Papers by Keyword: Nano-ZrO₂

Abstract: The uniform nanoparticle multilayers micrometer-sized silica particle have been fabricated by consecutively assembling of surfactant C₁₂H₂₅SO₄Na (SDS) and nanoparticles onto Silica microspheres and subsequently removing the surfactant by calcinations. The samples were characterized by X-ray diffraction, FT-IR,TG and SEM. Presence of the FT-IR bands with frequencies ranging from 800 to 900 cm-1 can be assigned to Si–O vibration, and to Zr–O–Si stretching vibration. XRD analysis showed obviously the characteristic diffraction peaks of tetragonal (T-ZrO₂) and nanoscale of ZrO₂. The SEM image showed that the surface layers of silica microspheres were coated by nanoparticles.

Abstract: Silica microspheres coated by nanoZrO₂ were prepared by the sol-gel process using butoxidesolution (TBOZ) as precursor. The nanomicrospheres were formed via hydrolysis and condension reaction of metal alkoxides with the hydroxyl (-OH) of silica microspheres by form Zr-O-Si bonds. The samples were characterized by X-ray diffraction, FT-IR and SEM. Presence of the FT-IR bands with frequencies ranging from 800 to 900 cm-1 can be assigned to SiO vibration, and to ZrOSi stretching vibration. XRD analysis shows obviously the characteristic diffraction peaks of tetragonal (T-ZrO₂) in the sample by heat-treatment at 400°C. The SEM image showed that the surface layers of silica microspheres were coated by nanoparticles.

Abstract: This paper carries out the research on using the toughening mechanism of phase transition of ZrO₂ to inhibit the WC grain and improve the toughness of the hard alloys. WC–ZrO2–8wt%Co hard metals was mixed with 0-2 wt% nano-ZrO₂ and prepared by conventional sintering (CS) for 2 h at 1440oC to see whether the addition of ZrO₂ could improve densification behavior, the microstructure and mechanical properties of the samples. Experimental results showed that the use of ZrO₂ nanoparticles could decrease the relative density because of the worse wetting effects; it could also inhibit the growth of the grains of WC-Co hardmetal to enhance the hardness of the alloy. The fracture toughness of sample has an increasing tendency as a whole because of the phase transition during the sintering process.

Abstract: In recent, the development of new die materials is one of the important topics in the field of die research. In this paper, effects of nano-ZrO2 addition on the microstructure and mechanical properties of Ti(C,N)-based cermets were studied. The newly developed Ti(C,N)-based cermet die materials with different contents of nano-ZrO2 of 0~25wt% were prepared by hot pressing technique under vacuum atmosphere at 1450°C for 30min. Moreover, the microstructure of this Ti(C,N)-based cermet die materials was observed by environmental scanning electron microscope. It indicates that the comprehensive mechanical properties can reach the optimum when the weight percent of the nano-ZrO2 is 10%. The corresponding flexural strength and fracture toughness is 967 MPa and 13.62 MPa•m1/2, respectively which is approximately 65% and 110% higher than that of the cermet without nano-ZrO2 addition. It suggests that the addition of nano-ZrO2 can improve the mechanical properties especially the fracture toughness and flexural strength of Ti(C,N)-based cermet die materials.

Abstract: Melamine polyphosphate (MPP) and pentaerythritol(PTL) were used as intumescent flame retardants to improve the flame retardance of polypropylene(PP). As a synergistic agent, nano-ZrO2 was incorporated into the composites at different proportions. The synergistic effects of nano-ZrO2 were studied by cone calorimeter tests and thermal gravimetric analysis (TGA). Based on scanning electron microscopy (SEM) and Fourier transform infrared spectra (FTIR), it was evident that nano-ZrO2 efficiently promoted the formation of charred layers with phosphocarbonaceous structures and enhanced the flame retardance of the composites.

Abstract: Nano-ZrO2 particles were modified by KH-570 (γ-methacryloxypropyltrimethoxysilane). The nano-ZrO2 before and after modified were characterized by UV-VIS spectrophotometer and transmission electron microscopy (TEM). The anti-wear and friction reduction properties of nano-ZrO2 used as additive in lubrication were analyzed by friction and wear test machine of MMU-10G. The results show that the polarity of nano-ZrO2 after modified is changed, the surface free energy is reduced, and both the dispersity and stability of the modified nano-ZrO2 in organic media are improved. The modified nano-ZrO2 can increase the anti-wear and friction reduction properties of the base oil. Lubrications containing 0.10wt% and 0.05wt% nano-ZrO2 have the best tribological properties in the four-ball test and the thrust-ring test, respectively. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) was used to analyze the protective layer formed on the rubbed surface, and Zr elements were found on the rubbed surface.