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INTRODUCTION A thermal shock resistant ceramic in the system Al2O3-ZrO2-TiO2 (AZT ceramic) with an alumina content that was greater than 90 % by weight was developed in previous work.1, 2 Tialite (aluminum titanate), zirconia, and srilankite were identified by XRD as crystalline phases after sintering besides the main component, corundum. Aluminum titanate (Al2TiO5) is characterized by a low coefficient of thermal expansion, low modulus of elasticity, and low mechanical strength. These characteristics are mainly caused by the anisotropy of thermal expansion within the tialite crystals leading to localized internal stresses and microcracking during cooling from sintering temperature.3 Pure tialite tends to decompose to corundum and rutile in the temperature range between approx. 900 °C and 1280 °C. The decomposition rate depends on temperature, dwell time, heating rate, phase purity, grain size, and atmosphere.4 The thermal stability of metastable Al2TiO5 can be improved by suitable additives such as MgO which leads to the formation of Al2TiO5-MgTi2O5 solid solution during sintering.5 After quenching the above-mentioned AZT ceramic from 1200 °C, X-ray diffractograms indicated decomposition of the aluminum titanate phase. The partial decomposition of Al2TiO5 was supposed to play an important role in improving the thermal shock resistance of the alumina-based ceramic on quenching. No significant Al2TiO5 decomposition was observed when the AZT ceramic was quenched from 950 °C.1, 2 This seems to be consistent with findings of Low and Oo6 who report insignificant decomposition of pure metastable aluminum titanate because of low rates of atomic diffusion below 1000 °C, but significant decomposition in the temperature range between 1000 °C and 1300 °C. |
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cmds1907
铁杆木虫 (著名写手)
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根本停不下: 金币+15, 翻译EPI+1, ★有帮助 2014-09-13 22:48:07
根本停不下: 金币+15, 翻译EPI+1, ★有帮助 2014-09-13 22:48:07
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引言 在以前的工作【1, 2】中，开发了一种抗热震陶瓷，该体系为氧化铝含量超过90%（按重量计）的Al2O3-ZrO2-TiO2(AZT陶瓷)。像烧结后的结晶相，除了主要成分刚玉之外，铝假板钛矿(钛酸铝)，氧化锆和锆钛矿已借助 XRD确认。钛酸铝(Al2TiO5)的特点是具有低的热膨胀系数，低的弹性模量和低的机械强度。这些特征主要是由钛酸铝晶体内热膨胀的各向异性引起的，这导致从烧结温度冷却时的局部内应力和微裂缝。【3】在900°C和1280°C的温度范围内，纯钛酸铝往往会分解成刚玉和金红石。其分解速率取决于温度、停留时间、升温速率、相纯度、粒度和气氛。【4】亚稳态的Al2TiO5的热稳定性可以通过合适的添加剂（例如MgO）提高，它导致在烧结过程中Al2TiO5-MgTi2O5固溶体的形成。【5】上述AZT陶瓷从1200°C淬火后， X射线衍射图表明钛酸铝相的分解。在提高氧化铝基陶瓷的抗热震淬火中，Al2TiO5的部分分解应该发挥重要的作用。当AZT陶瓷淬火从950°C时，没有观察到Al2TiO5的显著分解。【1, 2】这似乎是符合低世的研究结果，Oo【6】报道了纯亚稳态的钛酸铝的微不足道的分解，因为低于1000°C下原子扩散的低利率，但是在1000°C到1300°C的温度范围内则显著分解。 |
2楼2014-09-13 22:44:15
