High Pressure Sintering of Super-hard Boron Suboxide and Evaluation of Sintered Compacts

六氧化硼（B_6O）是一种超硬硼化合物，其显微硬度可与金刚石或立方氮化硼相媲美，有望在切削刀具或喷嘴零件上得到实际应用。然而，B_60是如此难以烧结和致密化的压坯，其机械或热性能迄今为止知之甚少。本文以自行合成的可烧结B_60粉末为原料，采用高压高温处理的方法制备了全密度的B_60烧结体。1. B_60粉末的合成与表征将B_2O_3和B（摩尔比1：16）的混合物在纯氩气中热处理（1350 ℃，4 h），合成了B_60粉末。通过SEM观察到合成的B_60粉末包含直径为1.2-1.4 μ m的结晶和可分散颗粒。 ...更多信息 B_60粉末的高压烧结及烧结体的力学性能和热性能研究采用环式高压烧结机对真空处理后的B_60粉末进行了最佳烧结条件的研究。在5 GPa、1700 ℃、20 min的高温高压处理条件下，制备了单相B6 O烧结体，其相对密度为97%，显微硬度为3400 kg/mm^2。TG-DTA分析表明，B_60烧结体的抗氧化性高于B_4C，B_60基烧结复合材料的制备及其在刀具上应用的可能性为了提高B_60烧结体的韧性，制备了cBN体系。真空处理后的B_60和B_4C/cBN混合粉末在3-8 GPa、150 ~ 1800 ℃、15-30 min的条件下进行高温高压处理，其显微硬度和断裂韧性的最大值分别为4600 kg/mm^2和1 ~ 1.8MNm^<-3/2>。少

Hexaboron oxide (B_6O) is one of the super-hard boron compounds which has a microhardness comparable to diamond or cubic boron nitride, and is expected to an actual application to cutting tools or nozzle parts. However, B_60 is so difficult to sinter and to densify the compact that its mechanical or thermal property is less known so far. In the present paper, we prepared B_60 sintered compact in full density by high pressure and high temperature treatment of sinterable B_60 powder which was synthesized in our laboratory. Then, we investigated the mechanical and thermal properties of the sintered compacts and evaluated the possibility of application to various tools.1.Synthesis and characterization of B_60 powderB_60 powder was synthesized by heat treatment (1350ﾟC, 4 h) of the mixture of amorphous B_20_3 and boron (1 : 16 in mol ratio) in an pure argon stream. The synthesized B_60 powder was observed by SEM to comprise crystalline and dispersible particles with 1.2-1.4 mu m diameters.2 … More .High pressure sintering of B_6O powder and the mechanical or thermal properties of the sintered compactAn optimum sintering condition of the vacuum treated B_60 powder was investigated using the girdle-type high pressure apparatus. A single phase B_6O sintered compact was prepared by the high pressure and temperature treatment at 5 GPa, 1700ﾟC and 20 min. The relative density and Vickers microhardness were 97% and 3400 kg/mm^2, respectively. TG-DTA analyses exhibited that B_60 sintered compact had an oxidation resistance higher than B4C, and a mild oxidation proceeded up to 1000ﾟC accompanied by a formation of protective layer of liquid B_2O_33.Preparation of B_60-based sintered composites and their possibility for application to toolsSintered composites in the B_60-B_4C system or B_60-cBN system were prepared in order to increase the toughness of B_60 sintered compact. High pressure and temperature treatments of the vacuum treated mixed powder of B_60 and B_4C/cBN were carried out under the conditions of 3-8 GPa, 150O-1800ﾟC and 15-30 min. Maximum values of microhardness and fracture toughness in both systems were 4600 kg/mm^2 and 1-1.8MNm^<-3/2>, respectively. Less