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991.
《Journal of the European Ceramic Society》2014,34(1):81-89
Thermally induced phase separation (TIPS) was used to produce spherical polypropylene–zirconia composite powder for selective laser sintering (SLS). The influence of the composition of the composite starting powder and the SLS parameters on the density and strength of the composite SLS parts was investigated, allowing realizing SLS parts with a relative density of 36%. Pressure infiltration (PI) and warm isostatic pressing (WIPing) were applied to increase the green density of the ZrO2–PP SLSed parts. Infiltrating the SLS parts with an aqueous 30 vol.% ZrO2 suspension allowed to increase the sintered density from 32 to 54%. WIPing (135 °C and 64 MPa) of the SLS and SLS/infiltrated complex shape green polymer–ceramic composite parts prior to debinding and sintering allowed raising the sintered density of the 3 mol Y2O3 stabilized ZrO2 parts to 92 and 85%, respectively. 相似文献
992.
《Journal of the European Ceramic Society》2014,34(10):2311-2316
Micro-Raman spectroscopy is a convenient tool to probe individual objects with a feature size on the submicron scale. The phase, composition, and orientation of Pb(Zr,Ti)O3 fibers fabricated via hydrothermal processing have been characterized by this technique, with the working principles given in the paper. It is shown that the prepared PZT submicron fibers are of a tetragonal pervoskite phase, with Zr/(Zr + Ti) varying from 0.05 to 0.25. The spontaneous polarization has been confirmed to be along the length direction and one of its {1 0 0} planes parallel to the substrate plane. 相似文献
993.
《Journal of the European Ceramic Society》2014,34(13):3151-3157
As a new black ceramic pigment, encapsulated carbon black pigment has been prepared by a sol–gel-spraying method. The obtained pigment sintered at 900 °C for 2 h in air has a deep black hue (L* = 19), indicating carbon black can be fully covered. In the pigment, a dense coating layer on carbon black is formed due to the fast transformation from sol into gel by rapid extraction of solvent. The transparent silica phase spaces out the fine crystalline (zirconia or zircon), which permits to display the color of carbon black. This preparation method provides a way to prepare the encapsulated pigments. It will provide more colorful ceramic pigment applied in ceramic decoration by encapsulating. 相似文献
994.
《Journal of the European Ceramic Society》2014,34(13):3139-3149
ZrB2 powder was coated with 5% ZrOC sol–gel precursor and sintered by SPS. Relative densities >98% were achieved at 1800 °C with minimal grain growth and an intergranular phase of ZrC. Carbon content in the precursor determined the type of reinforcing phase and porosity of the sintered composites. XRD, SEM and EDS studies indicated that carbon deficiency resulted in ZrO2 retention, improving ZrB2 densification with oxide particle reinforcement. Excess carbon resulted in ZrC formation as the reinforcing phase, but could yield porosity and residual carbon at grain boundaries. These two types of ZrB2 composites displayed different densification and microstructural evolution that explain their contrasting properties. In the extreme oxidative environment of oxyacetylene ablation, the composites with ZrC-C maintained superior leading edge geometry; whereas for mechanical strength, a bias towards the residual ZrO2 content was beneficial. This highlighted the sensitivity of processing carbon-precursors in the initial sol–gel process and the carbon content in ZrB2-based composite systems. 相似文献
995.
《Journal of the European Ceramic Society》2014,34(15):3579-3589
A novel polyborosilazane (PBSZ) precursor was synthesized by the reaction of copolysilazane (CPSZ) with dimethylaminoborane (DMAB). The resultant PBSZs were characterized by FT-IR and NMR spectroscopy. It was found that both, BH and NH bonds of DMAB, react with CPSZ leading to boron containing copolysilazanes. The polyborosilazanes were pyrolyzed at 900 °C in argon and the precursor-to-ceramic transformation was studied by TG-MS and FT-IR spectroscopy. The modification of CPSZ with DMAB enhances the cross-linking of the resulting PBSZ, which increases the final ceramic yield from 57.8% to 77.5–80.0%. Finally, the ceramics obtained at 900 °C were subsequently annealed at different temperatures ranging from 1200 to 1800 °C. The heat-treated products were characterized by X-ray powder diffraction and electron microscopy. Accordingly, the resulting SiBCN ceramics exhibit significantly enhanced high-temperature-resistance with respect to decomposition and crystallization as compared with boron-free CPSZ-derived SiCN ceramics. TEM results support that the thermal stability is due to the segregation of a BN(C) phase as interlayer between Si3N4 nanocrystals formed during heat-treatment of SiBCN at T > 1500 °C. 相似文献
996.
《Journal of the European Ceramic Society》2014,34(15):3635-3640
Laminated HfC–SiC/BN ceramics were successfully fabricated by tape casting and hot pressing. Fully dense HfC–SiC ultra-high temperature ceramics with homogeneous structure were obtained. The introduction of the weak BN layer resulted in a slight decrease of the flexural strength but significantly improved the fracture toughness compared with monolithic HfC–SiC ceramics. The fracture toughness of laminated HfC–SiC/BN ceramics in the parallel direction peaked at 8.06 ± 0.46 MPa m1/2, which increased by 115% than that of monolithic HfC–SiC ceramics. The composites showed non-catastrophic fracture behaviors in both parallel and perpendicular directions. It indicates that laminated structure design is a promising approach to obtain full density HfC–SiC ceramics with high fracture toughness. 相似文献
997.
《Journal of the European Ceramic Society》2014,34(16):4383-4388
Homogeneous transparent optical glass–ceramics precipitated with unique nonlinear crystals are promising materials for photonic applications. We have utilized heat treatment method to prepare transparent ZnO–Bi2O3–B2O3 glass–ceramic containing Bi2ZnB2O7 nonlinear nanocrystals. A large third-order nonlinear susceptibility χ(3) of glass–ceramic is measured by Z-scan technique, which mainly attributed to unique [BiO6] and [B2O5] units in Bi2ZnB2O7 crystal structure and the quantum size effect of nanoparticles. The discovery is of great potential in the application of nonlinear optical integrated devices. 相似文献
998.
《Food and Bioproducts Processing》2014,92(3):275-281
(−)-Epigallocatechin gallate (EGCg)-rich extract (EGCg > 700 mg g−1) was prepared from green tea leaves through a three-stage process consisting of liquid–liquid extraction and silica column purification. Crude tea extract was dissolved in ethyl acetate. After filtration, the solution was extracted by 10 g L−1 citric acid solution twice, and then passed through silica column. The catechins compounds in the ethyl acetate eluate were back extracted to the aqueous phase, then extracted with a mixed solution of n-hexane/ethyl acetate (2/5, v/v) 3 times, concentrated, and freeze dried. 12.8 g EGCg-rich extract containing 709 mg g−1 EGCg and 965 mg g−1 total catechins was obtained from 300 g green tea leaves, with an EGCg recovery of 26.1% and a yield of 4.3%. This method was suitable for bulk preparation of EGCg-rich catechins from green tea leaves. 相似文献
999.
Gen Ariyoshi Ryota Inatomi Daisuke Ito 《Journal of Nuclear Science and Technology》2018,55(3):239-253
Lead–bismuth two-phase flow in a cylindrical vessel and annulus was experimentally investigated by varying the surface wettability of the vessel wall. The test section used in this study was a cylindrical stainless vessel with/without inner sleeve to change the hydraulic diameter. Volume-averaged void fraction was measured by varying the surface wettability of the test section, which was enhanced by using a soldering flux. Measured void fraction was compared with existing two-phase flow correlations and with one-dimensional theoretical simulations assuming one-dimensional drift-flux model. From experimental results, measured distribution parameters of the lead–bismuth two-phase flow are much larger than that of ordinary two-phase flow regardless of the surface wettability. In the present work, the one-dimensional analysis was carried out for the cylindrical vessel to reproduce the distribution parameter. From the simulation results, predicted value for the cylindrical vessel showed good agreement with experimental results. However, in annulus, the distribution parameters in annulus were underestimated by the present model. It was suggested that, in case of annulus, steeper void fraction profile might be formed near the inner surface for poor wettability condition. 相似文献
1000.
Zhi-Guo Yuan Yu-Xia Wang You-Zhi Liu Dan Wang Wei-Zhou Jiao Peng-Fei Liang 《中国化学工程学报》2022,49(9):178-186
As the core component of the rotating packing bed, packing is a place for efficient gas–liquid mixing and mass transfer. In this paper, a 3D structured packing composed of a mesh structure and a support structure was designed. The mesh structure is a ring-shaped mesh surrounded by triangular meshes, which is stable in structure and can achieve a high degree of dispersion and aggregation of the liquid phase. The support structure is composed of ring-shaped structural units arranged at a certain a... 相似文献