Scanning transmission electron microscopy: A review of high angle annular dark field and annular bright field imaging and applications in lithium-ion batteries

Scanning transmission electron microscopy（STEM） has been shown as powerful tools for material characterization,especially after the appearance of aberration-corrector which greatly enhances the resolution of STEM. High angle annular dark field（HAADF） and annular bright field（ABF） imaging of the aberration-corrected STEM are widely used due to their high-resolution capabilities and easily interpretable image contrasts. However, HAADF mode of the STEM is still limited in detecting light elements due to the weak electron-scattering power. ABF mode of the STEM could detect light and heavy elements simultaneously, providing unprecedented opportunities for probing unknown structures of materials. Atomiclevel structure investigation of materials has been achieved by means of these imaging modes, which is invaluable in many fields for either improving properties of materials or developing new materials. This paper aims to provide a introduction of HAADF and ABF imaging techniques and reviews their applications in characterization of cathode materials, study of electrochemical reaction mechanisms, and exploring the effective design of lithium-ion batteries（LIBs）. The future prospects of the STEM are also discussed.

Enhanced photon emission by field emission resonances and local surface plasmon in tunneling junction

We investigated the photon emission spectra on Ag(111)surface excited by tunneling electrons using a low temperature scanning tunneling microscope in ultrahigh vacuum.Characteristic plasmon modes were illustrated as a function of the bias voltage.The one electron excitation process was revealed by the linear relationship between the luminescence intensity and the tunneling current.Luminescence enhancement is observed in the tunneling regime for the relatively high bias voltages,as well as at the field emission resonance with bias voltage increased up to 9 V.Presence of a silver(Ag)nanoparticle in the tunneling junction results in an abnormally strong photon emission at the high field emission resonances,which is explained by the further enhancement due to coupling between the localized surface plasmon and the vacuum.The results are of potential value for applications where ultimate enhancement of photon emission is desired.

Couple analyzing the acoustic emission characters from hard composite rock fracture

Rock mass is fractured media. Its fracture is a nonlinear process. Theaccumulation of acoustic emission (AF) is closely related to the degree of damage. The dynamicsproblem is simply described based on the non-equilibrium statistical theory of crack evolvement,trying to use the hybrid analysis of the statistical theory and scan electron microscopy (SEM), thecharacters of AE signals from rock damage in a mined-out area is synthetically analyzed andevaluated. These provide an evidence to reverse deduce and accurately infer the position of rockfracture for dynamical hazard control.

Metallic phases of Dong Ujimqin mesosiderite:A field emission scanning electron microscope study

The microstructure of Fe-Ni metallic phases in Dong Ujimqin mesosiderite was studied using the field emission SEM. Taenite is characterized by a zoned structure, consisting of outer clear taenite and inner cloudy zone (CZ). CZ has a typical 'island-honeycomb' microstructure. The average size of the island phase is about 358 nm, suggesting a cooling rate of～0.5℃/Ma at low temperature (【400℃). The Ni concentration profiles across kamacite and zoned taenite were also measured by electron probe microscope analysis (EPMA). Formation of the Fe-Ni metallic phases, microstructure in Dong Ujimqin mesosiderite was discussed based on the new low-temperature Fe-Ni phase diagram.

银耳多糖对麦醇溶蛋白纳米体系的影响及复合物的特性研究

该研究是以提高麦醇溶蛋白(gliadin,Gli)纳米颗粒(gliadin nanoparticles,GNPs)稳定性为目标,利用银耳多糖(Tremella fuciformis polysaccharides,TFPs)的乳化性能,探究TFPs添加量对GNPs稳定性的影响。采用反溶剂法制备银耳多糖和麦醇溶蛋白复合载体颗粒(gliadin-Tremella fuciformis polysaccharides composite nanoparticles,G/T NPs),并利用纳米粒度仪、傅里叶变换红外光谱仪、热场发射扫描电镜对G/T NPs的粒径和电位、相互作用、微观结构进行分析。结果表明,TFPs和Gli之间通过静电作用力和氢键作用力相结合,形成GNPs在内、TFPs外层附着的复合颗粒;TFPs的添加能够有效提高GNPs体系的稳定性,减少颗粒之间的聚集,制得的G/T_(4∶1)NPs的平均粒径、多分散指数(polydispersion index,PDI)、ζ-电位分别为(198.5±2.6)nm、0.269±0.005、(36.7±0.6)mV,且具有pH响应性。该研究为后续构建疏水营养成分的包埋和运载体系奠定了基础。

场发射扫描电镜的科学管理与规范操作

扫描电镜具有分辨率高、信号稳定、操作简便等优点,可观察试样的微观形貌,在材料测试中起着重要的作用。扫描电镜主要由真空系统、电子光学系统、显示系统以及附属设备等组成。随着科技的不断发展,扫描电镜变得越来越普及,多数操作人员缺乏系统性的培训,操作水平参差不齐,对设备维护方面不够了解。以FEI Nova NanoSEM 450型场发射扫描电镜为例,介绍了该设备的一系列科学管理与规范操作方法,以期为相关操作人员提供参考。

扫描电镜中透射-反射式STEM明场成像装置的研制及应用

本文研制了一套透射-反射式扫描透射(STEM)明场成像装置,该装置使用背散射电子探头接收经过铂片反射的透射电子信号,可安装在FEI Quanta FEG系列扫描电镜中实现STEM明场成像。分别以埃洛石、Au@ZIF-8纳米颗粒和喷金乳胶标样验证自制STEM明场成像装置的实用性。结果表明:埃洛石STEM明场像的衬度与透射电镜中STEM明场像一致,管腔和管壁具有明显的衬度差异,可以清晰辨识管腔结构;在Au@ZIF-8纳米颗粒的STEM明场像中,Au颗粒衬度较暗,ZIF-8衬度较亮,通过两者之间的衬度差异可以观察到核壳结构;喷金乳胶标样上纳米金颗粒之间可识别的最小距离为2.03 nm,进一步验证了自制STEM明场成像装置具有较高的分辨率。

基于流场仿真的某型涡轮叶片的表面微结构分析

利用流场仿真和扫描电子显微镜观测的方法,对某型涡轮叶片工作前后的表面微形貌进行了分析,研究了高温高压环境对叶片表面形貌变化的影响。首先为了提高计算效率,根据叶片形式,建立了涡轮叶片流场的周期性对称CFD模型,并利用有限体积法对流场的温度和压力进行计算分析;然后利用扫描电镜对工作叶片的表面形貌进行观测,分析叶片表面微缺陷形式;最后根据仿真与试验观测结果,分析了叶片缺陷产生的原因和影响叶片表面微结构变化的因素。结果表明:叶片前缘温度达到最高的860K,在几何结构和波系的共同作用下,叶片前后缘、叶尖、叶根附近流场流动特性复杂,流道内温度和压力分布不均匀;叶片后缘根部出现长约180μm的穿晶/沿晶混合模式的微裂纹,后缘叶尖处有长约30μm的夹杂物裂纹出现,这是叶片热应力、叶片表面金相转变、氧化、氢脆等共同作用的结果;应根据涡轮泵的实际任务情况对涡轮泵地面热试车程序进行合理的安排,尤其在关机阶段要考虑是否对涡轮叶片的冷却采取大气环境隔离措施。研究可为液体火箭发动机涡轮叶片寿命评估提供参考。

17份闽北茶树种质资源花粉形态扫描电镜观察

【目的】明确闽北茶树种质资源花粉形态特征,并探索其亲缘关系。【方法】利用冷场发射扫描电镜观测福建武夷山、建瓯、建阳等闽北茶区17份茶树种质的花粉形态,采用ImageJ 1.48V对花粉的赤道面观、极面观和萌发沟等相关性状特征进行测量,并利用SPSS软件对花粉相关特征指标进行主成分分析和聚类分析。【结果】17份闽北茶树种质资源的花粉属N3P4C5类型,其花粉大小为1 014.01~2 222.26μm^(2),属于中等花粉;花粉的赤道面观分为扁球形、长球形、卵圆形和超长球形,花粉萌发沟长度为12.68~35.49μm,花粉表皮纹饰外壁纹饰均呈现疣状,具有不同程度穿孔。根据花粉萌发沟长、萌发沟长/极轴长、极面观、赤道面观、外壁纹饰5个指标进行系统聚类分析,17份闽北茶树种质资源可分为两类。【结论】根据聚类分析结果和数量性状数据,花粉萌发沟长、萌发沟长/极轴长、极面观、赤道面观、外壁纹饰等性状特征可以为闽北茶树种质资源的亲缘关系以及分类提供理论依据。

Acoustical properties of a 3D printed honeycomb structure filled with nanofillers:Experimental analysis and optimization for emerging applications

The novelty of this research lies in the successful fabrication of a 3D-printed honeycomb structure filled with nanofillers for acoustic properties,utilizing an impedance tube setup in accordance with ASTM standard E 1050-12.The Creality Ender-3,a 3D printer,was used for printing the honeycomb structures,and polylactic acid(PLA)material was employed for their construction.The organic,inorganic,and polymeric compounds within the composites were identified using fourier transformation infrared(FTIR)spectroscopy.The structure and homogeneity of the samples were examined using a field emission scanning electron microscope(FESEM).To determine the sound absorption coefficient of the 3D printed honeycomb structure,numerous samples were systematically developed using central composite design(CCD)and analysed using response surface methodology(RSM).The RSM mathematical model was established to predict the optimum values of each factor and noise reduction coefficient(NRC).The optimum values for an NRC of 0.377 were found to be 1.116 wt% carbon black,1.025 wt% aluminium powder,and 3.151 mm distance between parallel edges.Overall,the results demonstrate that a 3Dprinted honeycomb structure filled with nanofillers is an excellent material that can be utilized in various fields,including defence and aviation,where lightweight and acoustic properties are of great importance.

一种表征可吸收胶原蛋白材料孔结构的方法研究

目的研究一种表征可吸收胶原蛋白材料微观形貌的方法,并分析其孔隙率和孔径。方法利用场发射扫描电子显微镜(Scanning Electron Microscope,SEM),在不同的加速电压下对未喷金样品和喷金样品进行拍摄,使用Image J软件对所得的SEM图像的孔隙率和孔径进行分析,并对结果的有效性进行验证。结果样品未喷金时使用低倍加速电压可获得清晰的SEM图像;样品喷金后其耐受电压能力明显提高,即使在较高的加速电压下依然能获得清晰的SEM图像。使用Image J软件可对拍摄的SEM图像的孔径和孔隙率进行分析,其中,平均孔隙率为50.9%,平均孔径为11.9μm;孔隙率离散系数为8.6%,孔径离散系数6.7%。结论场发射SEM结合Image J软件是一种表征可吸收胶原蛋白材料孔结构的有效方法,可解决相关标准中方法缺失的问题。

HITACHI SU5000热场发射扫描电镜的使用及参数选择

以HITACHI SU5000热场发射扫描电镜为例,以金银核壳纳米棒、ZIF-8、碳酸钙纳米微球和聚苯乙烯微球为研究对象,探讨不同参数对扫描电镜图像质量的影响。结果显示,对于导电性良好的样品,选择较高加速电压搭配适宜束流强度,可得到高分辨率的样品形貌。对于半导体样品,选择合适的电压,根据放大倍数来调整束流强度。对于不导电样品,电压和束流过低,聚焦困难;适当提高加速电压,增加电子束的穿透深度,可显著减少荷电现象,图像质量得到改善。

A Pioneering Approach to the Synthesis of Silver Nanoparticles

Our research introduces a groundbreaking chemical reduction method for synthesizing silver nanoparticles, marking a significant advancement in the field. The nanoparticles were meticulously characterized using various techniques, including optical analysis, structural analysis, transmission electron microscopy (TEM), and field-emission scanning electron microscope (FESEM). This thorough process instills confidence in the accuracy of our findings. The results unveiled that the silver nanoparticles had a diameter of less than 20 nm, a finding of great importance. The absorption spectrum decreased in the peak wavelength range (405 - 394 mm) with increasing concentrations of Ag nanoparticles in the range (1 - 5%). The XRD results indicated a cubic crystal structure for silver nanoparticles with the lattice constant (a = 4.0855 Å), and Miller indices were (111), (002), (002), and (113). The simulation on the XRD pattern showed a face center cubic phase with space group Fm-3m, providing valuable insights into the structure of the nanoparticles.

INFLUENCE OF MAGNETIC FIELD ON ACCURACY OF ECM BY CHANGING THE CONDUCTIVITY OF ANODE FILM

The change of conductivity, thickness and scanning electron microscopy （SEM） appearance of the anode film of CrWMn in 10% NaNO3 at different anode potential either with or without the magnetic field applied are investigated by testing film resistance, galvanostatic transient and using SEM to design magnetic circuit in magnetic assisted electrochemical machining （MAECM）. The experiments show that the anode film has semi-conducting property. Compared with the situation without magnetic field applied, the resistance of the film formed at 1 .SV （anode potential） increased and decreased at 4.0V while B=0.4T and the magnetic north pole points toward anode. The SEM photo demonstrates that the magnetic field will densify the film in the passivation area and quicken dissolution of the anode metal in over-passivation area. Based on the influence of magnetic field on electrochemical machining（ECM） due to the changes of the anode film conductivity behavior, the magnetic north pole should be designed to point towards the workpiece surface that has been machined. Process experiments agree with the results of test analysis.

偏硼酸锂熔融-电感耦合等离子体发射光谱法结合扫描电镜-能谱测定锡矿石中锡钨锌铜铁锰

锡石不溶于盐酸、硝酸及王水,测定其中元素含量时通常采用碱熔融分解样品,电感耦合等离子体发射光谱法(ICP-OES)测定。而传统的过氧化钠或其他氧化性熔剂会引入大量的盐类,酸化提取后的溶液需要进一步分离或稀释,这样不仅影响分析的准确度及较低含量元素的测定限,长时间测定还会引起等离子体信号降低,造成仪器损伤。本文将锡矿石经偏硼酸锂熔融,超声波水浴处理,用ICP-OES法同时测定锡、钨、铁、锰、铜、锌元素含量,在标准溶液中匹配等量锂盐,各待测元素之间无明显干扰,操作简单快捷,环境污染小。实验过程中结合扫描电镜-能谱(SEM-EDX)微区分析技术,观察和分析不同熔剂量下样品熔珠的形貌特征和成分差异,发现随着熔剂与样品比例从小至大,熔珠表面结构呈现由松散、易碎向细粒、致密均匀的规律性变化,当熔剂与样品的比例达到7∶1后,熔珠表面形态无明显变化,当熔剂与样品的比例为8∶1时,熔珠表面能明显检测出硼元素的存在,说明此时的熔剂过量,从而实现了应用SEM-EDX技术来确定ICP-OES法分析中熔剂与样品的最佳配比。本研究还探讨了锡矿石样品的熔融温度和时间、介质酸度,对锡矿石标准物质GBW07281进行分析测定,方法精密度(RSD)为1.20%~8.06%,方法检出限为0.0012%~0.0098%,满足了样品中元素定量分析的要求。

储粮品质检测评价方法研究进展

品质检测评价是粮食储藏管理工作中的关键环节,一直是研究人员高度关注的热点研究领域,其在保障粮食储藏安全以及加工制品中发挥至关重要的作用。为了今后更好地开展相关工作,本文首先回顾常规基于光学、声学、介电、理化等特性和挥发性物质的储粮品质检测评价方法的研究进展;然后阐述当前新型检测技术如强磁场、激光诱导击穿光谱、核磁共振波谱以及扫描电子显微镜在储粮品质评价中的应用,并对比分析各种技术方法的优缺点;最后展望储粮品质检测评价方法的未来研究方向。

鄂西地区深层页岩气储层岩相孔隙结构特征差异及其控制因素--以YT1和YT3井五峰—龙马溪组页岩为例

岩相页岩孔隙结构是影响页岩气储集及运移能力的重要因素。以鄂西地区五峰—龙马溪组深层页岩为例,采用小角中子散射、高压压汞和场发射扫描电镜等实验方法,对比不同岩相页岩孔隙结构特征,明确不同岩相页岩孔隙结构特征差异及其控制因素。结果表明:鄂西地区五峰—龙马溪组页岩划分为高有机质硅质页岩岩相、中有机质硅质页岩岩相和低有机质黏土/混合质页岩岩相,不同岩相总孔隙度为1.76%~4.27%;高有机质硅质页岩和中有机质硅质页岩储集空间以有机孔为主,低有机质黏土/混合质页岩储集空间以无机孔为主,微裂缝发育程度为高有机质硅质页岩>中有机质硅质页岩>低有机质黏土/混合质页岩;有机质丰度和矿物组分是不同岩相页岩孔隙结构差异主控因素,随总有机碳质量分数和硅质矿物质量分数降低,有机孔密度和孔径显著下降,孔隙结构非均质性减弱,微裂缝发育程度逐渐降低。高有机质硅质页岩相具有较强生烃潜力,微裂缝发育程度较高,为研究区段最优页岩相。总有机碳质量分数和矿物组分是五峰—龙马溪组深层页岩气储层不同岩相孔隙结构特征差异关键因素,高有机质硅质页岩相为研究区段最优页岩相。该结果为鄂西地区下寒武统五峰—龙马溪组深层页岩气储层评价和有利区预测提供支持。

低钠条件下超声处理对鸡肉肌原纤维蛋白乳液稳定性的影响

低钠条件下肌原纤维蛋白(myofibrillar protein,MP)作为乳化剂制备的乳液稳定性差,本实验采用高强度超声波(high intensity ultrasound,HIU)(频率20 kHz、功率450 W)对低钠条件下(0.15 mol/L NaCl)MP进行不同时间(0、3、6、9、12 min)处理,测定处理后MP乳液乳化活性指数(emulsifying activity index,EAI)、乳液稳定性指数(emulsion stability index,ESI)、Turbiscan稳定性指数(turbiscan stability index,TSI)和平均粒径等,并进行微观结构观察和流变性分析等,研究低钠条件下超声处理对鸡肉MP乳化特性及其乳液稳定性和流变性能的影响。结果表明:与对照组相比,随着超声处理时间延长,MP的EAI和ESI显著增加(P<0.05),MP制备乳液的TSI和粒径随着超声处理时间的延长明显减小,且乳液液滴分布均匀,乳液Zeta-电位的绝对值显著增加(P<0.05)。乳液的流变学特性分析结果表明超声波明显提高了MP乳液的黏弹性。MP乳液的油-水界面张力分析结果显示超声处理有效增强了MP的移动性,使界面张力迅速降低,同时超声处理显著增加了MP乳液吸附蛋白相对含量(P<0.05),这表明超声处理MP有助于稳定乳液。通过冷场扫描电子显微镜观察进一步证实了超声处理12 min MP制备的乳液液滴体积最小。综上,超声波能够有效提高低钠条件下MP的乳液稳定性,本实验可为超声处理在减盐乳化型肉制品中的应用提供理论参考。

扫描电镜中扫描透射成像装置的研制及应用

使用扫描电镜自带的背散射电子探头(BSED)作透射散射电子探测器,设计了一套适合FEI Quanta 650FEG扫描电镜使用的扫描透射(STEM)成像装置,并制定了该STEM成像装置的操作说明。以埃洛石复合ZrO_(2)纳米颗粒为观察对象,对自制STEM成像装置的实用性进行了验证。结果表明:STEM像衬度与背散射电子探头到样品之间的距离相关,通过调整背散射电子探头与样品之间的距离,可以实现高角环形暗场像的采集,使ZrO_(2)纳米颗粒的亮度明显高于埃洛石;STEM像衬度与透射电镜采集的HAADF-STEM像一致,元素分布状态也与埃洛石和ZrO_(2)纳米颗粒对应,表明所研制的STEM成像装置具有较好的实用性。

四维扫描透射电子显微镜技术:从材料微观结构到物性分析

扫描透射电子显微镜(Scanning transmission electron microscopy,STEM)目前已经达到了原子级分辨率,并且由于其具有灵活的多通道成像能力以及强大的与谱学分析相结合的特点,因此在材料科学、生命科学等领域展现出强大的微尺度表征能力。但传统STEM的探测器受单像素积分式探测机制的限制,使其只能收集特定角度的散射电子,这导致不仅丢失了散射电子的角分辨信息,还降低了入射电子的剂量效率,因此迫切需要发展全新成像技术来实现高通量、高电子剂量效率成像。近年来,电子探测技术和分区或像素化探测器的研发联合计算机运算、存储能力的大幅提高,推动了四维扫描透射电子显微镜技术(Four-dimensional scanning transmission electron microscopy,4D-STEM)的蓬勃发展,并为最大化、最高效挖掘散射电子信息带来希望。在采集4D-STEM数据时,会聚电子束在样品平面上进行二维扫描,与此同时使用一块具有高帧速、高动态范围以及高信噪比的像素化阵列式探测器在远场收集二维的衍射数据。因为这些衍射数据是角度解析的,所以既可以用来进行常规的STEM成像,也可以用来实现前沿的相位衬度成像。例如利用电子叠层重构(Ptychography)技术通过在不同空间位置测量的一系列衍射花样来重建样品物函数。此外,4D-STEM技术还可以被进一步挖掘从而获得更多关于材料内部结构的信息,这为材料的多尺度表征带来机会。本文从4D-STEM技术原理介绍开始,总结了4D-STEM技术从材料微观结构到物性分析方面的一系列应用。具体而言,内容包含了虚拟探测器成像、微区电磁场测量、微区晶体取向测量、微区应变分布测量以及材料局域厚度测量等材料微尺度表征方面的原理和应用。除此之外,利用4D-STEM数据实现的电子叠层重构成像技术因为具有较高的散射电子利用效率,所以在低电子剂量领域展现出极大的应用潜力,因此本文还对4D-STEM技术在低电子剂量领域的应用进行了探讨与展望。总而言之,随着电子探测器以及4D-STEM数据后处理分析软件的快速发展,相信新颖的4D-STEM技术最终将彻底取代传统的扫描透射电子显微镜。