富硼渣制备BN-MgAlON复合材料及氧化机理分析

在热力学分析的基础上以富硼渣和炭黑为主要原料合成了BN-MgAlON复合材料,并利用X射线衍射(XRD)、能谱分析(EDS)、扫描电镜(SEM)和DSC-TG等测定了产物的相组成、显微结构和氧化性能。实验结果表明,在实验条件下,富硼渣中的B2O3生成BN、MgO、Al2O3反应生成MgAlON相。BN-MgAlON复合粉体的主要成分为MgAlON、Sialon、BN。以制备的复合粉体为原料,Y2O3为添加剂,烧结制备出了BN-MgAlON复合材料,主要物相为Mg-AlON、Sialon和BN,有少量Al5Y3O12和CaYAl3O7相生成。复合材料氧化温度988℃左右,继续升高温度,试样开始增重,增重速率增大,随着温度的升高,温度高于1320℃时,最大增重率为5.54%。

热压烧结制备BN-MgAlON复合材料及其力学性能研究

以BN-MgAlON复合粉体为原料,Y2O3为烧结助剂,在N2气氛下热压烧结制备了BN-MgAlON复合材料,用X射线衍射和扫描电镜对材料的物相组成和显微结构进行了表征,研究了烧结温度对材料的物相组成、烧结性能和力学性能的影响。结果表明,在1650~1750℃可制备出致密的BN-MgAlON复合材料。材料主要成分为MgAlON、Sialon、BN和Ca YAl3O7,随烧结温度的提高,MgAlON的衍射峰逐渐增强。1750℃下所得材料结构均匀致密,材料中Al、Mg、O、N分布比较均匀。材料的抗弯强度、断裂韧性和显微硬度均随着烧结温度的升高而提高。1750℃下的材料性能最好,其体积密度为2.79 g·cm-3,显气孔率为0.3%,抗弯强度为283 MPa,断裂韧性为3.85 MPa·m1/2,硬度为15.33 GPa。并且1750℃,恒温1 h条件下烧结的得到的BN-MgAlON复合材料的抗冲刷性和耐磨性均远远优于耐磨钢B-hard-450。

Preparation and Oxidation Resistance of BN-MgAlON Composites by Hot-pressing Sintering

BN-MgA1ON composites were prepared by hot-pressing sintering under nitrogen atmosphere with BN-Mg- A1ON composite powders as raw material and Y2 O3 as sintering additive. Based on thermodynamic analysis, the oxi- dation resistance of BN-MgAION composites was investigated and the dynamics of oxidation process was also ana- lyzed. The oxidation process and the micro-morphology of the samples before and after oxidation were characterized by X-ray diffraction and scanning electron microscopy. The dynamics of oxidation resistance of the BN-MgA1ON composites was investigated via the analysis of the constant temperature oxidation mass gain curves. The results show that the main components of the material are MgA1ON, Sialon, BN and CaYAI3 07 at 1 650--1750 ＊C, and the content of CaYA1307 decreases as the sintering temperature increases. The BN-MgA1ON composites prepared at 1750 ℃ is uniform and compact with the balanced distributions of A1, Mg, O, and N. The oxidation process of BN- MgA1ON composites in air mainly consists of MgAION, Sialon and BN oxidation. The section after being oxidized at 1000--1300 ℃ involves three layers, namely, the outer layer, the middle layer and the inner layer. The oxidation process follows the parabola model. The apparent activation energy of the oxidation process is 2.13 × 10 5 J/mol and the frequency factor is 4.66 × 10 6.