【作者】 谢俊；

【导师】 程金树；

【作者基本信息】 武汉理工大学 ， 材料学， 2007， 博士

【摘要】 近年来，国内外对建筑装饰微晶玻璃，即以β-硅灰石为主要晶相的微晶玻璃（CaO-Al₂O₃-SiO₂系统）研究报导很多。随着CaO-Al₂O₃-SiO₂系统微晶玻璃产业的发展，在其工业生产中，存在难以解决的“变形”或“炸裂”等现象。这些问题的出现会大大降低产品的成品率，从而影响到企业的经济效益及行业的技术发展。究其产生原因，是由于微晶玻璃中存在的玻璃相和晶相，它们在热膨胀系数、转变温度、力学性质、微观结构等方向有或大或小的差异，这些性质的差异必然导致残余应力的产生。有关微晶玻璃中残余应力等科学问题是非常值得研究的。但是，目前，国内外对于这个方面的研究深度不够。由于金属材料良好的弹塑性、力学性能、机械加工性能，以及成熟的弹塑性力学的理论支持，所以在材料应力的研究方面，金属材料，金属薄膜，已经有了较深的研究，理论比较完善。而无机非金属材料中的有关应力问题，有研究，由于难度较大研究深度不够，理论也相对滞后。此外，如何控制并消除内应力，以最大限度降低因内应力对材料的破坏，这些科学问题都值得在理论上加以深入研究。因此，对于微晶玻璃的应力测试就尤显得重要。国内外在测试应力方面主要采用偏光仪、X射线应力测试仪、中子衍射应力仪、超声波应力测定仪等现代测试手段。本学位论文利用X射线应力测试法、中子衍射法及相关的软件和其他测试手段，研究和分析冷却速率、氧化物、玻璃厚度及玻璃颗粒大小对CaO-Al₂O₃-SiO₂系统微晶玻璃中的内应力的影响，探索相关基础理论问题，并将其与生产实践结合起来，指导同类材料的研究、开发与应用，都具有十分重要的意义。论文得到以下结论：1．X射线衍射法、中子衍射法可以定量的测定微晶玻璃中的应力。微晶玻璃在经过保温后经过不同冷却速率处理后，有不同的应力值，X射线衍射法测试结果表明随着冷却速率的增加，应力值由-59MPa向+57MPa变化，表现为压应力向张应力变化。中子衍射测试应力值结果随着冷却速率的增大从204.501MPa减小到135.342MPa后又增加到276.463MPa，即先减小后增大的趋势。相应的微晶玻璃试样晶面间距也有一个先减小后增大的趋势，结果同样表明微晶玻璃的应力由压应力向张应力变化。特别是微晶玻璃试样存保温后急冷到850℃时，即有压应力又有张应力。而当试样表面经过磨抛处理后，试样应力值较未磨抛试样的应力值要小，但也有一个由压应力向张应力变化。因此实际生产中可以在不改变微晶玻璃产品的性能，缩短玻璃生产的周期。如晶化保温后急冷到850℃以上。2．当CaO含量增加时，微晶玻璃中β-硅灰石晶体的含量从26.27％上升到37.52％，而且β-硅灰石晶体的长径比逐渐减小，从开始的针状变为后来的短柱状，抗折强度呈下降的趋势。随着CaO含量由15wt％增加到17wt％，微晶玻璃表面的残余应力由-463.2MPa减小到-333.9MPa，当CaO含量由17wt％增加到20wt％，微晶玻璃表面的残余应力由-333.9MPa增加到-959.9MPa。这是微晶玻璃中β-硅灰石晶体含量与晶体尺寸两方面作用的结果。考虑CaO含量对微晶玻璃残余应力、机械强度、以及其它各方面的影响，在CAS系统微晶玻璃的实际生产中，CaO含量取16～18wt％是较为合适。3．Al₂O₃对CaO-Al₂O₃-SiO₂系统微晶玻璃中β-硅灰石晶体的析出有抑制作用。当Al₂O₃含量增加时，微晶玻璃中β-硅灰石晶体的含量由35.72％下降到26.1％，且β-硅灰石晶体的长径比逐渐增大，从开始的短柱状变为后来的针状。Al₂O₃含量增加使剩余玻璃相的网络结构得到加强，热膨胀系数减小。随着Al₂O₃含量的增加，抗折强度先增大后减小，微晶玻璃表面的残余应力则是从-837.3MPa减小到-364.2MPa，这是微晶玻璃中β-硅灰石晶体含量与剩余玻璃相热膨胀系数减小两方面作用的结果。综合考虑Al₂O₃含量对微晶玻璃残余应力、抗折强度等方面的影响，在CAS系统微晶玻璃的实际生产中，Al₂O₃含量取6～8wt％是较为合适。4．在基础玻璃成分一定的情况下，研究了玻璃颗粒径在0.5～3mm范围的微晶玻璃应力与结构性能。当颗粒减小时，微晶玻璃中β-硅灰石晶体的含量有增加的趋势。由于β-硅灰石晶体的热膨胀系数要远小于剩余玻璃相的热膨胀系数，因此当β-硅灰石晶体增多时降低了微晶玻璃的热膨胀系数，使得两相的热膨胀不匹配加剧，微晶玻璃上表面的应力值也由-146.00 MPa变为-218.571 MPa，且为压应力值。另外从晶体的微观形貌分析，可以得出粒径在0.5～1.5mm的晶体分布均匀，晶体生长方向一致，晶相和玻璃相的结合较为致密，可以作为烧结法CaO-Al₂O₃-SiO₂系统微晶玻璃的颗粒粒径选择的参考。5．在基础玻璃一定的情况下，研究了厚度为30mm、25mm、20mm、18mm、15mm的微晶玻璃应力分布。测试结果表明：微晶玻璃的表面压应力随着厚度的增加从-45.8MPa增加到-441.1Mpa。因为在微晶玻璃冷却过程中由于样品上表面是流动的空气而下表面则是蓄热较好的材料，因此，下表面相对要比上表面要冷却的快一些。所以，在退火过程中，容易在试样表面产生压应力。此外，当改变样品的厚度时，不同试样厚度导致试样上下表面的温度冷却速度有差异，实验中得到证明。根据实际生产的经验和微晶玻璃表面压应力的要求，选择压应力值范围在-66.6 MPa～-78.9MPa之间，对应的微晶玻璃厚度在18mm～20mm。6．X射线衍射法测试微晶玻璃应力过程中，通过选择较高的衍射角并且延长衍射时间，提高了X射线衍射法测试微晶玻璃残余应力的精确度，减少了该方法在应力测量中的误差。中子衍射的穿透深度为毫米级远大于X射线衍射大约0.01毫米级的穿透深度，故可以测试块状样品的体应力分布，这也决定了中子衍射法测试应力不受材料表面的影响。该方法在应变测量中可以达到10⁴级的精确度，可以精确的测量材料的微应变。本文采用Rietveld全谱拟合方法测量衍射峰宽度的增加值为对应于材料的微应变，误差精确度达到10^-4级。更多还原

【Abstract】 Recently, there have been many researches on architectural decoratedglass-ceramic at home and abroad, and the main crystalline phase of that isβ-wollastonite. With the development of CAS glass-ceramic industry, there are someintractable problems in the industry process, such as transmogrification or burst. Theemergence of these problems can deeply reduce the rate of finished products, thusaffect the economic benefit of enterprises and the development of industrial technique.The residual stress in CAS glass-ceramics is the main reason for these phenomena.Unlike the normal glass, the CAS glass-ceramics, a heterogeneous composite material,consists ofβ-wollastonite crystal phase and glass phase. There are differences insome aspects between them, such as coefficient of thermal expansion, transitiontemperature, mechanical properties, microstructure, and so on, especially in the caseof being heated, which inevitably induce residual stress in glass-ceramics. Though itis very valuable to study residual stress in glass-ceramics, the work in the field is notenough.Because of good elastoplasticity, mechanical properties and machinability inmetal, and sophisticate elastopasticity theory, research on residual stress in metal ormetal film has had a magnificent achievement. But, to the inorganic non-metalmaterial, few reports about residual stress can be seen in the world, not to mentionin-depth research. On the other hand, how to control and reduce the residual stress tominimize the breakage caused by residual stress is an important problem must besolved.Now the main means on testing stresses are polariscope, X ray diffraction stressestesting instrument, neutron diffraction stresses testing instrument、ultrasonic stressestesting instrument and so on. In this study, X-ray diffraction、neutron diffractionmethod on residual stresses measurement was used. Then modern testing means wereused to test the properties and structure of CAS glass-ceramics, including XRD, andSEM, which was useful for elucidating what influence the residual stress in CASglass-ceramics. And the result of this research, combined with industry production,can help us to know the residual stress in other glass-ceramics and boost the invention of new glass-ceramics.Finally, the conclusions are as follows:1. The results of testing show that internal stresses in glass-ceramics could betested by X-ray diffraction and neutron diffraction. There were different magnitude ofstresses in glass-ceramics after annealing at different temperature, and the stresseschanged from compressive stress to tensile stress with the decrease of annealingtemperature. Especially, there were both the tensile stress and compressive stress inglass-ceramics when the annealing temperature was at 850℃. Thus, we couldsuitably control the annealing heat-treatment to shorten the glass-ceramics producingperiod without changing the property of the glass-ceramics. For example, we couldrapidly cool the glass-ceramics at the temperature above 850℃after crystallization.2. Theβ-wollastonite content changed from 26.27% to 37.52% when CaOcontent increased, but ratio of length vs diameter and bending strength decreased. Thestress changed from -463.2MPa to -333.9 MPa firstly, then increased to -959.9 MPawhen the CaO content changed from 15wt% to 17wt%.The change is due to both thecontent and size ofβ-wollastonite. In this study, the reasonable content of CaO isbetween 16wt% and 18wt%.3. For the Al₂O₃ restrain the growth ofβ-wollastonite in glass-ceramics, Soβ-wollastonite content decreased from 35.72% to 26.1% when the Al₂O₃ increased, andthe ratio of length vs diameter increased, the shape ofβ-wollastonite changed fromhistogram to acerose form. However, the bending strength increased firstly and thendecreased, the value of stress decreased from -837.3MPa to -364.2MPa, The changeis due to the contentβ-wollastonite and CTE of glass. So the optional content forAl₂O₃ is from 6wt% to 8wt%.4. Theβ-wollastonite content increased when glass granule minished, for theCTE ofβ-wollastonite is less than CTE of glass, so the large dismatch between theβ-wollastonite and glass and the value of compressive stress is from -146MPa to-218.571MPa.Otherwise,β-wollastonite distributed uniformity and conbined withglass more compact when the diameter of glass granule are between 0.5mm and1.5mm.5. Stress have studied with different thickness glass-ceramics without changing composition. Result showed that compressive stress changed from -45.8MPa to-444.1MPa when glass thickness increased. For the surface of glass was in contactwith the flowing gas and thus cooled much more rapidly, while the surface below wasin contact with fire-resistant material and cooled relatively slowly. Therefore, it iseasy to produce the compressive stress on the surface of the sample for thetemperature difference after annealing. Furthermore, when we changed the thicknessof the sample, the temperature more difference between the surface and below ofthe sample. So the optional thickness is between 18mm and 20mm.6. In this paper, the results showed that the stress line was fitted with the leastsquare calculator, in other ways, it means that error of measurement decreased whenwe increase diffraction angle and prolong diffraction time. Transmission depth ofneutron is millimeters relative to 0.01millimeter of X-ray diffraction, therefore, itmeans that neutron diffraction testing method will not be effected with surface ofsamples. The accuracy of stress close to 10^-4 with neutron diffraction, so microstrainof glass can be tested accurately.更多还原