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The preparation of large particles of cerium oxide with ammonium bicarbonate solution as precipitator was studied. The effects of reaction temperature, mass concentration of feed liquid, adding time of precipitator, amount of crystal seed, aging time and stirring speed on particle size and dispersion of cerium oxide were investigated. The heating rate and temperature of cerium carbonate were determined. The particle size and dispersion of cerium oxide were used as evaluation indexes to optimize the process conditions by orthogonal test. The results show that the particle size of cerium oxide prepared under suitable conditions is in the range of 25~55 µm, the dispersion is uniform and the quality is stable. [ABSTRACT FROM AUTHOR]

To solve the wear problem of stamping dies in high-speed machining，cathodic multi-arc ion plating is often used to improve surface properties，and the surface quality of cathode multi-arc ion plated coating is one of main factors affecting the life of stamping dies.In this paper，the effects of the DC bias voltage，flow rate of nitrogen and arc current on the surface quality of CrAlN coating were studied by the orthogonal experiments.The significance of the effects of DC bias voltage，flow rate of nitrogen and arc current on the surface quality of the CrAlN coating was analyzed by the extreme-range method and variance method.Results showed that the surface quality of the CrAlN coating was affected most significantly by the flow rate of nitrogen，and the DC bias voltage also influenced the number of large particles on the surface of the CrAlN coating.When the DC bias voltage was 160 V，the nitrogen flow rate was 1 600 mL/min，and the arc source current was 120 A，the as-prepared coating possessed the minimum number of large particles on the surface (42.5 per 10，000 μm2) and the optimal surface quality.