Papers by Keyword: Composite Ceramic

Abstract: Al₂O₃/SiC_p composite ceramics with 2 vol%, 5 vol% and 10 vol% SiC nanoparticles additions were hot pressed at 1650 °C. The polished ceramic discs were prepared and indented at high strain rate using a compressed gas gun with tiny tungsten carbide bullets. The microstructure and mechanical properties were obtained to explain the dynamic deformation behavior of Al₂O₃/SiC_p ceramics. Cr³⁺ fluorescence mapping was used to examine the residual stress and plastic deformation induced on the surface of each target. The residual compressive stress area around the crater was evenly distributed, while the greatest plastic deformation was found at the hitting point of the bullet tip. It can be calculated that the high temperature of 1400K may be produced at the instant of the bullet impact and result in large plastic deformation region and low residual stress of the Al₂O₃/SiC_p ceramic.

Abstract: The Ti₃SiC₂-TiB₂-TiC three-phase ceramics are prepared by Spark Plasma Sintering (SPS) method with Self-propagating High-temperature Synthesis (SHS) using Ti, Si, C andB₄C powders. The characterization of sintering product’s image and structure is analyzed by XRD and SEM. Most of TiB₂’s images are angular cuboid or short bar-shaped and most of TiC phase’s images are irregular spherical particles which are evenly embedded in Ti₃SiC₂ substrate and have a good combination interface with Ti₃SiC₂. In the composite ceramic SPS sintering process, sinter sample’s displacement along Z-axis goes through three stages of falling, balance and rising along with the change of heating temperature, which reflects the sample’s change rule between heated expansion force and pressure. Finally its machining performance is analyzed by wire cutting method and machining method. The Ti₃SiC₂-TiC-TiB₂ block composite ceramic proves to have a good machining performance.

Abstract: As the ceramic substrate materials in automobile oxygen sensor, 5YSZ/Al₂O₃ matrix composite ceramic with different amount of silica are prepared by ball-milling,tape casting and sintering.They are investigated for their microstructure and mechanical properties.The microstructure of the sample is analyzed by Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDX).Fracture strength is measured by ring-on-ring method. It is found that adding 1 wt.% SiO₂ into 5YSZ/Al₂O₃ matrix can improve the strength of composite ceramics.

Abstract: C_f/ZrC-xCu composite ceramics with different Cu content were prepared by self-propagating high-temperature synthesis/pseudo–hot isostatic pressing (SHS/PHIP). The effect of Cu content on the microstructure and properties of C_f/ZrC composite ceramics were investigated. Our results indicated that carbon fiber was serious chemical damaged in the absent of Cu, accompanied by attenuating of the reinforced effect.Whereas, the density of the complex was increased in the present of Cu content in a dose-dependent-way due to the better fluidity of Cu. Adding to Cu into the complex material leads to the increased diffusion resistance of the elements, decreased damage of the carbon fiber. Meanwhile, the ability of flexural strength manifested as incureasing-decreasing manners according to the elevation of Cu content, while, the fracture toughness was increased gradually. We finally concluded that we could get the best composite ceramic in the present of 25V% of Cu.

Abstract: Zirconyl chloride was used as zirconium source and fused silica particles were used as main raw material. First of all, the composite powders were prepared by wet chemical synthesis using ammonia as the precipitator and polyethylene glycol as the dispersant. Then, fused silica nanozirconia composite ceramic containing nanometer particle zirconia with different contents (5%, 15%, 25% and 35%) were fabricated in reduction atmosphere at 1300°C, 1350°C and 1400°C for 1 h. The bulk density and bending strength were measured, microstructure was observed by SEM. The result indicated bulk density and bending strength of composite ceramic increase and microstructure becomes denser with content of zirconia increasing. Bulk density of composite ceramic increases and bending strength which reaches maximum at 1350°C firstly increases then decreases with the increase of sintering temperature. Both high sintering temperature and nanozirconia possessing high energy interface can improve the composite ceramic sintering.

Abstract: Under the special circumstances, we cannot use the lubricating medium and want to overcome the lake of friction properties of the single material in the cutting process, we will be done mainly through two ways: prepared self-lubricating tool and preparation of coating tools, in order to work reliable under the extreme conditions.

Abstract: This research employs pressureless sintering process to study the impact of different amount of titanium diboride on the performance of silicon carbide-titanium diboride composite. Results show that: no new phase was produced, and the whole process is a solid-phases sintering process. In this experiment, it has the smallest relative density and loss on ignition and porosity, and highest degree of densification of the silicon carbide-titanium diboride composite ceramics sintered body when the titanium diboride content is 50g, and the quality of SiC and TiB2 ratio is 1:1.

Abstract: Alumina ceramic, with high mechanical strength, good electric insulation, high hardness and good corrosion resistance performance, has been widely used in machinery, electronic and electrical, chemical, medicine, construction and other high-tech areas. In this study, both silicon sol and zirconia particles are incorporated into the system and dense alumina composite ceramics were prepared by cold isostatic processing and pressureless sintering at 1550 . The influence of additives on phase composition, microstructure and mechanical properties were investigated. The XRD results show that mullite phase was generated in the composite ceramic. The composite ceramic has excellent comprehensive performance. For example, the sample with 3wt.% SiO₂ and 5wt.% ZrO₂ has density of 3.87g·cm^-3, Vickers hardness of 17.6GPa, flexural strength of 369.0MPa, youngs modulus of 374.2GPa and fracture toughness of 3.57MPa·m^1/2.

Abstract: Using air lubricants, wear tests of Si₃N₄-hBN composites with different hexagonal boron nitride (hBN) volume fraction sliding against Si₃N₄ ceramic were carried out on a MMU-5G type pin-on-disc tester. For comparison, Si₃N₄/Si₃N₄ pairs were also tested under the same conditions. The worn surfaces of specimens were observed under scanning electron microscope (SEM). Furthermore, the wear debris were analyzed by using X-ray diffraction (XRD). Wear debris layers are formed on the wearing surface when Si₃N₄-hBN composites slide against Si₃N₄ ceramic under air lubrication. In this situation, the friction coefficients are as high as 0.80-1.20 and the wear coefficients are above 10-5 mm³/Nm for all materials tested.

Abstract: A new composite ceramics of Si₃N₄/ SiC were prepared by a two step sintering method with SiC powders and Si powders as main material. Its properties and structures were characterized by the porosity, bulk density, flexural Strength, XRD, SEM and EDS. The effects of particle grade and sintering temperature on its properties were studied. The results show that bulk density of powders is the largest when coarse powder of SiC (average diameter 120 um) is about 40% (by weight), with average diameter 80um of SiC is about 20% (by weight) and fine powder (average diameter 35 um) of of SiC is 10% (by weight). A minimum porosity, a maximum bulk density and flexural Strength were achieved by nitriding at 1450 °C for 2h and then two states sintering at 1700 °C. XRD analysis indicated that the the main crystalline phase of the ceramic made from α-SiC, α-Si₃N₄ and β-Si₃N₄. SEM and EDS analysis indicated that a larger of wisker like α-Si₃N₄ and some little β-Si₃N₄ are found coating with SiC, giving its excellent mechanical properties.