Stress induced phase transformation of a cesium stabilized leucite porcelain and associated properties.
Stress induced phase transformation of a cesium stabilized leucite porcelain and associated properties.
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DOI：
10.1016/s0109-5641(98)00033-5
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发表时间：
1998-06
期刊：
影响因子：
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通讯作者：
S. Rasmussen;C. Groh;W. J. O'brien
中科院分区：
文献类型：
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作者：
S. Rasmussen;C. Groh;W. J. O'brien
目的：在牙科陶瓷中加入Cs2 O，可有效控制瓷的热膨胀和韧性。本文研究了一种白榴石瓷中Cs_2O含量对其热膨胀系数（α）、韧性、硬度和低熔点的影响。方法为了确定样品中低白榴石的量，使用定量X射线衍射技术获得低白榴石和铜的内标的X射线校准曲线。利用应力诱导的低白榴石和高白榴石之间的相变，确定高白榴石的x射线强度转换比（r），以便低白榴石的校准曲线可用于确定实验瓷器中存在的高白榴石的量。用不同量的Cs_2O（0.0、0.5、1.0、1.5、2.0mol%）制备试样，使得除了原样瓷（A）之外，所有试样都具有相同的热历史。在两个温度范围（30-500°C和30-640°C）内测试样品的低白榴石和高白榴石含量、硬度（维氏硬度）、韧性（压痕强度法）和热膨胀系数（α）。用扫描电子显微镜（SEM）检查断裂表面。对于每种特性，比较样本组的统计学差异。这些比较进行了统计分析，使用方差分析（ANOVA）和Fisher的保护最小的显着差异（PLSD）。结果磨损和热处理的标本的定量X射线检查表明，应力引起的相变发生，这可以通过热处理逆转。转化率测定为r=1.93±0.29。Cs2 O的加入使低白榴石的wt%从63±6%降低到0%，并使高白榴石的量从0%增加到62± 5%。方差分析表明，添加Cs2 O对α（p<0.0001）、硬度（p<0.005）和韧性（p<0.0001）有显著影响。Cs_2O显著降低高白榴石含量瓷的α（p<0.0001）、硬度（p<0.01）和韧性（p<0.0001）。通过稳定高白榴石（立方）至室温，可以控制白榴石瓷的α，其中高白榴石的分数取决于Cs2 O的加入量。建立了一种测定瓷器中高白榴石含量的方法。
ObjectivesThe addition of Cs2O to dental porcelains might provide a means for controlling the thermal expansion and toughness of feldspathic porcelains. The purpose of this investigation was to determine for a leucite porcelain the effect of Cs2O content upon its coefficient of thermal expansion (α), toughness, hardness, and content of low (tetragonal) leucite and high (cubic) leucite.MethodsIn order to determine the amount of low leucite in the specimens, an x-ray calibration curve for low leucite and an internal standard of copper was obtained using quantitative x-ray diffraction techniques. Utilizing a stress induced phase transformation between low and high leucite, an x-ray intensity conversion ratio (r) was determined for high leucite so that the calibration curve for low leucite could be used to determine the amount of high leucite present in the experimental porcelains. Specimens were prepared with various amounts of Cs2O (0.0, 0.5, 1.0, 1.5, 2.0mol%) so that, except for the as-received porcelain (A), all had the same thermal history. Specimens were tested for content of low and high leucite, hardness (Vickers), toughness (indentation-strength method), and coefficient of thermal expansion (α) over two temperature ranges (30–500°C and 30–640°C). Fractured surfaces were examined with a scanning electron microscope (SEM). For each property, specimen groups were compared for statistical differences. These comparisons were statistically analyzed using analysis of variance (ANOVA) and Fisher's protected least significant differences (PLSD).ResultsQuantitative x-ray examination of abraded and heat-treated specimens demonstrated that a stress induced phase transformation occurred which could be reversed by heat treatment. The conversion ratio was determined as r=1.93±0.29. The addition of Cs2O lowered the wt% of low leucite from 63±6% to 0% and increased the amount of high leucite from 0% to 62±5%. ANOVA showed that the addition of Cs2O had a significant effect on α (p<0.0001), hardness (p<0.005), and toughness (p<0.0001). Cs2O significantly (PLSD) lowered the α (p<0.0001), hardness (p<0.01), and toughness (p<0.0001) of a high-content leucite porcelain.SignificanceA stress induced phase transformation of high leucite to low leucite was demonstrated and, as a consequence, suggested the potential for phase transformation toughening. The α of a leucite porcelain could be controlled by stabilizing high (cubic) leucite to room temperature with the fraction of high leucite dependent upon the amount of Cs2O added. A method was developed to determine the amount of high leucite present in a porcelain.