The bound state in the continuum (BIC) and quasi-BIC are widely used in biosensing, lasers, and nonlinear optics due to their strong abilities of light-limiting and high-Q resonance. Most of the work is dedicated to achieving the goal of static conversion between BIC and quasi-BIC, but lacks sufficient attention to their dynamic continuous manipulation. To alleviate this situation, a type of graphene-metal hybrid metasurfaces for BIC and quasi-BIC of terahertz linearly polarized waves are proposed by combining the tunable properties of graphene with the C 2 asymmetry of the structure. The free continuous modulation can be achieved by the Fermi level driven by an external voltage. The transmission amplitude corresponding to the maximum radiation leakage is 0.13. The quasi-BIC can be actively modulated in the modulation range of 0.13 ~ 0.63, and the modulation depth is as high as 0.5. Based on this, the terahertz dynamic near-field imaging of five "UESTC" images with different contrasts is developed and demonstrated. All the features of the electric field intensity and arrow direction show good imaging results. This work provides a new way for the design of terahertz modulators based on metasurfaces, and enriches the applications of BIC and quasi-BIC.
{"title":"Metal-Graphene Hybrid Terahertz Metasurfaces Based on Bound States in the Continuum (Bic) and Quasi-Bic for Dynamic Near-Field Imaging","authors":"Fuyu Li, Yuanxun Li, Tingting Tang, Yulong Liao, Yongcheng Lu, Rui Peng, Qin Zhang, Xinyan Liu, Yang Luo, S. Wang, Qiye Wen","doi":"10.2139/ssrn.3943843","DOIUrl":"https://doi.org/10.2139/ssrn.3943843","url":null,"abstract":"The bound state in the continuum (BIC) and quasi-BIC are widely used in biosensing, lasers, and nonlinear optics due to their strong abilities of light-limiting and high-Q resonance. Most of the work is dedicated to achieving the goal of static conversion between BIC and quasi-BIC, but lacks sufficient attention to their dynamic continuous manipulation. To alleviate this situation, a type of graphene-metal hybrid metasurfaces for BIC and quasi-BIC of terahertz linearly polarized waves are proposed by combining the tunable properties of graphene with the C 2 asymmetry of the structure. The free continuous modulation can be achieved by the Fermi level driven by an external voltage. The transmission amplitude corresponding to the maximum radiation leakage is 0.13. The quasi-BIC can be actively modulated in the modulation range of 0.13 ~ 0.63, and the modulation depth is as high as 0.5. Based on this, the terahertz dynamic near-field imaging of five \"UESTC\" images with different contrasts is developed and demonstrated. All the features of the electric field intensity and arrow direction show good imaging results. This work provides a new way for the design of terahertz modulators based on metasurfaces, and enriches the applications of BIC and quasi-BIC.","PeriodicalId":10639,"journal":{"name":"Computational Materials Science eJournal","volume":"150 7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83151516","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}
Chuanxiao Cheng, Z. Lai, T. Jin, Zhi-cheng Jing, Wangning Geng, T. Qi, Shiquan Zhu, Jun Zhang, Jian-xiu Liu, Fan Wang, Hongsheng Dong, Lunxiang Zhang
Conceptually a new method to promote rapid nucleation and growth of hydrates was proposed and investigated to deal with the existing condition of complex hydrate growth and nucleation. It is based on self-circulation of tetrafluoroethane boiling-condensation process in enclosed water volume. Under this cyclic system, hydrate formation interface increased from two to four, which included the water–gas tetrafluoroethane, water–liquid tetrafluoroethane, water–bubble, and water–droplet interfaces. A number of nucleation sites provided by bubbles and droplets accompanied by energy disturbance effectively strengthened the hydrate nucleation. Thus, the accumulation of hydrates can be completed efficiently and rapidly by an order of magnitude at non-additive and non-mechanical conditions. The experimental results indicate that 1.703 mol of hydrate was generated within 35 min, and the rate of hydrates increased by 4000 times. Furthermore, the hydrate reformation presented a different nucleation and growth morphology and promoted the hydrate conversion amount. The experiments also obtained the optimum hydrate formation condition by comparing the hydrate conversion amount and induction time at different tested temperatures and thermal stimulation temperatures. Thus, the new method of boiling–condensing has greatly accelerated the application of gas hydrates in cold storage, seawater desalination, and gas separation.
{"title":"Rapid Nucleation and Growth of Tetrafluoroethane Hydrate in the Cyclic Process of Boiling–Condensation","authors":"Chuanxiao Cheng, Z. Lai, T. Jin, Zhi-cheng Jing, Wangning Geng, T. Qi, Shiquan Zhu, Jun Zhang, Jian-xiu Liu, Fan Wang, Hongsheng Dong, Lunxiang Zhang","doi":"10.2139/ssrn.3935554","DOIUrl":"https://doi.org/10.2139/ssrn.3935554","url":null,"abstract":"Conceptually a new method to promote rapid nucleation and growth of hydrates was proposed and investigated to deal with the existing condition of complex hydrate growth and nucleation. It is based on self-circulation of tetrafluoroethane boiling-condensation process in enclosed water volume. Under this cyclic system, hydrate formation interface increased from two to four, which included the water–gas tetrafluoroethane, water–liquid tetrafluoroethane, water–bubble, and water–droplet interfaces. A number of nucleation sites provided by bubbles and droplets accompanied by energy disturbance effectively strengthened the hydrate nucleation. Thus, the accumulation of hydrates can be completed efficiently and rapidly by an order of magnitude at non-additive and non-mechanical conditions. The experimental results indicate that 1.703 mol of hydrate was generated within 35 min, and the rate of hydrates increased by 4000 times. Furthermore, the hydrate reformation presented a different nucleation and growth morphology and promoted the hydrate conversion amount. The experiments also obtained the optimum hydrate formation condition by comparing the hydrate conversion amount and induction time at different tested temperatures and thermal stimulation temperatures. Thus, the new method of boiling–condensing has greatly accelerated the application of gas hydrates in cold storage, seawater desalination, and gas separation.","PeriodicalId":10639,"journal":{"name":"Computational Materials Science eJournal","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73198375","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}
Mayank Baranwal, Lavanya Marla, Carolyn L. Beck, S. Salapaka
We present a novel modeling and algorithmic approach, a Maximum Entropy Principle (MEP) heuristic for Routing and Scheduling, for a large class of problems including the Traveling Salesman Problem (TSP), multiple Traveling Salesmen Problem (mTSP), the Vehicle Routing Problem (VRP) and the Close-Enough Traveling Salesman Problem (CETSP). Our approach models these routing and scheduling problems as ‘equivalent’ facility location problems with side-constraints, and then employs tools from statistical physics for assigning resources (routes/vehicles) to each node (city) such that the resource allocation results in feasible, sub-optimal routes. The approach is very flexible and can incorporate side-constraints such as minimum tour-lengths, capacity constraints, schedule constraints, and reachability constraints (like CETSP). Analytically, our model results in a second-order non-linear system of complex implicit equations; and we show that an iterative approach effectively solves these equations, is equivalent to a gradient descent and converges to a local minimum. While the optimization model is non-linear, the algorithm converges to an integer optimal solution. Computationally, we compare our approach to the Simulated Annealing (SA) heuristic, the CMT-14 benchmark instances for the VRP and randomly generated instances for the CETSP. Our approach consistently outperforms SA for all constrained routing problems. On the CMT-14 benchmark instances, our approach finds the optimal (when verifiable) number of vehicles, with a cumulative tour distance within 5.7% and in comparable computation times of the best-known solutions (over all approaches for each instance). We also demonstrate the efficacy of our approach on randomly generated instances of the CETSP and discuss our results.
{"title":"A Unified Maximum Entropy Principle Approach for a Large Class of Routing Problems","authors":"Mayank Baranwal, Lavanya Marla, Carolyn L. Beck, S. Salapaka","doi":"10.2139/ssrn.3448703","DOIUrl":"https://doi.org/10.2139/ssrn.3448703","url":null,"abstract":"We present a novel modeling and algorithmic approach, a Maximum Entropy Principle (MEP) heuristic for Routing and Scheduling, for a large class of problems including the Traveling Salesman Problem (TSP), multiple Traveling Salesmen Problem (mTSP), the Vehicle Routing Problem (VRP) and the Close-Enough Traveling Salesman Problem (CETSP). Our approach models these routing and scheduling problems as ‘equivalent’ facility location problems with side-constraints, and then employs tools from statistical physics for assigning resources (routes/vehicles) to each node (city) such that the resource allocation results in feasible, sub-optimal routes. The approach is very flexible and can incorporate side-constraints such as minimum tour-lengths, capacity constraints, schedule constraints, and reachability constraints (like CETSP). Analytically, our model results in a second-order non-linear system of complex implicit equations; and we show that an iterative approach effectively solves these equations, is equivalent to a gradient descent and converges to a local minimum. While the optimization model is non-linear, the algorithm converges to an integer optimal solution. Computationally, we compare our approach to the Simulated Annealing (SA) heuristic, the CMT-14 benchmark instances for the VRP and randomly generated instances for the CETSP. Our approach consistently outperforms SA for all constrained routing problems. On the CMT-14 benchmark instances, our approach finds the optimal (when verifiable) number of vehicles, with a cumulative tour distance within 5.7% and in comparable computation times of the best-known solutions (over all approaches for each instance). We also demonstrate the efficacy of our approach on randomly generated instances of the CETSP and discuss our results.","PeriodicalId":10639,"journal":{"name":"Computational Materials Science eJournal","volume":"62 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84979027","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}
J. Poplawsky, R. Pillai, Qing-Qiang Ren, A. Breen, B. Gault, M. Brady
Poor oxidation resistance is a key contributor to material failure within extreme environments. Understanding oxygen solubility is important for computation aided design of new high strength, high-temperature oxidation resistant alloys. Oxygen solubility within pure metals, such as Ni, has been studied using a multitude of techniques, but Atom Probe Tomography (APT) has not been used for such a measurement to date. APT is the only technique offering both a high chemical sensitivity (<10 ppm) and resolution (<1 nm) allowing for a composition measurement within nms of the oxide/metal interface. APT was employed to measure the oxygen content at different depths from the oxide/metal interface as well as grain boundaries for a high and low purity Ni sample oxidized at 1000 °C for 48 hours. The results reveal <10s of ppm oxygen solubility within Ni metal at all depths and 100s of ppm of oxygen within GBs.
{"title":"Measuring Oxygen Solubility in Ni Grains and Boundaries after Oxidation Using Atom Probe Tomography","authors":"J. Poplawsky, R. Pillai, Qing-Qiang Ren, A. Breen, B. Gault, M. Brady","doi":"10.2139/ssrn.3886368","DOIUrl":"https://doi.org/10.2139/ssrn.3886368","url":null,"abstract":"Poor oxidation resistance is a key contributor to material failure within extreme environments. Understanding oxygen solubility is important for computation aided design of new high strength, high-temperature oxidation resistant alloys. Oxygen solubility within pure metals, such as Ni, has been studied using a multitude of techniques, but Atom Probe Tomography (APT) has not been used for such a measurement to date. APT is the only technique offering both a high chemical sensitivity (<10 ppm) and resolution (<1 nm) allowing for a composition measurement within nms of the oxide/metal interface. APT was employed to measure the oxygen content at different depths from the oxide/metal interface as well as grain boundaries for a high and low purity Ni sample oxidized at 1000 °C for 48 hours. The results reveal <10s of ppm oxygen solubility within Ni metal at all depths and 100s of ppm of oxygen within GBs.","PeriodicalId":10639,"journal":{"name":"Computational Materials Science eJournal","volume":"71 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77019157","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}
Jun Gao, D. Fan, Qinghua Chu, Haixia Lyu, Zeng-hong Xie
In this study, a novel surface molecularly imprinted polymer based on zeolitic imidazolate framework (ZIF-7@MIP) was prepared using dibutyl phthalate (DBP) as template via “one-pot” method. The obtained ZIF-7@MIP was characterized by fourier transform infrared spectrometer (FT-IR), energy dispersive spectrum (EDS), scanning electron microscopy (SEM), nitrogen adsorption-desorption and contact angle tester. Compared with the other four adsorbents prepared, ZIF-7@MIP had higher adsorption capacity and selectivity for phthalates (PAEs) owing to combining the high specific surface area and excellent stability of ZIF and the specific recognition of MIP. An analysis method based ZIF-7@MIP coupled with high performance liquid chromatography (HPLC) was established. The linear range was 1-100 μg L-1, and the detection limit range was 0.05-0.8 μg L-1. The spiked recovery rate of PAEs from drinking water, carbonated beverages and fruit juices was 79.05-101.87%, with a relative standard deviation of 0.73-3.37% (n=3). The results indicated that the ZIF-7@MIP could be effectively employed for pretreatment of ultra-trace level of PAEs in food.
{"title":"Fabrication of a Novel Surface Molecularly Imprinted Polymer Based on Zeolitic Imidazolate Framework-7 for Selective Extraction of Phthalates","authors":"Jun Gao, D. Fan, Qinghua Chu, Haixia Lyu, Zeng-hong Xie","doi":"10.2139/ssrn.3932113","DOIUrl":"https://doi.org/10.2139/ssrn.3932113","url":null,"abstract":"In this study, a novel surface molecularly imprinted polymer based on zeolitic imidazolate framework (ZIF-7@MIP) was prepared using dibutyl phthalate (DBP) as template via “one-pot” method. The obtained ZIF-7@MIP was characterized by fourier transform infrared spectrometer (FT-IR), energy dispersive spectrum (EDS), scanning electron microscopy (SEM), nitrogen adsorption-desorption and contact angle tester. Compared with the other four adsorbents prepared, ZIF-7@MIP had higher adsorption capacity and selectivity for phthalates (PAEs) owing to combining the high specific surface area and excellent stability of ZIF and the specific recognition of MIP. An analysis method based ZIF-7@MIP coupled with high performance liquid chromatography (HPLC) was established. The linear range was 1-100 μg L-1, and the detection limit range was 0.05-0.8 μg L-1. The spiked recovery rate of PAEs from drinking water, carbonated beverages and fruit juices was 79.05-101.87%, with a relative standard deviation of 0.73-3.37% (n=3). The results indicated that the ZIF-7@MIP could be effectively employed for pretreatment of ultra-trace level of PAEs in food.","PeriodicalId":10639,"journal":{"name":"Computational Materials Science eJournal","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76033191","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. Dryepondt, P. Nandwana, K. Unocic, R. Kannan, Patxi Fernandez Zelaia, F. List
Extremely fast cooling rates during laser powder-bed fusion (LPBF) can result in materials with unique microstructures. For LPBF 316L stainless steel, the formation of sub-grain cellular structures with high dislocation density has been linked to superior tensile properties at room temperature. This cellular structure offers also a new route for the development of high temperature LPBF steels with the nucleation of nano-size strengthening carbides in the cell walls. HK30Nb steel (Fe-25Cr-20Ni-Nb-C) was, therefore, fabricated by LPBF to evaluate its potential for high temperature applications. Optimization of the fabrication parameters yielded material with density greater than 99.7%, with nano Nb-rich precipitates in the cell walls. Annealing at 800 °C for 5h resulted in the nucleation and growth of additional precipitates mainly in the cell wall and at grain boundaries. The high dislocation density led to yield strength at 20-900 C two to three times higher than yield strength for cast HK30Nb and the nano carbides in the cell walls significantly improved the cellular structure stability at 800 °C.
{"title":"High Temperature High Strength Austenitic Steel Fabricated by Laser Powder-Bed Fusion","authors":"S. Dryepondt, P. Nandwana, K. Unocic, R. Kannan, Patxi Fernandez Zelaia, F. List","doi":"10.2139/ssrn.3885872","DOIUrl":"https://doi.org/10.2139/ssrn.3885872","url":null,"abstract":"Extremely fast cooling rates during laser powder-bed fusion (LPBF) can result in materials with unique microstructures. For LPBF 316L stainless steel, the formation of sub-grain cellular structures with high dislocation density has been linked to superior tensile properties at room temperature. This cellular structure offers also a new route for the development of high temperature LPBF steels with the nucleation of nano-size strengthening carbides in the cell walls. HK30Nb steel (Fe-25Cr-20Ni-Nb-C) was, therefore, fabricated by LPBF to evaluate its potential for high temperature applications. Optimization of the fabrication parameters yielded material with density greater than 99.7%, with nano Nb-rich precipitates in the cell walls. Annealing at 800 °C for 5h resulted in the nucleation and growth of additional precipitates mainly in the cell wall and at grain boundaries. The high dislocation density led to yield strength at 20-900 C two to three times higher than yield strength for cast HK30Nb and the nano carbides in the cell walls significantly improved the cellular structure stability at 800 °C.","PeriodicalId":10639,"journal":{"name":"Computational Materials Science eJournal","volume":"54 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77452341","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. Roy, R. Devanathan, Duane D. Johnson, G. Balasubramanian
Multi-principal element alloys (MPEAs) continue to garner interest due to their remarkable mechanical properties, especially at elevated temperatures. Here, we examine a representative nanocrystalline refractory MPEA and identify a crossover from a Hall-Petch to inverse-Hall-Petch relation. While the considered MPEA predominantly assumes a single-phase BCC lattice, the presence of grain boundaries imparts amorphous phase distributions that increase with decreasing grain size (i.e., increasing grain boundary volume fraction). Using molecular dynamics simulations, we find that the yield strength of the MPEA increases with decreasing average grain size, but below a critical grain size < 23.2 nm the yield strength decreases. This change in the deformation behavior is driven by the transition from dislocation slip to grain-boundary slip as the predominant mechanism. Our results reveal that the change from Hall-Petch to inverse-Hall-Petch regime is correlated to dislocation stacking at the grain boundary when dislocation density reaches a maximum.
{"title":"Grain-Size Effects on the Deformation in Nanocrystalline Multi-Principal Element Alloy","authors":"A. Roy, R. Devanathan, Duane D. Johnson, G. Balasubramanian","doi":"10.2139/ssrn.3797413","DOIUrl":"https://doi.org/10.2139/ssrn.3797413","url":null,"abstract":"Multi-principal element alloys (MPEAs) continue to garner interest due to their remarkable mechanical properties, especially at elevated temperatures. Here, we examine a representative nanocrystalline refractory MPEA and identify a crossover from a Hall-Petch to inverse-Hall-Petch relation. While the considered MPEA predominantly assumes a single-phase BCC lattice, the presence of grain boundaries imparts amorphous phase distributions that increase with decreasing grain size (i.e., increasing grain boundary volume fraction). Using molecular dynamics simulations, we find that the yield strength of the MPEA increases with decreasing average grain size, but below a critical grain size < 23.2 nm the yield strength decreases. This change in the deformation behavior is driven by the transition from dislocation slip to grain-boundary slip as the predominant mechanism. Our results reveal that the change from Hall-Petch to inverse-Hall-Petch regime is correlated to dislocation stacking at the grain boundary when dislocation density reaches a maximum.","PeriodicalId":10639,"journal":{"name":"Computational Materials Science eJournal","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84112874","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}
Yunyun Ji, Fei Fan, Ziyang Zhang, Jierong Cheng, Shengjiang Chang
Liquid crystal (LC) materials are a good candidate for active phase and polarization devices. However, they also encounter significant challenges in the lack of transparent electrodes and the difficulty of LC alignment due to the thick LC cell for sub-mm wavelength in the terahertz (THz) regime. Here, we presented a strategy to overcome these difficulties, that is, using a super-aligned carbon nanotube (CNT) film with dual functions for both transparent electrodes and the aligning layer for THz LC cell. The LC molecules are uniformly aligned along the orientation direction of the CNT film because of its surface anchoring effect. The experiment results show that the active THz polarization conversions are controlled by the bias voltage tuning from 0 to 30 V between the upper and lower CNT films, and the output polarization state is converted between linear polarization and circular polarization. This work may pave a simple and flexible path toward the development of various active THz liquid crystal devices for spatial light modulation, dynamic imaging, and wavefront control.
{"title":"Active Terahertz Liquid Crystal Device with Carbon Nanotube Film as Both Alignment Layer and Transparent Electrodes","authors":"Yunyun Ji, Fei Fan, Ziyang Zhang, Jierong Cheng, Shengjiang Chang","doi":"10.2139/ssrn.3943844","DOIUrl":"https://doi.org/10.2139/ssrn.3943844","url":null,"abstract":"Liquid crystal (LC) materials are a good candidate for active phase and polarization devices. However, they also encounter significant challenges in the lack of transparent electrodes and the difficulty of LC alignment due to the thick LC cell for sub-mm wavelength in the terahertz (THz) regime. Here, we presented a strategy to overcome these difficulties, that is, using a super-aligned carbon nanotube (CNT) film with dual functions for both transparent electrodes and the aligning layer for THz LC cell. The LC molecules are uniformly aligned along the orientation direction of the CNT film because of its surface anchoring effect. The experiment results show that the active THz polarization conversions are controlled by the bias voltage tuning from 0 to 30 V between the upper and lower CNT films, and the output polarization state is converted between linear polarization and circular polarization. This work may pave a simple and flexible path toward the development of various active THz liquid crystal devices for spatial light modulation, dynamic imaging, and wavefront control.","PeriodicalId":10639,"journal":{"name":"Computational Materials Science eJournal","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81731074","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}
Pola Shriber, M. Tkachev, Ayelet Atkins, I. Perelshtein, S. Bretler, B. Schmerling, G. Mariotto, M. Giarola, Y. Fleger, G. D. Nessim
Similarly to other transition metal sulfides, nickel sulfide nanocrystals can be potentially used for functional device applications. However, controlling morphology and stoichiometry to target specific applications is a synthesis challenge. In this work we developed a rapid, one-step, chemical vapor deposition synthesis of nickel sulfide dendritic nanostructures with fractal geometry. Microtome-EDS compositional analysis of the mature crystal indicates a trend of decreasing sulfur and increasing nickel concentration towards the tip of the mature crystals. Following thorough investigation of these nanocrystals at different stages of their nucleation and growth by means of XRD, HR-SEM, HR-TEM, and Raman spectroscopy, we suggest possible kinetic mechanisms for the crystal formation and development. This work contributes to the understanding of growth mechanisms of dendritic structures with complex morphology.
{"title":"Synthesis of Nickel Sulfide Dendrites from Nickel Foil Using Thermal Annealing","authors":"Pola Shriber, M. Tkachev, Ayelet Atkins, I. Perelshtein, S. Bretler, B. Schmerling, G. Mariotto, M. Giarola, Y. Fleger, G. D. Nessim","doi":"10.2139/ssrn.3935489","DOIUrl":"https://doi.org/10.2139/ssrn.3935489","url":null,"abstract":"Similarly to other transition metal sulfides, nickel sulfide nanocrystals can be potentially used for functional device applications. However, controlling morphology and stoichiometry to target specific applications is a synthesis challenge. In this work we developed a rapid, one-step, chemical vapor deposition synthesis of nickel sulfide dendritic nanostructures with fractal geometry. Microtome-EDS compositional analysis of the mature crystal indicates a trend of decreasing sulfur and increasing nickel concentration towards the tip of the mature crystals. Following thorough investigation of these nanocrystals at different stages of their nucleation and growth by means of XRD, HR-SEM, HR-TEM, and Raman spectroscopy, we suggest possible kinetic mechanisms for the crystal formation and development. This work contributes to the understanding of growth mechanisms of dendritic structures with complex morphology.","PeriodicalId":10639,"journal":{"name":"Computational Materials Science eJournal","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75555137","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. F. Andreoli, Rafael G Mendes, V. Witusiewicz, O. Shuleshova, M. V. van Huis, K. Nielsch, I. Kaban
Time- and temperature-resolved phase formation in the equiatomic NbTiVZr refractory high-entropy alloy has been studied in situ using high-energy synchrotron X-ray diffraction and high-speed video imaging during non-equilibrium solidification. Phase formation upon solidification is shown to be dependent on the processing conditions. When the melt is undercooled over 80 K it crystallizes as a bcc single-phase solid solution despite solute partitioning between dendrites and interdendritic regions. When the sample is for some time kept in the semisolid state, two additional bcc phases form in the interdendritic regions. The crystal growth velocity, as estimated from the high-speed videos, shows pronounced sluggish kinetics compared to the literature data of other medium- and high-entropy alloys.
{"title":"Phase Constitution and Microstructure of the NbTiVZr Refractory High-Entropy Alloy Solidified Upon Different Processing","authors":"A. F. Andreoli, Rafael G Mendes, V. Witusiewicz, O. Shuleshova, M. V. van Huis, K. Nielsch, I. Kaban","doi":"10.2139/ssrn.3885870","DOIUrl":"https://doi.org/10.2139/ssrn.3885870","url":null,"abstract":"Time- and temperature-resolved phase formation in the equiatomic NbTiVZr refractory high-entropy alloy has been studied in situ using high-energy synchrotron X-ray diffraction and high-speed video imaging during non-equilibrium solidification. Phase formation upon solidification is shown to be dependent on the processing conditions. When the melt is undercooled over 80 K it crystallizes as a bcc single-phase solid solution despite solute partitioning between dendrites and interdendritic regions. When the sample is for some time kept in the semisolid state, two additional bcc phases form in the interdendritic regions. The crystal growth velocity, as estimated from the high-speed videos, shows pronounced sluggish kinetics compared to the literature data of other medium- and high-entropy alloys.","PeriodicalId":10639,"journal":{"name":"Computational Materials Science eJournal","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81699733","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}
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