NaCl改性SiO_2微球的制备及其自组装光子晶体研究

为提高SiO2微球的表面电荷密度,通过改进Stober法,引入电解质NaCl合成SiO2微球,并采用垂直沉积法制备出光子晶体.通过Zeta电位粒度仪、带EDS能谱仪的场发射扫描电子显微镜(SEM)和紫外-可见-近红外光谱仪对其电学性能、显微形貌和光学性能进行测试分析.Zeta电位测试结果显示改性SiO2:微球的Zeta电位平均提高11.39mV;EDS能谱分析表明微球中含有钠元素;SEM照片表明样品平均粒径为334 nm,平均标准偏差小于5%,所得光子晶体为面心立方密排结构;吸收光谱表明在725nm处具有光子晶体带隙.     

单分散SiO2胶体球制备及其胶体晶体组装

运用胶体化学法在乙醇介质中合成SiO2胶体球,将制得的样品在30℃下用双氧水浸泡处理48h.用扫描电子显微镜(SEM)、傅立叶红外光谱(FT-TR)、Zeta电位仪和标准氢氧化钠滴定法对其形貌、结构和表面电学性质进行分析.结果表明样品平均粒径为292nm,平均标准偏差小于5%;经双氧水浸泡处理后,SiO2胶体球表面羟基数目增多,在水溶液中的Zeta电位从-55.72mV提高到-63.26mV,表面电荷密度从0.19μC/cm2提高到0.28μC/cm2.通过垂直沉积法,在40℃和60%相对湿度条件下制备出有序性较好、密排结构的SiO2胶体晶体.在SEM下,观察到这种胶体晶体是面心立方(fcc)密排结构,其(111)晶面平行于基底.透射光谱表明,所制备的胶体晶体在(111)方向具有光子晶体的不完全带隙性质.     

CdSe-SiO2光子晶体的垂直沉积及近红外变频特性

在氧化铟锡玻璃上电化学合成了CdSe薄膜,采用垂直沉积法首次在CdSe薄膜上制备了SiO2胶体晶体, 实现了CdSe表面介电常数的调节.扫描电镜观察表明,500nm微球在CdSe薄膜上呈面心立方密堆结构排列,在微米尺度上胶体晶体显示出一定的多晶序.与SiO2胶体晶体相比,CdSe-SiO2光子晶体的UV-vis-NIR透射谱只有一个较宽的光子带隙,带隙在近红外波段随入射角减小向短波方向移动.所得CdSe-SiO2光子晶体样品可作为地面目标针对红外卫星成像的伪装材料.     

单分散SiO2微球的合成及胶体晶体的生长

对传统的"Stober-Fink"合成SiO2微球的工艺进行了改进,运用"籽晶生长法"合成了单分散SiO2微球,该法可以准确地控制微球尺寸,提高微球的球形度.采用垂直沉积法制备了胶体晶体,并对样品的结构和光学性能进行了表征.研究了微球尺寸对垂直沉积SiO2胶体晶体光子带隙的影响,结果表明,通过控制微球粒径,可调节光子晶体的带隙位置.     

Se-SiO2三维光子晶体的制备

报道了一种新的调节二氧化硅光子晶体带隙的方法;通过化学镀向SiO2胶体晶体中填充半导体材料Se,获得了Se-SiO2两种介质复合的三维光子晶体;采用扫描电子显微镜(SEM)、X射线衍射和紫外-可见光谱仪(UV-VIS)等对Se-SiO2三维光子晶体的形貌、结构和光学性能进行了观察测试.研究结果表明,Se以纳米晶粒的形式均匀地包覆在SiO2微球表面,形成了Se壳层,与相同晶格周期的SiO2光子晶体相比,Se-SiO2光子晶体的带隙发生了明显的红移.     

近红外光学带隙硅三维光子晶体的制备

用溶剂蒸发法将单分散SiO2微球组装成三维有序结构的胶体晶体模板,用低压化学气相沉积法填充高折射率材料硅,酸洗去除SiO2模板,获得了硅反蛋白石三维光子晶体.通过扫描电镜、X射线衍射仪和紫外-可见-近红外光谱仪对硅反蛋白石三维光子晶体的形貌、成分、结构和光学性能进行了表征.研究结果表明:Si在SiO2微球空隙内具有较高的结晶质量,填充致密均匀;通过控制沉积条件,可控制硅的填充率;制备的硅反蛋白三维光子晶体在近红外区(1.4μm左右)具有明显的光学反射峰,表现出光学带隙效应,测试的光学性能与理论计算基本吻合.     

SiO2胶体晶体的自组装结构及其带隙特征

光子晶体是一种具有光子带隙的新型功能材料.利用垂直沉积自组装法制成SiO2胶体晶体,并利用扫描电子显微镜和紫外分光度计对胶体晶体的显微形貌和光学特征进行了研究.结果表明,利用垂直沉积法自组装得到的SiO2胶体晶体具有面心立方结构;在可见光波段,胶体晶体在＜111＞面方向存在光子带隙.     

双基片垂直沉降法自组装二氧化硅胶体晶体

采用St(o)ber法制备了适于自组装的单分散性的SiO2球体颗粒,再采用双基片垂直沉积法在无水乙醇中制备出SiO2胶体晶体.通过X射线衍射仪和场发射扫描电子显微镜(SEM)对胶体晶体的晶型和显微形貌进行测试分析.结果表明:所得SiO2球体颗粒为无定形态,粒径为70～380nm,粒径随着氨水浓度的增大而增大;随着双基片间距增大,胶体晶体周期性排列越紧密有序,相同基片间距下,双尺寸胶体晶体更难以获得.     

改进Stober法制备光子晶体用SiO2微球

为获得光子晶体用单分散性较好、表面光滑的SiO2球形颗粒.对传统Stober法进行改进,分析了氨水和正硅酸乙酯(TEOS)浓度对SiO2微球粒径的影响,提出了单分散SiO2微球的形成机理,利用X射线衍射分析仪(XRD)和场发射扫描电子显微镜(SEM)对样品结构和形貌进行了表征.XRD分析表明,合成的SiO2微球为无定形态;SEM照片显示SiO2微球粒径在292～750nm范围内,微球粒径偏差均在5%以下.     

SiO2/CdS光子晶体的制备及其光学性能

用化学浴沉淀法(CBD)在SiO2胶体晶体中生长了CdS半导体材料, 并用UV-VIS-NIR光谱仪和荧光光分度计测试了其光学性能.测试结果表明,在SiO2胶体晶体中随着CdS填充量的增加,光子带隙向长波段方向移动且变宽;当发射出的光与基体材料的光子带隙相匹配时,可控制半导体材料的光致发光,同时,可通过控制SiO2胶体颗粒粒经的大小来调节CdS的光致发光性能.     

凝固科学技术与材料

从凝固科学与实践发展的角度介绍了当前凝固材料体系的基本框架和凝固科学主要发展阶段的基本理论。作为材料科学与工程的基本组成，凝固科学技术正在现代科学理论的基础上针对传统材料的改性提高和新材料的发展需求，以控形、控构、控性为目标开展优质铸件的定向、晶体生长、快凝、深过冷及各种新型和超常领域凝固过程的研究，并介绍了其中某些方面和展望了可能的发展趋势。     

江澳两地高校文创设计的协同研究与商业实践

目的 探索江门世遗文化的传承、发展和转化的新思路,践行国家在《粤港澳大湾区发展规划》纲要中要求江门承担与港澳地区文化创意合作与开发任务的分工。方法 与澳门高校紧密合作,开展专业培训课程,以开平碉楼为例,从人文视角开展设计研究,梳理开平碉楼的文化脉络,把世遗文化的元素和其背后的文化融入文创产品中,提升文创产品的附加值,推动当地文创产业结构的变革。结果 两地高校构建了稳定的科研团队,开设长期有效的设计培训课程,与景区建立了研究协作关系,帮助景区构建了一套产销研的商业模式。结论 以跨区域高校合作为平台,以文创产品为抓手,依托江澳两地的资源优势,可以构建江门世遗文化全新的品牌形象,最终推动开平世遗文化的活化。     

The Candela and Photometric and Radiometric Measurements

The national measurement system for photometric and radiometric quantities is presently based upon techniques that make these quantities traceable to a high-accuracy cryogenic radiometer. The redefinition of the candela in 1979 provided the opportunity for national measurement laboratories to base their photometric measurements on optical detector technology rather than on the emission from high-temperature blackbody optical sources. The ensuing technical developments of the past 20 years, including the significant improvements in cryogenic radiometer performance, have provided the opportunity to place the fundamental maintenance of photometric quantities upon absolute detector based technology as was allowed by the 1979 redefinition. Additionally, the development of improved photodetectors has had a significant impact on the methodology in most of the radiometric measurement areas. This paper will review the status of the NIST implementation of the technical changes mandated by the 1979 redefinition of the candela and its effect upon the maintenance and dissemination of optical radiation measurements.     

Creation and motion of dislocations and fracture in metal and silicon crystals

By making a step on one surface ( ) of a rectangular small paralellepiped copper crystal, dislocations could be created by the molecular dynamic method. The dislocation created was not a complete edge dislocation but a pair of Heidenreich-Shockley partial dislocations. Each time a dislocation was created, the stress on the surface was released. Small copper crystals having a notch were pulled (until fracture), compressed and buckled by use of the molecular dynamic method. An embedded atom potential was used to represent the interaction between atoms. Dislocations were created near the tip of the notch. A very sharp yield stress was observed. The results of high speed deformations of pure silicon small crystals using the molecular dynamics are presented. The results suggest that plastic deformation may be possible for the silicon with a high speed deformation even at room temperature. Another small size single crystal, the same size and the same surfaces, was compressed using molecular dynamic method. The surfaces are {110}, {112} and {111}. The compressed direction was [111]. It was found that silicon crystals are possible to be compressed with a high speed deformation. This may suggest that silicon may be plastically deformed with high speed deformation.     

Error and uncertainty in modeling and simulation

This article develops a general framework for identifying error and uncertainty in computational simulations that deal with the numerical solution of a set of partial differential equations (PDEs). A comprehensive, new view of the general phases of modeling and simulation is proposed, consisting of the following phases: conceptual modeling of the physical system, mathematical modeling of the conceptual model, discretization and algorithm selection for the mathematical model, computer programming of the discrete model, numerical solution of the computer program model, and representation of the numerical solution. Our view incorporates the modeling and simulation phases that are recognized in the systems engineering and operations research communities, but it adds phases that are specific to the numerical solution of PDEs. In each of these phases, general sources of uncertainty, both aleatory and epistemic, and error are identified. Our general framework is applicable to any numerical discretization procedure for solving ODEs or PDEs. To demonstrate this framework, we describe a system-level example: the flight of an unguided, rocket-boosted, aircraft-launched missile. This example is discussed in detail at each of the six phases of modeling and simulation. Two alternative models of the flight dynamics are considered, along with aleatory uncertainty of the initial mass of the missile and epistemic uncertainty in the thrust of the rocket motor. We also investigate the interaction of modeling uncertainties and numerical integration error in the solution of the ordinary differential equations for the flight dynamics.     

PSD和PWELCH函数的分析改进及应用

针对MATLAB中两个内建功率谱密度计算函数psd()和pwelch()计算结果迥异的现象,在功率谱密度估计理论的基础上,根据经典的周期图理论和Welch平均周期图方法,通过详细分析源程序,解析计算方法,发现psd()计算的并不是工程单边功率谱密度,而是采样信号双边谱,故与pwelch()结果迥异,另外pwelch()不能对分段信号数据进行预处理。就上述不足提出了相应的改进措施,比较验证表明改进措施行之有效。     

Miniature and MEMS-type vacuum sensors and pumps

In the paper, the observable trends of the actual research and development of selected types of miniature and MEMS-type vacuum sensors are presented. Some information about the new types of active vacuum gauges, which are offered by the leading manufacturers of the vacuum measurement instruments, is given. Next, the list of MEMS devices that need vacuum for proper operation is presented. Some aspects of vacuum-encapsulation of MEMS devices, on wafer level and package level are shown. The new conceptions of obtaining and maintenance of high and ultra-high vacuum in MEMS devices are described. They concern the conception of integration of a miniature orbitron pump on-chip with MEMS-type device or with vacuum part of the portable advanced instruments such as electron microscope, ion mass spectrometer, and free electron laser.