多元醇法制备纳米Fe3O4及其静磁性能的研究

以氯化亚铁为前驱物,1,2-丙二醇为还原剂,采用多元醇法意外获得Fe3O4纳米粒子.通过X射线衍射分析标定了获得样品的物相为面心立方结构的Fe3O4,用透射电镜观察了样品的形貌,颗粒形貌为球形,大小为50～70nm,反应机理的研究表明,Fe2 发生了歧化反应,反应主要向氧化的方向进行.用振动样品磁强计表征了样品的静磁性能,测得的饱和磁化强度为74.30A·m2/kg,矫顽力仅为102.68A/m,粒子具有超顺磁性.     

磁性Fe3O4纳米颗粒的可控制备及生长研究

采用热法合成磁性Fe3O4纳米颗粒,通过精细调控实验条件能对其形状和大小进行有效控制。采用X射线衍射仪、透射电镜、振动样品磁强计等对Fe3O4纳米颗粒的成分、形貌及磁性等进行了表征测试。结果表明,Fe3O4纳米颗粒的饱和磁化强度为62.5emu/g。最后探讨了Fe3O4纳米颗粒的合成机理。     

高分散度Fe3O4纳米球的粒径控制合成及磁性能

采用CTAB作保护荆,在较低温度下,成功地制备出高分散度的Fe3O4纳米材料.通过改变反应条件和保护刺的种类,可在20～360nm范围内有效调控Fe3O4纳米颗粒的粒径.利用X射线衍射仪、透射电子显微镜和扫描电子显微镜等对样品的晶体结构、粒径、形貌和化学组成进行了分析.结果表明:所得Fe3O4纳米晶的粒径均匀,形貌为球形,分散度好.利用振动样品磁强计测量了室温下140nm粒径样品的磁性能.结果表明,Fe3O4纳米材料具有典型的软磁特性.     

铁前驱体对FeN/ZIF-8催化剂氧还原活性的影响

近年来,ZIF-8因具有比表面积大、孔道结构规则等优点而被用作氧还原催化剂载体.以ZIF-8为载体,1,10-菲啰啉为氮源,分别以FeSO4·7 H2 O,FeAc,FeCl3·6 H2 O和FeC10 H10为铁前驱体制备阴极氧还原催化剂,考察不同铁前驱体对FeN/ZIF-8催化剂结构及性能的影响.使用X射线衍射、比表面积和孔径分布测试、透射电子显微镜、热重分析等方法对催化剂的结构、形貌及催化剂前驱体的热性质等进行表征,使用线性扫描伏安法对催化剂的氧还原活性进行测试.结果表明:以FeSO4·7H2O为铁前驱体制备的催化剂,其起始电位约为0.93 V,氧还原反应为4电子过程,具有更好的氧还原催化活性;其在制备过程中形成的适中的比表面积及孔径大小,较好的晶型结构及较均匀的颗粒分散情况,且X射线衍射结果表明催化剂中存在少量的Fe3 C,这是其具有较好的氧还原催化活性的可能原因.     

菱形十二面体磷酸银的制备及其可见光催化性能研究

采用离子交换法,通过调控N,N-二甲基甲酰胺(DMF)与H_2O比例,制备出了具有可见光催化活性的菱形十二面体磷酸银。利用X射线衍射仪(XRD)、扫描电镜(SEM)、傅里叶红外光谱(FT-IR)和紫外-可见光谱仪(UV-Vis)等方法对催化剂进行了表征,并且考察了该催化剂的可见光催化性能。结果表明:通过调控DMF/H_2O比制备的菱形十二面体磷酸银晶型完整、形貌规则,对可见光的吸收增强。与无规则磷酸银相比较,菱形十二面体磷酸银表现出了较高的光催化活性,且DMF∶H_2O=5∶15为降解罗丹明B(Rh B)的最佳比例,超氧阴离子(·O_2~-)和空穴(h~+)为参与可见光催化降解Rh B的主要活性物种。     

共沉淀制备不同粒径Fe3O4纳米颗粒及磁性能的研究

以氯化铁(FeCl3·6H2O)和氯化亚铁(FeCl2·4H2O)为原料,氢氧化钠(NaOH)为沉淀剂,在无表面活性剂作用下共沉淀制备出了不同粒径的Fe3O4纳米颗粒.采用X射线衍射(XRD)、透射电子显微镜(TEM)和振动样品磁强计(VSM)对产物的晶体结构、形貌、粒径及磁性能进行了表征.实验结果表明,n(Fe2+)...     

NdF3十二面体微纳米晶的形貌控制合成及表征

无机微纳米材料的形貌与尺寸对他们的物理和化学性质有很大的影响。因此，控制无机微纳米材料形貌与尺寸的合成就显得十分重要。我们利用简单的水热方法，通过添加络合试剂Na2HzEDTA，以控制反应试剂的释放速度，降低晶体的生长速度，最终达到控制晶体形貌的目的。本实验合成了NdF3十二面体微纳米晶，研究了NdR的形成机理。接着我们用X射线衍射仪（XRD）、扫描电镜（SEM）对样品结构和形貌进行表征。通过一系列的实验，我们发现反应条件对无机纳米材料的形貌和尺寸有很大的影响     

NaYF4∶Yb,Er-Fe3O4纳米复合颗粒的制备与表征

以NaYF4:Yb,Er纳米颗粒作为种晶,选用二氨基十二烷等双官能团配体作为偶联剂,采用直接偶联法制备了NaYF4;Yb,Er-Fe3O4纳米复合颗粒.通过透射电镜、X射线衍射仪和能量色散X射线光谱仪对NaYF4∶Yb,Er-Fe3O4纳米复合颗粒的结构、形貌以及组成进行了表征,比较了不同双官能团配体对纳米复合结构形成的影响.结果表明,双官能团配体的使用对纳米复合结构的形成至关重要;配体所具有官能团的种类以及NaYF4∶Yb,Er种晶粒径会影响NaYF4:Yb,Er与Fe3O4纳米颗粒之间的偶联作用.     

溶剂热法制备Fe_3O_4/氧化石墨烯复合材料及其性能研究

以氧化石墨和二茂铁为原料,采用溶剂热法原位一步合成了Fe3O4/还原氧化石墨烯(Fe3O4/RGO)复合物,通过X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、扫描电镜(SEM)、透射电镜(TEM)、振动样品磁强计(VSM)、循环伏安测试等手段对复合材料的形貌、结构、磁性能和电化学性能进行了表征。结果表明,该方法具有简单、可控的优点,通过调变前驱物中氧化石墨和二茂铁的比例,可以控制复合物中Fe3O4纳米粒子的负载量。所制备Fe3O4/RGO复合材料由平均粒径约20nm的Fe3O4纳米颗粒高度分散在还原氧化石墨烯片层上组成,具有较好的超顺磁性,电化学稳定性和良好的倍率性能。     

共沉淀法制备T-ZnOw/Fe_3O_4复合物的研究

以四针状氧化锌晶须(T-ZnOw)为基体,采用共沉淀法,制备了T-ZnOw/Fe3O4复合物.通过扫描电子显微镜(SEM)、X射线衍射仪(XRD)对复合物形貌和结构进行分析和表征,确定了制备T-ZnOw/Fe3O4复合物的最佳工艺条件.在该条件下制备的复合物由ZnO和Fe3O4晶体组成,且形貌完整,Fe3O4颗粒平均粒径在19.99nm左右.     

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。     

Development and challenges of planning and scheduling for petroleum and petrochemical production

Production planning and scheduling are becoming the core of production management, which support the decision of a petrochemical company. The optimization of production planning and scheduling is attempted by every refinery because it gains additional profit and stabilizes the daily production. The optimization problem considered in industry and academic research is of different levels of realism and complexity, thus increasing the gap. Operation research with mathematical programming is a conventional approach used to address the planning and scheduling problem. Additionally, modeling the processes, objectives, and constraints and developing the optimization algorithms are significant for industry and research. This paper introduces the perspective of production planning and scheduling from the development viewpoint.     

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.     

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。     

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。     

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.     

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.