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.
nd - fe -b基永磁体广泛应用于能量转换领域。然而，由于相对于nd2fe14b化合物的各向异性场(H A)，它们的矫顽力(H c)相对较低，通常为0.2 H A，因此在高温下使用它们是困难的。在这项工作中，我们发现(Nd 0.8 Dy 0.2)-Fe-B烧结磁体的矫顽力可以达到0.4 H A，这是其无Dy对应物的H c / H A的两倍。详细的显微组织表征、密度泛函理论和微磁模拟表明，矫顽力的大值(H c = 0.4 H A)不仅源于主相的H A增强(内在因素)，也源于薄晶间相磁化强度的降低(外在因素)。后者归因于4 at的溶解。% Dy在与Fe反铁磁耦合的晶间相中。晶间相磁化强度的降低导致矫顽力的角依赖性从无Dy磁体的Kondorsky型转变为含Dy磁体的stoner - wohlfarth型，表明随着Dy取代降低了晶间相的磁化强度，典型的钉钉控制矫顽力机制开始呈现成核特征。
{"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.
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The design of composite powders for exploiting the multifunctionality of metallic nanocomposites via laser additive manufacturing (AM) is challenging. Conventional ball-milling processes are prone to cause uncontrollable powder morphology and reduced flowability, while recently developed nanodecoration technologies are limited by complicated processing and impurity inclusion. Herein, a facile and scalable approach was developed using ultrafine bubble (UFB)-assisted heteroagglomeration to fabricate high-concentration, impurity-free nanoceramic/metal composite powders. Individual ZrO2 or Al2O3 nanoparticles up to ~10 wt% were homogeneously decorated on the surface of Ti-6Al-4V powders through the bridging effect of the negatively charged UFBs, leading to enhanced flowability and laser absorptivity. The nanoceramics were completely decomposed and dissolved into the matrix upon laser irradiation; therefore, a unique Ti nanocomposite exhibiting both high strength and ductility was obtained. Our work provides new insights into the application of UFBs and the fabrication of multifunctional AM components. Researchers have developed a novel ultrafine bubble-assisted heteroagglomeration (UFBH) method to economically fabricate high-concentration, impurity-free nanoceramic/metal powders for additive manufacturing. Using negatively charged UFBs, they successfully promoted the uniform decoration of positively charged nanoceramic particles on metal powder surfaces via electrostatic self-assembly. The resulting 1 wt% ZrO2/Ti64 component fabricated by laser powder bed fusion (L-PBF) exhibited a unique combination of high tensile strength and high ductility due to significant solid solution strengthening and grain refinement. This study introduces a facile and scalable approach using UFBH and laser AM processes to design multifunctional metallic components, paving the way for the production of novel composite powders and high-performance AM components. A facile and scalable approach was developed using ultrafine bubble (UFB)-assisted heteroagglomeration to fabricate high-concentration, impurity-free nanoceramic/metal composite powders for additive manufacturin. Individual ZrO2 or Al2O3 nanoparticles up to ~10 wt% were homogeneously decorated on the surface of Ti-6Al-4V powders through the bridging effect of the negatively charged UFBs. The nanoceramics were completely decomposed and dissolved into the matrix upon laser irradiation; therefore, a unique Ti nanocomposite exhibiting both high strength and ductility was obtained.
{"title":"Ultrafine-bubble-water-promoted nanoceramic decoration of metal powders for additive manufacturing","authors":"Mingqi Dong, Weiwei Zhou, Suxia Guo, Naoyuki Nomura","doi":"10.1038/s41427-023-00494-9","DOIUrl":"10.1038/s41427-023-00494-9","url":null,"abstract":"The design of composite powders for exploiting the multifunctionality of metallic nanocomposites via laser additive manufacturing (AM) is challenging. Conventional ball-milling processes are prone to cause uncontrollable powder morphology and reduced flowability, while recently developed nanodecoration technologies are limited by complicated processing and impurity inclusion. Herein, a facile and scalable approach was developed using ultrafine bubble (UFB)-assisted heteroagglomeration to fabricate high-concentration, impurity-free nanoceramic/metal composite powders. Individual ZrO2 or Al2O3 nanoparticles up to ~10 wt% were homogeneously decorated on the surface of Ti-6Al-4V powders through the bridging effect of the negatively charged UFBs, leading to enhanced flowability and laser absorptivity. The nanoceramics were completely decomposed and dissolved into the matrix upon laser irradiation; therefore, a unique Ti nanocomposite exhibiting both high strength and ductility was obtained. Our work provides new insights into the application of UFBs and the fabrication of multifunctional AM components. Researchers have developed a novel ultrafine bubble-assisted heteroagglomeration (UFBH) method to economically fabricate high-concentration, impurity-free nanoceramic/metal powders for additive manufacturing. Using negatively charged UFBs, they successfully promoted the uniform decoration of positively charged nanoceramic particles on metal powder surfaces via electrostatic self-assembly. The resulting 1 wt% ZrO2/Ti64 component fabricated by laser powder bed fusion (L-PBF) exhibited a unique combination of high tensile strength and high ductility due to significant solid solution strengthening and grain refinement. This study introduces a facile and scalable approach using UFBH and laser AM processes to design multifunctional metallic components, paving the way for the production of novel composite powders and high-performance AM components. A facile and scalable approach was developed using ultrafine bubble (UFB)-assisted heteroagglomeration to fabricate high-concentration, impurity-free nanoceramic/metal composite powders for additive manufacturin. Individual ZrO2 or Al2O3 nanoparticles up to ~10 wt% were homogeneously decorated on the surface of Ti-6Al-4V powders through the bridging effect of the negatively charged UFBs. The nanoceramics were completely decomposed and dissolved into the matrix upon laser irradiation; therefore, a unique Ti nanocomposite exhibiting both high strength and ductility was obtained.","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":"15 1","pages":"1-8"},"PeriodicalIF":8.6,"publicationDate":"2023-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41427-023-00494-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46540504","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 : 2023-08-25DOI: 10.1038/s41427-023-00492-x
Wenqiang Zhang, Jingzhuo Zhou, Yanwen Jia, Juzheng Chen, Yiru Pu, Rong Fan, Fanling Meng, Qi Ge, Yang Lu
Active metamaterials with shapes or mechanical properties that can be controlled remotely are promising candidates for soft robots, flexible electronics, and medical applications. However, current active metamaterials often have long response times and short ranges of linear working strains. Here, we demonstrate magnetoactive microlattice metamaterials constructed from 3D-printed, ultra-flexible polymer shells filled with magnetorheological (MR) fluid. Under compressive stress, the magnetorheological fluid develops hydrostatic pressure, allowing for a linear compression strain of more than 30% without buckling. We further show that under a relatively low magnetic field strength (approximately 60 mT), the microlattices can become approximately 200% stiffer than those in a relaxed state, and the energy absorption increases ~16 times. Furthermore, our microlattices showed an ultra-low response time with “field on” and “field off” times of ~200 ms and ~50 ms, respectively. The ability to continuously tune the mechanical properties of these materials in real time make it possible to modulate stress‒strain behavior on demand. Our study provides a new route toward large-scale, highly tunable, and remotely controllable metamaterials with potential applications in wearable exoskeletons, tactile sensors, and medical supports. A liquid–solid dual-phase magnetoactive microlattice metamaterial composed of flexible 3D-printed polymer shell and magnetorheological (MR) fluid has been designed and fabricated. The MR fluid-filled magnetoactive microlattices demonstrated remarkable recoverability (~50%) and be substantially stiffened in the presence of a magnetic field, with an ~200% increment in stiffness at 60 mT. Based on specific applications, the mechanical properties of this magnetoactive microlattice metamaterial can be modulated on demand, leading to certain programmable stress-strain behavior.
{"title":"Magnetoactive microlattice metamaterials with highly tunable stiffness and fast response rate","authors":"Wenqiang Zhang, Jingzhuo Zhou, Yanwen Jia, Juzheng Chen, Yiru Pu, Rong Fan, Fanling Meng, Qi Ge, Yang Lu","doi":"10.1038/s41427-023-00492-x","DOIUrl":"10.1038/s41427-023-00492-x","url":null,"abstract":"Active metamaterials with shapes or mechanical properties that can be controlled remotely are promising candidates for soft robots, flexible electronics, and medical applications. However, current active metamaterials often have long response times and short ranges of linear working strains. Here, we demonstrate magnetoactive microlattice metamaterials constructed from 3D-printed, ultra-flexible polymer shells filled with magnetorheological (MR) fluid. Under compressive stress, the magnetorheological fluid develops hydrostatic pressure, allowing for a linear compression strain of more than 30% without buckling. We further show that under a relatively low magnetic field strength (approximately 60 mT), the microlattices can become approximately 200% stiffer than those in a relaxed state, and the energy absorption increases ~16 times. Furthermore, our microlattices showed an ultra-low response time with “field on” and “field off” times of ~200 ms and ~50 ms, respectively. The ability to continuously tune the mechanical properties of these materials in real time make it possible to modulate stress‒strain behavior on demand. Our study provides a new route toward large-scale, highly tunable, and remotely controllable metamaterials with potential applications in wearable exoskeletons, tactile sensors, and medical supports. A liquid–solid dual-phase magnetoactive microlattice metamaterial composed of flexible 3D-printed polymer shell and magnetorheological (MR) fluid has been designed and fabricated. The MR fluid-filled magnetoactive microlattices demonstrated remarkable recoverability (~50%) and be substantially stiffened in the presence of a magnetic field, with an ~200% increment in stiffness at 60 mT. Based on specific applications, the mechanical properties of this magnetoactive microlattice metamaterial can be modulated on demand, leading to certain programmable stress-strain behavior.","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":"15 1","pages":"1-8"},"PeriodicalIF":8.6,"publicationDate":"2023-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41427-023-00492-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46566773","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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