Stainless steel is widely used in various industrial fields due to its excellent corrosion resistance and mechanical properties. The key to this corrosion resistance is the thin passive film that naturally forms on the metal surface. Passive films are characterized by oxide film theory and adsorption theory, each uniquely explaining the structure and mechanism of the protective film on the metal surface. Research on the semiconductive properties of passive films on stainless steel offers diverse viewpoints, classifying theories into the point defect model and the bipolar fixed charge-induced passivity. Specific changes in passive film attributes that lead to degradation, however, are not fully understood. In this study, we analyzed the inner and outer layers of the passive film on super austenitic stainless steel SR-50A under various conditions in acidic and alkaline chloride environments. The interpretations of these results were based on the point defect model and the bipolar model for the passivation mechanism, and correlations between p-type and n-type semiconductor properties and passivation behavior were examined. The surface of the stainless steel forms a passive film comprising two layers with p-type and n-type semiconductive properties, independent of the pH of the solutions. The corrosion resistance increases as the p-type and n-type semiconductive tendencies become more balanced, consequently enhancing the properties of the passive film.
不锈钢具有优异的耐腐蚀性和机械性能，因此被广泛应用于各个工业领域。这种耐腐蚀性的关键在于金属表面自然形成的一层薄薄的被动膜。氧化膜理论和吸附理论分别对金属表面保护膜的结构和机理做出了独特的解释。有关不锈钢被动膜半导体特性的研究提供了多种观点，将理论分为点缺陷模型和双极固定电荷诱导钝化。然而，人们对导致降解的无源薄膜属性的具体变化并不完全了解。在本研究中，我们分析了超级奥氏体不锈钢 SR-50A 在酸性和碱性氯化物环境中各种条件下被动膜的内层和外层。对这些结果的解释基于钝化机理的点缺陷模型和双极模型，并研究了 p 型和 n 型半导体特性与钝化行为之间的相关性。不锈钢表面形成了一层钝化膜，由具有 p 型和 n 型半导体特性的两层膜组成，与溶液的 pH 值无关。随着 p 型和 n 型半导体特性趋于平衡，耐腐蚀性也随之增强，从而提高了被动膜的特性。
{"title":"Semiconductive Tendency of the Passive Film Formed on Super Austenitic Stainless Steel SR-50A in Acidic or Alkaline Chloride Solutions","authors":"Seung-Heon Choi, Young-Ran Yoo, Young-Sik Kim","doi":"10.3390/cryst14090766","DOIUrl":"https://doi.org/10.3390/cryst14090766","url":null,"abstract":"Stainless steel is widely used in various industrial fields due to its excellent corrosion resistance and mechanical properties. The key to this corrosion resistance is the thin passive film that naturally forms on the metal surface. Passive films are characterized by oxide film theory and adsorption theory, each uniquely explaining the structure and mechanism of the protective film on the metal surface. Research on the semiconductive properties of passive films on stainless steel offers diverse viewpoints, classifying theories into the point defect model and the bipolar fixed charge-induced passivity. Specific changes in passive film attributes that lead to degradation, however, are not fully understood. In this study, we analyzed the inner and outer layers of the passive film on super austenitic stainless steel SR-50A under various conditions in acidic and alkaline chloride environments. The interpretations of these results were based on the point defect model and the bipolar model for the passivation mechanism, and correlations between p-type and n-type semiconductor properties and passivation behavior were examined. The surface of the stainless steel forms a passive film comprising two layers with p-type and n-type semiconductive properties, independent of the pH of the solutions. The corrosion resistance increases as the p-type and n-type semiconductive tendencies become more balanced, consequently enhancing the properties of the passive film.","PeriodicalId":10855,"journal":{"name":"Crystals","volume":"20 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142202537","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kevin D. Vallejo, Zachery E. Cresswell, Volodymyr Buturlim, Brian S. Newell, Krzysztof Gofryk, Brelon J. May
Rare-earth nitrides are an exciting family of materials with a wide variety of properties desirable for new physics and applications in spintronics and superconducting devices. Among them, samarium nitride is an interesting compound reported to have ferromagnetic behavior coupled with the potential existence of p-wave superconductivity. Synthesis of high-quality thin films is essential in order to manifest these behaviors and understand the impact that vacancies, structural distortions, and doping can have on these properties. In this study, we report the synthesis of samarium nitride monocrystalline thin films on magnesium oxide (001) substrates with a chromium nitride capping layer using molecular beam epitaxy (MBE). We observed a high-quality monocrystalline SmN film with matching orientation to the substrate, then optimized the growth temperature. Despite the initial 2 nm of growth showing formation of a potential samarium oxide layer, the subsequent layers showed high-quality SmN, with semiconducting behavior revealed by an increase in resistivity with decreasing temperature. These promising results highlight the importance of studying diverse heteroepitaxial schemes and open the door for integration of rare-earth nitrides and transition metal nitrides for future spintronic devices.
稀土氮化物是一个令人兴奋的材料家族，它具有各种各样的特性，是自旋电子学和超导设备中新物理学和应用的理想材料。其中，氮化钐是一种有趣的化合物，据报道它不仅具有铁磁性，还可能具有 p 波超导性。为了体现这些行为，了解空位、结构畸变和掺杂对这些特性的影响，合成高质量的薄膜至关重要。在本研究中，我们报告了利用分子束外延（MBE）技术在带有氮化铬封盖层的氧化镁（001）基底上合成氮化钐单晶薄膜的情况。我们观察到了与基底取向匹配的高质量单晶 SmN 薄膜，然后优化了生长温度。尽管在最初 2 纳米的生长过程中形成了潜在的氧化钐层，但随后的薄膜层显示出高质量的 SmN，电阻率随温度降低而增加，显示出半导体特性。这些充满希望的结果凸显了研究各种异质外延方案的重要性，并为未来自旋电子器件整合稀土氮化物和过渡金属氮化物打开了大门。
{"title":"Synthesis of Samarium Nitride Thin Films on Magnesium Oxide (001) Substrates Using Molecular Beam Epitaxy","authors":"Kevin D. Vallejo, Zachery E. Cresswell, Volodymyr Buturlim, Brian S. Newell, Krzysztof Gofryk, Brelon J. May","doi":"10.3390/cryst14090765","DOIUrl":"https://doi.org/10.3390/cryst14090765","url":null,"abstract":"Rare-earth nitrides are an exciting family of materials with a wide variety of properties desirable for new physics and applications in spintronics and superconducting devices. Among them, samarium nitride is an interesting compound reported to have ferromagnetic behavior coupled with the potential existence of p-wave superconductivity. Synthesis of high-quality thin films is essential in order to manifest these behaviors and understand the impact that vacancies, structural distortions, and doping can have on these properties. In this study, we report the synthesis of samarium nitride monocrystalline thin films on magnesium oxide (001) substrates with a chromium nitride capping layer using molecular beam epitaxy (MBE). We observed a high-quality monocrystalline SmN film with matching orientation to the substrate, then optimized the growth temperature. Despite the initial 2 nm of growth showing formation of a potential samarium oxide layer, the subsequent layers showed high-quality SmN, with semiconducting behavior revealed by an increase in resistivity with decreasing temperature. These promising results highlight the importance of studying diverse heteroepitaxial schemes and open the door for integration of rare-earth nitrides and transition metal nitrides for future spintronic devices.","PeriodicalId":10855,"journal":{"name":"Crystals","volume":"59 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142202536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Inconel 625 deposited metal was prepared by gas metal arc welding. The solid solution treatment temperature was set at 1140 °C for 4 h using the DSC test method, followed by secondary aging at 750 °C/4 h and 650 °C/24 h. The specimens in the prepared state and after heat treatment were subjected to high temperature tensile at 600 °C, respectively. The fracture morphology, thermal deformation behavior, and strengthening mechanism of the samples in different states were analyzed. The results showed that the stress–strain curves of the deposited metals exhibited obvious work-hardening behavior at 600 °C. The solid solution and aging heat-treated samples have higher tensile and yield strength, but the plasticity is obviously lower than that of the deposited metal. It was also found that the γ″ phase and M23C6 carbides, as well as the continuous stacking faults in the alloy, were the main reasons for the increase in tensile strength of the solution and aging heat-treated sample.
{"title":"Effect of Solution and Aging Heat Treatment on the Microstructure and Mechanical Properties of Inconel 625 Deposited Metal","authors":"Yingdi Wang, Yunhai Su, Zhiyong Dai","doi":"10.3390/cryst14090764","DOIUrl":"https://doi.org/10.3390/cryst14090764","url":null,"abstract":"Inconel 625 deposited metal was prepared by gas metal arc welding. The solid solution treatment temperature was set at 1140 °C for 4 h using the DSC test method, followed by secondary aging at 750 °C/4 h and 650 °C/24 h. The specimens in the prepared state and after heat treatment were subjected to high temperature tensile at 600 °C, respectively. The fracture morphology, thermal deformation behavior, and strengthening mechanism of the samples in different states were analyzed. The results showed that the stress–strain curves of the deposited metals exhibited obvious work-hardening behavior at 600 °C. The solid solution and aging heat-treated samples have higher tensile and yield strength, but the plasticity is obviously lower than that of the deposited metal. It was also found that the γ″ phase and M23C6 carbides, as well as the continuous stacking faults in the alloy, were the main reasons for the increase in tensile strength of the solution and aging heat-treated sample.","PeriodicalId":10855,"journal":{"name":"Crystals","volume":"6 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142202535","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This review delves into the forefront of upconversion luminescence (UCL) research, focusing on KY3F10-based compounds, particularly their cubic α-phase. These materials are renowned for their exceptional luminescent properties and structural stability, making them prime candidates for advanced photonic applications. The synthesis methods and structural characteristics of the existing works in the literature are meticulously analyzed alongside the transformative effects of various doping strategies on UCL efficiency. Incorporating rare earth (RE) sensitizer ions such as Yb3+, along with activator ions like Er3+, Ho3+, Nd3+, or Tm3+, researchers have achieved remarkable enhancements in emission intensity and spectral control. Recent and past breakthroughs in understanding the local structure and phase transitions of single-, double-, and triple-RE3+-doped KY3F10 nanocrystals are highlighted, revealing their pivotal role in fine-tuning luminescent properties. Furthermore, the review underscores the untapped potential of lesser-known crystal structures, such as the metastable δ-phase of KY3F10, which offers promising avenues for future exploration. By presenting a comprehensive analysis and proposing innovative research directions, this review aims to inspire continued advancements in the field of upconversion materials, unlocking new potentials in photonic technologies.
{"title":"Fantastic Photons and Where to Excite Them: Revolutionizing Upconversion with KY3F10-Based Compounds","authors":"Pablo Serna-Gallén","doi":"10.3390/cryst14090762","DOIUrl":"https://doi.org/10.3390/cryst14090762","url":null,"abstract":"This review delves into the forefront of upconversion luminescence (UCL) research, focusing on KY3F10-based compounds, particularly their cubic α-phase. These materials are renowned for their exceptional luminescent properties and structural stability, making them prime candidates for advanced photonic applications. The synthesis methods and structural characteristics of the existing works in the literature are meticulously analyzed alongside the transformative effects of various doping strategies on UCL efficiency. Incorporating rare earth (RE) sensitizer ions such as Yb3+, along with activator ions like Er3+, Ho3+, Nd3+, or Tm3+, researchers have achieved remarkable enhancements in emission intensity and spectral control. Recent and past breakthroughs in understanding the local structure and phase transitions of single-, double-, and triple-RE3+-doped KY3F10 nanocrystals are highlighted, revealing their pivotal role in fine-tuning luminescent properties. Furthermore, the review underscores the untapped potential of lesser-known crystal structures, such as the metastable δ-phase of KY3F10, which offers promising avenues for future exploration. By presenting a comprehensive analysis and proposing innovative research directions, this review aims to inspire continued advancements in the field of upconversion materials, unlocking new potentials in photonic technologies.","PeriodicalId":10855,"journal":{"name":"Crystals","volume":"511 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142202539","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Supersaturated alloys can exhibit superior properties and electrodeposition is a cost-effective and versatile technique to produce them. In this review, the chemical, mechanical and structural properties of supersaturated alloys are discussed, and connections with metallic glasses and high entropy alloys are also exposed. After discussing mechanisms causing supersaturation in electrodeposited alloys, an overview of the most important electrodeposited metastable alloys is provided, showing that they are mainly used as protective coatings able to improve corrosion resistance and tribological performance of a large variety of industrial components. Composition of the electrolytic baths and deposition parameters are also considered and discussed.
{"title":"Properties and Applications of Supersaturated Metastable Alloys Obtained via Electrodeposition","authors":"Roberto Bernasconi, Luca Nobili, Luca Magagnin","doi":"10.3390/cryst14090761","DOIUrl":"https://doi.org/10.3390/cryst14090761","url":null,"abstract":"Supersaturated alloys can exhibit superior properties and electrodeposition is a cost-effective and versatile technique to produce them. In this review, the chemical, mechanical and structural properties of supersaturated alloys are discussed, and connections with metallic glasses and high entropy alloys are also exposed. After discussing mechanisms causing supersaturation in electrodeposited alloys, an overview of the most important electrodeposited metastable alloys is provided, showing that they are mainly used as protective coatings able to improve corrosion resistance and tribological performance of a large variety of industrial components. Composition of the electrolytic baths and deposition parameters are also considered and discussed.","PeriodicalId":10855,"journal":{"name":"Crystals","volume":"1 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142202538","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sergei A. Zubkov, Elena D. Finashina, Valery N. Zakharov, Leonid Kustov
Chromium-substituted aluminophosphate (CrAPO-5) with the AFI crystal structure was prepared for the first time by using microwave conditions at the stage of gel formation and crystallization. This approach allowed the reduction of the time required for the synthesis of CrAPO-5 from 60–70 h to 6 h. CrAPO-5 metal aluminophosphate prepared by microwave-assisted synthesis is studied by UV-visible and IR spectroscopy and X-ray photoelectron spectroscopy. The material is characterized by the presence of Cr3+ and Cr2+ ions in the framework with predominating Cr3+ ions introduced via isomorphous substitution, as well as some minor amounts of extra-framework Cr3+ species, which are present presumably in the state of α-Cr2O3. The latter species can be partially reduced to Cr2+ species in the presence of CO or H2. XPS study of CrAPO-5 revealed the presence of Cr3+ ions in the framework. A TPR experiment showed that the reduction of chromium starts at about 450–500 °C.
{"title":"Characterization of Chromium Cations in CrAPO-5 Metal Aluminophosphate","authors":"Sergei A. Zubkov, Elena D. Finashina, Valery N. Zakharov, Leonid Kustov","doi":"10.3390/cryst14090758","DOIUrl":"https://doi.org/10.3390/cryst14090758","url":null,"abstract":"Chromium-substituted aluminophosphate (CrAPO-5) with the AFI crystal structure was prepared for the first time by using microwave conditions at the stage of gel formation and crystallization. This approach allowed the reduction of the time required for the synthesis of CrAPO-5 from 60–70 h to 6 h. CrAPO-5 metal aluminophosphate prepared by microwave-assisted synthesis is studied by UV-visible and IR spectroscopy and X-ray photoelectron spectroscopy. The material is characterized by the presence of Cr3+ and Cr2+ ions in the framework with predominating Cr3+ ions introduced via isomorphous substitution, as well as some minor amounts of extra-framework Cr3+ species, which are present presumably in the state of α-Cr2O3. The latter species can be partially reduced to Cr2+ species in the presence of CO or H2. XPS study of CrAPO-5 revealed the presence of Cr3+ ions in the framework. A TPR experiment showed that the reduction of chromium starts at about 450–500 °C.","PeriodicalId":10855,"journal":{"name":"Crystals","volume":"23 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142202542","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gagik Demirkhanyan, Narine Babajanyan, Frida Voskanyan, Ninel Kokanyan, Marco Bazzan, Edvard Kokanyan
Holmium-doped congruent-composition lithium niobate (LiNbO3:Ho, LN:Ho) crystals were grown by the Czochralski method. The absorption of the LN:1at% Ho3+ crystal was recorded at room temperature. On the basis of the analysis of emission and absorption spectra of the LN:1at% Ho3+ crystal, the possibilities of obtaining, at room temperature, radiation-balanced (RB) lasing in the region of 640–670 nm wavelengths corresponding to the inter-Stark transitions of manifolds 5F5 and 5I8 was theoretically investigated. The RB lasing parameters were calculated and the optimal pump and laser wavelengths were determined: λOP=652.1 nm, λOL=653.6 nm. The values for the RB lasing efficiency and radiation amplification in the considered wavelength region were obtained: Feff=3.23×10−22cm2, Fgain=6.08×10−22 cm2.
{"title":"LiNbO3:Ho3+ Crystal as a Material for Radiation-Balanced Lasing in the 640–670 nm Region","authors":"Gagik Demirkhanyan, Narine Babajanyan, Frida Voskanyan, Ninel Kokanyan, Marco Bazzan, Edvard Kokanyan","doi":"10.3390/cryst14090760","DOIUrl":"https://doi.org/10.3390/cryst14090760","url":null,"abstract":"Holmium-doped congruent-composition lithium niobate (LiNbO3:Ho, LN:Ho) crystals were grown by the Czochralski method. The absorption of the LN:1at% Ho3+ crystal was recorded at room temperature. On the basis of the analysis of emission and absorption spectra of the LN:1at% Ho3+ crystal, the possibilities of obtaining, at room temperature, radiation-balanced (RB) lasing in the region of 640–670 nm wavelengths corresponding to the inter-Stark transitions of manifolds 5F5 and 5I8 was theoretically investigated. The RB lasing parameters were calculated and the optimal pump and laser wavelengths were determined: λOP=652.1 nm, λOL=653.6 nm. The values for the RB lasing efficiency and radiation amplification in the considered wavelength region were obtained: Feff=3.23×10−22cm2, Fgain=6.08×10−22 cm2.","PeriodicalId":10855,"journal":{"name":"Crystals","volume":"105 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142202548","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The prototype misfit layer compound (SnS)1.17NbS2 consists alternatingly of a metallic triatomic NbS2 layer, in which Nb atoms are sandwiched by S atoms, and an insulating SnS double layer featuring a NaCl-type structure. Here we investigate the effect of lattice misfit on the stability and chemical bonding in the misfit layer compound using a first-principles density functional theory approach. The calculations show that for the (SnS)1+xNbS2 approximants, the most stable one has x = 0.167, close to the experimental observations. Charge analysis finds a moderate charge transfer from SnS to NbS2. Sn or S vacancies in the SnS part affect the electronic properties and interlayer interactions. The obtained information here helps in understanding the mechanism of formation and stability of misfit layer compounds and ferecrystals and further contributes to the design of novel multilayer compounds and emerging van der Waals heterostructures.
错配层化合物 (SnS)1.17NbS2 原型由金属三原子 NbS2 层和具有 NaCl 型结构的绝缘 SnS 双层交替组成。在此，我们采用第一原理密度泛函理论方法研究了晶格错配对错配层化合物的稳定性和化学键的影响。计算结果表明，对于 (SnS)1+xNbS2 近似值，最稳定的近似值为 x = 0.167，接近实验观测值。电荷分析发现，SnS 与 NbS2 之间存在适度的电荷转移。SnS 部分的 Sn 或 S 空位会影响电子特性和层间相互作用。本文获得的信息有助于理解错配层化合物和非晶体的形成机理和稳定性，并进一步促进新型多层化合物和新兴范德华异质结构的设计。
{"title":"Effect of Lattice Misfit on the Stability of the Misfit Layer Compound (SnS)1+xNbS2","authors":"Changming Fang","doi":"10.3390/cryst14090756","DOIUrl":"https://doi.org/10.3390/cryst14090756","url":null,"abstract":"The prototype misfit layer compound (SnS)1.17NbS2 consists alternatingly of a metallic triatomic NbS2 layer, in which Nb atoms are sandwiched by S atoms, and an insulating SnS double layer featuring a NaCl-type structure. Here we investigate the effect of lattice misfit on the stability and chemical bonding in the misfit layer compound using a first-principles density functional theory approach. The calculations show that for the (SnS)1+xNbS2 approximants, the most stable one has x = 0.167, close to the experimental observations. Charge analysis finds a moderate charge transfer from SnS to NbS2. Sn or S vacancies in the SnS part affect the electronic properties and interlayer interactions. The obtained information here helps in understanding the mechanism of formation and stability of misfit layer compounds and ferecrystals and further contributes to the design of novel multilayer compounds and emerging van der Waals heterostructures.","PeriodicalId":10855,"journal":{"name":"Crystals","volume":"7 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142202540","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We study the nested topological band-gap structure of one-dimensional (1D) photonic super-lattices. One cell of the super-lattice is composed of two kinds of photonic crystals (PhCs) with different topologies so that there is a domain wall (DW) state at the interface between the two PhCs. We find that the coupling of periodic DWs could form a new band-gap structure inside the original gap. The new band-gap structure could be topologically nontrivial, and a topological phase transition can occur if the structural or material parameters of the PhCs are tuned. Theoretically, we prove that the Hamiltonian of such coupled DWs can be reduced to the simple Su–Schrieffer–Heeger (SSH) model. Then, if two super-lattices carrying different topological phases are attached, a new topological interface state can occur at the interface between the two super-lattices. Finally, we find the nested topological band-gap structure in two-dimensional (2D) photonic super-lattices. Consequently, such nested topological structures can widely exist in complex super-lattices. Our work improves the topological study of photonic super-lattices and provides a new way to realize topological interface states and topological phase transitions in 1D and 2D photonic super-lattices. Topological interface states in super-lattices are sensitive to frequency and have high accuracy, which is desired for high-performance filters and high-finesse cavities.
{"title":"The Nested Topological Band-Gap Structure for the Periodic Domain Walls in a Photonic Super-Lattice","authors":"Zhen Lai, Yufu Liu, Yunlin Li, Xuezhi Wang, Xunya Jiang","doi":"10.3390/cryst14090757","DOIUrl":"https://doi.org/10.3390/cryst14090757","url":null,"abstract":"We study the nested topological band-gap structure of one-dimensional (1D) photonic super-lattices. One cell of the super-lattice is composed of two kinds of photonic crystals (PhCs) with different topologies so that there is a domain wall (DW) state at the interface between the two PhCs. We find that the coupling of periodic DWs could form a new band-gap structure inside the original gap. The new band-gap structure could be topologically nontrivial, and a topological phase transition can occur if the structural or material parameters of the PhCs are tuned. Theoretically, we prove that the Hamiltonian of such coupled DWs can be reduced to the simple Su–Schrieffer–Heeger (SSH) model. Then, if two super-lattices carrying different topological phases are attached, a new topological interface state can occur at the interface between the two super-lattices. Finally, we find the nested topological band-gap structure in two-dimensional (2D) photonic super-lattices. Consequently, such nested topological structures can widely exist in complex super-lattices. Our work improves the topological study of photonic super-lattices and provides a new way to realize topological interface states and topological phase transitions in 1D and 2D photonic super-lattices. Topological interface states in super-lattices are sensitive to frequency and have high accuracy, which is desired for high-performance filters and high-finesse cavities.","PeriodicalId":10855,"journal":{"name":"Crystals","volume":"8 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142202541","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Electrolytic plasma nitriding is an attractive chemical heat treatment used to improve the surface properties of steel by implementing nitrogen saturation. This method is widely applied to steel and iron-based alloys operating under various operating conditions. In this work, using liquid-phase plasma nitriding technology, a nitrided layer was obtained on the surface of 40CrNi steel in electrolytes of different concentrations. The microstructure and phase composition of the nitrided layer were investigated and analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD), and we performed Vickers hardness and wear resistance tests using the ball-on-disc method. The microhardness and wear resistance of nitrided 40CrNi steel were significantly improved due to the lubricating properties of the ε-Fe2N phase formed on its surface.
电解等离子氮化是一种极具吸引力的化学热处理方法，通过氮饱和来改善钢的表面性能。这种方法被广泛应用于各种工作条件下的钢和铁基合金。在这项工作中，利用液相等离子氮化技术，在不同浓度的电解液中，在 40CrNi 钢表面获得了氮化层。我们使用扫描电子显微镜（SEM）和 X 射线衍射（XRD）对氮化层的微观结构和相组成进行了研究和分析，并使用球盘法进行了维氏硬度和耐磨性测试。由于氮化 40CrNi 钢表面形成的 ε-Fe2N 相具有润滑性，因此其显微硬度和耐磨性得到了显著提高。
{"title":"Surface Modification of Chromium–Nickel Steel by Electrolytic Plasma Nitriding Method","authors":"Zarina Satbayeva, Bauyrzhan Rakhadilov, Zhangabay Turar, Nurbol Berdimuratov, Daryn Baizhan, Almasbek Maulit","doi":"10.3390/cryst14090759","DOIUrl":"https://doi.org/10.3390/cryst14090759","url":null,"abstract":"Electrolytic plasma nitriding is an attractive chemical heat treatment used to improve the surface properties of steel by implementing nitrogen saturation. This method is widely applied to steel and iron-based alloys operating under various operating conditions. In this work, using liquid-phase plasma nitriding technology, a nitrided layer was obtained on the surface of 40CrNi steel in electrolytes of different concentrations. The microstructure and phase composition of the nitrided layer were investigated and analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD), and we performed Vickers hardness and wear resistance tests using the ball-on-disc method. The microhardness and wear resistance of nitrided 40CrNi steel were significantly improved due to the lubricating properties of the ε-Fe2N phase formed on its surface.","PeriodicalId":10855,"journal":{"name":"Crystals","volume":"11 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142202543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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