Highly efficient electrocatalysts for the hydrogen evolution reaction (HER) are essential for sustainable hydrogen energy. The controllable production of hydrogen energy by water decomposition depends heavily on the catalyst, and it is extremely important to seek sustainable and highly efficient water-splitting electrocatalysts for energy applications. Herein, bimetallic RuYO2−x nanoparticles (Ru: 8.84 at.% and Y: 13 at.%) with high densities and low loadings were synthesized and anchored on graphene through a simple solvothermal strategy by synthesizing hydrogen yttrium ketone (HxYO2−x) serving as an inserted medium. Electron microscopy demonstrated that the RuYO2−x/C was composed of densely arranged particles and graphene flakes. Electrochemical results showed that the RuYO2−x/C had a remarkably low overpotential of η10 = 56 mV at a current density of 10 mA cm−2 in alkaline media, a Tafel slope of 63.18 mV dec−1, and 24 h of stability. The oxygen vacancies of RuYO2−x/C provided a large proton storage capacity and a strong tendency to bind hydrogen atoms. DFT calculations showed that RuYO2−x/C catalysts with more Ru-O-Y bonds and VO dramatically decreased the energy barrier for breaking H-OH bonds. Moreover, the robust metal-support interactions provided optimized energies for hydrogen adsorption and desorption, which explained the high activity and favorable kinetics for RuYO2−x/C catalytic hydrogen precipitation in alkaline electrolyte reactions. This work presents a hydrogen insertion method for the preparation of low-loading, high-density, high-performance and stable water decomposition catalysts for hydrogen production. We present a strategy for significantly increasing the H contents on catalysts for the HER in alkaline electrolyte solutions, which were generated by combining ruthenium with HxYO2−x on an oxygen vacancy-rich graphene system. This strategy greatly increased the hydrogen coverage on the RuYO2−x/C catalyst to enhance the HER performance.
{"title":"Implanting HxYO2−x sites into Ru-doped graphene and oxygen vacancies for low-overpotential alkaline hydrogen evolution","authors":"Xiang Li, Wei Deng, Yun Weng, Jingjing Zhang, Haifang Mao, Tiandong Lu, Wenqian Zhang, Renqiang Yang, Fei Jiang","doi":"10.1038/s41427-023-00501-z","DOIUrl":"10.1038/s41427-023-00501-z","url":null,"abstract":"Highly efficient electrocatalysts for the hydrogen evolution reaction (HER) are essential for sustainable hydrogen energy. The controllable production of hydrogen energy by water decomposition depends heavily on the catalyst, and it is extremely important to seek sustainable and highly efficient water-splitting electrocatalysts for energy applications. Herein, bimetallic RuYO2−x nanoparticles (Ru: 8.84 at.% and Y: 13 at.%) with high densities and low loadings were synthesized and anchored on graphene through a simple solvothermal strategy by synthesizing hydrogen yttrium ketone (HxYO2−x) serving as an inserted medium. Electron microscopy demonstrated that the RuYO2−x/C was composed of densely arranged particles and graphene flakes. Electrochemical results showed that the RuYO2−x/C had a remarkably low overpotential of η10 = 56 mV at a current density of 10 mA cm−2 in alkaline media, a Tafel slope of 63.18 mV dec−1, and 24 h of stability. The oxygen vacancies of RuYO2−x/C provided a large proton storage capacity and a strong tendency to bind hydrogen atoms. DFT calculations showed that RuYO2−x/C catalysts with more Ru-O-Y bonds and VO dramatically decreased the energy barrier for breaking H-OH bonds. Moreover, the robust metal-support interactions provided optimized energies for hydrogen adsorption and desorption, which explained the high activity and favorable kinetics for RuYO2−x/C catalytic hydrogen precipitation in alkaline electrolyte reactions. This work presents a hydrogen insertion method for the preparation of low-loading, high-density, high-performance and stable water decomposition catalysts for hydrogen production. We present a strategy for significantly increasing the H contents on catalysts for the HER in alkaline electrolyte solutions, which were generated by combining ruthenium with HxYO2−x on an oxygen vacancy-rich graphene system. This strategy greatly increased the hydrogen coverage on the RuYO2−x/C catalyst to enhance the HER performance.","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":"15 1","pages":"1-14"},"PeriodicalIF":8.6,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41427-023-00501-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135566807","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-13DOI: 10.1038/s41427-023-00502-y
Dongjoon Shin, Seunghoon Chae, Seonghyun Park, Byungseok Seo, Wonjoon Choi
High-entropy oxides (HEOs) are promising conversion-type anode materials for Li-ion batteries (LIBs) owing to their excellent cycling stabilities and rate capabilities. However, the conventional syntheses and screening processes are time-consuming and complex and require phase and interfacial segregation of individual elements. Herein, we report a rational screening strategy for LIB anodes using precisely tunable HEOs fabricated by one-step combustion syntheses with different fuel-to-oxidizer ratios (φ). A slightly lean fuel mixture (φ-0.95) enabled a suitable temperature and non-reducing atmosphere for optimal HEO syntheses. This provided high crystallinity, perfectly homogeneous elemental distributions, and adequate pore structures without selective precipitation, whereas lower or higher fuel-to-oxidizer ratios resulted in excessively porous morphologies or elemental segregation. HEO-based anodes with φ-0.95 exhibited outstanding specific capacities (1165 mAh g−1, 80.9% retention at 0.1 A g−1, and 791 mAh g−1 even at 3 A g−1), excellent rate capabilities, and stable cycling lifetimes (1252 mAh g−1, 80.9% retention after 100 cycles at 0.2 A g−1). This design strategy will provide fascinating HEO electrodes that cannot be prepared with conventional fabrication methods. Precisely tunable high-entropy oxides (HEO) via controllable one-step combustion within a few seconds offers the rational design capability of optimal phases, structures and configurational entropy. The screened HEO-based anodes exhibit outstanding specific capacity (1165 mAh g−1, 80.9% retention at 0.1 A g−1, and 791 mAh g−1 even at 3 A g−1), excellent rate capability, and stable cycling life (1252 mAh g−1, 80.9% retention after 100 cycles at 0.2 A g−1).
高熵氧化物（HEOs）具有良好的循环稳定性和倍率性能，是锂离子电池（LIBs）极有前途的转换型负极材料。然而，传统的合成和筛选过程耗时且复杂，并且需要对单个元素进行相分离和界面分离。在此，我们报告了一种合理的筛选策略，使用一步燃烧合成的具有不同燃料-氧化剂比（φ）的精确可调谐HEOs来筛选锂离子电池阳极。稍稀薄的燃料混合物（φ-0.95）为最佳的HEO合成提供了合适的温度和非还原气氛。这提供了高结晶度、完全均匀的元素分布和足够的孔隙结构，没有选择性沉淀，而较低或较高的燃料与氧化剂比会导致过度多孔形态或元素偏析。φ-0.95的heo基阳极具有出色的比容量（1165 mAh g−1，在0.1 A g−1下保持80.9%，在3 A g−1下保持791 mAh g−1），优异的倍率能力和稳定的循环寿命（1252 mAh g−1，在0.2 A g−1下循环100次后保持80.9%）。这种设计策略将提供传统制造方法无法制备的令人着迷的HEO电极。高熵氧化物（HEO）通过可控的一步燃烧在几秒钟内精确可调，提供了优化相、结构和构型熵的合理设计能力。所筛选的heo基阳极具有出色的比容量（1165 mAh g−1，在0.1 A g−1下保持80.9%，在3 A g−1下保持791 mAh g−1），优异的倍率能力和稳定的循环寿命（1252 mAh g−1，在0.2 A g−1下循环100次后保持80.9%）。
{"title":"Rational engineering of high-entropy oxides for Li-ion battery anodes with finely tuned combustion syntheses","authors":"Dongjoon Shin, Seunghoon Chae, Seonghyun Park, Byungseok Seo, Wonjoon Choi","doi":"10.1038/s41427-023-00502-y","DOIUrl":"10.1038/s41427-023-00502-y","url":null,"abstract":"High-entropy oxides (HEOs) are promising conversion-type anode materials for Li-ion batteries (LIBs) owing to their excellent cycling stabilities and rate capabilities. However, the conventional syntheses and screening processes are time-consuming and complex and require phase and interfacial segregation of individual elements. Herein, we report a rational screening strategy for LIB anodes using precisely tunable HEOs fabricated by one-step combustion syntheses with different fuel-to-oxidizer ratios (φ). A slightly lean fuel mixture (φ-0.95) enabled a suitable temperature and non-reducing atmosphere for optimal HEO syntheses. This provided high crystallinity, perfectly homogeneous elemental distributions, and adequate pore structures without selective precipitation, whereas lower or higher fuel-to-oxidizer ratios resulted in excessively porous morphologies or elemental segregation. HEO-based anodes with φ-0.95 exhibited outstanding specific capacities (1165 mAh g−1, 80.9% retention at 0.1 A g−1, and 791 mAh g−1 even at 3 A g−1), excellent rate capabilities, and stable cycling lifetimes (1252 mAh g−1, 80.9% retention after 100 cycles at 0.2 A g−1). This design strategy will provide fascinating HEO electrodes that cannot be prepared with conventional fabrication methods. Precisely tunable high-entropy oxides (HEO) via controllable one-step combustion within a few seconds offers the rational design capability of optimal phases, structures and configurational entropy. The screened HEO-based anodes exhibit outstanding specific capacity (1165 mAh g−1, 80.9% retention at 0.1 A g−1, and 791 mAh g−1 even at 3 A g−1), excellent rate capability, and stable cycling life (1252 mAh g−1, 80.9% retention after 100 cycles at 0.2 A g−1).","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":"15 1","pages":"1-14"},"PeriodicalIF":8.6,"publicationDate":"2023-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41427-023-00502-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135805511","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-13DOI: 10.1038/s41427-023-00500-0
Yangbo Dong, Danyang Feng, Wei Li, Rui Zhang, Shuzhen Dou, Luoqi Wang, Yan Yang, Li Wang, Yang Yang, Feng Wei, Zhen-An Qiao
Gradient porous structures enable the fast capillary-directed mass transport and enhance the chemical reaction rate with optimal efficiency and minimal energy consumption. Rational design and facile synthesis of functional mesoporous materials with sheet structure and gradient mesopores still face challenges of stacked structures and unadjustable pore sizes. Herein, an interfacial co-assembly strategy for gradient mesoporous hollow silica sheets is reported. The modulated oil-water interface allows the assembly of gradient mesoporous silica layers on the water-removable ammonium sulfate crystals. The obtained mesoporous silica layers possess narrow pore size distributions (~2.2 nm and ~6.6 nm). Owing to the good mono-dispersity, sheet structure and proper pore size, the designed gradient mesoporous hollow silica sheets can serve as flexible building blocks for fabricating nanoscale molecule filtration device. Experiments reveal that the obtained nanofiltration device shows remarkable gradient rejection rates (range from 23.5 to 99.9%) for molecules with different sizes (range from 1.2 to 4.4 nm). An interfacial co-assembly strategy for synthesizing gradient mesoporous hollow silica sheets is reported. The SO42− and NH4+ were aggregated by protonated amphiphilic polymer PVP and formed (NH4)2SO4 crystals at the n-pentanol-water interface. Negatively charged silica oligomers can be confined on the (NH4)2SO4 crystal surface by the Coulomb interaction of NH4+ and co-assembled with CTAB under the catalysis of ammonia molecules. After removing the (NH4)2SO4 cores and CTAB template by washing and extraction, the first layer of mesoporous hollow silica was formed. Modulating the n-pentanol-water interface to n-hexane-water interface, n-hexane swelled CTAB micelle co-assembled with silica oligomers and formed the second layer of mesoporous silica with larger pore size. The finally obtained gradient mesoporous silica sheet shows remarkable gradient rejection rates for molecules with different sizes.
{"title":"Interfacial co-assembly strategy towards gradient mesoporous hollow sheet for molecule filtration","authors":"Yangbo Dong, Danyang Feng, Wei Li, Rui Zhang, Shuzhen Dou, Luoqi Wang, Yan Yang, Li Wang, Yang Yang, Feng Wei, Zhen-An Qiao","doi":"10.1038/s41427-023-00500-0","DOIUrl":"10.1038/s41427-023-00500-0","url":null,"abstract":"Gradient porous structures enable the fast capillary-directed mass transport and enhance the chemical reaction rate with optimal efficiency and minimal energy consumption. Rational design and facile synthesis of functional mesoporous materials with sheet structure and gradient mesopores still face challenges of stacked structures and unadjustable pore sizes. Herein, an interfacial co-assembly strategy for gradient mesoporous hollow silica sheets is reported. The modulated oil-water interface allows the assembly of gradient mesoporous silica layers on the water-removable ammonium sulfate crystals. The obtained mesoporous silica layers possess narrow pore size distributions (~2.2 nm and ~6.6 nm). Owing to the good mono-dispersity, sheet structure and proper pore size, the designed gradient mesoporous hollow silica sheets can serve as flexible building blocks for fabricating nanoscale molecule filtration device. Experiments reveal that the obtained nanofiltration device shows remarkable gradient rejection rates (range from 23.5 to 99.9%) for molecules with different sizes (range from 1.2 to 4.4 nm). An interfacial co-assembly strategy for synthesizing gradient mesoporous hollow silica sheets is reported. The SO42− and NH4+ were aggregated by protonated amphiphilic polymer PVP and formed (NH4)2SO4 crystals at the n-pentanol-water interface. Negatively charged silica oligomers can be confined on the (NH4)2SO4 crystal surface by the Coulomb interaction of NH4+ and co-assembled with CTAB under the catalysis of ammonia molecules. After removing the (NH4)2SO4 cores and CTAB template by washing and extraction, the first layer of mesoporous hollow silica was formed. Modulating the n-pentanol-water interface to n-hexane-water interface, n-hexane swelled CTAB micelle co-assembled with silica oligomers and formed the second layer of mesoporous silica with larger pore size. The finally obtained gradient mesoporous silica sheet shows remarkable gradient rejection rates for molecules with different sizes.","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":"15 1","pages":"1-8"},"PeriodicalIF":8.6,"publicationDate":"2023-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41427-023-00500-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135806023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-06DOI: 10.1038/s41427-023-00496-7
Guangyang Dai, Yating Jia, Bo Gao, Yi Peng, Jianfa Zhao, Yanming Ma, Changfeng Chen, Jinlong Zhu, Quan Li, Runze Yu, Changqing Jin
Recently, topological insulators (TIs) KHgX (X = As, Sb, Bi) with hourglass-shaped dispersion have attracted great interest. Different from the TIs protected by either time-reversal or mirror crystal symmorphic symmetry tested in previous experiments, these materials were proposed as the first material class whose band topology relies on nonsymmorphic symmetries. As a result, KHgX shows many exotic properties, such as hourglass-shaped electronic channels and three-dimensional doubled quantum spin Hall effects. To date, high-pressure experimental studies on these nonsymmorphic TIs are minimal. Here, we carried out high-pressure electrical measurements up to 55 GPa, together with high-pressure X-ray diffraction measurements and high-pressure structure prediction on KHgAs. We found a pressure-induced semiconductor-metal transition between ~16 and 20 GPa, followed by the appearance of superconductivity with a Tc of ~3.5 K at approximately 21 GPa. The superconducting transition temperature was enhanced to a maximum of ~6.6 K at 31.8 GPa and then slowly decreased until 55 GPa. Furthermore, three high-pressure phases within 55 GPa were observed, and their crystal structures were established. Our results showed the high-pressure phase diagram of KHgAs and determined the pressure-induced superconductivity in nonsymmorphic TIs. Thus, our study can be used to facilitate further research on superconductivity and topologically nontrivial features protected by nonsymmorphic symmetries. We observed a pressure-induced semiconductor-metal transition, which was followed by the emergence of superconductivity in the nonsymmorphic topological insulator KHgAs. The superconducting transition temperature reaches a maximum of approximately 6.6 K at 31.8 GPa, after which it slightly decreases up to 55 GPa. We identified the pressure-induced phase transitions and determined the structures of three high-pressure phases of KHgAs through structure prediction. Our findings establish the high-pressure phase diagram of the hourglass fermion compound KHgAs and demonstrate the potential coexistence of superconductivity with a topologically nontrivial feature protected by nonsymmorphic symmetries.
{"title":"Pressure-induced superconductivity in the nonsymmorphic topological insulator KHgAs","authors":"Guangyang Dai, Yating Jia, Bo Gao, Yi Peng, Jianfa Zhao, Yanming Ma, Changfeng Chen, Jinlong Zhu, Quan Li, Runze Yu, Changqing Jin","doi":"10.1038/s41427-023-00496-7","DOIUrl":"10.1038/s41427-023-00496-7","url":null,"abstract":"Recently, topological insulators (TIs) KHgX (X = As, Sb, Bi) with hourglass-shaped dispersion have attracted great interest. Different from the TIs protected by either time-reversal or mirror crystal symmorphic symmetry tested in previous experiments, these materials were proposed as the first material class whose band topology relies on nonsymmorphic symmetries. As a result, KHgX shows many exotic properties, such as hourglass-shaped electronic channels and three-dimensional doubled quantum spin Hall effects. To date, high-pressure experimental studies on these nonsymmorphic TIs are minimal. Here, we carried out high-pressure electrical measurements up to 55 GPa, together with high-pressure X-ray diffraction measurements and high-pressure structure prediction on KHgAs. We found a pressure-induced semiconductor-metal transition between ~16 and 20 GPa, followed by the appearance of superconductivity with a Tc of ~3.5 K at approximately 21 GPa. The superconducting transition temperature was enhanced to a maximum of ~6.6 K at 31.8 GPa and then slowly decreased until 55 GPa. Furthermore, three high-pressure phases within 55 GPa were observed, and their crystal structures were established. Our results showed the high-pressure phase diagram of KHgAs and determined the pressure-induced superconductivity in nonsymmorphic TIs. Thus, our study can be used to facilitate further research on superconductivity and topologically nontrivial features protected by nonsymmorphic symmetries. We observed a pressure-induced semiconductor-metal transition, which was followed by the emergence of superconductivity in the nonsymmorphic topological insulator KHgAs. The superconducting transition temperature reaches a maximum of approximately 6.6 K at 31.8 GPa, after which it slightly decreases up to 55 GPa. We identified the pressure-induced phase transitions and determined the structures of three high-pressure phases of KHgAs through structure prediction. Our findings establish the high-pressure phase diagram of the hourglass fermion compound KHgAs and demonstrate the potential coexistence of superconductivity with a topologically nontrivial feature protected by nonsymmorphic symmetries.","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":"15 1","pages":"1-8"},"PeriodicalIF":8.6,"publicationDate":"2023-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41427-023-00496-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135303754","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nd-Fe-B-based permanent magnets are widely used for energy conversion applications. However, their usage at elevated temperatures is difficult due to the relatively low coercivity (Hc) with respect to the anisotropy field (HA) of the Nd2Fe14B compound, which is typically 0.2HA. In this work, we found that the coercivity of an (Nd0.8Dy0.2)-Fe-B sintered magnet could reach 0.4HA, which was twice as high as the Hc/HA of its Dy-free counterpart. Detailed microstructural characterizations, density functional theory and micromagnetic simulations showed that the large value of coercivity, Hc = 0.4HA, originated not only from the enhanced HA of the main phase (intrinsic factor) but also from the reduced magnetization of the thin intergranular phase (extrinsic factor). The latter was attributed to the dissolution of 4 at.% Dy in the intergranular phase that anti-ferromagnetically coupled with Fe. The reduction in the magnetization of the intergranular phase resulted in a change in the angular dependence of coercivity from the Kondorsky type for the Dy-free magnet to the Stoner–Wohlfarth-like shape for the Dy-containing magnet, indicating that the typical pinning-controlled coercivity mechanism began to show nucleation features as the magnetization of the intergranular phase was reduced by Dy substitution. The low coercivity in Nd-Fe-B-based magnets, which is limited to around 20% of the anisotropy field (HA) of the main phase, is a bottleneck for their usage at elevated temperatures. Herein, we overcome the limit and demonstrate a coercivity of 40% HA by tuning the magnetism of grain boundaries, enabling their applications at elevated temperatures.
{"title":"Unveiling the origin of the large coercivity in (Nd, Dy)-Fe-B sintered magnets","authors":"Xin Tang, Jiangnan Li, Hossein Sepehri-Amin, Anton Bolyachkin, Andres Martin-Cid, Shintaro Kobayashi, Yoshinori Kotani, Motohiro Suzuki, Asako Terasawa, Yoshihiro Gohda, Tadakatsu Ohkubo, Tetsuya Nakamura, Kazuhiro Hono","doi":"10.1038/s41427-023-00498-5","DOIUrl":"10.1038/s41427-023-00498-5","url":null,"abstract":"Nd-Fe-B-based permanent magnets are widely used for energy conversion applications. However, their usage at elevated temperatures is difficult due to the relatively low coercivity (Hc) with respect to the anisotropy field (HA) of the Nd2Fe14B compound, which is typically 0.2HA. In this work, we found that the coercivity of an (Nd0.8Dy0.2)-Fe-B sintered magnet could reach 0.4HA, which was twice as high as the Hc/HA of its Dy-free counterpart. Detailed microstructural characterizations, density functional theory and micromagnetic simulations showed that the large value of coercivity, Hc = 0.4HA, originated not only from the enhanced HA of the main phase (intrinsic factor) but also from the reduced magnetization of the thin intergranular phase (extrinsic factor). The latter was attributed to the dissolution of 4 at.% Dy in the intergranular phase that anti-ferromagnetically coupled with Fe. The reduction in the magnetization of the intergranular phase resulted in a change in the angular dependence of coercivity from the Kondorsky type for the Dy-free magnet to the Stoner–Wohlfarth-like shape for the Dy-containing magnet, indicating that the typical pinning-controlled coercivity mechanism began to show nucleation features as the magnetization of the intergranular phase was reduced by Dy substitution. The low coercivity in Nd-Fe-B-based magnets, which is limited to around 20% of the anisotropy field (HA) of the main phase, is a bottleneck for their usage at elevated temperatures. Herein, we overcome the limit and demonstrate a coercivity of 40% HA by tuning the magnetism of grain boundaries, enabling their applications at elevated temperatures.","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":"15 1","pages":"1-13"},"PeriodicalIF":8.6,"publicationDate":"2023-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41427-023-00498-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135132513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-29DOI: 10.1038/s41427-023-00499-4
Sudip Majumder, J. L. Drobitch, Supriyo Bandyopadhyay, Anjan Barman
We observed strong tripartite magnon-phonon-magnon coupling in a two-dimensional periodic array of magnetostrictive nanomagnets deposited on a piezoelectric substrate, forming a 2D magnetoelastic “crystal”; the coupling occurred between two Kittel-type spin wave (magnon) modes and a (non-Kittel) magnetoelastic spin wave mode caused by a surface acoustic wave (SAW) (phonons). The strongest coupling occurred when the frequencies and wavevectors of the three modes matched, leading to perfect phase matching. We achieved this condition by carefully engineering the frequency of the SAW, the nanomagnet dimensions and the bias magnetic field that determined the frequencies of the two Kittel-type modes. The strong coupling (cooperativity factor exceeding unity) led to the formation of a new quasi-particle, called a binary magnon-polaron, accompanied by nearly complete (~100%) transfer of energy from the magnetoelastic mode to the two Kittel-type modes. This coupling phenomenon exhibited significant anisotropy since the array did not have rotational symmetry in space. The experimental observations were in good agreement with the theoretical simulations. This article reveals a study on magnon-phonon coupling in two-dimensional artificial magneto-elastic crystals. Researchers fabricated a 2D periodic array of magnetostrictive nanomagnets on a piezoelectric substrate and observed strong tripartite coupling involving two magnons and a phonon. This coupling transfers all or nearly all of the power from a magneto-elastic mode caused by surface acoustic waves (SAWs) to two Kittel-type spin wave modes. The findings highlight the importance of engineering SAW frequency, magnetic field, and nanomagnet dimensions to ensure near-perfect phase matching between all modes. This discovery could pave the way for future developments in energy-efficient computing, communications, and data storage. A two-dimensional array of magnetostrictive nanomagnets was used to demonstrate strong coupling between two different magnons (kM1′ and kM1′′) mediated by a phonon (kph). The coupling is strong, leading to the formation of a new quasi-particle – binary magnon-polaron. These two different magnons show 180° phase difference which is reminiscent of dark magnon modes. We show that it is possible to engineer this magnon-phonon coupling by choosing the frequency and wavelength of the acoustic wave to match the frequency and wavelength of the spin wave, the latter being controlled by a magnetic field.
{"title":"Formation of binary magnon polaron in a two-dimensional artificial magneto-elastic crystal","authors":"Sudip Majumder, J. L. Drobitch, Supriyo Bandyopadhyay, Anjan Barman","doi":"10.1038/s41427-023-00499-4","DOIUrl":"10.1038/s41427-023-00499-4","url":null,"abstract":"We observed strong tripartite magnon-phonon-magnon coupling in a two-dimensional periodic array of magnetostrictive nanomagnets deposited on a piezoelectric substrate, forming a 2D magnetoelastic “crystal”; the coupling occurred between two Kittel-type spin wave (magnon) modes and a (non-Kittel) magnetoelastic spin wave mode caused by a surface acoustic wave (SAW) (phonons). The strongest coupling occurred when the frequencies and wavevectors of the three modes matched, leading to perfect phase matching. We achieved this condition by carefully engineering the frequency of the SAW, the nanomagnet dimensions and the bias magnetic field that determined the frequencies of the two Kittel-type modes. The strong coupling (cooperativity factor exceeding unity) led to the formation of a new quasi-particle, called a binary magnon-polaron, accompanied by nearly complete (~100%) transfer of energy from the magnetoelastic mode to the two Kittel-type modes. This coupling phenomenon exhibited significant anisotropy since the array did not have rotational symmetry in space. The experimental observations were in good agreement with the theoretical simulations. This article reveals a study on magnon-phonon coupling in two-dimensional artificial magneto-elastic crystals. Researchers fabricated a 2D periodic array of magnetostrictive nanomagnets on a piezoelectric substrate and observed strong tripartite coupling involving two magnons and a phonon. This coupling transfers all or nearly all of the power from a magneto-elastic mode caused by surface acoustic waves (SAWs) to two Kittel-type spin wave modes. The findings highlight the importance of engineering SAW frequency, magnetic field, and nanomagnet dimensions to ensure near-perfect phase matching between all modes. This discovery could pave the way for future developments in energy-efficient computing, communications, and data storage. A two-dimensional array of magnetostrictive nanomagnets was used to demonstrate strong coupling between two different magnons (kM1′ and kM1′′) mediated by a phonon (kph). The coupling is strong, leading to the formation of a new quasi-particle – binary magnon-polaron. These two different magnons show 180° phase difference which is reminiscent of dark magnon modes. We show that it is possible to engineer this magnon-phonon coupling by choosing the frequency and wavelength of the acoustic wave to match the frequency and wavelength of the spin wave, the latter being controlled by a magnetic field.","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":"15 1","pages":"1-11"},"PeriodicalIF":8.6,"publicationDate":"2023-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41427-023-00499-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135132931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-22DOI: 10.1038/s41427-023-00497-6
Tumesh Kumar Sahu, Saroj Pratap Sahu, K. P. S. S. Hembram, Jae-Kap Lee, Vasudevanpillai Biju, Prashant Kumar
Two-dimensional gallium nitride (2D GaN) with a large direct bandgap of ~5.3 eV, a high melting temperature of ~2500 °C, and a large Young’s modulus ~20 GPa developed for miniaturized interactive electronic gadgets can function at high thermal and mechanical loading conditions. Having various electronic, optoelectronic, spintronic, energy storage devices and sensors in perspective and the robust nature of 2D GaN, it is highly imperative to explore new pathways for its synthesis. Moreover, free-standing sheets will be desirable for large-area applications. We report our discovery of the synthesis of free-standing 2D GaN atomic sheets employing sonochemical exfoliation and the modified Hummers method. Exfoliated 2D GaN atomic sheets exhibit hexagonal and striped phases with microscale lateral dimensions and excellent chemical phase purity, confirmed by Raman and X-ray photoelectron spectroscopy. 2D GaN is highly stable, as confirmed by TGA measurements. While photodiode, FET, spintronics, and SERS-based molecular sensing, IRS element in 6G wireless communication applications of 2D GaN have been demonstrated, its nanocomposite with PVDF exhibits an excellent thermoplastic and piezoelectric behavior. The photodiode, FET, spintronic, piezoelectric, thermoplastic and molecular sensing applications of free-standing 2D GaN synthesized by sonochemical and Hummer’s method.
{"title":"Free-standing 2D gallium nitride for electronic, excitonic, spintronic, piezoelectric, thermoplastic, and 6G wireless communication applications","authors":"Tumesh Kumar Sahu, Saroj Pratap Sahu, K. P. S. S. Hembram, Jae-Kap Lee, Vasudevanpillai Biju, Prashant Kumar","doi":"10.1038/s41427-023-00497-6","DOIUrl":"10.1038/s41427-023-00497-6","url":null,"abstract":"Two-dimensional gallium nitride (2D GaN) with a large direct bandgap of ~5.3 eV, a high melting temperature of ~2500 °C, and a large Young’s modulus ~20 GPa developed for miniaturized interactive electronic gadgets can function at high thermal and mechanical loading conditions. Having various electronic, optoelectronic, spintronic, energy storage devices and sensors in perspective and the robust nature of 2D GaN, it is highly imperative to explore new pathways for its synthesis. Moreover, free-standing sheets will be desirable for large-area applications. We report our discovery of the synthesis of free-standing 2D GaN atomic sheets employing sonochemical exfoliation and the modified Hummers method. Exfoliated 2D GaN atomic sheets exhibit hexagonal and striped phases with microscale lateral dimensions and excellent chemical phase purity, confirmed by Raman and X-ray photoelectron spectroscopy. 2D GaN is highly stable, as confirmed by TGA measurements. While photodiode, FET, spintronics, and SERS-based molecular sensing, IRS element in 6G wireless communication applications of 2D GaN have been demonstrated, its nanocomposite with PVDF exhibits an excellent thermoplastic and piezoelectric behavior. The photodiode, FET, spintronic, piezoelectric, thermoplastic and molecular sensing applications of free-standing 2D GaN synthesized by sonochemical and Hummer’s method.","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":"15 1","pages":"1-11"},"PeriodicalIF":8.6,"publicationDate":"2023-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41427-023-00497-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136010416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-15DOI: 10.1038/s41427-023-00495-8
Keonhee Kim, Jae Gwang Lim, Su Man Hu, Yeonjoo Jeong, Jaewook Kim, Suyoun Lee, Joon Young Kwak, Jongkil Park, Gyu Weon Hwang, Kyeong-Seok Lee, Seongsik Park, Wook-Seong Lee, Byeong-Kwon Ju, Jong Keuk Park, Inho Kim
Various memristive devices have been proposed for use in neuromorphic computing systems as artificial synapses. Analog synaptic devices with linear conductance updates during training are efficiently essential to train neural networks. Although many different analog memristors have been proposed, a more reliable approach to implement analog synaptic devices is needed. In this study, we propose the memristor of a Cu/SiOx/implanted a-SiGex/p++ c-Si structure containing an a-Si layer with properly controlled conductance through Ge implantation. The a-SiGex layer plays a multifunctional role in device operation by limiting the current overshoot, confining the heat generated during operation and preventing the silicide formation reaction between the active metal (Cu) and the Si bottom electrode. Thus, the a-SiGex interface layer enables the formation of multi-weak filaments and induces analog switching behaviors. The TEM observation shows that the insertion of the a-SiGex layer between SiOx and c-Si remarkably suppresses the formation of copper silicide, and reliable set/reset operations are secured. The origin of the analog switching behaviors is discussed by analyzing current-voltage characteristics and electron microscopy images. Finally, the memristive-neural network simulations show that our developed memristive devices provide high learning accuracy and are promising in future neuromorphic computing hardware. Researchers develop a multilayered memristor with gradual switching behavior for neuromorphic computing applications. The device consists of Cu/SiOx/a-SiGex/c-Si layers, and its resistance is controlled by varying the implantation dose of Ge ions. This approach suppresses abrupt switching and induces gradual switching in CBRAM devices, enabling precise modulation of conductance levels and improved performance in neuromorphic computing. The Cu-based bilayer device exhibits promising analog behavior, maintaining high on-off ratios through the insertion and conductivity tuning of the current limiting layer. Simulations using memristive neural networks show a high recognition efficiency approaching 90%, demonstrating the potential for Cu-based bilayer memristor devices as artificial synapses in neuromorphic computing systems. This work presents a design guide for anlog memristive devices for artificial synapses in neuromorphic computing. Ge implanted a-Si serves multiple fuctions to induce multifilamentary switching and prevent silicide formation. The linear synapse update behaviors were observed thanks to multi-filament formation, which was confirmed by TEM.
{"title":"Multifilamentary switching of Cu/SiOx memristive devices with a Ge-implanted a-Si underlayer for analog synaptic devices","authors":"Keonhee Kim, Jae Gwang Lim, Su Man Hu, Yeonjoo Jeong, Jaewook Kim, Suyoun Lee, Joon Young Kwak, Jongkil Park, Gyu Weon Hwang, Kyeong-Seok Lee, Seongsik Park, Wook-Seong Lee, Byeong-Kwon Ju, Jong Keuk Park, Inho Kim","doi":"10.1038/s41427-023-00495-8","DOIUrl":"10.1038/s41427-023-00495-8","url":null,"abstract":"Various memristive devices have been proposed for use in neuromorphic computing systems as artificial synapses. Analog synaptic devices with linear conductance updates during training are efficiently essential to train neural networks. Although many different analog memristors have been proposed, a more reliable approach to implement analog synaptic devices is needed. In this study, we propose the memristor of a Cu/SiOx/implanted a-SiGex/p++ c-Si structure containing an a-Si layer with properly controlled conductance through Ge implantation. The a-SiGex layer plays a multifunctional role in device operation by limiting the current overshoot, confining the heat generated during operation and preventing the silicide formation reaction between the active metal (Cu) and the Si bottom electrode. Thus, the a-SiGex interface layer enables the formation of multi-weak filaments and induces analog switching behaviors. The TEM observation shows that the insertion of the a-SiGex layer between SiOx and c-Si remarkably suppresses the formation of copper silicide, and reliable set/reset operations are secured. The origin of the analog switching behaviors is discussed by analyzing current-voltage characteristics and electron microscopy images. Finally, the memristive-neural network simulations show that our developed memristive devices provide high learning accuracy and are promising in future neuromorphic computing hardware. Researchers develop a multilayered memristor with gradual switching behavior for neuromorphic computing applications. The device consists of Cu/SiOx/a-SiGex/c-Si layers, and its resistance is controlled by varying the implantation dose of Ge ions. This approach suppresses abrupt switching and induces gradual switching in CBRAM devices, enabling precise modulation of conductance levels and improved performance in neuromorphic computing. The Cu-based bilayer device exhibits promising analog behavior, maintaining high on-off ratios through the insertion and conductivity tuning of the current limiting layer. Simulations using memristive neural networks show a high recognition efficiency approaching 90%, demonstrating the potential for Cu-based bilayer memristor devices as artificial synapses in neuromorphic computing systems. This work presents a design guide for anlog memristive devices for artificial synapses in neuromorphic computing. Ge implanted a-Si serves multiple fuctions to induce multifilamentary switching and prevent silicide formation. The linear synapse update behaviors were observed thanks to multi-filament formation, which was confirmed by TEM.","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":"15 1","pages":"1-12"},"PeriodicalIF":8.6,"publicationDate":"2023-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41427-023-00495-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135354161","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-08DOI: 10.1038/s41427-023-00493-w
Masato Wakeda, Tetsu Ichitsubo
Fragility is a fundamental property of glass-forming liquids. Here, we evaluated the liquid fragility and structural and dynamic heterogeneity of glassy solids for four model binary alloys. The most fragile alloy exhibited the maximum dynamic heterogeneity in the mechanical unfreezing process. The local atomic order contributed to structural and dynamic heterogeneities in the glassy solid. We observed that atomic displacement significantly correlated with degrees of clustering of local atomic orders. The clustering produced during the glass-forming quenching process enhanced structural and dynamic heterogeneities, especially in fragile glass alloys. Therefore, this alloy system exhibited correlations among liquid fragility, dynamic heterogeneity in liquid alloys, and dynamic and structural heterogeneities in glassy solids. We discussed the underlying physics of the correlation based on a theoretical model for fragility. These structural and dynamic analyses also provided deeper insights into the features of structural heterogeneity in glassy solids. The alloy with the most fragility exhibited the largest difference in atomic mobility between the densely and loosely packed local atomic orders, implying the greatest heterogeneity in the degree of packing density. Researchers reveal correlations among liquid fragility, dynamic heterogeneity in liquid and glassy solids, and structural heterogeneity in glassy solids using molecular dynamics simulations on binary Cu-Zr alloy models. The study shows that the development of local order in supercooled liquid induces structural heterogeneity in glass solids, affecting fragility. Fragile alloys have a large fraction of densely packed regions and a small fraction of loosely packed regions, with a significant difference in the degree between densely and loosely packed states. This study highlights the connection between liquid fragility and structural heterogeneity in metallic glasses, providing valuable insights for future research and applications. We evaluated the liquid fragility and structural and dynamic heterogeneity of glassy solids. The most fragile alloy exhibited the maximum dynamic heterogeneity in the mechanical unfreezing process. We observed that atomic displacement significantly correlated with degrees of clustering of local atomic orders. The clustering produced during the glass-forming quenching process enhanced structural and dynamic heterogeneities. Therefore, there are correlations among liquid fragility, dynamic heterogeneity in liquid alloys, and dynamic and structural heterogeneities in glassy solids. In addition, the alloy with the most fragility exhibited the largest difference in atomic mobility between the densely and loosely packed local atomic orders.
{"title":"Atomistic study of liquid fragility and spatial heterogeneity of glassy solids in model binary alloys","authors":"Masato Wakeda, Tetsu Ichitsubo","doi":"10.1038/s41427-023-00493-w","DOIUrl":"10.1038/s41427-023-00493-w","url":null,"abstract":"Fragility is a fundamental property of glass-forming liquids. Here, we evaluated the liquid fragility and structural and dynamic heterogeneity of glassy solids for four model binary alloys. The most fragile alloy exhibited the maximum dynamic heterogeneity in the mechanical unfreezing process. The local atomic order contributed to structural and dynamic heterogeneities in the glassy solid. We observed that atomic displacement significantly correlated with degrees of clustering of local atomic orders. The clustering produced during the glass-forming quenching process enhanced structural and dynamic heterogeneities, especially in fragile glass alloys. Therefore, this alloy system exhibited correlations among liquid fragility, dynamic heterogeneity in liquid alloys, and dynamic and structural heterogeneities in glassy solids. We discussed the underlying physics of the correlation based on a theoretical model for fragility. These structural and dynamic analyses also provided deeper insights into the features of structural heterogeneity in glassy solids. The alloy with the most fragility exhibited the largest difference in atomic mobility between the densely and loosely packed local atomic orders, implying the greatest heterogeneity in the degree of packing density. Researchers reveal correlations among liquid fragility, dynamic heterogeneity in liquid and glassy solids, and structural heterogeneity in glassy solids using molecular dynamics simulations on binary Cu-Zr alloy models. The study shows that the development of local order in supercooled liquid induces structural heterogeneity in glass solids, affecting fragility. Fragile alloys have a large fraction of densely packed regions and a small fraction of loosely packed regions, with a significant difference in the degree between densely and loosely packed states. This study highlights the connection between liquid fragility and structural heterogeneity in metallic glasses, providing valuable insights for future research and applications. We evaluated the liquid fragility and structural and dynamic heterogeneity of glassy solids. The most fragile alloy exhibited the maximum dynamic heterogeneity in the mechanical unfreezing process. We observed that atomic displacement significantly correlated with degrees of clustering of local atomic orders. The clustering produced during the glass-forming quenching process enhanced structural and dynamic heterogeneities. Therefore, there are correlations among liquid fragility, dynamic heterogeneity in liquid alloys, and dynamic and structural heterogeneities in glassy solids. In addition, the alloy with the most fragility exhibited the largest difference in atomic mobility between the densely and loosely packed local atomic orders.","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":"15 1","pages":"1-13"},"PeriodicalIF":8.6,"publicationDate":"2023-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41427-023-00493-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43973492","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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