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排序方式: 共有10000条查询结果,搜索用时 93 毫秒
1.
Shammya Afroze Nico Torino Md Sumon Reza Nikdalila Radenahmad Quentin Cheok Paul F. Henry Abul K. Azad 《Ceramics International》2021,47(1):541-546
The structural and electrochemical properties of the double perovskite-type oxide, PrBaMnMoO6-δ, was investigated using neutron diffraction with in-situ conductivity measurement under a dry Argon atmosphere from 25 °C to 700 °C. A Rietveld refinement of the neutron diffraction data confirmed monoclinic symmetry in the P21/n space group. Rietveld refinement also confirms the unit cell parameters of a = 5.6567 (1) Å, b = 5.6065 (2) Å, c = 7.9344 (1) Å and β = 84.43° with reliable atomic positions and refinement factors (R-factors). Neutron diffraction data refinement shows two minor phases (<5%), an orthorhombic AB2O5 type phase of PrMn2O5 in the Pbam (No. 32) space group with unit cell parameters, a = 7.9672 (1) Å, b = 8.9043 (2) Å and c = 5.8540 (1) Å and a scheelite phase of BaMoO4 in the tetragonal I41/a (88) space group with the unit cell parameters, a = b = 5.9522 (1) Å, and c = 12.3211 (2) Å. Morphological images revealed a porous and intertwined microstructure. In-situ conductivity measurement shows that the total conductivity of this material was 130.84 Scm?1 at 700 °C. 相似文献
2.
Víctor I. Hernández Domingo I. García-Gutiérrez Juan A. Aguilar-Garib Román J. Nava-Quintero 《Ceramics International》2021,47(1):310-319
In the current study two different batches of X7R-0603 BME-MLCCs displayed dissimilar electrical performance, despite having the same chemical composition, tape casting, and sintering conditions; with the only difference between them being the ore deposits where the raw materials were extracted from to synthesize the BaTiO3. Specifically, they presented different electrical response to highly accelerated life tests (HALT). Although the chemical analysis of each slip showed the same composition, the trace elements of the BaTiO3 sources could have acted as dopants or produced different secondary phases. A search for precipitates in the two samples was conducted by means of Scanning (SEM) and Transmission Electron Microscopy (TEM) techniques. SEM observations confirmed the presence of precipitates formed within the structure of the MLCCs exhibiting the greatest decrement in their electrical resistance results during the HALT. In order to further characterize the observed precipitates, samples were prepared by Focused Ion Beam (FIB) lift-out method, to make TEM characterization of specific precipitates feasible. TEM studies were performed on the precipitates to obtain electron diffraction patterns and complementary Energy Dispersive X-Ray Spectroscopy (EDXS) chemical analysis. Based on the crystal and chemical data obtained, it can be concluded that the precipitates are a hexagonal anhydrous silicate oxyapatite phase with a stoichiometry of Ca3Y16Si10O13, and lattice parameters of a = 0.9353 nm and c = 0.6970 nm; this phase was not found in the JCPDS data base. Differences in raw materials coming from different ore deposits can produce undesired precipitates that affect the electrical performance of MLCCs. 相似文献
3.
Xuye Wang Guopu Shi Qinggang Li Junyan Wu Hao Wu Liu Zhang Zhi Wang 《Ceramics International》2021,47(2):2280-2287
Owing to the good physicochemical compatibility and complementary mechanical properties of Ti3SiC2 and Al2O3, Ti3SiC2/Al2O3 composites are considered as ideal structural materials. However, TiC and TiSi2 typically coexist during the synthesis of Ti3SiC2/Al2O3 composites through an in-situ reaction, which adversely affects the mechanical properties of the resulting composites. In this study, Ti3SiC2/Al2O3 composites were prepared via in-situ hot pressing sintering at 1450 °C. Ge, which was used as a sintering aid, improved the purity and mechanical properties of the Ti3SiC2/Al2O3 composites. This is because Ge replaced some of the Si atoms to compensate the evaporation loss of Si to form Ti3(Si1-xGex)C2, which showed a crystal structure similar to that of Ti3SiC2. Furthermore, the molten Ge accelerated the diffusion reaction of the raw materials, increasing the overall density of the Ti3SiC2/Al2O3 composites. The optimum Ge amount for improving the mechanical properties of the composites was found to be 0.3 mol. The flexural strength, fracture toughness, and microhardness of the composite with the optimum Ge amount were 640.2 MPa, 6.57 MPa m1/2, and 16.21 GPa, respectively. The formation of Ti3(Si1-xGex)C2 was confirmed by carrying out X-ray diffraction, energy dispersive spectroscopy, and transmission electron microscopy analyses. A model crystal structure of Ti3(Si1-xGex)C2 doped with 0.3 mol Ge was established by calculating the solid solubility of Ge. 相似文献
4.
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
5.
Alessio Zandona Bernd Rüdinger Joachim Deubener 《Journal of the American Ceramic Society》2021,104(2):1146-1155
Glass powder samples of cordierite composition (doped with 8 mol% TiO2) were heat-treated to produce a series of increasingly SiO2-enriched Mg-bearing quartz solid solutions (Qss). The obtained materials were then analyzed by X-ray diffraction: Rietveld structural refinements revealed that Mg-bearing Qss phases possess trigonal symmetry and a compositionally dependent intermediate structural arrangement between those of low and high quartz. High-temperature diffraction measurements were performed up to 700°C to characterize the thermal expansion behavior of the crystals. At SiO2-rich compositions, a reversible high-to-intermediate inversion of the quartz structure is observed, which shifts with increasing stuffing to lower temperatures than the conventional 573°C for pure quartz. Similarities and differences to the better-established Li-bearing Qss are discussed in the text. 相似文献
6.
《Ceramics International》2021,47(22):31920-31926
The Sr and Ba bearing Tl-1212 phase, Tl(Ba,Sr)CaCu2O7 is an interesting superconductor. The Sr only bearing TlSr2CaCu2O7 is not easily prepared in the superconducting form. The Ba only bearing TlBa2CaCu2O7 on the other hand does not show improvement in the transition temperature with elemental substitution. In this work the influence of multivalent Se (non-metal) and Te (metalloid) substitutions at the Tl-site of Tl1-xMx(Ba,Sr)CaCu2O7 (M = Se or Te) superconductors for x = 0–0.6 was studied. The samples were prepared via the conventional solid-state reaction method. XRD patterns showed a single Tl-1212 phase for x = 0 and 0.1 Se substituted samples. The critical current density at the peak temperature, Tp of the imaginary (χ”) part of the AC susceptibility (χ = χ’ +χ”), Jc-inter(Tp) for all samples was between 15 and 21 A cm−2. The highest superconducting transition temperature was shown by the x = 0.3 Se-substituted sample (Tc-onset = 104 K, Tc-zero = 89 K, Tcχ’ = 104 K and Tp = 80 K). Te suppressed the superconductivity of Tl-1212 phase. The order of highest transition temperatures are as follows: Tl1-xTex(Ba,Sr)CaCu2O7<Tl(Ba,Sr)CaCu2O7<Tl1-xSex(Ba,Sr)CaCu2O7. This work showed that Se was better than Te in improving the transition temperature and flux pinning of the Tl-1212 phase. The roles of ionic radius of Se and Te on the superconductivity of Tl(Ba,Sr)CaCu2O7 are discussed in this paper. 相似文献
7.
《Advanced Powder Technology》2022,33(2):103390
In the present work, a comprehensive study of mechanical alloying of Ni-carbon nanotubes (CNT) and Ni-Graphite equiatomic powder mixtures under the same technological modes has provided to reveal the features of using different types of carbon (CNT or graphite) as a charge component. The as-milled powders were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and magnetometric study. A novel nanoscale fcc NiC monocarbide was synthesized regardless the type of the charge used. According to the XRD study the formation of this phase takes place in two stages. A two-step carbide formation mechanism has been proposed. The associated changes in the nickel lattice, such as changes in the lattice parameter, lattice strain and residual stresses, which led to the formation of NiC monocarbide were also evaluated and discussed. Parameters of the electronic structure of NiC were calculated using the MStudio MindLab 7.0 software package with the experimental data on the crystal structure of the NiC phase obtained as input. Temperature dependencies of magnetic susceptibility of NiC synthesized have been studied up to 950 K. Carbides synthesized were found to be weak ferromagnets at the room temperature and their Curie temperature TC ranges within 670 – 725 K. The calculated value of the magnetic moment per nickel atom (2.83μB) is higher than that of a bulk Ni (1.3μB). Likely, the observed increase of μ is caused by the presence of a certain amount of residual single-domain ferromagnetic Ni nanoparticles in the samples synthesized. 相似文献
8.
《International Journal of Hydrogen Energy》2022,47(22):11500-11510
Herein, a novel ZnTe-based photocatalyst is successfully synthesized via a facile combination of water-bath and hydrothermal processes. Morphology characterization and X-ray diffraction analysis reveal that ZnTe presents irregular granular shape and cubic crystal structure. Moreover, Mott-Schottky measurement shows that the conduction band potential of ZnTe is ?0.84 V (vs NHE). With Eosin Y (EY) sensitization, ZnTe exhibits superior photocatalytic hydrogen evolution activity (223.5 μmol g?1 h?1). Meanwhile, WC-ZnTe heterojunction is constructed by depositing ZnTe nanoparticles on bulk WC and obtains the optimal H2 generation rate (559.1 μmol g?1 h?1) under EY sensitization. Electrochemical and photoluminescence results further prove that WC as electron bridge could reduce the interfacial resistance and suppress e?-h+ pairs recombination. This study explores the potential application of ZnTe as a newly active photocatalyst in photocatalytic water splitting, and emphasizes the synergistic effect of dye sensitization and bridge engineering. 相似文献
9.
《Ceramics International》2022,48(3):3362-3367
The influence of high-energy ball milling on structural, microstructural, and optical properties of TiO2 by modifying the nanoparticle size was studied. Five samples were extracted at different milling times (0, 2, 4, 8, and 13 h). The average particle sizes estimated by dynamic light scattering (DLS) were 205, 155.8, 116.8, 82.9, and 82.7 nm at 0, 2, 4, 8, and 13 h, respectively. X-ray diffraction analysis confirmed progressive broadening of the peaks as the milling time elapsed. Besides, a correlation was found between d spacing and the average crystal size. The UV–Vis diffuse reflectance spectra of TiO2 revealed a decrease in reflectance due to particle size reduction. Similarly, an alteration of the bandgap transition energy was presented, whose values gradually decreased from 2.966 eV to 2.861 eV for the sample without and with the maximum duration milling performed (13 h), respectively. Likewise, the SEM analysis showed a distribution in nanoparticle size that became more homogeneous and smaller average grain size as the milling duration was longer. 相似文献
10.
《Advanced Powder Technology》2022,33(11):103627
Naringin (NAR), a major flavanone (FVA) glycoside, is a component of food mainly obtained from grapefruit. We used NAR as a food additive to improve the solubility and permeability of hydrophobic polyphenols used as supplements in the food industry. The spray-dried particles (SDPs) of NAR alone show an amorphous state with a glass transition temperature (Tg) at 93.2 °C. SDPs of hydrophobic polyphenols, such as flavone (FVO), quercetin (QCT), naringenin (NRG), and resveratrol (RVT) were prepared by adding varying amounts of NAR. All SDPs of hydrophobic polyphenols with added NAR were in an amorphous state with a single Tg, but SDPs of hydrophobic polyphenols without added NAR showed diffraction peaks derived from each crystal. The SDPs with NAR could keep an amorphous state after storage at a high humidity condition for one month, except for SDPs of RVT/NAR. SDPs with NAR enhanced the solubility of hydrophobic polyphenols, especially NRG solubility, which was enhanced more than 9 times compared to NRG crystal. The enhanced solubility resulted in the increased membrane permeability of NRG. The antioxidant effect of the hydrophobic NRG was also enhanced by the synergetic effect of NAR. The findings demonstrated that NAR could be used as a food additive to enhance the solubility and membrane permeability of hydrophobic polyphenols. 相似文献