低辐射中红外Y2O3透明陶瓷窗口的制备及性能表征
文献类型：学位论文
| 作者 | 李晓凯 |
| 文献子类 | 博士 |
| 导师 | 张龙 |
| 关键词 | Y2O3透明陶瓷 Y2O3 transparent ceramics 热等静压 HIP 烧结助剂 Sintering additives 光学性能 Optical properties 性能表征 Properties characterization |
| 其他题名 | Preparation and characterization of low-radiation infrared Y2O3 transparent ceramic windows |
| 英文摘要 | 氧化钇（Y2O3）透明陶瓷因较宽的光谱透过范围、适中的力学性能、较好的抗热振损伤性能和极低的高温辐射率等独特优点，成为高超音速中红外窗口/整流罩的候选。本论文分别以La2O3、ZrO2、TiO2为烧结助剂，采用真空烧结法和热等静压烧结法（HIP），制备出高光学质量的Y2O3透明陶瓷。研究了陶瓷制备过程中各工艺参数（如掺杂剂成分、掺杂剂含量、球磨时间、粉体预烧温度、陶瓷烧结温度、陶瓷真空预烧温度等）对Y2O3透明陶瓷的晶粒形貌、烧结致密化过程、光学性能、热学性能和力学性能等的影响；研究了制备过程中遇到的特殊现象（如掺杂La2O3的Y2O3陶瓷裂纹的产生、掺杂ZrO2的Y2O3陶瓷真空烧结产生的棕黑色）、主要问题（裂纹的消除，陶瓷烧结温度较高、强度较低，高掺杂热导率低，放大化制备等）的分析与解决。随后生产出大尺寸的陶瓷并对陶瓷性能进行了表征。 创新点及重要成果如下： （1）选用La2O3的前驱体La(OH)3和La2O2CO3作为制备掺杂La3+的Y2O3透明陶瓷的烧结助剂，避免因La2O3在空气中吸水和CO2造成的重量增加和称量的不准确性。其烧结收缩致密化温度更低，在相同的烧结条件下，采用La(OH)3和La2O2CO3做烧结助剂的陶瓷光学特性更优异，在4μm的透过率高达82.72%和83.34%。 （2）制备较大尺寸的La3+掺杂Y2O3透明陶瓷，在较低的粉体预烧温度下产生了不穿透裂纹。其原因是低温预烧时La2O3与Y2O3未完全固溶，会吸收水和CO2形成的La(OH)3和La2O2CO3，在后期烧结过程分解引起的体积收缩和La2O3与Y2O3进行固溶反应造成的体积膨胀的共同作用产生了裂纹。 （3）真空烧结法制备La3+掺杂Y2O3透明陶瓷，其优化的制备条件为：粉体在1200℃预烧2h，La3+的最佳掺杂量为6.00at%，烧结温度为1800℃；陶瓷在空气中退火，退火温度为1000℃。真空烧结法制备ZrO2掺杂Y2O3透明陶瓷，其优化的制备条件为：粉体球磨36h，ZrO2的最佳掺杂量为5.00at%，烧结温度为1850℃；陶瓷在空气中退火，退火温度为800℃。 （4）真空烧结法制备的ZrO2掺杂Y2O3陶瓷为棕黑色的根源是Zr3+和Vo+缺陷。Zr3+缺陷位于导带底部，Vo+缺陷位于价带顶部，它们使掺杂ZrO2的Y2O3的带隙由4.70eV降低到2.72eV，对应的光波波长为456nm，位于蓝光范围内（400–480nm），陶瓷显示的颜色为蓝光的互补色红棕色。色坐标为（0.4180，0.4119），位于CIE色品图的棕色区，带隙内光子从Vo+缺陷能级到Zr3+缺陷能级跃迁。 （5）比较了真空制备的掺杂6.00at%La2O3和5.00at%ZrO2的Y2O3透明陶瓷性能。结果发现，掺杂La2O3的Y2O3陶瓷红外截止波长为8.30μm，大于掺杂ZrO2的Y2O3陶瓷的7.80μm；两者的热膨胀系数和热导率接近，后者的软化点更高；掺杂ZrO2的Y2O3陶瓷抗弯强度和维氏硬度都高于掺杂La2O3的Y2O3陶瓷，分别为167MPa/133MPa，8.50GPa/7.51GPa；掺杂ZrO2的Y2O3陶瓷的折射率也相对较高。 （6）用热等静压法制备ZrO2掺杂Y2O3透明陶瓷，最佳的ZrO2掺杂浓度为0.50at%，真空预烧温度为1650–1750℃。掺杂浓度过低，陶瓷晶粒内有气孔，晶粒大，透过率随预烧温度升高而降低；掺杂浓度过高，短波透过率随着预烧温度的升高而降低。陶瓷的维氏硬度随着掺杂浓度的升高而升高，热导率随掺杂浓度的升高降低幅度较大，但在0.50at%时维氏硬度和室温热导率保持在8.42GPa和10.90W/(m?K)。 （7）以TiO2为烧结助剂，用热等静压法制备Y2O3透明陶瓷，TiO2的添加量可低至0.04wt%。优化的烧结条件为：真空预烧1500℃×5h，热等静压1500℃×3h，TiO2掺杂量为0.16wt%。掺杂TiO2的Y2O3比掺杂ZrO2的Y2O3预烧和烧结温度低约200℃，热导率与未掺杂样品接近。 （8）用改性的振动造粒法过筛粉体，设备尺寸小，无污染，损耗低；粉体制备工艺简单，效率高；获得粉体为微米级颗粒，粉体流动性好，休止角小（34.09°），表观密度和振实密度比人工过筛粉体分别增大50.54%和32.07%；采用热等静压烧结陶瓷在2μm波长透过率在82%以上。 （9）本实验制备的透明陶瓷，目前最大尺寸为φ100mm，陶瓷最大强度为217MPa；掺杂La2O3的Y2O3陶瓷热障温度达364℃；400℃高温下透过率不降低，截止波长有较小蓝移；300℃高温辐射率较低。; Owing to the broader transmittance range, the moderate mechanical properties, the preferable thermal shock resistance and the extremely low emissivity at elevated temperatures, Y2O3 transparent ceramics are considered as a candidate for use in hypersonic guided-missile windows and domes. In the present thesis, high optical quality Y2O3 transparent ceramics were prepared using La2O3, ZrO2 and TiO2 as sintering additives by vacuum sintering and hot isostatic pressing (HIP). The effect of processing conditions of additives and their contents, ball milling time, calcine temperature of powders, vacuum pre-sintering temperature and sintering temperature on the microstructure of ceramics, densification process, optical properties, thermal properties and mechanical properties were investigated. Some unique phenomena, such as the cracks of La2O3-doped Y2O3, the brown black color of vacuum-sintered ZrO2-doped Y2O3 ceramics were discussed. Some problems, for example, the eliminate of cracks, the higher sintering temperature and lower flexural strength, the lower thermal conductivity at higher doping content and the scale-up preparation of transparent ceramics were studied. At last, large-scale ceramics were manufactured and characterized. The innovations and important achievements are as follows: (1) La(OH)3 and La2O2CO3 were proposed to replace La2O3 as sintering additives for the preparation of Y2O3 transparent ceramics, avoiding the weight change and the weighing inaccuracy by the absorption of moisture and carbon dioxide in air. The lower densification temperatures and better optical transmittances achieved for La(OH)3 or La2O2CO3 doped Y2O3 ceramics with transmittances of 82.72% and 83.34% at 4 μm. (2) The larger size Y2O3 transparent ceramics prepared with powders doped with La3+ and calcined at temperature of 1000 °C produced the non-breakthrough cracks. The calcined powder can absorb water and CO2 again to form La(OH)3 and La2O2CO3. The cracks were rooted in the combined effect of volume shrinkage by the decomposition of La(OH)3 and La2O2CO3 and volume expansion by the solid solution reaction of La2O3 and Y2O3. (3) The optimized preparation conditions of the vacuum-sintered La3+ doped Y2O3 transparent ceramics are as follows: The powders were calcined at 1200 °C for 2 h with the optimal La3+ content of 6.00 at%; The La3+ doped Y2O3 ceramics should sinter at 1800 °C in vacuum and anneal at 1000 °C in air. The optimized preparation conditions of the vacuum-sintered ZrO2-doped Y2O3 transparent ceramics are as follows: The powders were calcined at 1000 °C with the optimal ZrO2 content of 5.00 at%; The ZrO2 doped Y2O3 ceramics should sinter at 1850 °C in vacuum and anneal at 800 °C in air. (4) The brown black color in vacuum-sintered ZrO2-doped Y2O3 transparent ceramics originated from the Zr3+ and Vo+ defects, which located at the bottom of the conduction band and the top of the valence band, resulting in the reduce of band gap from 4.70 eV to 2.72 eV, corresponding to the blue light (400–480 nm) of 456 nm. The ceramic reveals a brown color complementary to the blue light, companioning with the CIE chromaticity diagram of (0.4180, 0.4119) within brown region that a photon can transfer from Vo+ defect energy level to Zr3+ defect energy level. (5) Compared the properties of 6.00 at% La2O3-doped Y2O3 transparent ceramics with that of 5.00 at% ZrO2-doped Y2O3 ceramics, the infrared cutoff wavelength of the former is 8.30 μm, about 0.50 μm higher than the latter. The coefficient of thermal expansion of the two samples is equal except for a higher softening point for ZrO2-doped Y2O3 ceramics. The mechanical properties of ZrO2-doped Y2O3 are better than La2O3-doped Y2O3 transparent ceramics with flexural strength and Vickers hardness of 167/133 MPa and 8.50/7.51 GPa respectively for La2O3 and ZrO2 doped Y2O3 transparent ceramics. The ZrO2-doped Y2O3 ceramics have a higher refractive index as well. (6) The ZrO2-doped Y2O3 transparent ceramics prepared by HIP process have a lower optimal ZrO2 content of 0.50 at% and a broader pre-sintering temperature of 1650–1750 °C. At lower doping content of 0.20 at%, the large grain size and pores embedded in the grain reduces the transmittance; a higher pre-sintering temperature leads to a lower transmittance. While at higher doping content, the transmittance at short wavelength decreases as the increasing of pre-sintering temperature. The Vickers hardness of the ceramics increases as the increasing of ZrO2 content, while the thermal conductivity decreases at higher ZrO2 content, which are 8.42 GPa and 10.90 W/(m?K) for the 0.50 at% ZrO2-doped Y2O3 transparent ceramics, respectively. (7) The TiO2-doped Y2O3 transparent ceramics were prepared by HIP with minimum TiO2 content of 0.04 wt%. The optimized sintering procedure is pre-sintered at 1500 °C in vacuum for 5 h prior to post HIP treatment at 1500 °C for 3 h with the optimal TiO2 content of 0.16 wt%. The sintering temperature of TiO2-doped Y2O3 transparent ceramics is about 200 °C lower than that of ZrO2-doped Y2O3 transparent ceramics. A higher thermal conductivity obtained for the lower TiO2-doped Y2O3 ceramic. (8) A modified simple and efficient vibrating granulation method was employed to prepare Y2O3 powders for the preparation of transparent ceramics. The granulation device is small in size with no pollution and low loss of powders. The sub-micron Y2O3 particles were converted into micron granules after granulation. Compared with the original powders, the granulated powders had a smaller repose angle of 34.09° and larger apparent and tap densities with sharp rises of 50.54 and 32.07%, respectively, indicating a good flowability and filling properties. A high transmittance of 82% at 2 μm was achieved for ceramics prepared using the granulated powders by HIP. (9) The size of the transparent ceramics manufactured in the present study is as large as φ 100 mm with the highest flexural strength of 217 MPa; The thermal barrier temperature of La2O3-doped Y2O3 is 364 °C; The transmittance at 400 °C is similar to that of the room temperature except for a little blue-shift of infrared cutoff wavelength; The emissivity at 300 °C is quite low. |
| 学科主题 | 材料学 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/30939]  |
| 专题 | 中国科学院上海光学精密机械研究所 |
| 作者单位 | 中国科学院上海光学精密机械研究所 |
| 推荐引用方式 GB/T 7714 | 李晓凯. 低辐射中红外Y2O3透明陶瓷窗口的制备及性能表征[D]. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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