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首頁(yè)> 外文學(xué)位 >Pressureless sintered self-reinforced yttrium-silicon aluminum oxygen nitride ceramics.
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Pressureless sintered self-reinforced yttrium-silicon aluminum oxygen nitride ceramics.

機(jī)譯:無壓燒結(jié)自增強(qiáng)釔硅鋁氧氮化物陶瓷。

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摘要

This thesis is concerned with the study of the self-reinforcement behaviour and mechanical properties (hardness, fracture toughness and flexural strength) of Yttrium stablized SiAlON ceramics, which are the solid solutions of Si 3N4, Al2O3 and AlN. The overall objective of this work is to develop composition and microstructure of Si3N 4 ceramics that will possess a fracture toughness approaching that of beta-Si 3N4 while maintaining Vicker's hardness close to that of alpha-SiAlON.;In this study, Y doped SiAlON was selected where the level of Al and oxygen was varied. Systematic studies of the effect of chemical composition, morphology of grains and sintering temperature on the densification and mechanical properties of pressureless sintered Y-SiAlON ceramics were performed. It was found that Si3N4 could be pressureless sintered in excess of 98% theoretical density to form SiAlON ceramics by using alumina (Al 2O3), aluminium nitride (AIN) and yttria (Y2O 3) as the sintering additives at sintering temperatures ranging from 1750 to 1920 °C. The typical microstructure is elongated alpha- and/or beta-SiAlON grains uniformly distributed in a matrix of equiaxed or slightly elongated grains. The highest fracture toughness of 6.3 MPa·m1/2, fracture strength of 520 MPa and hardness of 17.5 GPa was found for Y 0.667Si8.5Al3.5O1.5N14.5 (single phase (alpha-SiAlON) sintered at 1850 °C for 120 mins. For this composition, the maximum aspect ratio of elongated grains is ∼7 (maximum grain length ∼14 mum and diameter ∼2 mum).;The effect of CeO2 addition on sintering temperature, microstructure and mechanical properties has also been studied. Significant change in grain morphology of Y-SiAlON was observed after CeO2 was added. Samples containing ceria additive had a much larger volume fraction of the elongated grains compared to samples without ceria. The highest fracture toughness of 10.5 MPa·m1/2 was measured in samples with composition Y0.167Si10Al2O1.5N 14.5 (mixed alpha+beta-SiAlON) and ceria content of 6.5 wt. % while the samples retained the hardness at 16 GPa. The average aspect ratio of the elongated grains is 9 (maximum grain length ∼9 mum and diameter ∼1 mum) for this composition. The XRD and EDS analyses revealed that most of CeO 2 precipitated at the grain boundaries and a small amount of CeO 2 dissolved into a phase. Crack bridging and crack deflection are identified as the major toughening mechanisms in the investigated Y and/or Ce doped SiAlON system.
機(jī)譯:本文主要研究釔穩(wěn)定的SiAlON陶瓷的自增強(qiáng)行為和力學(xué)性能(硬度,斷裂韌性和撓曲強(qiáng)度),它們是Si 3N4,Al2O3和AlN的固溶體。這項(xiàng)工作的總體目標(biāo)是開發(fā)Si3N 4陶瓷的組成和微觀結(jié)構(gòu),該陶瓷的斷裂韌性將接近β-Si3N4,同時(shí)保持維氏硬度接近α-SiAlON。在本研究中,摻Y(jié)的SiAlON為選擇鋁和氧氣含量變化的地方。系統(tǒng)研究了化學(xué)成分,晶粒形態(tài)和燒結(jié)溫度對(duì)無壓燒結(jié)Y-SiAlON陶瓷致密化和力學(xué)性能的影響。結(jié)果發(fā)現(xiàn),在1750至750的燒結(jié)溫度范圍內(nèi),通過使用氧化鋁(Al 2O3),氮化鋁(AIN)和氧化釔(Y2O 3)作為燒結(jié)添加劑,可以對(duì)Si3N4進(jìn)行無壓燒結(jié),使其超過理論密度的98%,從而形成SiAlON陶瓷。 1920°C。典型的微結(jié)構(gòu)是細(xì)長(zhǎng)的α-和/或β-SiAlON晶粒,它們均勻分布在等軸或略微細(xì)長(zhǎng)的晶粒矩陣中。 Y 0.667Si8.5Al3.5O1.5N14.5(單相(α-SiAlON)在1850°C燒結(jié))的最高斷裂韌性為6.3 MPa·m1 / 2,斷裂強(qiáng)度為520 MPa,硬度為17.5 GPa。 120分鐘對(duì)于這種成分,細(xì)長(zhǎng)晶粒的最大長(zhǎng)徑比約為7(最大晶粒長(zhǎng)約為14微米,直徑約為2微米);還研究了CeO2的添加對(duì)燒結(jié)溫度,微觀結(jié)構(gòu)和力學(xué)性能的影響。添加CeO2后觀察到Y(jié)-SiAlON的晶粒形貌發(fā)生了顯著變化,含有氧化鈰添加劑的樣品與沒有氧化鈰的樣品相比具有更大的伸長(zhǎng)晶粒體積分?jǐn)?shù),最高斷裂韌性為10.5 MPa·m1 / 2。組成為Y0.167Si10Al2O1.5N 14.5(混合的α+β-SiAlON)的樣品,二氧化鈰含量為6.5 wt。%,而樣品的硬度保持在16 GPa。拉長(zhǎng)晶粒的平均長(zhǎng)徑比為9(最大晶粒長(zhǎng)為- 9毫米直徑?1毫米)位置。 XRD和EDS分析表明,大部分CeO 2沉淀在晶界處,少量CeO 2溶解在相中。在研究的摻Y(jié)和/或Ce的SiAlON系統(tǒng)中,裂紋橋接和裂紋變形被認(rèn)為是主要的增韌機(jī)理。

著錄項(xiàng)

  • 作者

    Zhou, Changran.;

  • 作者單位

    Queen's University (Canada).;

  • 授予單位 Queen's University (Canada).;
  • 學(xué)科 Engineering Materials Science.
  • 學(xué)位 Ph.D.
  • 年度 2005
  • 頁(yè)碼 154 p.
  • 總頁(yè)數(shù) 154
  • 原文格式 PDF
  • 正文語種 eng
  • 中圖分類 工程材料學(xué);
  • 關(guān)鍵詞

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