Papers by Keyword: Alumina Ceramic

Abstract: In this paper, alumina ceramics were prepared with alumina powder and lanthanum nitrate. The influence of La₂O₃ on the microstructure and properties of alumina ceramics were studied. The result showed that the addition of La₂O₃ contributed to the mechanical property of the samples. The alumina ceramics with adding of 0.05wt% La₂O₃ sintered at 1490°C had the best mechanical properties. And the flexural strength, fracture toughness of the ceramics could reach 571.902MPa and 5.82MPa•m^1/2，which were improved by 37.55% and 10.65% respectively compared with the alumina ceramics without La₂O₃. Besides, the average grain size of alumina ceramic is about 2.8μm, and the effect of inhibition on grain growth of alumina ceramics was obvious.

Abstract: Laser machining is one of the most widely used advanced noncontact machining processes used for creating new surfaces, structures, cavities and also complex electro-mechanical devices, usually with very small dimensions, by laser radiation. It is the process in which the material’s thermophysical properties rather than mechanical properties determine the machinability. Design of process parameters is highly critical for successful material removal and high machine surface quality. In the paper the laser beam milling is experimentally studied applying the nanosecond pulse fibre laser and alumina ceramic as working material. The influence of pulse energy, pulse repetition rate, scanning speed and tracks displacement on material removal efficiency and the quality of machined surface is reported.

Abstract: The sintering of alumina ceramics with high-purity has gained much attention due to their wide range applications. The improved sinteirng methods, such as the spark plasma sintering, super-high pressure sintering, two-step sintering, and so on, have advantages on the decreasing the sinteirng temperature or inhibiting the grain coarsening, compared with the conventional sintering.

Abstract: Ultrasonic vibration improved the machining performance of a variety of brittle materials, and achieved good results in brittle materials machining applications. In this paper, the experiment about precision sawing engineering ceramic by using a thin diamond blade with and without ultrasonic vibration conditions was investigated. It is aimed to explore the effect of ultrasonic vibration on specific energy. The results show that ultrasonic vibration makes specific sawing energy having a significant reduction during material removal process. Under the ultrasonic vibration condition, the engineering ceramic’s materials removal way is changed. It changed from plastic removal to the removal of brittle fracture, which reduced the energy consumption of material removal.

Abstract: In this paper, according to the principle and the existing technology of ELID grinding, we use the existing lapping machine of Wenzhou Runsheng ceramic water valves factory as the experiment platform to develop an ELID lapping process system. Then utilizing ELID ultra-precision lapping technology to process alumina ceramic seals obtained a good effect. The roughness of processing samples reached about 15nm which was demanded by the enterprise, the efficiency increased 60% and the cost reduced 50%. On this basis, we designed an ELID lapping prototype. It laid a solid theoretical and practical basis for the production of ELID lapping machine in the future.

Abstract: In order to improve the wear resistance and reduce the sintering temperature of alumina ceramics, Y₂O₃ powder added in the system of MgO-CaO-SiO₂-Al₂O₃ alumina ceramics were prepared by the technique of pressureless sintering. The properties of the ceramic samples were investigated by the measurements of bulk density, wear rate, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that the wear rate of alumina ceramic contenting Y2O3 of the 0.8wt% is 0.041‰. Adding the yttrium oxide to the raw materials and then calcine them to ceramics, which can reduces the sintering temperature, promote the densification and improve wear-resistant property of alumina ceramics.

Abstract: The effects of Cr₂O₃ additions on the mechanical and electrical properties of alumina ceramics were investigated. The phase composition, organizational structure of ceramics were analyzed and observed using XRD and SEM. The results show that doping with small amount (<7wt.%) of Cr₂O₃ can improve the mechanical (15% for bending strength, 83% for Vickers hardness) and electrical properties (minimum resistivity 9.8 × 10¹²Ω·cm), but when doping amount above 7wt.% , these properties were decreased.

Abstract: In this work, machining test was carried out in various machining conditions using ultrasonical vibration capable CNC machine. For work material, alumina ceramic (Al2O3) was used while for tool material diamond electroplated grinding wheel was used. To evaluate ultrasonical vibration effect, grinding test was performed with and without ultrasonic vibration in same machining condition. In ultrasonic mode, ultrasonic vibration of 20kHz was generated by HSK 63 ultrasonic actuator. On the other hand, grinding forces were measured by KISTLER dynamometer. And an optimal sampling rate for grinding force measurement was obtained by a signal processing and frequency analysis. The surface roughness of the ceramic was also measured using stylus type surface roughness instrument and atomic force microscope (AFM). Besides, the scanning electron microscope (SEM) was used for observation of surface integrarity.

Abstract: This article describes the alumina ceramic mixed with two kinds of additives in order to improve the performance of ceramic, such as mixed with submicron ZrO₂ and MnO₂ Monoclinic zirconia (m-ZrO₂) and tetragonal zirconia (t-ZrO₂) of reversible phase transition of volume change is used to improve the toughness and wear resistance of composite alumina ceramic. Through doing various tests about fired products, including hardness testing, SEM test and bulk density measurement, we can understand the microstructure and mechanical properties of samples.

Abstract: To obtain complex shape alumina ceramic parts, a composite powder of epoxy resin binder E-06 and alumina powder were laser sintered combined with cold isostatic pressing (CIP). Experiments on selective laser sintering (SLS) and CIP were carried out to probe the influencing factors in the processes of forming alumina green parts. When laser power, scan speed, scan spacing and layer thickness were, respectively, 21 w, 1800 mm/s, 100 μm and 150 μm, the density and bending strength of alumina parts were relatively high. Following that, we experimented on different CIP maximum pressure which had different effects on densification of SLS alumina parts, the whole process in CIP was divided into two stages of I and II. Finally, the optimized SLS/CIP alumina parts were degreased and then sintered in 1600 °C for 2 h to produce crack-free alumina parts.