共查询到18条相似文献,搜索用时 140 毫秒
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采用真空坩埚下降法在石墨坩埚中生长了大尺寸CaF2晶体.通过高温氟化获得无水高纯原料,自发成核发育籽晶,以<2mm/h的生长速率,成功生长了直径170mm的CaF2晶体.研究了晶体的顶部析晶形貌、包裹体、解理等生长缺陷. 相似文献
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悬浮区域熔炼法制备REB6(LaB6、CeB6)单晶体及其表征 总被引:1,自引:0,他引:1
采用区域熔炼法成功制备出了高质量、高纯度、大尺寸的LaB6、CeB6单晶体。系统分析了制备过程中每个参数对晶体生长的影响,确定了晶体成长最佳工艺:(1)LaB6:转速为30r/min,生长速度为8~10mm/h,两次区熔;(2)CeB6:转速为30r/min,生长速度15~20mm/h,一次区熔。然后对晶体进行表征,主要方法有单晶衍射、断面扫描、拉曼衍射、摇摆曲线。由此可知悬浮区域熔炼法是制备高质量、高纯度、大尺寸REB6的最佳方法。 相似文献
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Guigen Wang Hongbo Zuo Huayu Zhang Qibao Wu Mingfu Zhang Xiaodong He Zhaohui Hu Lin Zhu 《Materials & Design》2010,31(2):706-711
Sapphire (i.e., Al2O3 single crystal) window and dome are important sensor components. Large-sized sapphire crystal was prepared by an improved Kyropoulos method, and its machining technique of ultrasonic vibration was also reported. The quality and structure were evaluated by illumination of a He–Ne laser transmission electron microscopy (TEM), double crystal X-ray diffraction (DCXRD) and Raman spectroscopy. For practical window and dome application, its high-temperature mechanical strength and optical transmission were both measured, and a modification measure of sputtering Mg film on sapphire surface followed by annealing and subsequent quenching was demonstrated. Large-sized sapphire crystals with high quality and different profiles were successfully grown by adjustment of pulling velocity and crucible size, design of suitable temperature field. Moreover, a series of sapphire windows and domes were fabricated for different optical application. The biaxial flexure strength of sapphire crystal decreases with increasing temperature, and the infrared transmission is also slightly degraded at high temperature. In addition, it should be noted that there is sharp strength drop in the temperature range of 400° to 600 °C which is related with twin formation in sapphire crystal. Submicron MgAl2O4 spinel precipitation can effectively harden sapphire crystal and do not induce large optical-scattering loss, which is a potential modification method for window and dome application of sapphire crystal. 相似文献
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直径300mm硅片的生产技术是当今硅材料生产研究的重要方向之一,而晶体生长 界面的形状、温度分布、晶体中氧的浓度和均匀性等对熔体流动状态十分敏感,采用实验的方 法来测量熔体的流动、温度场分布是很困难的,因此很难通过实验的方法获得熔体的流动是如 何影响晶体生长的质量的,而数值模拟能提供熔体流动、温度分布等详细内容,为单晶硅的生 长提供有利的指导.本文采用低雷诺数的K-ε紊流模型,对直径300mm的大直径单晶硅生 长进行了数值模拟,通过熔体在有、无勾形磁场作用时的流场、温度场的分析,阐明了勾形磁 场影响熔体流动的机理. 相似文献
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We have built a setup with high temporal resolution to measure the very fast photoelastic lensing effect, which is on the scale of microseconds in a Ti:sapphire crystal pumped by very strong laser pulses (up to 5 J/cm2). The experimental results measured by this method and the real multimode beam profile taken by a CCD camera are applied to a three-dimensional crystal model to calculate one of the photoelastic constants of Ti:sapphire crystal, which is found to be p31=-0.03±0.01. This value is helpful to evaluate the photoelastic lensing effect in Ti:sapphire crystal for a laser beam polarized along the c axis, commonly used for laser amplification. 相似文献
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通过导模法(EFG)成功生长了蓝宝石单晶光纤(直径400~1000 μm, 长度500 mm)。光纤的横截面大致为圆形, 侧面无明显的小面, 直径变化小于40 μm。本研究对晶体缺陷, 例如微气泡, 包裹物和生长条纹等进行观察与分析, 得出: 大多数微气泡是球状的, 且存在于光纤的外侧缘; 在蓝宝石光纤外侧面也观察到少量的钼包裹物元素; 新模具在前几次使用中往往会产生更多的钼夹杂物, 在多次使用后降低。通过对熔体膜流体流动的实验和数值模拟, 研究蓝宝石光纤中微气泡尺寸和分布, 实验和数值模拟的结果显示出良好的一致性。微气泡的分布取决于熔体膜处的流体流动模式, 流体流动的涡流使微气泡在热毛细对流作用下移动到蓝宝石光纤外侧缘。633 nm处的吸收损耗为9 dB/m, 包裹物和表面不规则性会增加散射损耗。 相似文献
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Taro Shimaoka Hiroyuki Kagi Makoto Natsuisaka Satoshi Adachi Yuko Inatomi 《Microgravity science and technology》2005,16(1-4):104-106
We carried out several analytical studies in order to determine the butanol distribution on a salol-butanol crystal. This work is required for a research using microgravity condition focused upon the in-situ observation with an interferometer of the temperature and concentration field for the organic transparent crystal (salol-butanol). In order to evaluate the concentration field for the liquid phase with an interferometer in case of crystal growth from solution in space, it is significant to determine the distribution of solute (butanol) on starting crystal before sample launching using a non-destructive analytical method. The Micro Raman Spectroscopy (MRS) was choice as the most appropriate analytical method among several analytical methods. We prepared a salol-butanol crystal enclosed into the 1mm thick quartz glass ampoule in order to verify the propriety for MRS. Obtained Raman spectrums for salol, butanol and salolbutanol crystal show that the butanol 2D-distribution on salolbutanol crystal can be determined by MRS. These results also demonstrate that there are no influences of thick glass cell upon measurements and that 3D-measurement is possible. In conclusion, we argue that MRS is the most appropriate method for determination of the 2D- and/or 3D- distribution of solute on the crystal among several non-destructive analytical methods. 相似文献
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Hartnett JG Tobar ME Ivanov EN Krupka J 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2006,53(1):34-38
The anisotropic loss tangent has been determined in monocrystalline sapphire for components parallel and perpendicular to the crystal axis, using the whispering gallery (WG) mode method. The Q-factors of quasi-TE and quasi-TM modes were measured precisely in four cylindrical sapphire resonators at room temperature, from which was determined a maximum attainable Q-factor of (2.1 +/- 0.2) x 10(5) at 9 GHz in a quasi-TM mode. Sapphire dielectric material from three different manufacturers was compared over the 270-345 K temperature range and the 5-16 GHz frequency range. 相似文献
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以氮化镓(GaN)为代表的第三代半导体材料,是我国重要战略发展方向之一,而氢化物气相外延(HVPE)作为一种重要材料生长技术,是有效制备单晶材料的工艺手段,本文提出了一种分层次递变流速下HVPE流场与温度场,在垂直腔结构条件下,模拟从腔体中间区域到边缘区域不同流速层次条件下,腔内材料生长区域反应前驱物分布,得出结论:在边缘喷射区域流速为中心区域流速三倍时,反应前驱物可以有效分布在衬底托盘表面。最后,在蓝宝石衬底GaN籽晶表面进行HVPE材料生长,获得平均厚度为20.1μm,均匀性起伏6.9%的GaN单晶,证明理论优化设计下生长出良好的单晶薄膜材料。 相似文献