本文選題：氮化硅 + 低溫相變��； 參考：《沈陽(yáng)工業(yè)大學(xué)》2017年碩士論文

【摘要】：氮化硅陶瓷因具有高強(qiáng)度、高硬度、耐磨損等優(yōu)良性能,被廣泛應(yīng)用于航天航空、機(jī)械、化工等領(lǐng)域。針對(duì)氮化硅制備過(guò)程中低溫相變和致密化規(guī)律,及其對(duì)高溫?zé)Y(jié)影響的研究較少,本文以α-Si_3N_4為原料,Al_2O_3-Y_2O_3為燒結(jié)助劑,通過(guò)液相燒結(jié)來(lái)制備致密的氮化硅陶瓷,并對(duì)其微觀組織結(jié)構(gòu)和性能進(jìn)行研究。在低溫?zé)o壓預(yù)燒結(jié)中,探索燒結(jié)溫度(1410~1510℃)、燒結(jié)助劑含量(4%~10%)和保溫時(shí)間(4h~10h)對(duì)氮化硅相變及致密化的影響。發(fā)現(xiàn)氮化硅致密化過(guò)程先于α→β相變過(guò)程發(fā)生,低溫制得的β-Si_3N_4長(zhǎng)徑比小。當(dāng)保溫時(shí)間為6h,燒結(jié)助劑含量為10%,燒結(jié)溫度由1410℃升高到1510℃時(shí),β相含量從15%增加到95%,相對(duì)密度從55%增加到78%。當(dāng)保溫時(shí)間為6h,燒結(jié)溫度為1490℃,燒結(jié)助劑含量由4%增加到10%時(shí),β相含量變化不大,從77%增加到78%,但相對(duì)密度變化較大,從48%增加到85%。在高溫(1700℃)無(wú)壓燒結(jié)中,探索低溫段氮化硅相變和致密化程度對(duì)最終氮化硅陶瓷性能的影響。發(fā)現(xiàn)當(dāng)預(yù)燒溫度為1470℃,保溫時(shí)間為6h時(shí),氮化硅試樣相變較少(β相含量低于50%)、致密度較高(相對(duì)密度接近80%);再經(jīng)1700℃燒結(jié)2h,可以得到相對(duì)密度為96.94%、斷裂韌性為6.15MPa·m1/2的β-Si_3N_4陶瓷材料。在氣壓燒結(jié)中,探索氮?dú)鈮毫?0.2MPa~1.6MPa)對(duì)氮化硅相變的影響。發(fā)現(xiàn)氮?dú)鈮毫?.2MPa增加到1.2MPa時(shí),Si_3N_4的α→β相轉(zhuǎn)變百分比減小約7%;而氮?dú)鈮毫?.2MPa增加到1.6MPa時(shí),Si_3N_4的α→β相轉(zhuǎn)變百分比又出現(xiàn)了明顯增加的趨勢(shì),增加量約為9%。
[Abstract]:Silicon nitride ceramics are widely used in aerospace, machinery, chemical industry and other fields because of their high strength, high hardness, wear resistance and other excellent properties. In view of the low temperature phase transition and densification in the preparation of silicon nitride and its influence on high temperature sintering, this paper uses 偽 -Si _ 3N _ 4 as the raw material, Al2O3-Y _ S _ 2O _ 3 as sintering assistant, to prepare compact silicon nitride ceramics by liquid sintering. The microstructure and properties of these materials were studied. In low temperature pressureless pre-sintering, the effects of sintering temperature (1410 ~ 1510 鈩，

本文編號(hào)：1915908