Abstract: A positive electrode active material for a lithium secondary battery has secondary micro particles having an average particle size (D50) of 1 to 10 ?m formed by agglomeration of primary macro particles having an average particle size (D50) of 0.5 to 3 ?m and a lithium-M oxide coating layer on all or part of a surface, wherein M is at least one selected from the group consisting of boron, cobalt, manganese and magnesium. The secondary macro particles have an average particle size (D50) of 5 to 20 ?m formed by agglomeration of primary micro particles having a smaller average particle size (D50) than the primary macro particles. The primary macro particles and the primary micro particles are represented by LiaNi1?b?c?dCobMncQdO2+?, wherein 1.0?a?1.5, 0<b<0.2, 0<c<0.2, 0?d?0.1, 0<b+c+d?0.2, ?0.1???1.0, and Q is at least one type of metal selected from the group consisting of Al, Mg, V, Ti and Zr.

Abstract: A SiAlON composite includes a SiAlON phase including ?-SiAlON phase, ?-SiAlON phase and grain boundary phase. The SiAlON composite is prepared from a starting powder mixture including a silicon nitride powder and at least one powder providing aluminum, oxygen, nitrogen, yttrium (Y) and erbium (Er) to the SiAlON composite. The SiAlON composite contains the SiAlON phase of at least 90 vol %, z-value of the ?-SiAlON phase ranges between 0.27 and 0.36 and thermal diffusivity of the SiAlON composite is equal to or greater than 2.4 (mm2/sec) and equal to or less than 5.2 (mm2/sec).

Abstract: A ceramic material includes of ?-sialon (Si(6-z)AlzOzN(8-z)), polytype 15R, an intergranular phase, and yttrium. The polytype 15R includes twin grains.

Abstract: A SiAlON composite includes a SiAlON phase including ?-SiAlON phase, ?-SiAlON phase and grain boundary phase. The SiAlON composite is prepared from a starting powder mixture including a silicon nitride powder and at least one powder providing aluminum, oxygen, nitrogen, yttrium (Y) and erbium (Er) to the SiAlON composite. The SiAlON composite contains the SiAlON phase of at least 90 vol %, z-value of the ?-SiAlON phase ranges between 0.27 and 0.36 and thermal diffusivity of the SiAlON composite is equal to or greater than 2.4 (mm2/sec) and equal to or less than 5.2 (mm2/sec).

Abstract: A ceramic material includes of ?-sialon (Si(6-z)AlzOzN(8-z)), polytype 15R, an intergranular phase, and yttrium. The polytype 15R includes twin grains.

Abstract: A cutting insert has only cutting edge portion thereof made of SiC whisker reinforced ceramics brazed to the shank with active solder. This provides improved cutting performance by increased toughness and high strength of the SiC whisker reinforced ceramics without limitation in shape while reducing manufacturing costs. The cutting insert includes a cutting edge portion made of SiC whisker reinforced ceramics, and a shank to which the cutting edge portion is mounted. The cutting edge portion is brazed to the shank using an active solder, and the whiskers are disorderedly arranged and agglomerated in the cutting edge portion.