空间胶体晶体生长实验装置关键技术研究

【作者】 杨皓；

【导师】 翟光杰；

【作者基本信息】 中国科学院研究生院（空间科学与应用研究中心） ， 计算机应用技术， 2011， 博士

【摘要】 胶体晶体(colloidal crystal)是指由亚微米级(submicro)或纳米级(nano)胶体颗粒经过特定排列方式构成的类似于晶体结构的有序体系。胶体晶体结构具有类似于原子晶体的有序结构,且其空间尺度和相变时间尺度都较原子晶体大几个数量级,是研究晶体相变规律的理想模拟体系之一;另一方面由胶体晶体制备的光子晶体也促进了光子器件的发展,在微波通讯、滤波技术、隐身技术等方面有极强的应用潜力。因此近30年来,胶体晶体研究成为凝聚态物理和应用研究中的热点。由于胶体颗粒尺寸上比原子晶体大几个数量级,其颗粒间的作用力与原子比相对较弱,其结晶过程与结晶结构产生容易受到重力的影响。减小重力对结晶过程的影响,探索其结晶过程的本质特征成为胶体晶体研究中的重要研究方向。空间微重力环境为胶体晶体研究提供了独一无二的条件。本论文是国内空间微重力胶体晶体生长实验课题的一部分,该课题拟在国际上首次使用Kossel线衍射方法在空间微重力环境研究三种不同分散体系的带电胶体晶体的相变动力学过程,进行长达180天的空间实验,获得完整的结晶动力学变化过程中图像结果,研究胶体晶体随温度与电场变化的“结晶”与“弥散”过程。通过对空间胶体晶体生长实验装置研制中的关键技术进行深入研究,取得以下主要研究成果:1、通过遥控操作拍摄三种体系样品衍射图像、形态图像本实验研究的是微重力环境下胶体晶体结晶动力学过程中的图像变化过程,如何获得高分辨率衍射图像、形态图像成为一项关键技术。本研究首次构筑具有遥控功能的Kossel线成像系统,该系统在胶体晶体生长实验过程中能够全程记录胶体晶体Kossel线的相变过程;使用的高分辨率1394总线CCD满足分辨Kossel线衍射角0.5度变化的精度要求;为了增加空间实验的可靠性,对激光器进行了主备份冗余设计处理,利用光的偏振态设计了协调两个激光器设备的光路;通过转位机构,能够切换观察三种不同体系胶体晶体的衍射图像和形态图像。2、提出胶体晶体Kossel线衍射图像增强算法本研究需要通过Kossel线图像精确分析胶体晶体对称性结构,而本研究胶体晶体Kossel线衍射图像属于暗场像,其对比度较差,原始图像中有效信息的Kossel线不够明显,若直接使用原始图像,依赖于研究人员的分析胶体晶体Kossel衍射图像的主观经验,人为因素较多,需要实现图像增强。实验表明,典型的传统算法运用在本研究衍射图像的增强效果都不够明显。本文根据Kossel线图像的特点,针对性地提出了胶体晶体Kossel衍射图像的增强算法,使原始图像的Kossel线有效信息得到加强,使得对图像结果的分析更加客观,为空间胶体晶体生长实验图像科学数据分析提供了必要的技术保障。3、胶体晶体多体系样品高精度温度控制带电胶体晶体形成主要原因是胶体颗粒表面带有负电荷,颗粒之间的静电排斥力与颗粒的布朗运动达到一种平衡状态,形成长程有序结构。温度的微小波动便会引起布朗运动的强弱变化,从而影响胶体晶体的结晶状态与结晶过程,研究胶体晶体随温度变化的相变过程是空间科学实验的一项重要内容,实验过程中必须对胶体晶体溶液进行全程高精度低波动温度控制。本文针对胶体晶体样品溶液池的特点,研发出可协调控制三种不同体系胶体晶体样品的高精度温度控制方式,温度控制范围覆盖35℃至60℃的科学实验温度范围,控制精度达到0.1℃,满足空间胶体晶体生长实验的需要。4、具备灵活的遥控调整功能本论文工作是为进行二元组合带电胶体晶体生长的空间微重力实验提供直接的技术实现,而科学实验的流程存在依据空间实验结果进行调整的可能性。为最大化利用空间实验的资源,获取更丰富的实验结果,本研究通过设置六条总线加载指令,使实验装置能在多种工作模式间灵活切换,另外通过设置九条数据注入指令,使实验装置可以灵活进行实验参数的修改,包括样品温度、样品电场、搅拌开关、拍照参数和转位位置等,最大程度的适应空间实验需求的变化以及可能存在的实验装置超期服役需求。这也是国内空间科学实验装置首次拥有如此灵活的实验设置修改功能。更多还原

【Abstract】 The colloidal crystal (CC) is an ordered array of sub micro or nano particles, analogous to a atomic crystal. In the past three decades, there are two reasons that CC is one of the hotspots in the condense matter. Firstly, the observable space and time in the disorder phase transition of CC are several orders in magnitude greater than that of atomic crystals. Secondly, CC can be made of photon crystal, which has the particular optical property. Furthermore, the photon crystals can promote the development of photonic devices related to many fields, such as microwave communication, filter technique and invisible technology.Because the elastic modulus of CC is weak, gravity has important influence in the crystal growth. The study of the effects of gravity on the colloidal crystallization can be preceded in a long-term micro gravity environment. Kossel diffraction image faithfully reflects three-dimensional information on the symmetry of CC. We will be the first in the world to study CC by Kossel diffraction method in the space environment of micro gravity. In this dissertation, we focus on the key technology of manufacture space for the apparatus of colloidal crystal experimental. The main contributions are as follows:1. We obtain high resolution diffraction and form images of three specimens by remote control. All Kossel line image systems require manual operation at present. We set up high resolution diffraction Kossel line image systems by remote control for the first time. High resolution CCD is capable of distinguishing the 0.5 degree variation with angle of diffraction. In order to strengthen reliability of the space experiments, we use two laser devices in our systems and devise the light path to coordinate them. In addition, we can switch observation diffraction and morphological images of three specimens by a transposition mechanism in the apparatus.2. We propose and realize an algorithm of diffraction image enhancement with Kossel line for CC. The diffraction images of CC have the low contrast ratio, and the efficient information of Kossel line is not distinct enough due to transmission imaging approach. We propose the algorithm, firstly, which emphasizes and doesn’t change proficient information of Kossel line. The algorithm provides competent support for the structural analysis of CC.3. A high precision control method for experimental temperature of the multiple specimen of CC is proposed. The method in accordance with three kinds of specimen cells is studied. The control error is less than±0.1℃,which achieves the most accurate system. This temperature control method satisfies the requirement of space experiments. The transformation of diffraction and images with different temperatures are obtained on the ground.4. The apparatus is provided with flexible functions of remote control. Its operating modes are easy to switch by six bus load instructions, and the experiment parameters can be modulated easily by nine data input. The experiment apparatus can satisfy the requirement of space experiments’assignments. The flexible operation of the apparatus is better than the previous devices of the space experiment.更多还原