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21.
《Advanced Powder Technology》2021,32(8):3023-3033
Coccoliths are micro-structured biomineral particles found in cell protective covering layers of coccolithophore species. They are mainly composed of CaCO3 and their individual crystal entities are arranged in such a way that they construct complex and unique structures. This complexity is found down to the individual particle level and appears to have promising properties to offer. This study focuses on the essential step prior to any kind of implementation, which is the recovery of the material. It summarizes cleaning protocols found in literature, compares them for the first time for the same freshly cultivated material and addresses challenges that still need to be overcome. Further, it highlight the advantages and disadvantages of the best cleaning protocols, suggests optimizations with promising results and uses size distribution measurements to analyse the recovery efficiency. To that end, further characterization techniques, new for coccoliths, are introduced and used to improve our current knowledge of the particles behaviour. 相似文献
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ABSTRACTThe effect of extrusion temperature on the microstructures and mechanical properties of as-extruded Zn–22Al alloys was investigated in this study. With decrease of extrusion temperature from 350 to 200°C, the elongation of as-extruded Zn–22Al alloys increases remarkably at low strain rate and has no change at high strain rate, which implies that the Zn–22Al alloys extruded at lower temperature exhibit high-ductility behaviour. X-ray diffraction and electron back-scattered diffraction analysis demonstrated that the maximum elongation of Zn–22Al alloys extruded at the extrusion temperature of 200°C can be attributed to the elimination of the lamellar structure and the refinement in grain size of the Zn-rich phase. 相似文献
25.
Ireneusz Buganski Kotoba Toyonaga Hiroyuki Takakura Tsunetomo Yamada Marc de Boissieu Olivier Perez 《Materials Science & Technology》2020,36(9):989-995
ABSTRACTWe report a successful growth of the ZnMgHf F-type icosahedral quasicrystal in the form of faceted single grains. By varying the heat treatment parameters we were able to obtain single crystals with a quality suitable for a single crystal X-ray diffraction which was conducted in a synchrotron facility. Ab initio structure solution by a charge flipping algorithm manifests the existence of two types of Bergman clusters. Clusters are differentiated by the preferential occupation of the high-symmetry positions by hafnium in a rhombic triacontahedron, being the outer shell of the atomic cluster.This paper is part of a Thematic Issue on The Crystallographic Aspects of Metallic Alloys. 相似文献
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Solomon Hanson Duntu Francis Tetteh Iftikhar Ahmad Mohammad Islam Solomon Boakye-Yiadom 《Ceramics International》2021,47(1):367-380
The onset of hybrid alumina-based composites, which combines two or more nano-particles within the alumina matrix has already shown promising improvements in the matrix material. However, variations in mechanical properties including the optimum compositions that give improved properties faced with the development of alumina-based composites require further studies to understand the underlying mechanisms and synergistic effects of the nano-particle additions on the alumina matrix. In the current study, the structure and properties of Al?O?-graphene (0.5 wt%) and Al?O?–ZrO? (4 wt% and 10 wt%) composites fabricated via hot-pressing was studied as a baseline for multiple combinations. Even though the addition of 10 wt%ZrO? resulted in a 23% reduction in the grain size of the alumina matrix, the 4 wt%ZrO? addition resulted in a 14% increase in grain size as compared to the parent alumina matrix. X-ray diffraction analysis revealed that there was approximately 85% monoclinic (m-ZrO2) vs. 15% tetragonal (t-ZrO2) crystal structures in the A4ZrO? sample whilst the A10ZrO? had approximately 93% m-ZrO2 vs. 7% t-ZrO2. The high-volume fraction of the monoclinic crystal structures in the A10ZrO? accounts for the induced microcracks in the sample since the transition from the ductile-tetragonal to brittle-monoclinic is associated with the exertion of compressive stresses on the alumina matrix by the associated elastic volume expansion of m-ZrO2. Also, the addition of 0.5 wt%graphene resulted in about 37% reduction in the grain size of the alumina matrix, and approximately 10% increase in hardness as a result of the distribution of graphene along the grain boundaries of the parent alumina matrix, which restricts grain coalescence and growth during processing. Furthermore, an increase up to 115% and 164% were observed in the fracture toughness (KIC) with the inclusion of 0.5 wt%graphene and 10 wt%ZrO? respectively, which was primarily ascribed to the fine-grained microstructures and toughening mechanisms of the intergranular graphene and ZrO? particles. 相似文献
28.
Yuzhu Su Junpu Wang Xin Li Qiqi Tang Jing Yang Li Lei Yi Tian Zhiwei Wang Duanwei He 《Ceramics International》2021,47(15):21077-21082
The in situ axial X-ray diffraction patterns of four ceramic powder samples (MgO, Al2O3, AlN, and cBN) that were compressed in a diamond anvil cell under uniaxial non-hydrostatic conditions were recorded. The microscopic deviatoric stress as a function of the pressure was determined from the X-ray diffraction peak broadening analysis: the curves increased approximately linearly with the pressure at the initial compression stage and then levelled off under further compression. Pressure-induced transparency was observed in all of the samples under compression, and the pressure at the turning point on the curves of the microscopic deviatoric stress versus pressure corresponded to the pressure at which the samples became transparent. Analysis of the microstructural features of the pressure-induced transparent samples indicated that the compression caused the grains to fracture, and the broken grains bonded with each other. We demonstrated that the ceramics’ pressure-induced transparency was a process during which the grains were squeezed and broken, the pores were close between the grains, and the broken grains were re-bonded under compression. 相似文献
29.
SnO2 nanomaterials and SnO2/Li2SnO3 composite nanomaterials doped with different Li contents were synthesized via a simple one-step thermal evaporation method. X-ray diffraction patterns showed that with the increase of Li doping, the intensity of Li2SnO3 diffraction peaks gradually increased, while that of SnO2 diffraction peaks gradually decreased. With the increase of Li doping, the width of nanobelts gradually increased, with the morphology changing from banded structure to standard hexagonal sheet structure. The Raman scattering spectra indicated that with the increase of Li doping, the peak of Li2SnO3 at 588.8 cm?1 kept increasing, and the strongest vibration mode A1g in SnO2 gradually weakened. X-ray photoelectron spectroscopy revealed that with the increase of Li doping, the surface electrophilic oxygen species in SnO2/Li2SnO3 composite nanomaterials greatly increased. Under the condition of light irradiation with a wavelength of 505 nm, the bright current of the Li-doped SnO2 samples was higher than the dark current, while that of the SnO2/Li2SnO3 composite nanomaterials was higher than the dark current, which was mainly due to more oxygen vacancies in SnO2/Li2SnO3 composite nanomaterials than electrons excited by light. Consequently, positive photoconductivity gradually weakened, and even the negative photoconductivity emerged. 相似文献
30.
K.R. Acchutharaman N. Santhosh R. Isaac Daniel Muthu Senthil Pandian P. Ramasamy 《Ceramics International》2021,47(15):21263-21270
Titanium dioxide (TiO2) nanoparticles (NPs) were synthesized through solvothermal route by changing the rate of hydrolysis in the catalytic process. In order to change the hydrolysis rate, the concentration of acetic acid, as additive, was varied as 2 M, 3 M and 4 M. The synthesized NPs were examined by various physico-chemical characterization techniques. The powder X-ray diffraction (PXRD) analysis of the NPs reveals only the anatase phase of TiO2. The spherical shaped morphology of the NPs was observed in the high-resolution transmission electron microscopy (HR-TEM) analysis. The optical behaviour such as absorption, bandgap, diffuse reflectance and photoluminescence (PL) emission of the NPs were studied. The material's nature and behaviors were scrutinized and they were employed as photoanode in dye sensitized solar cell (DSSC) and as electron transport layer (ETL) in carbon-based perovskite solar cell (C-PSC). The charge transfer at the interface of the devices was studied with electrochemical impedance spectroscopy (EIS). The fabricated DSSC and C-PSC show highest power conversion efficiency (PCE) of 6.1% and 10.6%, respectively. The highest current collection was detected in C-PSC and the results are discussed in detail. 相似文献