35 results on '"Zhuang Wang"'
Search Results
2. Economical synthesis of functional aromatic polythioamides from KOH-assisted multicomponent polymerizations of sulfur, aromatic diamines and dialdehydes
- Author
-
Yang Hu, Lihui Zhang, Zhuang Wang, Rongrong Hu, and Ben Zhong Tang
- Subjects
Polymers and Plastics ,Organic Chemistry ,Bioengineering ,Biochemistry - Abstract
A series of aromatic polythioamides with high gold extraction efficiency and high refractive index have been synthesized through the KOH-assisted multicomponent polymerization of elemental sulfur, aromatic diamines and aromatic dialdehydes.
- Published
- 2023
3. Electrochemical α-C(sp3)–H/O–H cross-coupling of isochromans and alcohols assisted by benzoic acid
- Author
-
Zhuang Wang, Kaikai Niu, Yuxiu Liu, Hongjian Song, and Qingmin Wang
- Subjects
Materials Chemistry ,Metals and Alloys ,Ceramics and Composites ,General Chemistry ,Catalysis ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Abstract
We report a mild, convenient protocol for synthesis of α-alkoxy isochroman derivatives by means of electrochemical α-C(sp3)–H/O–H cross-coupling reactions of isochromans and alcohols in the presence of benzoic acid.
- Published
- 2022
4. Localized electronic and vibrational states in amorphous diamond
- Author
-
Wen-Cai Lu, Cai-Zhuang Wang, Kai-Ming Ho, and Rong Cheng
- Subjects
Quenching ,Materials science ,Band gap ,Wide-bandgap semiconductor ,General Physics and Astronomy ,Diamond ,02 engineering and technology ,engineering.material ,Low frequency ,021001 nanoscience & nanotechnology ,Amorphous diamond ,01 natural sciences ,Molecular physics ,Amorphous solid ,Condensed Matter::Materials Science ,Molecular vibration ,0103 physical sciences ,engineering ,Physical and Theoretical Chemistry ,010306 general physics ,0210 nano-technology - Abstract
Amorphous diamond structures are generated by quenching high-density high-temperature liquid carbon using tight-binding molecular-dynamics simulations. We show that the generated amorphous diamond structures are predominated by strong tetrahedral bonds with the sp3 bonding fraction as high as 97%, thus exhibit an ultra-high incompressibility and a wide band gap close to those of crystalline diamond. A small amount of sp2 bonding defects in the amorphous sample contributes to localized electronic states in the band gap while large local strain gives rise to localization of vibrational modes at both high and low frequency regimes.
- Published
- 2021
5. Third time's the charm: intricate non-centrosymmetric polymorphism in LnSiP3 (Ln = La and Ce) induced by distortions of phosphorus square layers
- Author
-
Bing Yuan, Cai-Zhuang Wang, Gordon J. Miller, Kai-Ming Ho, Kirill Kovnir, Adedoyin N. Adeyemi, Frédéric A. Perras, Justin Mark, Juyeon Won, Shannon Lee, Alexander L. Paterson, Gayatri Viswanathan, Feng Zhang, Brennan C. McBride, Sabyasachi Sen, and Georgiy Akopov
- Subjects
Inorganic Chemistry ,symbols.namesake ,Crystallography ,Materials science ,Solid-state nuclear magnetic resonance ,Electrical resistivity and conductivity ,symbols ,Spin–lattice relaxation ,Space group ,Electronic structure ,Crystal structure ,Resonance (chemistry) ,Raman spectroscopy - Abstract
Complex polymorphic relationships in the LnSiP3 (Ln = La and Ce) family of compounds are reported. An innovative synthetic method was developed to overcome differences in the reactivities of the rare-earth metal and refractory silicon with phosphorus. Reactions of atomically mixed Ln + Si with P allowed for selective control over the reaction outcomes resulting in targeted isolation of three new polymorphs of LaSiP3 and two polymorphs of CeSiP3. In situ X-ray diffraction studies revealed that the developed method bypasses formation of the thermodynamic dead-end, the binary SiP. Careful re-determination of the crystal structure ruled out the previously reported ordered centrosymmetric structure of CeSiP3 and showed that the main LnSiP3 polymorphs crystallize in the non-centrosymmetric Pna21 and Aea2 space groups featuring distinct distortions of the regular P square net to yield either cis–trans 1D phosphorus chains (Pna21) or disordered-2D phosphorus layers (Aea2). The disordered 2D nature of the P layers in the Aea2 LaSiP3 polymorph was confirmed by Raman spectroscopy. A unique centrosymmetric P21/c polymorph was observed for LaSiP3 and has a completely different crystal structure lacking P layers. Consecutive polymorphic transformations at increasing temperatures for LaSiP3(Pna21 → P21/c → Aea2) were derived from optimized synthetic profiles and confirmed by a combination of phonon computations and experimental in situ and ex situ annealings. Crystal structures of the LaSiP3 polymorphs were verified via advanced solid state NMR analysis using 31P MAS and 31P{139La} double resonance techniques. A combination of phonon and electronic structure calculations, NMR T1 relaxation times, UV/Vis/NIR spectroscopy, and resistivity measurements revealed that all the reported polymorphs are semiconductors with resistivities and thermal conductivities strongly dependent on the degree of distortion of P square layers in the crystal structure. Reported here, non-centrosymmetric LnSiP3 polymorphs with tunable resistivity and thermal conductivity provide a platform for the development of novel functional materials with a wide range of applications.
- Published
- 2021
6. Reagent-assisted hydrothermal synthesis of NiCo2O4 nanomaterials as electrodes for high-performance asymmetric supercapacitors
- Author
-
Zhifeng Zheng, Dipan Xuan, Duo Wang, Jie Liu, Zhe Lu, Yueyuan Ye, Zhuang Wang, Shuirong Li, Qian Liu, and Dechao Wang
- Subjects
Supercapacitor ,Chemical engineering ,Chemistry ,Specific surface area ,Reagent ,Electrode ,Materials Chemistry ,Hydrothermal synthesis ,General Chemistry ,Mesoporous material ,Catalysis ,Nanoneedle ,Nanomaterials - Abstract
In this study, mesoporous nickel cobaltate (NiCo2O4) nanomaterials were loaded onto nickel foam through a simple and environment-friendly reagent assisted hydrothermal method. The impacts of reagents on the micro-morphology and electrochemical capacitive properties were studied. The NiCo2O4 nanoneedle arrays prepared with cetyltrimethylammonium bromide (CTAB) as the auxiliary reagent exhibited a relatively higher specific surface area, convenient charge transport channel, excellent specific capacitance (1153.2 F g−1 at a current density of 1 A g−1), remarkable rate performance (10 A g−1, 812 F g−1) and good cycling stability (75% of the initial value is retained at 10 A g−1 after 1000 cycles). The asymmetric supercapacitor assembled by the optimized NiCo2O4 nanomaterial as the positive electrode and activated carbon as the negative electrode provides an energy density of 22.5 W h kg−1 at 800 W kg−1, and displays an excellent cycle performance of 97.1% after 1000 cycles at 1 A g−1. It is suggested that the CTAB-assisted nanoneedle array-structured NiCo2O4 electrode material could be a potential candidate for supercapacitors.
- Published
- 2021
7. Metal-doped carbon nitrides: synthesis, structure and applications
- Author
-
Yanfei Shen, Zhuang Wang, Yongjun Zheng, Songqin Liu, Qing Hong, Yuhan Bai, and Yuanjian Zhang
- Subjects
Fabrication ,chemistry.chemical_element ,Nanotechnology ,02 engineering and technology ,General Chemistry ,Nitride ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrocatalyst ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Characterization (materials science) ,chemistry.chemical_compound ,chemistry ,Materials Chemistry ,Photocatalysis ,Organic synthesis ,0210 nano-technology ,Carbon ,Carbon nitride - Abstract
Metal doping is a common strategy for the regulation of the structure of carbon nitride materials at the molecular level. A wide range of intriguing applications of metal-doped carbon nitride (M–CN) materials have recently been investigated from the mainstream of photocatalysis to other emerging fields, including electrocatalysis, organic synthesis, biosensors, and nanozymes. From a fundamental point of view, M–CN is an essential branch of carbon nitride materials and opens a new avenue for the preparation of single-atom catalysts and even endows the materials with new exciting properties. In particular, M–Nx structures as active sites in numerous M–CN materials have been widely demonstrated using both experiments and theoretical calculations. This review summarizes the state-of-the-art preparation methods, characterization techniques, and diverse applications of M–CN. Finally, future perspectives on the fabrication and application prospects of M–CN materials are discussed.
- Published
- 2021
8. Lithium nickel borides: evolution of [NiB] layers driven by Li pressure
- Author
-
Cai-Zhuang Wang, Colin P. Harmer, Xin Zhao, Raquel A. Ribeiro, Volodymyr Gvozdetskyi, Julia V. Zaikina, Scott L. Carnahan, Kai-Ming Ho, Aaron J. Rossini, Yang Sun, Gourab Bhaskar, Paul C. Canfield, and Feng Zhang
- Subjects
Diffraction ,Materials science ,Hydride ,Solid-state ,chemistry.chemical_element ,Nuclear magnetic resonance spectroscopy ,Quantum chemistry ,Synchrotron ,law.invention ,Inorganic Chemistry ,Crystallography ,Nickel ,chemistry ,law ,Lithium - Abstract
Here we show the effect of Li chemical pressure on the structure of layered polymorphs with LiNiB composition: RT-LiNiB (room temperature polymorph) and HT-LiNiB (high temperature polymorph), resulting in stabilization of the novel RT-Li1+xNiB (x ∼ 0.17) and HT-Li1+yNiB (y ∼ 0.06) phases. Depending on the synthesis temperature and initial Li content, precisely controlled via hydride route synthesis, [NiB] layers undergo structural deformations, allowing for extra Li atoms to be accommodated between the layers. In situ variable temperature synchrotron and time-dependent laboratory powder X-ray diffraction studies suggest Li step-wise deintercalation processes: RT-Li1+xNiB → RT-LiNiB (high temp.) → LiNi3B1.8 → binary Ni borides and HT-Li1+yNiB → HT-LiNiB (high temp.) → LiNi3B1.8 → binary Ni borides. Quantum chemistry calculations and solid state 7Li and 11B NMR spectroscopy shed light on the complexity of real superstructures of these compounds determined from high resolution synchrotron powder diffraction data.
- Published
- 2021
9. Stabilizing the crystal structures of NaFePO4 with Li substitutions
- Author
-
Kai-Ming Ho, Renhai Wang, Feng Zhang, Cai-Zhuang Wang, Xin Zhao, Shunqing Wu, and Zijing Lin
- Subjects
Battery (electricity) ,Olivine ,Materials science ,General Physics and Astronomy ,chemistry.chemical_element ,Thermodynamics ,02 engineering and technology ,Maricite ,Crystal structure ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Cathode ,0104 chemical sciences ,law.invention ,chemistry ,law ,Phase (matter) ,engineering ,Lithium ,Chemical stability ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
Due to the high cost and insufficient resources of lithium, alternative sodium-ion batteries have been widely investigated for large-scale applications. NaFePO4 has the highest theoretical capacity of 154 mA h g-1 among the iron-based phosphates, which makes it an attractive cathode material for Na-ion batteries. Experimentally, LiFePO4 has been highly successful as a cathode material in Li-ion batteries because its olivine crystal structure provides a stable framework during battery cycling. In NaFePO4, maricite replaces olivine as the most stable phase. However, the maricite phase is experimentally found to be electrochemically inactive under normal battery operating voltages (0-4.5 V). We found that partial substitutions of Na with Li stabilize the olivine structure and may be a way to improve the performance of NaFePO4 cathodes. Using the previously developed structural LiFePO4 database, we examined the low-energy crystal structures in the system when we replace Li with Na. The known maricite and olivine NaFePO4 phases are reconfirmed and an unreported phase with energy between them is identified by our calculations. Besides, the Li-doped olivine type compound LixNa1-xFePO4 with mixed alkali ions retains better energetic stability compared with the other two types of structures of the same composition, as long as the proportion of Li exceeds 0.25. The thermodynamic stability of o-type LixNa1-xFePO4 can be further improved at finite temperatures. The primary limitation of the calculations is that we mainly focus on the zero-temperature condition; however, the relative stability of the structures may vary depending on the ambient temperature.
- Published
- 2020
10. Polyamorphism in K2Sb8Se13 for multi-level phase-change memory
- Author
-
Xiaomin Cheng, Kai-Ming Ho, Hao Tong, Songyou Wang, Cai-Zhuang Wang, Kan-Hao Xue, Chong Qiao, Ming Xu, Xiangshui Miao, and Meng Xu
- Subjects
Materials science ,Stacking ,3D XPoint ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electron localization function ,0104 chemical sciences ,Amorphous solid ,Phase-change memory ,Chemical physics ,Phase (matter) ,Polyamorphism ,Materials Chemistry ,Density of states ,0210 nano-technology - Abstract
Phase change memory is an excellent candidate for next-generation memory technologies with a high operation speed, but the memory capacity is not very satisfactory, due to which engineers have to add the 3D stacking technology (3D XPoint) for new products. Alternatively, multi-level storage is an easy approach to enable large data density and probably future neuromorphic computing. Lately, K2Sb8Se13 has attracted considerable attention as a multi-level phase change material because it exhibits an interesting amorphous-to-amorphous (polyamorphic) transformation before crystallization, and these two polyamorphic states as well as the crystalline phase show distinct resistances, adding a new data state to the existing “0” and “1”. Understanding and stabilizing this new amorphous state is the key to the application of this material; here, we have investigated these two amorphous states through ab initio simulations. We found that these two states showed obvious differences in the local structures, and the void concentration revealed by the low-electron-density areas indicated stronger interactions between the atomic clusters in the denser phase. The density of states and electron localization function were analyzed and we confirmed that adding electronic holes were largely responsible for the decrease in resistance. In this work, we have discovered the origin of multi-level resistance states in K2Sb8Se13, paving the way for the design of new phase change memory devices based on this material.
- Published
- 2020
11. Origin of short- and medium-range order in supercooled liquid Ge3Sb2Te6 using ab initio molecular dynamics simulations
- Author
-
Y. R. Guo, Kai-Ming Ho, Cai-Zhuang Wang, Yu Jia, Songyou Wang, and Chong Qiao
- Subjects
Materials science ,Coordination number ,General Physics and Astronomy ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,law.invention ,Amorphous solid ,Ab initio molecular dynamics ,Bond length ,Order (biology) ,Chemical bond ,Chemical physics ,law ,0103 physical sciences ,Physical and Theoretical Chemistry ,Crystallization ,010306 general physics ,0210 nano-technology ,Supercooling - Abstract
Phase-change materials such as Ge–Sb–Te compounds have attracted much attention due to their potential value in electrical data storage. In contrast to the amorphous and crystalline phases, supercooled liquids are far from being deeply understood despite their inevitable role in both amorphization and crystallization processes. To this end, we have studied the dynamics properties and structural characteristics of liquid and supercooled liquid Ge3Sb2Te6 during the fast cooling process. As the temperature decreases, chemical bonds become more homogeneous, but coordination numbers of Ge, Sb and Te atoms change very little. Meanwhile, the structural order of short-range configuration is obviously enhanced. Further studies suggest that Ge-centered, Sb-centered and Te-centered configurations change to the more ordered defective octahedrons mainly by adjusting the bond-angle relationship and bond length, rather than just by changing the coordination environment. It is the more ordered octahedrons that promote the formation of medium-range order. Our findings provide a deep insight into the origin of local structural order in supercooled liquid Ge3Sb2Te6, which is of great importance for the comprehensive understanding of amorphization and crystallization processes.
- Published
- 2020
12. Adsorption behaviors of branched cationic gemini surfactants and wettability in quartz–solution–air systems
- Author
-
Lu Zhang, Feng Yan, Ming Gao, Xiao-Guang Wang, Ma Desheng, Qun Zhang, Weifeng Lv, Zhao-Hui Zhou, Lei Zhang, and Hong-Zhuang Wang
- Subjects
Aqueous solution ,Materials science ,technology, industry, and agriculture ,02 engineering and technology ,General Chemistry ,Adhesion ,respiratory system ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,complex mixtures ,01 natural sciences ,0104 chemical sciences ,Contact angle ,Surface tension ,Adsorption ,Chemical engineering ,Pulmonary surfactant ,Critical micelle concentration ,Wetting ,0210 nano-technology - Abstract
The adsorption and wetting on quartz surfaces by aqueous solutions of xylyl-substituted biquaternary ammonium salt gemini surfactants with different spacer groups (C3 and C6), have been investigated. The interfacial properties of surfactant solutions such as contact angle, adhesional tension (γLV cos θ), quartz–water interfacial tension (γSL) as well as adhesion work (WA) have been estimated. The obtained results show that C3 and C6 have similar adsorption behavior on quartz surfaces. Before critical micelle concentration (cmc) is reached, the contact angles of gemini surfactants slowly increase with the increasing concentration, and the adsorption amount at the water–air interface is almost the same as those at a quartz–water interface. After reaching cmc, the gemini surfactant Cn molecules form a more compact adsorption film through bending the flexible spacer chain, instead of forming a bi-layer. As a result, a further increase in quartz–liquid interfacial tension (γSL) and a consequent increase in contact angle have been observed after cmc. Gemini C6 shows a stronger ability towards hydrophobic modification at a quartz surface than C3, demonstrating the contribution of the longer methylene spacer to the hydrophobic modification of the quartz surface.
- Published
- 2020
13. Synergistic computational and experimental discovery of novel magnetic materials
- Author
-
Cai-Zhuang Wang, Kai-Ming Ho, Masahiro Sakurai, Xiaoshan Xu, Balamurugan Balasubramanian, David J. Sellmyer, and James R. Chelikowsky
- Subjects
Materials science ,Global challenges ,Process Chemistry and Technology ,Biomedical Engineering ,Energy Engineering and Power Technology ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Magnetocrystalline anisotropy ,01 natural sciences ,Engineering physics ,Industrial and Manufacturing Engineering ,Chemistry (miscellaneous) ,Fabrication methods ,Metastability ,0103 physical sciences ,Genetic algorithm ,Materials Chemistry ,Chemical Engineering (miscellaneous) ,Curie temperature ,010306 general physics ,0210 nano-technology ,Throughput (business) ,Energy (signal processing) - Abstract
New magnetic materials for energy and information-processing applications are of paramount importance in view of significant global challenges in environmental and information security. The discovery and design of materials requires efficient computational and experimental approaches for high throughput and efficiency. When increasingly powerful computational techniques are combined with special non-equilibrium fabrication methods, the search can uncover metastable compounds with desired magnetic properties. Here we review recent results on novel Fe-, Co- and Mn-rich magnetic compounds with high magnetocrystalline anisotropy, saturation magnetization, and Curie temperature created by combining experiments, adaptive genetic algorithm searches, and advanced electronic-structure computational methods. We discuss structural and magnetic properties of such materials including Co– and/or Fe–X compounds (X = N, Si, Sn, Zr, Hf, Y, C, S, Ti, or Mn), and their prospects for practical applications.
- Published
- 2020
14. Understanding CrGeTe3: an abnormal phase change material with inverse resistance and density contrast
- Author
-
Meng Xu, Xiangshui Miao, Kai-Ming Ho, Xiaomin Cheng, Hao Tong, Ming Xu, Cai-Zhuang Wang, Zhenhai Yu, Songyou Wang, Y. R. Guo, Chao Chen, and Kailang Xu
- Subjects
Dynamic random-access memory ,Materials science ,Condensed matter physics ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Atomic packing factor ,01 natural sciences ,Phase-change material ,0104 chemical sciences ,Amorphous solid ,law.invention ,Phase-change memory ,Non-volatile memory ,law ,Materials Chemistry ,Thermal stability ,Crystallization ,0210 nano-technology - Abstract
Phase change memory is an emerging nonvolatile memory technology, recently becoming the center of attention to bridge the speed gap between fast dynamic random access memory and slow flash-based solid-state drives. Lately, CrGeTe3 has been investigated as a special phase change material with an inverse resistance and density change. This material has excellent properties such as good thermal stability, ultralow-energy glass formation process and almost zero mass-density change upon crystallization. Here, we analyzed the amorphous structure of this abnormal material in detail through ab initio simulations and discovered that the metallic-like tight atomic packing is the origin of the high carrier concentration and high mass density in the amorphous phase. Furthermore, the bonding analysis confirms that it is the short Cr–Cr bonds that lead to high packing efficiency in the amorphous local order. Our results discovered the material gene of the amorphous CrGeTe3, paving the way for the design of high-performance memory devices based on this material.
- Published
- 2019
15. Wetting of polymer surfaces by aqueous solutions of branched cationic Gemini surfactants
- Author
-
Lu Zhang, Ma Desheng, Rong Wang, Weifeng Lv, Hong-Zhuang Wang, Zhao-Hui Zhou, Lei Zhang, Wen-Li Luo, and Qun Zhang
- Subjects
chemistry.chemical_classification ,Materials science ,Tension (physics) ,02 engineering and technology ,General Chemistry ,Adhesion ,Polymer ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Surface tension ,Hydrophobic effect ,Contact angle ,Adsorption ,Chemical engineering ,chemistry ,Wetting ,0210 nano-technology - Abstract
The adsorption of xylyl-substituted biquaternary ammonium salt Gemini surfactants with different spacer (C3 and C6) at polytetrafluoroethylene (PTFE) and polymethylmethacrylate (PMMA) surfaces has been investigated and the different adsorption parameters such as surface tension, contact angle, adhesional tension, solid-water interfacial tension and work of adhesion have been estimated. The results show that C3 and C6 have similar adsorption behaviors at PTFE and PMMA surfaces. C3 and C6 adsorb gradually at a PFTE-water interface via hydrophobic interactions and the adsorption amounts at the water-air interface are almost three times higher than those at the PTFE-water interface due to the steric hindrance effect. However, the contact angle keeps constant throughout the experimental concentration range because the decrease in surface tension just counterbalances the decrease in PFTE-water interfacial tension. On the other hand, C3 and C6 adsorb at the PMMA surface via polar interactions between xylyl and functional groups of PMMA before CMC. Similar to PTFE, the increase in PMMA-water interfacial tension compensates the decrease in surface tension and the contact angle also shows a stationary value before the CMC. A bi-layer structure of C3 and C6 will be formed at the PMMA-water interface via hydrophobic interaction and PMMA-water interfacial tension decreases consequently after the CMC, which results in the decrease in contact angle.
- Published
- 2019
16. Novel superconducting structures of BH2 under high pressure
- Author
-
Wen-Cai Lu, Cai-Zhuang Wang, Wen-Hua Yang, Xu-Yan Xue, Kai-Ming Ho, Qing-Jun Zang, and Shan-Dong Li
- Subjects
Superconductivity ,Materials science ,Condensed matter physics ,General Physics and Astronomy ,02 engineering and technology ,Crystal structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Metal ,visual_art ,Phase (matter) ,High pressure ,Homogeneous space ,visual_art.visual_art_medium ,Coupling (piping) ,Density functional theory ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
The crystal structures of boron hydrides in a pressure range of 50-400 GPa were studied using the genetic algorithm (GA) method combined with first-principles density functional theory calculations. BH4 and BH5 are predicted to be thermodynamically unstable. Two new BH2 structures with Cmcm and C2/c space group symmetries, respectively, were predicted, in which the B atoms tend to form two-dimensional sheets. The calculated band structures showed that in the pressure range of 50-150 GPa, the Cmcm-BH2 phase has very small gaps, while the C2/c-BH2 phase at 200-400 GPa is metallic. The superconductivity of the C2/c-BH2 structure was also investigated, and electron-phonon coupling calculations revealed that the estimated Tc values of C2/c-BH2 are about 28.18-37.31 K at 250 GPa.
- Published
- 2019
17. Unraveling the structural and bonding nature of antimony sesquichalcogenide glass for electronic and photonic applications
- Author
-
Cai-Zhuang Wang, Songyou Wang, Hao Tong, Xiaomin Cheng, Kai-Ming Ho, Rongchuan Gu, Xiangshui Miao, Ming Xu, Chong Qiao, and Meng Xu
- Subjects
Materials science ,business.industry ,Band gap ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Amorphous solid ,Antimony ,chemistry ,Ab initio quantum chemistry methods ,Distortion ,Materials Chemistry ,Optoelectronics ,Thermal stability ,Photonics ,0210 nano-technology ,business ,Porosity - Abstract
Sb-Based phase-change materials have exhibited tremendous advantages in both data storage and reconfigurable photonic devices. Despite the intensive studies on their structures and properties in the crystalline state, the widely used amorphous phase remains elusive. Here, we investigate amorphous Sb2Te3, Sb2Se3, and Sb2S3 through ab initio calculations to link their unique properties to the local structure and bonding nature. We discover that Sb forms shorter and stronger bonds with Se and S than Te, and the average bonding angles of Se (92.0°) and S (94.1°) show larger distortion than that of Te (91.5°). This leads to larger Peierls-like distortion in Sb2Se3 and Sb2S3. On the other hand, more charge transfer and void fraction are presented, opening band gaps and leading to different electronic and optical properties. In contrast, Sb2Te3, due to its semiconducting behavior and low thermal stability, enables its application in phase-change memory. Our results reveal the physics of vastly different electronic and optical properties induced by S, Se, and Te alloying, providing an effective strategy for materials design.
- Published
- 2021
18. Evolution of short- and medium-range order in the melt-quenching amorphization of Ge2Sb2Te5
- Author
-
Songyou Wang, Jiao Wang, Yu-Xiang Zheng, Y. R. Guo, Cai-Zhuang Wang, F. Dong, Ming Xu, Hong Shen, Chong Qiao, Xiangshui Miao, Kai-Ming Ho, Liang-Yao Chen, and R. J. Zhang
- Subjects
Work (thermodynamics) ,Phase transition ,Materials science ,02 engineering and technology ,General Chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Amorphous solid ,law.invention ,Molecular dynamics ,Octahedron ,Chemical physics ,law ,0103 physical sciences ,Materials Chemistry ,Cluster (physics) ,Crystallization ,010306 general physics ,0210 nano-technology ,Supercooling - Abstract
Phase-change memory takes advantage of the fast phase transition between amorphous and crystalline phases of phase-change materials (e.g., Ge2Sb2Te5 or GST). To date, while the “SET” process (crystallization of GST glass) has been intensively studied, studies on the “RESET” process (melt-quenching amorphization of GST) are still limited. In this work, we explored the structural changes of GST upon rapid cooling by ab initio molecular dynamics simulations and atomistic cluster alignment (ACA) analysis. Different from other methods which only focus on the nearest bonding atoms, the ACA method can study both the short- and medium-range order clusters containing atoms beyond the first-neighboring shell and enables us to explore the changes of cluster structures in a larger scale. The results reveal that low-coordinated octahedral clusters tend to become high-coordinated ones, and Ge-centered octahedral structures change to tetrahedrons whereas Sb-centered tetrahedrons transform to octahedral structures during the amorphization process. Interestingly, tetrahedrons show aggregation in liquid and supercooled liquid in contrast to 6-fold octahedrons which present notable aggregation in amorphous GST. Moreover, our study showed that wrong bonds (Ge–Ge, Sb–Sb, Ge–Sb and Te–Te bonds) can promote the formation of large rings, and irreducible rings tend to separate into smaller and larger rings as the temperature is decreased. Our findings provide useful insights into the formation process and the structure of amorphous GST, which is valuable for facilitating the application of phase change materials.
- Published
- 2018
19. Structural signature and transition dynamics of Sb2Te3 melt upon fast cooling
- Author
-
Jiao Wang, Songyou Wang, Y. R. Guo, Chong Qiao, Cai-Zhuang Wang, R. J. Zhang, F. Dong, Ming Xu, Liang-Yao Chen, Yu-Xiang Zheng, and Kai-Ming Ho
- Subjects
Quenching ,Work (thermodynamics) ,Phase transition ,Materials science ,General Physics and Astronomy ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Amorphous solid ,Fragility ,Distribution function ,Chemical physics ,Topological insulator ,0103 physical sciences ,Atomic number ,Physical and Theoretical Chemistry ,010306 general physics ,0210 nano-technology - Abstract
Crystalline Sb2Te3 is widely studied due to its important applications in memory materials and topological insulators. The liquid and amorphous structures of this compound as well as the dynamics upon quenching, however, are yet to be fully understood. In this work, we have systematically studied the dynamical properties and local structure of Sb2Te3 at different temperatures using ab initio molecular dynamics simulations. The calculated structure factors agree well with the experimental results. The atomic number density and mean-squared displacement as a function of temperature clearly indicate three states as the temperature decreases, namely, melt, undercooled liquid and glass state, respectively. By analyzing the chemical environments and bond-angle distribution functions, we demonstrate that the most probable short-range motifs in the Sb2Te3 system are defective octahedrons, and they are connected with each other via four-fold rings. This interesting structural feature may be responsible for the high fragility and easy phase transition upon glass forming that is applied in memory devices.
- Published
- 2018
20. Fe–Si networks and charge/discharge-induced phase transitions in Li2FeSiO4 cathode materials
- Author
-
Zi-Zhong Zhu, Manh Cuong Nguyen, Zijing Lin, Xin Zhao, Cai-Zhuang Wang, Kai-Ming Ho, Xiaobao Lv, and Shunqing Wu
- Subjects
Phase transition ,Work (thermodynamics) ,Materials science ,General Physics and Astronomy ,Charge (physics) ,02 engineering and technology ,Crystal structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Cathode ,0104 chemical sciences ,law.invention ,Chemical physics ,law ,Formula unit ,Atom ,Physical and Theoretical Chemistry ,0210 nano-technology ,Charge discharge - Abstract
Structural phase transitions of electrode materials are responsible for poor reversibility during charge/discharge cycling in Li-ion batteries. Using previously developed structural databases, we investigate a structural landscape for LixFeSiO4 systems at x = 1. Starting with low-energy Li2FeSiO4 crystal structures, we explore the crystal structures of the material in different states of charge. The as-prepared Li2FeSiO4 materials adopt low energy structures characterized by two-dimensional (2D) Fe-Si networks. After the removal of one Li per formula unit to form LiFeSiO4, the structures with three-dimensional (3D) diamond-like Fe-Si networks become more energetically favorable without a significant impact on the charge capacity, which agrees with previous experimental and theoretical work. However, we reveal that the structure with a 3D diamond-like Fe-Si network can further transform into a new structure at x = 1. And the Li atom is hard to reinsert into these new structures. Consequently the system is prevented from returning to the Li2FeSiO4 state. We believe that the formation of this new structure plays an important role in the loss of reversible capacity of Li2FeSiO4 electrode materials.
- Published
- 2018
21. A scheme for the generation of Fe–P networks to search for low-energy LiFePO4 crystal structures
- Author
-
Manh Cuong Nguyen, Ping Wu, Yang Sun, Cai-Zhuang Wang, Kai-Ming Ho, Zijing Lin, Xin Zhao, Shunqing Wu, Yongliang Shi, and Xiaobao Lv
- Subjects
Scheme (programming language) ,Renewable Energy, Sustainability and the Environment ,Network generation ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,Crystal structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Polyhedron ,Crystallography ,Low energy ,chemistry ,Chemical physics ,Tetrahedron ,General Materials Science ,Lithium ,0210 nano-technology ,computer ,Complement (set theory) ,computer.programming_language - Abstract
Herein we present a network generation scheme to explore the structural diversity of LiFePO4, which is an important cathode material in Li-ion batteries. With our scheme, networks of Fe and P atoms were initially constructed as the backbone structures using structural motifs for the FePx and FePx configurations, obtained from existing structural databases. Then, O atoms were added, resulting in the formation of PO4 tetrahedra and different types of Fe–O polyhedra. Finally, Li atoms were inserted into the vacancies within the generated FePO4 structures. We searched structures with FeO4, FeO5, or FeO6 polyhedra (unit cell with sizes of up to 4 formula units) and obtained ∼8 times more low-energy structures through our database than through existing databases. Furthermore, using our more comprehensive structural database, we unveiled a number of rules for identifying low-energy structures. These improved results complement the existing databases and are valuable for further research on structural transformations in similar materials by changing lithium or sodium cation populations.
- Published
- 2017
22. Si-centered capped trigonal prism ordering in liquid Pd82Si18 alloy study by first-principles calculations
- Author
-
G. Q. Yue, F. Dong, Cai-Zhuang Wang, Y. Sun, Zhuo Wang, Kai-Ming Ho, Wan-Sheng Su, Songyou Wang, Ren Zhang, Chong Qiao, Y. R. Guo, Yinying Zheng, Lingdi Chen, and Matthew J. Kramer
- Subjects
Diffraction ,Materials science ,General Chemical Engineering ,Alloy ,02 engineering and technology ,General Chemistry ,engineering.material ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular dynamics ,Crystallography ,Trigonal prism ,0103 physical sciences ,engineering ,010306 general physics ,0210 nano-technology ,Eutectic system - Abstract
First-principles molecular dynamic (MD) simulation and X-ray diffraction were employed to study the local structures of Pd–Si liquid at the eutectic composition (Pd82Si18). A strong repulsion is found between Si atoms, and Si atoms prefer to be evenly distributed in the liquid. The dominate local structures around Si atoms are found to be with of a trigonal prism capped by three half-octahedra and an archimedean anti-prism. The populations of these clusters increase significantly upon cooling, and may play an important role in the formation of Pd82Si18 alloy glass.
- Published
- 2017
23. Novel penta-graphene nanotubes: strain-induced structural and semiconductor–metal transitions
- Author
-
Kai-Ming Ho, Liang-Yao Chen, Zhanyu Wang, Wan-Sheng Su, Xinran Cao, Yu-Xiang Zheng, Cai-Zhuang Wang, R. J. Zhang, Chong Qiao, Songyou Wang, Bih-Yaw Jin, and Yuan-Jia Fan
- Subjects
Phase transition ,Nanotube ,Materials science ,business.industry ,Band gap ,Phonon ,Penta-graphene ,Nanotechnology ,02 engineering and technology ,Carbon nanotube ,021001 nanoscience & nanotechnology ,01 natural sciences ,law.invention ,Molecular dynamics ,Semiconductor ,Chemical physics ,law ,0103 physical sciences ,General Materials Science ,010306 general physics ,0210 nano-technology ,business - Abstract
Research into novel one-dimensional (1D) materials and associated structural transitions is of significant scientific interest. It is widely accepted that a 1D system with a short-range interaction cannot have 1D phase transition at finite temperature. Herein, we propose a series of new stable carbon nanotubes by rolling up penta-graphene sheets, which exhibit fascinating well-defined 1D phase transitions triggered by axial strain. Our first-principles calculations show that such penta-graphene nanotubes (PGNTs) are dynamically stable by phonon calculations, but transform from a tri-layer structure to a highly defective single-walled nanotube at low temperature in molecular dynamics simulations. We show that moderate compressive strains can drive structural transitions of (4,4), (5,5), and (6,6) PGNTs, during which the distances of neighboring carbon dimers in the inner shell have a sudden drop, corresponding to dimer-dimer nonbonding to bonding transitions. After such transition, the tubes become much more thermally stable and undergo semiconductor-metal transitions under increasing strain. The band gaps of PGNTs are not sensitive to chirality whereas they can be tuned effectively from visible to short-wavelength infrared by appropriate strain, making them appealing materials for flexible nano-optoelectronics. These findings provide useful insight into unusual phase transitions in low-dimensional systems.
- Published
- 2017
24. Crystal genes in a marginal glass-forming system of Ni50Zr50
- Author
-
Cai-Zhuang Wang, Ling Tang, Nan Wang, Yang Sun, Kai-Ming Ho, and Tongqi Wen
- Subjects
Materials science ,Amorphous metal ,General Physics and Astronomy ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter::Disordered Systems and Neural Networks ,01 natural sciences ,Glass forming ,Annealing (glass) ,Condensed Matter::Soft Condensed Matter ,Crystal ,Metal ,Crystallography ,Molecular dynamics ,Chemical physics ,Metastability ,visual_art ,0103 physical sciences ,visual_art.visual_art_medium ,Physical and Theoretical Chemistry ,Analysis tools ,010306 general physics ,0210 nano-technology - Abstract
The marginal glass-forming ability (GFA) of a binary Ni-Zr system is an issue to be explained considering numerous bulk metallic glasses (BMGs) found in a Cu-Zr system. Using molecular dynamics, the structures and dynamics of Ni50Zr50 metallic liquid and glass are investigated at the atomistic level. To achieve a well-relaxed glassy sample, a sub-Tg annealing method is applied and the final sample is closer to the experiments than the models prepared by continuous cooling. With the state-of-the-art structural analysis tools such as cluster alignment and pair-wise alignment methods, two glass-forming motifs with some mixed traits of a metastable B2 crystalline phase and a crystalline Ni-centered B33 motif are found to be dominant in the undercooled liquid and glass samples. A new chemical order characterization on each short-range order (SRO) structure is accomplished based on the cluster alignment method. The significant amount of the crystalline motif and the few icosahedra in the glassy sample deteriorate the GFA.
- Published
- 2017
25. In silico prediction of serious eye irritation or corrosion potential of chemicals
- Author
-
Zhuang Wang, Xiao Li, Weihua Li, Yingchun Cai, Qin Wang, Guixia Liu, Yin-Yin Wang, Yun Tang, and Hongbin Yang
- Subjects
0301 basic medicine ,Corrosion potential ,Training set ,business.industry ,General Chemical Engineering ,In silico ,External validation ,Eye irritation ,General Chemistry ,Toxicology ,03 medical and health sciences ,030104 developmental biology ,Health hazard ,Statistics ,Medicine ,Information gain ,business - Abstract
Rapidly and correctly identifying eye irritants or corrosive chemicals is an important issue in health hazard assessment. The purpose of this study is to describe the development of in silico methods for the classification of chemicals into irritants/corrosives or non-irritants/non-corrosives. A total of 5220 chemicals for a serious eye irritation (EI) dataset and 2299 chemicals as an eye corrosion (EC) dataset were collected from available databases and literature. Structure–activity relationship (SAR) models were developed to separately predict serious EI or EC via machine learning methods. According to the overall prediction accuracy, the Pub-SVM model gave the best results for both serious EI (overall classification accuracy CA = 0.946) and EC (CA = 0.959). The sensitivity and specificity of serious EI were 97.3% and 86.7% for the training set, and 96.9% and 82.7% for the external validation set, respectively. Similarly, the sensitivity and specificity of EC were 95.5% and 96.2% for the training set, and 94.9% and 96.2% for the external validation set, respectively. The high specificity and sensitivity indicated that our models were reliable and robust, which can be used to predict the potential seriousness of EI/EC of compounds. Moreover, several structural alerts for characterizing serious EI/EC were identified using the combination of information gain and substructure frequency analysis.
- Published
- 2017
26. Effect of morphology on the oxygen evolution reaction for La0.8Sr0.2Co0.2Fe0.8O3−δelectrochemical catalyst in alkaline media
- Author
-
Jianan Han, Chenghao Liang, Liquan Fan, Mian Li, Zhuang Wang, and Yueping Xiong
- Subjects
Materials science ,General Chemical Engineering ,Oxygen evolution ,Nanoparticle ,Nanotechnology ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electrospinning ,0104 chemical sciences ,Catalysis ,Chemical engineering ,Nanofiber ,Specific surface area ,Nanorod ,0210 nano-technology ,Perovskite (structure) - Abstract
A series of perovskite oxides La0.8Sr0.2Co0.2Fe0.8O3−δ (LSCF-10%, LSCF-20% and LSCF-30%) with different morphologies (nanofibers, nanorods and nanoparticles) are synthesized as oxygen evolution reaction (OER) electrocatalysts by an electrospinning technique. In alkaline media, the LSCF-10% catalyst exhibits remarkable electrocatalytic activity and stability for OER, affording a low onset potential of 1.583 V and a stable current density of 10 mA cm−2 with a potential of 1.643 V. The excellent catalytic activity of OER for LSCF-10% is mainly attributed to the morphological characteristics of one-dimensional nanofibers. Compared with the nanorods and nanoparticles, one-dimensional nanofibers not only increase the specific surface area, but also enhance the efficient transport pathways for electrons and ions. Thus, the rational design of the morphology is beneficial to enhance the OER catalytic activities of the perovskite oxides.
- Published
- 2016
27. Electrochemically self-doped hierarchical TiO2 nanotube arrays for enhanced visible-light photoelectrochemical performance: an experimental and computational study
- Author
-
Cai-Zhuang Wang, Jianjun Liao, Yue Yang, Shiwei Lin, Na Li, Yanfang Li, and Xiankun Cao
- Subjects
Photocurrent ,Materials science ,Nanostructure ,business.industry ,General Chemical Engineering ,Doping ,Nanotechnology ,02 engineering and technology ,General Chemistry ,Electron ,Conductivity ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,0104 chemical sciences ,Optoelectronics ,0210 nano-technology ,business ,Shallow donor ,Visible spectrum - Abstract
A two-step electrochemical anodization method was used to prepare typical hierarchical top-ring/bottom-tube TiO2 nanotube arrays (TNTAs). Ti3+ self-doping into TiO2 was achieved via electrochemical reduction at different negative potentials in the range from −1.0 V to −1.6 V. Compared with the pristine TNTAs, the TNTAs reduced at −1.4 V presented a dramatically enhanced photoelectrochemical performance, which showed a 2.4 times enhancement in photocurrent density under simulated AM 1.5G illumination and 2.3 times increase in visible-light photocurrent density. Approximately 100% improvement in photoelectrochemical catalytic efficiency was obtained in a phenol degradation experiment. First-principles calculations demonstrated that the new states induced by Ti3+ self-doping might act as a shallow donor level to promote the separation of photogenerated electron–hole pairs. Moreover, the light absorption improved by the hierarchical nanostructure and the excellent electron conductivity induced by Ti3+ doping also account for the enhancement in the photoelectrochemical performance. These results suggest a reasonable design of photoelectrodes for efficient photoelectrochemical applications in the future.
- Published
- 2016
28. An effective approach to protect the Sm0.5Sr0.5Co3−δ (SSC) cathode from SO2 in SOFCs
- Author
-
Zhuang Wang, Yueping Xiong, Xiaotian Liu, Keqing Gao, and Chenghao Liang
- Subjects
Materials science ,020209 energy ,General Chemical Engineering ,Cathodic polarization ,02 engineering and technology ,General Chemistry ,021001 nanoscience & nanotechnology ,Microstructure ,Durability ,Cathode ,Electrospinning ,law.invention ,Ambient air ,Chemical engineering ,law ,Nanofiber ,0202 electrical engineering, electronic engineering, information engineering ,0210 nano-technology ,Layer (electronics) - Abstract
An issue associated with the use of Sm0.5Sr0.5Co3−δ (SSC) as the cathode in SOFCs is the unexpected reactions between Sm or/and Sr and SO2 from ambient air, forming a passivated layer on the surface of the SSC cathode and thus lowering the durability of the SSC cathode. Here, we develop four types of SSC cathode (SSC-particles, SSC-particles with Mg/Fe layer, SSC-nanofibers and SSC-nanofibers with Mg/Fe layer) and carry out four different cell tests with the four kinds of cathode to examine the durability of Sm0.5Sr0.5Co3−δ (SSC) cathode when exposed to ambient air containing SO2. SSC-particles and SSC-nanofibers are prepared by sol–gel method and electrospinning method, and Mg/Fe protective layer is infiltrated into SSC-particles and SSC-nanofibers to form the cathode with Mg/Fe layer, respectively. It is shown that after discharging with the ambient air containing SO2, the microstructure and cathodic polarization resistances of all the four cathode are changed. More impressively, compared with the SSC-particles cathode, the use of the SSC-nanofibers cathode with Mg/Fe layer decreases the decline rate of current up to 50%. The significant improvement in the durability is mainly attributed to the fact that a specific network space of the nanofibers can make the Mg/Fe layer surround and run through the entire cathode, and the Mg/Fe layer will react with SO2 first to protect the cathode. It is suggested that the combination of the nanofiber structure and the Mg/Fe protective layer is an effective approach to protect the SSC cathode from SO2.
- Published
- 2016
29. Growth mode and structures of magnetic Mn clusters on graphene
- Author
-
Xiaojie Liu and Cai-Zhuang Wang
- Subjects
Range (particle radiation) ,Materials science ,Condensed matter physics ,Magnetic moment ,Graphene ,General Chemical Engineering ,Nucleation ,02 engineering and technology ,General Chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,law.invention ,Adsorption ,Chemical physics ,law ,0103 physical sciences ,010306 general physics ,0210 nano-technology - Abstract
We present a systematic study of Mn clusters on graphene by first-principles calculations. We show that the growth of Mn on graphene follows a three-dimensional (3D) mode. Both adsorption and attachment energies show that (Mn)3 and (Mn)6 on graphene are energetically favorable in the size range (Mn)1–7. Moreover, the larger formation energy for Mn clusters on graphene implies that the incoming Mn atoms are likely to nucleate and grow into bigger and bigger Mn clusters on graphene. The magnetic moments of (Mn)1,5,7 on graphene are enhanced by 11%, 186%, and 26% from their values at free-standing clusters, respectively. By contrast, the net magnetic moment of (Mn)2,3,4,6 on graphene is reduced from that of the corresponding free-standing clusters. The origin of the magnetic moment changes can be attributed to the charge transfer within the Mn clusters and between the clusters and graphene upon adsorption.
- Published
- 2016
30. A Gd0.2Ce0.8O1.9 impregnated Pr0.4Sr0.6Co0.2Fe0.7Nb0.1O3−δ nanofiber-structured composite anode in solid oxide fuel cells
- Author
-
Xiaotian Liu, Zhuang Wang, Liquan Fan, Yueping Xiong, and Keqing Gao
- Subjects
Materials science ,Hydrogen ,General Chemical Engineering ,Composite number ,Oxide ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Redox ,0104 chemical sciences ,Anode ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,0210 nano-technology ,Polarization (electrochemistry) - Abstract
In this study, comparative experiments were conducted based on La0.8Sr0.2Ga0.8Mg0.2O3−δ (LSGM) electrolytes, which supported single solid oxide fuel cells (SOFCs) with pure nanofiber-structured Pr0.4Sr0.6Co0.2Fe0.7Nb0.1O3−δ (PSCFN) anodes or Gd0.2Ce0.8O1.9 (GDC) impregnated PSCFN nanofiber-structured composite anodes. The polarization resistance (Rp) values of the pure nanofiber-structured PSCFN anode and the PSCFN–GDC nanofiber-structured composite anode with an optimal mass ratio of 1:0.56 were recorded as 1.573 Ω cm2 and 0.212 Ω cm2 at 850 °C in wet H2 (97% H2–3% H2O), respectively. After impregnating the GDC materials, the maximum power density (Pmax) of the single cell with the PSCFN–GDC nanofiber-structured composite anode was found to be about 1.5 times greater than that of the pure nanofiber-structured PSCFN anode at 850 °C in wet H2. The cell with the PSCFN–GDC nanofiber-structured composite anode presented a significant electrochemical performance in wet H2. Meanwhile it also showed excellent thermal cycling and long-term stability during the redox and constant-current discharge testing (300 mA cm−2) at 850 °C in wet H2. All of these results indicated that the PSCFN–GDC nanofiber-structured composite anode acted as an efficient and competitive power anode operating in hydrogen fuels.
- Published
- 2016
31. Distribution of boundary planes in a (La0.67Nd0.33)B6polycrystalline bulk prepared by spark plasma sintering
- Author
-
Zhuang Wang, Xiaokun Yuan, Jiuxing Zhang, Qiang Ma, Ming Yue, Dongtao Zhang, Shenlin Zhou, and Jie Zhu
- Subjects
Phase boundary ,Materials science ,Misorientation ,Condensed matter physics ,Boundary (topology) ,General Chemistry ,Type (model theory) ,Condensed Matter Physics ,Orientation (vector space) ,Crystallography ,General Materials Science ,Grain boundary ,Crystallite ,Electron backscatter diffraction - Abstract
The electron backscatter diffraction approach and five parameter analysis method are used to investigate the orientation textures of boundary planes in a (La0.67Nd0.33)B6 polycrystalline bulk prepared by spark plasma sintering. While the entire boundaries overall favour the {001} orientation, the orientation textures of various boundary planes are not homogeneous. If divided by the boundary type, the LaB6/LaB6 grain boundary planes favour the {001} orientation, the NdB6/NdB6 grain boundary plane orientation approaches the {011} position, and the LaB6/NdB6 phase boundary planes favour the {011} orientation. If divided by the misorientation angle, boundaries with a misorientation angle lower than 10° favour the {011} orientation and boundaries with a misorientation angle higher than 10° favour the {001} orientation. Possible origins of the anisotropic distribution of boundary planes are analyzed. The potential effects of anisotropy in boundary plane distributions on electron emissivity are also suggested.
- Published
- 2015
32. Effect of selective solvent on the aggregate behavior of the mixed Langmuir monolayers of PS-b-PEO and PS-b-PMMA
- Author
-
Hongfei Li, Zhuang Wang, Xiaoqun Wang, Gangyao Wen, Changchun Huang, Tongfei Shi, and Fengyang Zhao
- Subjects
Langmuir ,Aggregate (composite) ,Morphology (linguistics) ,Ethylene oxide ,General Chemical Engineering ,technology, industry, and agriculture ,General Chemistry ,Micelle ,Solvent ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,Monolayer ,Organic chemistry ,Methyl methacrylate - Abstract
A selective solvent was used to study the aggregate behavior of mixed Langmuir monolayers of polystyrene-b-poly(ethylene oxide) (PS-b-PEO) and polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA). A peculiar hysteresis phenomenon is reported for the first time, in which the expansion curves cross their corresponding compression curves, and the final surface pressures after the expansion processes are significantly higher than, instead of close to, their initial compression values. The mixed Langmuir–Blodgett (LB) films exhibit more mixed circular micelles and fewer mixed rod-like aggregates with the increase of the PS-b-PEO content, which is quite different from those that only exhibit mixed circular micelles by using a nonselective solvent. So far we have carried out the progressive morphology evolution and the aggregate density control in the mixed LB films by using the selective spreading solvent and adjusting the blend composition and transfer pressure, which is an interesting way to control and design morphology into an ultrathin film for some applications such as nanopatterns and nanotemplates.
- Published
- 2014
33. Aggregation behavior of the blends of PS-b-PEO-b-PS and PS-b-PMMA at the air/water interface
- Author
-
Gangyao Wen, Yunbo Shi, Xiaoqun Wang, Zhuang Wang, and Changchun Huang
- Subjects
Langmuir ,Materials science ,Ethylene oxide ,General Chemical Engineering ,General Chemistry ,Micelle ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,Amphiphile ,Monolayer ,Polymer chemistry ,Copolymer ,Molecule ,Methyl methacrylate - Abstract
In order to explore the aggregation mechanisms of mixed polymeric Langmuir monolayers and enrich the structures of their corresponding Langmuir–Blodgett (LB) films, a predominantly hydrophilic triblock copolymer polystyrene-block-poly(ethylene oxide)-block-polystyrene (SEOS69K, Mn = 69 000, 43.5 wt% PEO) was mixed with an amphiphilic diblock copolymer polystyrene-block-poly(methyl methacrylate) (SMMA34K, Mn = 33 500, 26.9 wt% PMMA). The Langmuir monolayers and LB films of SEOS69K, SMMA34K, and their blends were characterized by the Langmuir monolayer technique and tapping mode atomic force microscopy (AFM), respectively. The isotherms of the samples deviate to large areas with the increase of the SEOS69K content and exhibit pseudo-plateaus for the samples with above 80 wt% SEOS69K. The hysteresis degree of the mixed Langmuir monolayer with 80 wt% SEOS69K compressed up to 30 mN m−1 is significantly larger than that with 20 wt% SEOS69K, which can be interpreted by a reasonable schematic illustration combining the predominant PEO and the few PEO/PMMA chain entanglements in the former with the low mobility of PEO and PMMA blocks. The mixed LB films with 10 wt% SEOS69K transferred at different pressures exhibit mixed structures of circular micelles and rod-like aggregates. However, all the other mixed LB films only exhibit circular micelles composed of PS cores and mixed PEO/PMMA coronas. Upon compression, the large close-packed aggregates split into small ones with more uniform sizes, which shows that the addition of SEOS69K can really improve the structure homogeneity of the mixed LB films. Moreover, a very simple formula was deduced to transform the isotherm of a mixed Langmuir monolayer as a function of a certain copolymer molecule area or repeating unit area.
- Published
- 2014
34. Metals on graphene: correlation between adatom adsorption behavior and growth morphology
- Author
-
Yongxin Yao, Cai-Zhuang Wang, Xiaojie Liu, Wen-Cai Lu, Myron Hupalo, Michael C. Tringides, and Kai-Ming Ho
- Subjects
Materials science ,Diffusion barrier ,Magnetic moment ,Graphene ,Inorganic chemistry ,General Physics and Astronomy ,Alkali metal ,law.invention ,Metal ,Adsorption ,Transition metal ,law ,Ab initio quantum chemistry methods ,Chemical physics ,visual_art ,visual_art.visual_art_medium ,Physical and Theoretical Chemistry - Abstract
We present a systematic study of metal adatom adsorption on graphene by ab initio calculations. The calculations cover alkali metals, sp-simple metals, 3d and group 10 transition metals, noble metals, as well as rare earth metals. The correlation between the adatom adsorption properties and the growth morphology of the metals on graphene is also investigated. We show that the growth morphology is related to the ratio of the metal adsorption energy to its bulk cohesive energy (E(a)/E(c)) and the diffusion barrier (ΔE) of the metal adatom on graphene. Charge transfer, electric dipole and magnetic moments, and graphene lattice distortion induced by metal adsorption would also affect the growth morphologies of the metal islands. We also show that most of the metal nanostructures on graphene would be thermally stable against coarsening.
- Published
- 2012
35. Comparing efficiencies of genetic and minima hopping algorithms for crystal structure prediction
- Author
-
Kai-Ming Ho, Min Ji, and Cai-Zhuang Wang
- Subjects
Maxima and minima ,Crystal ,Search algorithm ,Lattice (order) ,Genetic algorithm ,Evolutionary algorithm ,General Physics and Astronomy ,A priori and a posteriori ,Physical and Theoretical Chemistry ,Algorithm ,Crystal structure prediction ,Mathematics - Abstract
In this work several crystal structure prediction problems which have been studied by first-principles evolutionary algorithms recently are revisited. We increased the system size to see how the search efficiency changes with respect to problem size. We find that the relative performance and underlying mechanism of genetic algorithms in crystal structure searches for Al(x)Sc(1-x) strongly depend on the system composition as well as the size of the problem. Because of this strong dependence, caution should be taken in generalizing performance comparison from one problem to another even though they may appear to be similar. We also investigate the performance of the search algorithm for crystal structure prediction of boron with and without a priori knowledge of the lattice vectors. The results show that the degree of difficulty increases dramatically if the lattice vectors of the crystal are allowed to vary during the search. Comparison of the minima hopping algorithm with the genetic algorithm at small (10 atoms) to larger problem sizes is also carried out. At the small sizes we have tested, both methods show comparable efficiency. But at large sizes the genetic algorithm becomes advantageous over minima hopping.
- Published
- 2010
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.