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排序方式: 共有10000条查询结果,搜索用时 234 毫秒
61.
Huiyu Chen Xuming Du Jiale Sun Runze Wu Ya Wang Chunju Xu 《Ceramics International》2021,47(1):716-724
In this paper, a novel Co3O4 micro-bundles structure (Co3O4 MBs) was obtained at 120 °C after a hydrothermal reaction for 24 h and followed by an annealing treatment at 300 °C in air. The unique Co3O4 MBs are constructed by many adjacent flakes with 0.4 μm in thickness, and exhibit a large surface area of 81.2 m2 g?1 and a mean pore diameter of 6.14 nm, which may facilitate a sufficient contact with electrolyte and then shorten the diffusion pathway of ions. A remarkable electrochemical behavior including specific capacity of 282.3 C g?1 at 1 A g?1 and 205.9 C g?1 at 10 A g?1, and an excellent cycling performance with 74.6% capacity retention after 4000 charge-discharge process at 5 A g?1 are achieved when the test of Co3O4 MBs-modified electrode is performed using three-electrode configuration. Additionally, a hybrid supercapacitor (HSC) was fabricated with the obtained Co3O4 MBs as positive electrode and commercial activated carbon (AC) as negative electrode. The HSC exhibits a specific capacity of 144.1 C g?1 at 1 A g?1 and 126.4% capacity retention after 5000 cycles at 5 A g?1. An energy density of 38.5 W h kg?1 can be obtained at a power density of 962.0 W kg?1, and 29.5 W h kg?1 is still retained at 8532.5 W kg?1. The simple synthetic strategy can be applicable to the synthesis of other transition metal oxides with superior electrochemical performance. 相似文献
62.
《Journal of the European Ceramic Society》2022,42(13):5893-5903
Technical ceramics exhibit exceptional high-temperature properties, but unfortunately their extreme crack sensitivity and high melting point make it challenging to manufacture geometrically complex structures with sufficient strength and toughness. Emerging additive manufacturing technologies enable the fabrication of large-scale complex-shape artifacts with architected internal topology; when such topology can be arranged at the microscale, the defect population can be controlled, thus improving the strength of the material. Here, ceramic micro-architected materials are fabricated using direct ink writing (DIW) of an alumina nanoparticle-loaded ink, followed by sintering. After characterizing the rheology of the ink and extracting optimal processing parameters, the microstructure of the sintered structures is investigated to assess composition, density, grain size and defect population. Mechanical experiments reveal that woodpile architected materials with relative densities of 0.38–0.73 exhibit higher strength and damage tolerance than fully dense ceramics printed under identical conditions, an intriguing feature that can be attributed to topological toughening. 相似文献
63.
《Journal of the European Ceramic Society》2022,42(6):2957-2973
Functionally graded ceramics (FGC), which combine properties of different ceramics in one part, usually have better comprehensive function and structural efficiency. In this study, four different gradient transition Al2O3-ZrO2 FGC samples were prepared by laser directed energy deposition (LDED) method. The results show that there is an obvious interface in direct transition sample. The transition section bears tensile stress caused by difference of thermophysical properties of materials, resulting in significant longitudinal cracks. Element transition in interface region shows a step sharp transition. The direct transition sample shows intergranular fracture and the bonding strength is very low. Gradient transition mode can effectively suppress cracks, and avoid the step transition of microstructure and elements. Elements, microhardness of 25, 20 wt% FGC samples realized a nearly linear smooth transition. The interface fracture of FGC samples changed to transgranular fracture, bonding strength was significantly improved, and the maximum flexural strength reached 160.19 MPa. 相似文献
64.
《Ceramics International》2022,48(8):10506-10515
The search for materials and methods capable of reducing human impacts on the environment is of utmost importance nowadays. This study's primary purpose was to analyze the technical feasibility of ceramic composites production utilizing Fundão Dam's Iron Ore Tailings (IOT), Blast Furnace Slag (BFS) from charcoal, and Foundry Sand (FS) as partial substitutes for the traditional raw materials – sand and clay – for application in building industry materials. The composites were molded in rectangular specimens and fired at temperatures of 900, 950, 1000, 1050, and 1200 °C. The developed materials were analyzed and characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Thermogravimetry (TGA), and Differential Thermal Analysis (DTA). The obtained materials had flexural strength modulus of up to 12.19 MPa, water absorption ranging from 2 to 22%, linear shrinkage ranging from 0.02 to 6.50%, and apparent density ranging from 2.03 to 1.63 g/cm3. The study of the internal structure formation process revealed the formation of amorphous structures in the composites. The results demonstrated that these waste materials may be jointly used in construction materials, contributing to the reduction of natural resource extraction, besides enabling their correct disposal, minimizing environmental impacts, and improving the life quality of the surrounding communities. 相似文献
65.
《Ceramics International》2022,48(17):24157-24191
Great progress in the development of low-cost ceramic membranes from alternative materials have been achieved recently towards various application especially water and wastewater treatment. However, their significance has not been fully recognized and understood especially in term of their microstructural analysis such as formation of grain growth and microcracks. This review paper summarizes fabrication method, alternative materials, microstructure, wettability, mechanical properties and application of low-cost ceramic membrane. The fabrication method including slip casting, tape casting, extrusion, pressing method and phase inversion technique are described. Alternative materials used in low-cost ceramic membrane fabrication are discussed and categorized into clays, agricultural waste, industrial waste and animal bone waste. The mechanisms of morphology formation, microstructure and wettability properties are analysed. Modification strategies for the surface of low-cost ceramic membrane are discussed, and classified into modification for separation application, modification for photocatalytic application and modification for membrane distillation and membrane contactor system. Modification improves the membrane structure by changing the pore size, porosity and wettability properties of low-cost ceramic membranes. Mechanical properties of low-cost ceramic membranes are also discussed in detail towards several mechanism, like grain growth phenomenon and formation of microcracks which also considered as membrane defects. Grain growth phenomenon can be divided into normal and abnormal grain growth. Meanwhile, formation of microcracks could be occurred in single-phase polycrystalline ceramics that have anisotropic grains or biphasic polycrystalline grains. The application of low-cost ceramic membrane in seawater desalination, oily wastewater treatment, heavy metal adsorption, textile separation and photocatalytic application are reviewed. Finally, some possible opportunities and challenges for further development of low-cost ceramic membrane are pointed out. 相似文献
66.
Upconversion phosphors are known as a material system that can convert near-infrared light into visible/ultraviolet emissions by sequentially absorbing multiple photons. The studies on upconversion materials often use two rare earth (RE) ions as a sensitizer-activator pair. We investigated the influences on luminescence intensity depending on Cr-doping content (x) of hexagonal NaLu0.98–xCrxF4Er0.02 (x = 0–0.9) upconversion material by substituting Lu3+ ions with Cr3+in the absence of Gd3+. The change in upconversion luminescence intensity appears with saddle-like shape. We suggest that Cr3+ ions play the dual role as a constituent in host lattice and a sensitizer in the upconversion process. Optimal conditions for gaining the strongest upconversion emission correspond to x = 0.3–0.5, where there are effective energy transfers between Cr3+ and Er3+ ions and CrEr dimers. Apart from these values, the emission intensity decreases rapidly which can be ascribed to the absence of multiple-photon absorption for the case of low Cr3+ contents, and to the coupling between Cr3+ and/or Er3+ ions for the case of high Cr3+ contents. Magnetization and electron-spin-resonant measurements were performed to understand the correlation between the optical and magnetic properties. 相似文献
67.
The aim of this study was to investigate the structure and corrosion resistance of amorphous, amorphous‐crystalline, and crystalline Mg67Zn29Ca4 alloy for biodegradable applications. This paper presents a preparation method and results of the structural characterization and corrosion resistance analysis of the material. Samples were prepared in the form of 3 mm diameter rods. The structure of the alloy was examined with the use of X‐ray diffractometry and scanning electron microscopy. The thermal properties of the samples were examined with differential scanning calorimetry (DSC). Results of DSC analysis were used to determine heat treatment temperatures, allowing to obtain different fractures of crystalline phase in the material. Corrosion resistance of heat‐treated samples was investigated by immersion tests and electrochemical measurements performed in the simulated body fluid. The X‐ray diffraction results confirmed that the prepared Mg67Zn29Ca4 alloy's structure is fully amorphous. After heat treatment, samples with different fractions of amorphous phase in the structure were obtained. Immersion tests of the samples showed that the structure significantly influenced corrosion resistance in examined materials. It should be pointed out, that certain amounts of crystalline phase in amorphous matrix can greatly improve the corrosion resistance of Mg67Zn29Ca4 alloy. 相似文献
68.
69.
70.
《International Journal of Hydrogen Energy》2019,44(2):587-593
A solid-state photoelectrochemical (SSPEC) cell is an attractive approach for solar water splitting, especially when it comes to monolithic device design. In a SSPEC cell the electrodes distance is minimized, while the use of polymer-based membranes alleviates the need for liquid electrolytes, and at the same time they can separate the anode from the cathode. In this work, we have made and tested, firstly, a SSPEC cell with a Pt/C electrocatalyst as the cathode electrode, under purely gaseous conditions. The anode was supplied with air of 80% relative humidity (RH) and the cathode with argon. Secondly, we replaced the Pt/C cathode with a photocathode consisting of 2D photocatalytic g-C3N4, which was placed in tandem with the photoanode (tandem-SSPEC). The tandem configuration showed a three-fold enhancement in the obtained photovoltage and a steady-state photocurrent density. The mechanism of operation is discussed in view of recent advances in surface proton conduction in absorbed water layers. The presented SSPEC cell is based on earth-abundant materials and provides a way towards systems of artificial photosynthesis, especially for areas where water sources are scarce and electrical grid infrastructure is limited or nonexistent. The only requirements to make hydrogen are humidity and sunlight. 相似文献