effect of the capillary pressure only. In addition, this approximate profile is matched with the liquid profile inside the groove, which serves as a boundary condition. Although intuitive, validity of the matching is not straightforward, and its limitations have never been discussed in the literature, despite the presence of experimental findings to the contrary. In the current study, the effect of disjoining pressure and matching conditions with the groove is investigated using a comprehensive model. The results suggest that for small temperature differences and small slopes, the effect of disjoining pressure is non-negligible, and beyond limiting values of edge angles, the effect of disjoining pressure precludes solutions where the fin top film matches the groove in a smooth transition.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"23 1","pages":"289 - 303"},"PeriodicalIF":4.1,"publicationDate":"2019-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/15567265.2019.1633712","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42529676","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-19DOI: 10.1080/15567265.2019.1628136
Onur Yenigun, M. Barisik
ABSTRACT Nanoscale heat transfer between two parallel silicon slabs filled with deionized water was studied under varying electric field in heat transfer direction. Two oppositely charged electrodes were embedded into the silicon walls to create a uniform electric field perpendicular to the surface, similar to electrowetting-on-dielectric technologies. Through the electrostatic interactions, (i) surface charge altered the silicon/water interface energy and (ii) electric field created orientation polarization of water by aligning dipoles to the direction of the electric field. We found that the first mechanism can manipulate the interface thermal resistance and the later can change the thermal conductivity of water. By increasing electric field, Kapitza length substantially decreased to 1/5 of its original value due to enhanced water layering, but also the water thermal conductivity lessened slightly since water dynamics were restricted; in this range of electric field, heat transfer was doubled. With a further increase of the electric field, electro-freezing (EF) developed as the aligned water dipoles formed a crystalline structure. During EF (0.53 V/nm), water thermal conductivity increased to 1.5 times of its thermodynamic value while Kapitza did not change; but once the EF is formed, both Kapitza and conductivity remained constant with increasing electric field. Overall, the heat transfer rate increased 2.25 times at 0.53 V/nm after which it remains constant with further increase of the electric field.
{"title":"Electric Field Controlled Heat Transfer Through Silicon and Nano-confined Water","authors":"Onur Yenigun, M. Barisik","doi":"10.1080/15567265.2019.1628136","DOIUrl":"https://doi.org/10.1080/15567265.2019.1628136","url":null,"abstract":"ABSTRACT Nanoscale heat transfer between two parallel silicon slabs filled with deionized water was studied under varying electric field in heat transfer direction. Two oppositely charged electrodes were embedded into the silicon walls to create a uniform electric field perpendicular to the surface, similar to electrowetting-on-dielectric technologies. Through the electrostatic interactions, (i) surface charge altered the silicon/water interface energy and (ii) electric field created orientation polarization of water by aligning dipoles to the direction of the electric field. We found that the first mechanism can manipulate the interface thermal resistance and the later can change the thermal conductivity of water. By increasing electric field, Kapitza length substantially decreased to 1/5 of its original value due to enhanced water layering, but also the water thermal conductivity lessened slightly since water dynamics were restricted; in this range of electric field, heat transfer was doubled. With a further increase of the electric field, electro-freezing (EF) developed as the aligned water dipoles formed a crystalline structure. During EF (0.53 V/nm), water thermal conductivity increased to 1.5 times of its thermodynamic value while Kapitza did not change; but once the EF is formed, both Kapitza and conductivity remained constant with increasing electric field. Overall, the heat transfer rate increased 2.25 times at 0.53 V/nm after which it remains constant with further increase of the electric field.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"23 1","pages":"304 - 316"},"PeriodicalIF":4.1,"publicationDate":"2019-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/15567265.2019.1628136","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48298925","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-13DOI: 10.1080/15567265.2019.1628135
O. Kwon, Geoff Wehmeyer, C. Dames
ABSTRACT Rebuilding phonon mean free path (MFP) spectra from experimental data is integral to phonon MFP spectroscopy. However, being based on effective thermal conductivity, the current integral equation for this precludes the use of certain heat sources of convenient shapes, such as a cylindrical nanoline. Herein, to enable using diverse specimens exhibiting a ballistic effect, we develop a ballistic thermal resistance-based integral equation, utilizing the ease and accuracy of the modified ballistic–diffusive equations demonstrated in the companion paper. The availability of more diverse shapes of specimens will enhance further development and widen use of phonon MFP spectroscopy.
{"title":"Modified Ballistic–Diffusive Equations for Obtaining Phonon Mean Free Path Spectrum from Ballistic Thermal Resistance: II. Derivation of Integral Equation Based on Ballistic Thermal Resistance","authors":"O. Kwon, Geoff Wehmeyer, C. Dames","doi":"10.1080/15567265.2019.1628135","DOIUrl":"https://doi.org/10.1080/15567265.2019.1628135","url":null,"abstract":"ABSTRACT Rebuilding phonon mean free path (MFP) spectra from experimental data is integral to phonon MFP spectroscopy. However, being based on effective thermal conductivity, the current integral equation for this precludes the use of certain heat sources of convenient shapes, such as a cylindrical nanoline. Herein, to enable using diverse specimens exhibiting a ballistic effect, we develop a ballistic thermal resistance-based integral equation, utilizing the ease and accuracy of the modified ballistic–diffusive equations demonstrated in the companion paper. The availability of more diverse shapes of specimens will enhance further development and widen use of phonon MFP spectroscopy.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"23 1","pages":"334 - 347"},"PeriodicalIF":4.1,"publicationDate":"2019-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/15567265.2019.1628135","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43826674","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-05-30DOI: 10.1080/15567265.2019.1619885
O. Kwon, Geoff Wehmeyer, C. Dames
ABSTRACT Phonon mean free path (MFP) spectra are essential for the accurate prediction and utilization of the classical size effect. Rebuilding an MFP spectrum from experimental data remains challenging. It requires solving the thermal transport phenomenon of a heat source of a given shape across the entire size range. Herein, to do this for a heat source embedded in an infinite medium, we derive a new set of modified ballistic–diffusive equations by analyzing the cause of the erroneous results observed in a steady-state solution of the original ballistic-diffusive equations. We demonstrate their ease and accuracy by obtaining the effective thermal conductivity for a spherical nanoparticle embedded in an infinite medium in an explicit closed-form and comparing it with that obtained by the Boltzmann transport equation (differences estimated as <3%).
{"title":"Modified ballistic–diffusive equations for obtaining phonon mean free path spectrum from ballistic thermal resistance: I. Introduction and validation of the equations","authors":"O. Kwon, Geoff Wehmeyer, C. Dames","doi":"10.1080/15567265.2019.1619885","DOIUrl":"https://doi.org/10.1080/15567265.2019.1619885","url":null,"abstract":"ABSTRACT Phonon mean free path (MFP) spectra are essential for the accurate prediction and utilization of the classical size effect. Rebuilding an MFP spectrum from experimental data remains challenging. It requires solving the thermal transport phenomenon of a heat source of a given shape across the entire size range. Herein, to do this for a heat source embedded in an infinite medium, we derive a new set of modified ballistic–diffusive equations by analyzing the cause of the erroneous results observed in a steady-state solution of the original ballistic-diffusive equations. We demonstrate their ease and accuracy by obtaining the effective thermal conductivity for a spherical nanoparticle embedded in an infinite medium in an explicit closed-form and comparing it with that obtained by the Boltzmann transport equation (differences estimated as <3%).","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"23 1","pages":"259 - 273"},"PeriodicalIF":4.1,"publicationDate":"2019-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/15567265.2019.1619885","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49146407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-04-07DOI: 10.1080/15567265.2019.1600622
Peiyuan Yu, Anubhav Jain, R. Prasher
ABSTRACT Thermal fluids have many applications in the storage and transfer of thermal energy, playing a key role in heating, cooling, refrigeration, and power generation. However, the specific heat capacity of conventional thermal fluids, which is directly linked to energy density, has remained relatively low. To tackle this challenge, we explore a thermochemical energy storage mechanism that can greatly enhance the heat capacity of base fluids (by up to threefold based on simulation) by creating a solution with reactive species that can absorb and release additional thermal energy. Based on the classical theory of equilibrium thermodynamics, we developed a macroscale theoretical model that connects fundamental properties of the underlying reaction to the thermophysical properties of the liquids. This framework allows us to employ state-of-the-art molecular scale computational tools such as density functional theory calculations to identify and refine the most suitable molecular systems for subsequent experimental studies. Our approach opens up a new avenue for developing next-generation heat transfer fluids that may break traditional barriers to achieve high specific heat and energy storage capacity.
{"title":"Enhanced Thermochemical Heat Capacity of Liquids: Molecular to Macroscale Modeling","authors":"Peiyuan Yu, Anubhav Jain, R. Prasher","doi":"10.1080/15567265.2019.1600622","DOIUrl":"https://doi.org/10.1080/15567265.2019.1600622","url":null,"abstract":"ABSTRACT Thermal fluids have many applications in the storage and transfer of thermal energy, playing a key role in heating, cooling, refrigeration, and power generation. However, the specific heat capacity of conventional thermal fluids, which is directly linked to energy density, has remained relatively low. To tackle this challenge, we explore a thermochemical energy storage mechanism that can greatly enhance the heat capacity of base fluids (by up to threefold based on simulation) by creating a solution with reactive species that can absorb and release additional thermal energy. Based on the classical theory of equilibrium thermodynamics, we developed a macroscale theoretical model that connects fundamental properties of the underlying reaction to the thermophysical properties of the liquids. This framework allows us to employ state-of-the-art molecular scale computational tools such as density functional theory calculations to identify and refine the most suitable molecular systems for subsequent experimental studies. Our approach opens up a new avenue for developing next-generation heat transfer fluids that may break traditional barriers to achieve high specific heat and energy storage capacity.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"23 1","pages":"235 - 246"},"PeriodicalIF":4.1,"publicationDate":"2019-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/15567265.2019.1600622","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46867160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-03-18DOI: 10.1080/15567265.2019.1586804
Joon-soo Kim, Sung‐Yu Ku, N. Economou, Woongsik Jang, D. H. Wang
ABSTRACT We demonstrate the selectively p- or n-type doping behavior of conjugated block copolymer (BCP). The poly(3-hexylthiophene)-b-poly{[N,N-9-bis(2-octyldodecyl)-naphtalene-1, 4, 5, 7-bis(dicarboximide)-2,6-diyl]-alt-5,59-(2,29-bithiophene)}, P3HT-b-P(NDI2OD-T2), has been successfully synthesized via Stille-coupling polymerization, and these p- and n-type blocks containing BCP can be doped using either F4TCNQ or N-DMBI, generating holes or electrons as carriers, respectively. The electrical conductivity of p-doped BCP is 1.4 × 10−3 S·cm−1, whereas, for n-doped BCP, the film conductivity is 1.7 × 10−4 S·cm−1 using the four-probe method. Further, we investigate the Seebeck coefficient of doped BCP, evaluating the potential properties for thermoelectric applications. The analysis results show that the synthesized conjugated BCP can be doped either way to induce holes or electrons from a single composite polymer, and when one block is doped, the other un-doped block has no influence on the electrical conductivity. Accordingly, doping either the p- or n-type phenomenon of a single polymer is demonstrated in this study, realizing a new strategy not only for thermoelectric materials but also for overall organic electric applications.
{"title":"Selective Doping of Conjugated Block Copolymer for Organic Thermoelectric Applications","authors":"Joon-soo Kim, Sung‐Yu Ku, N. Economou, Woongsik Jang, D. H. Wang","doi":"10.1080/15567265.2019.1586804","DOIUrl":"https://doi.org/10.1080/15567265.2019.1586804","url":null,"abstract":"ABSTRACT We demonstrate the selectively p- or n-type doping behavior of conjugated block copolymer (BCP). The poly(3-hexylthiophene)-b-poly{[N,N-9-bis(2-octyldodecyl)-naphtalene-1, 4, 5, 7-bis(dicarboximide)-2,6-diyl]-alt-5,59-(2,29-bithiophene)}, P3HT-b-P(NDI2OD-T2), has been successfully synthesized via Stille-coupling polymerization, and these p- and n-type blocks containing BCP can be doped using either F4TCNQ or N-DMBI, generating holes or electrons as carriers, respectively. The electrical conductivity of p-doped BCP is 1.4 × 10−3 S·cm−1, whereas, for n-doped BCP, the film conductivity is 1.7 × 10−4 S·cm−1 using the four-probe method. Further, we investigate the Seebeck coefficient of doped BCP, evaluating the potential properties for thermoelectric applications. The analysis results show that the synthesized conjugated BCP can be doped either way to induce holes or electrons from a single composite polymer, and when one block is doped, the other un-doped block has no influence on the electrical conductivity. Accordingly, doping either the p- or n-type phenomenon of a single polymer is demonstrated in this study, realizing a new strategy not only for thermoelectric materials but also for overall organic electric applications.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"23 1","pages":"222 - 234"},"PeriodicalIF":4.1,"publicationDate":"2019-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/15567265.2019.1586804","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43987367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-03-14DOI: 10.1080/15567265.2019.1586017
Martí Sala-Casanovas, Anirudh Krishna, Ziqi Yu, Jaeho Lee
ABSTRACT While dynamic photonic materials have attracted much attention and there are well-known examples of color-changing species in nature, dynamic thermal control via modulation of optical properties has made relatively little progress. By replicating unique properties of desert ants and chameleons, here we present a stretchable selective emitter based on corrugated nickel that can modulate the emissivity to provide dynamic thermal control on human bodies. By evaporating nickel on a pre-strained polymer, we create 700-nm periodic corrugations that increase the nickel absorptivity from 0.3 to 0.7 in 0.2–2.5 µm wavelengths due to multiple scattering, as supported by spectroscopy and computations. The optical change is reversible and accompanies ambient surface temperature variations in 305–315 K. We demonstrate a wearable system, and the corrugated nickel on a human body at 309 K allows a heat flux of 62 Wm−2 out of the skin when stretched and 79 Wm−2 into the skin when released.
{"title":"Bio-Inspired Stretchable Selective Emitters Based on Corrugated Nickel for Personal Thermal Management","authors":"Martí Sala-Casanovas, Anirudh Krishna, Ziqi Yu, Jaeho Lee","doi":"10.1080/15567265.2019.1586017","DOIUrl":"https://doi.org/10.1080/15567265.2019.1586017","url":null,"abstract":"ABSTRACT While dynamic photonic materials have attracted much attention and there are well-known examples of color-changing species in nature, dynamic thermal control via modulation of optical properties has made relatively little progress. By replicating unique properties of desert ants and chameleons, here we present a stretchable selective emitter based on corrugated nickel that can modulate the emissivity to provide dynamic thermal control on human bodies. By evaporating nickel on a pre-strained polymer, we create 700-nm periodic corrugations that increase the nickel absorptivity from 0.3 to 0.7 in 0.2–2.5 µm wavelengths due to multiple scattering, as supported by spectroscopy and computations. The optical change is reversible and accompanies ambient surface temperature variations in 305–315 K. We demonstrate a wearable system, and the corrugated nickel on a human body at 309 K allows a heat flux of 62 Wm−2 out of the skin when stretched and 79 Wm−2 into the skin when released.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"23 1","pages":"173 - 187"},"PeriodicalIF":4.1,"publicationDate":"2019-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/15567265.2019.1586017","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46508137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","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：