Papers by Keyword: Nano-Composite Ceramic

Abstract: The ultrasonic polishing test of the nanoZrO₂-Al₂O₃ composite ceramics is done under the two-dimensional ultrasonic polishing device, which is developed by us. In this process, the ultrasonic amplitude-frequency characteristic testing is done by the DASP software. There are certain amplitudes at some frequency points, which can be seen from the spectrum and the three-dimensional spectral array maps, but only one the largest amplitude appears. This shows the resonance points appear when the ultrasonic is passed to the nanocomposite ceramic plate after it is amplified by the horn. This phenomenon is analyzed by the second-order surface wave theory and the waves are surface waves, which are generated by surface waves. These explain the good polishing surface quality and high efficiency under the two-dimensional ultrasonic polishing in the same conditions.

Abstract: In processing of structure ceramics materials with diamond grinding wheel, grinding heat is one of vital factors influencing workpiece surface quality. Grinding parameters have important influences on workpiece surface temperature distribution. Contrast experiments on grinding temperature field of ZrO2 in common and ultrasonic grinding were carried out in the paper by manual thermocouple method. The relationship between grinding parameters and temperature were researched theoretically and experimentally. The results show that the farther the distance from grinding surface, the smaller the peak value of temperature is. With the increases of grinding depth, grinding speed and feedrate, the surface temperature will heightens accordingly. It was proved that grinding depth is the most vital factor influencing grinding temperature field through orthogonal experiments. Furthermore, comparing with high surface layer temperature which often results in grinding burn in traditional grinding, ultrasonic grinding can reduce grinding temperature effectively.

Abstract: The surface roughness of nano-composite ceramics machined by means of multi-frequency ultrasonic vibration grinding was investigated with the diamond grinding wheel dressed by elliptical vibration. The results indicate that the surface roughness is influenced by ultrasonic vibration frequency, feeding speed, grinding depth. The ultrasonic vibration frequency and the grinding depth are not the higher the better and there are suitable values. The surface roughness gets worse with the increase of feeding speed.

Abstract: The effects of multiple ultrasonic frequencies on grinding surface quality of Al2O3-ZrO2 nano-composite ceramics are researched to provide optimization laws for ultrasonic grinding parameters. Some SEM photographs of ultrasonic grinding surface with different frequencies are provided to research the surface quality. The enhanced surface quality of ceramics with ultrasonic grinding is explained as the transition of single abrasive particle removal mode from brittle to ductile, which is resulted from the reduction of equivalent rigidity on surface under ultrasonic vibration. And this phenomenon becomes more evident as frequency increases. Through the XRD experiment, the phase transition from tetragonal phase t-ZrO2 to monoclinic phase m-ZrO2 becomes increasingly obvious by the action of ultrasonic vibration. The compressive stress generated during this phase transition can suppress the initiation and expansion of microcracks on the processing surface. The research shows that, the grinding surface quality with ultrasonic vibration is superior to that without ultrasonic vibration, and increasing ultrasonic frequency can contribute to the improvement of the surface quality.

Abstract: Based on the requirements for ceramic materials of cutting tool and die and the aim of improving comprehensive mechanical properties of ceramic tool and die materials, nanocomposite ceramic tool and die materials with high mechanical properties were fabricated successfully with nanometer composite method. Friction and wear properties of the developed ZrO2/Ti(C7N3) nanocomposite ceramic tool and die materials were experimentally studied in detail. Morphologies of the worn surfaces were observed and analyzed by ESEM. Wear mechanisms of nanocomposite ceramic tool and die materials were discussed with comparison with that of single-phase ZrO2 ceramics. It indicates that wear mechanisms of ZrO2/Ti(C7N3) nanocomposite ceramic tool and die materials are mechanical cold welding, abrasive wear and adhesive wear.

Abstract: The effects of ultrasonic frequency on the grinding force and surface quality were analyzed from the grinding experiment on ZTA nano-composite ceramics. The results indicate that, in the same parameters, ultrasonic normal grinding force is about 65 to 85 percents of the ordinary grinding condition, and the surface quality is better than that of ordinary grinding condition, as the frequency increasing, this trend will be more evident. The reasons for it were also discussed from microscopic and the nonlocal theory in this paper.

Abstract: A multi-scale and multi-phase nanocomposite ceramic cutting tool material Al2O3/TiC/TiN(LTN) with high comprehensive mechanical properties has been successfully fabricated by means of adding micro-scale TiC and nano-scale TiN particles. The cutting performance and wear mechanisms of this advanced ceramic cutting tool were researched by turning two kinds of hardened steel 40Cr and T10A respectively. Compared with the commercial ceramic tool LT55, LTN showed a superior wear resistance with certain machining parameters. The machining tests indicated that the new materials tool is suitable for continuously dry cutting of hardened steel with high hardness at high speed.

Abstract: A new Monte Carlo Potts′ model for the sintering process of two-phase nano-composite ceramic materials with various grain size of initial matrix is set up. The grain growth process is successfully investigated assuming the green body is completely dense. The effect of the initial matrix grain size on microstructure evolution is observed and discussed quantitatively.

Abstract: Under the liquid-phase hot-pressing technique, the multi-scale titanium diboride matrix nanocomposite ceramic tool materials were fabricated by adding both micro-scale and nano-scale TiN particles into TiB2 with Ni and Mo as sintering aids. The effect of content of nano-scale TiN and sintering temperature on the microstructure and mechanical properties was studied. The result showed that flexural strength and fracture toughness of the composites increased first, and then decreased with an increase of the content of nano-scale TiN, while the Vickers hardness decreased with an increase of the content of nano-scale TiN. The optimal mechanical properties were flexural strength 742 MPa, fracture toughness 6.5 MPa•m1/2 and Vickers hardness 17GPa respectively. The intergranular and transgranular fracture mode were observed in the composites. The metal phase can cause ductility toughening and crack bridging, while crack deflection and transgranular fracture mode could be brought by micro-scale TiN and nano-scale TiN respectively.

Abstract: This paper presents a research on the effects of ultrasonic frequencies of 19.9 kHz, 23.6 kHz and 29.3 kHz on both of cyclic amplitude and fatigue life of Al2O3-ZrO2 nano-composite ceramics. According to the high-cyclic-life tests at low load level, some prohibition influence on the process of crack initiation and propagation under ultrasonic vibration is revealed as frequencies are raised from 19.9 kHz to 29.3 kHz. During the low load level tests, the toughness increment induced by the transcrystalline fracture is found in the scanning electronic micrographs of the fractures, which shows the existence of the inhibition effect on the crack initiation and propagation. At the same time, the fracture XRD indicates that t-m phase transition of ZrO2 under 29.3 kHz is higher than that under 19.9 kHz, which means that both the required cyclic amplitude and the fatigue life can be improved if the ultrasonic frequency is increased to 23.6 kHz. All the test results show that high frequencies exhibit stronger toughening improvements than the lower ones do. This paper is a pre-research for the ultrasonic ceramic grinding and the conclusions obtained are meaningful for the study of the crack propagation mechanism during the grinding.