Beam-field Emission Scanning Electron Research Articles

Porous Covalent Organic Polymer Coordinated Single Co Site Nanofibers for Efficient Oxygen-Reduction Cathodes in Polymer Electrolyte Fuel Cells.

Nitrogen-coordinated single-cobalt-atom electrocatalysts, particularly ones derived from high-temperature pyrolysis of cobalt-based zeolitic imidazolate frameworks (ZIFs), have emerged as a new frontier in the design of oxygen reduction cathodes in polymer electrolyte fuel cells (PEFCs) due to their enhanced durability and smaller Fenton effects related to the degradation of membranes and ionomers compared with emphasized iron-based electrocatalysts. However, pyrolysis techniques lead to obscure active-site configurations, undesirably defined porosity and morphology, and fewer exposed active sites. Herein, a highly stable cross-linked nanofiber electrode is directly prepared by electrospinning using a liquid processability cobalt-based covalent organic polymer (Co-COP) obtained via pyrolysis-free strategy. The resultant fibers can be facilely organized into a free-standing large-area film with a uniform hierarchical porous texture and a full dispersion of atomic Co active sites on the catalyst surface. Focused ion beam-field emission scanning electron microscopy and computational fluid dynamics experiments confirm that the relative diffusion coefficient is enhanced by 3.5 times, which can provide an efficient route both for reactants to enter the active sites, and drain away the produced water efficiently. Resultingly, the peak power density of the integrated Co-COP nanofiber electrode is remarkably enhanced by 1.72 times along with significantly higher durability compared with conventional spraying methods. Notably, this nanofabrication technique also maintains excellent scalability and uniformity.

Distinguishing the Effects of the Space-Charge Layer and Interfacial Side Reactions on Li10GeP2S12-Based All-Solid-State Batteries with Stoichiometric-Controlled LiCoO2.

All-solid-state lithium batteries (ASSLBs) with high volumetric energy density and enhanced safety are considered one of the most promising next-generation batteries. Elucidating the capacity-fading mechanism caused by the space-charge layer (SCL) and the interfacial side reaction (ISR) is crucial for the future development of high-energy-density ASSLBs with a longer cycle life. Here, a systematic study to probe the electrochemical performance of Li10GeP2S12-based ASSLBs with stoichiometric-controlled LixCoO2 was performed with the aid of density functional theory (DFT) calculations, X-ray photoelectron spectroscopy (XPS), focused ion beam-field emission scanning electron microscopy (FIB-SEM), and solid-state nuclear magnetic resonance (NMR) spectroscopy. We discovered that the overstoichiometric Li1.042CoO2 shows a high capacity at first cycle with the smallest overpotential, but the capacity gradually decreases, which is ascribed to the weak SCL effect and strong interfacial side reactions. On the contrary, the lithium-deficient Li0.945CoO2 achieves the best cycling stability with a very low capacity associated with the strongest SCL effect and weak interfacial side reactions. The SCL effect is indeed coupled with ISR, which eventually leads to capacity fading in long-term operation. We believe that the new insights gained from this work will accelerate the future development of LiCoO2/LGPS-based ASSLBs with both a mitigated SCL effect and a longer cycle life.

Comparisons of the synthesis and photoluminescence properties of ZnO nanorods under different solution concentrations

In this study, the sol–gel method was used to prepare ZnO seed layer for synthesizing ZnO nanorods, and we would investigate the effects of different Zn(CH3COO)2 and C6H[Formula: see text]N4 concentrations on the synthesized characteristics of ZnO nanorods. First, the ZnO gel was dipped on the surface of the [Formula: see text]-type [Formula: see text] wafer as a seed layer. Then, the hydrothermal method with different Zn(CH3COO)2 and C6H[Formula: see text]N4 concentrations as precursors was used to synthesize ZnO nanorods on [Formula: see text]-type [Formula: see text] wafer. X-ray diffraction (XRD) pattern, focused ion beam-field emission scanning electron microscopy (FIB-FESEM) and photoluminescence (PL) spectrometry were employed to observe and analyze the crystal properties, surface morphologies, and optical properties of the prepared ZnO seed layer and synthesized ZnO nanorods. [Formula: see text]C and 60 min were used as the synthesis temperature and time, and we found that Zn(CH3COO)2 and C6H[Formula: see text]N4 concentrations had an apparent effect on the height, diameter, total surface area, total volume, density, and PL property of ZnO nanorods. The maximum PL emission intensity of ZnO nanorods presented in the samples with Zn(CH3COO)2 and C6H[Formula: see text]N4 concentrations of 0.2 M. The results of XRD patterns suggest that ZnO nanorods have the property of [Formula: see text]-axis preferred orientation. We showed that the different Zn(CH3COO)2 concentrations had large effects on the average height, average diameter, aspect ratio, total surface area (S, nm[Formula: see text], total volume (V, nm[Formula: see text], S/V ratio, and PL property of ZnO nanorods.

Application of focused ion beam-field emission scanning electron microscopy-X-ray microanalysis in the study of the surface alterations of archaeological tin-glazed ceramics

The historical evolution of tin-glazed ceramics is a subject that has attracted the attention of many scientists and, consequently, abundant archaeometrical studies can be found in the specialized literature. Nevertheless, a lesser number of studies aimed at the characterization of the alterations undergone by archaeological glazes has been reported. This work describes some unusual alteration processes found in tin-glazes depending on the environmental conditions surrounding the piece during centuries. For this purpose, focused ion beam-field emission scanning electron microscopy-X-ray microanalysis (FIB-FESEM-EDX), an advanced instrumental technique for surface analysis at the nanoscale, has been used for the first time, complementarily to optical microscopy (OM), FESEM-EDX and Fourier transform Infrared spectroscopy (FTIR). In the buried glaze the nanostructure of the outer lamellar corrosion layer due to humidity-dryness cycles is described. Unusual and selective erosion of the glaze matrix due to the silicification metabolism of diatoms is observed in a submarine glaze. A nanometric outer corrosion layer formed by precipitated corrosion products and unspecific organic matter that has been partially degraded to lead and calcium oxalates is found in a glazed tile subjected to an atmospheric environment.

Multiple-scan voltammetry of immobilized particles of ancient copper/bronze coins

The application of a multiple-scan strategy to study the structure of the corrosion patina of copper/bronze ancient objects using the voltammetry of immobilized microparticles (VIMP) is described. Upon nanosample attachment to graphite electrodes in contact with aqueous acetate buffer, voltammetric signatures characterizing cuprite with variable degree of crystallinity are recorded by means of successive cathodic scans reflecting the composition of the corrosion patina. The reported methodology, complemented with ion beam-field emission scanning electron microscopy (FIB-FESEM) and high-resolution field emission scanning electron microscopy (HRFESM-EDX), is applied to a set of coins fabricated between 1709 and 1962 revealing different corrosion patterns.

FIB-FESEM and EMPA results on Antoninianus silver coins for manufacturing and corrosion processes

A set of ancient Antoninianus silver coins, dating back between 249 and 274 A.D. and minted in Rome, Galliae, Orient and Ticinum, have been characterized. We use, for the first time, a combination of nano-invasive (focused ion beam-field emission scanning electron microscopy-X-ray microanalysis (FIB-FESEM-EDX), voltammetry of microparticles (VIMP)) and destructive techniques (scanning electron microscopy (SEM-EDX) and electron microprobe analysis (EMPA)) along with non-invasive, i.e., micro-Raman spectroscopy. The results revealed that, contrary to the extended belief, a complex Ag-Cu-Pb-Sn alloy was used. The use of alloys was common in the flourishing years of the Roman Empire. In the prosperous periods, Romans produced Ag-Cu alloys with relatively high silver content for the manufacture of both the external layers and inner nucleus of coins. This study also revealed that, although surface silvering processes were applied in different periods of crisis under the reign of Antoninii, even during crisis, Romans produced Antoninianus of high quality. Moreover, a first attempt to improve the silvering procedure using Hg-Ag amalgam has been identified.

Characterization of Pulse Anodized Titanium Dioxide Nanotubes

TiO2 nanotubes with a highly ordered structure were grown by a self-organized electrochemical anodization in the viscous organic electrolyte. The alteration pulse anodization waveforms were applied. The applied potentials were between positive of 20 V 10 min and a reverse voltage of 0 V or -5 V 20 sec. The morphologies of samples were examined using a field emission scanning electron microscope and focused ion beam field emission scanning electron microscopes (FIB-FESEM). The crystalline structures of the TiO2 nanotubes were confirmed by X-ray diffraction. The UV–Vis diffuse reflection absorption were recorded by a UV–vis spectrometer. All TiO2 nanotube samples prepared by pulse anodization technique were anatase phase and responded to UV region. The best-defined TiO2 nanotube morphology was obtained from the anodization condition: 20 V 10 min/-5 V 20 sec for 1 h. The thickness of the oxide layer increased with the increasing anodization time. All eight TiO2 nanotube samples responded to the light in the wavelength ranging from 190-360 nm which was UV region indicated the good photocatalytic property of these materials. Properties of anodized titanium dioxide nanotube from this work can be the useful indicators for the responsiveness of ultraviolet light which enhances the good property in photocatalytic process.

Electrochemical discrimination of mints: The last Chinese emperors Kuang Hsü and Hsüan T'ung monetary unification

An electrochemical methodology for discriminating monetary emissions, a recurrent problem in much archaeological studies, is introduced. The method is based on the record of voltammetric signatures of cuprite and tenorite corrosion products in the patina using a minimally invasive nanosampling following the voltammetry of immobilized particles methodology. A model for the depth variation of voltammetric electrochemical parameters characterizing the composition of the corrosion patinas is presented. This model permits to rationalize electrochemical data and discriminate different monetary emissions. The application of this technique, corroborated by electrochemical impedance spectroscopy (EIS) and focusing ion beam-field emission scanning electron microscopy (FIB-FESEM-EDX), to a series of 10 cash copper coins produced around the Kuang Hsu and Hsüan T’ung last Chinese emperors permits to discern different provincial mints and reveals that the monetary unification developed in this period was not uniform.

Simultaneous ohmic contacts to p- and n-type 4H-SiC by phase segregation annealing of co-sputtered Pt-Ti

A new concept, Phase Segregation Annealing (PSA), was investigated for implementing simultaneous ohmic contacts (SOCs) to p- and n-type 4H-SiC. Test structures with selected ratio compositions of co-sputtered Pt:Ti contacts were fabricated in p-type 4H-SiC epitaxial layers having aluminum acceptor concentrations, Na = 2 × 1019, 7 × 1019, and 2.5 × 1020 cm−3, and a nitrogen doped n-type epitaxial layer having donor concentration, Nd = 7 × 1018 cm−3. The ratios of the co-sputtered Pt-Ti metallization were 80:20, 50:50, and 30:70 at. %. After rapid thermal annealing (RTA) ranging between 800 and 1200 °C in vacuum and confirming SOCs by linear current-voltage (I-V) measurement, the specific contact resistance (ρc) values were extracted using the Transfer Length Measurement method. SOCs were realized with the Pt80:Ti20 composition starting from 1000 °C, and the Pt30:Ti70 composition from 1100 °C, with both exhibiting eutectic and segregated phases. The Pt50:Ti50 composition produced no SOC and eutectic and segregated phases were absent. The Pt80:Ti20 composition had the lowest pair of average ρc values of 7 × 10−5 Ω cm2 and 7.3 × 10−4 Ω cm2 on the highest doped p-type and the n-type samples after RTA at 1000 °C, respectively. Auger electron spectroscopy and focused ion beam field emission scanning electron microscopy with energy dispersive x-ray spectroscopy indicated distinct phase segregation via the eutectic-liquidus-eutectic transitions, the coalescence of likely Pt3Si and Pt2Si binary phases, and solid phases of Ti3Si, Ti5Si3, and TiC, with all the active phases maintaining intimate contact to both the p- and n-type 4H-SiC surfaces. The SOC formation was attributed to the disparate work functions of these phases, which was in good agreement with the proposed PSA model.

Micro-pore Structure and Gas Accumulation Characteristics of Shale in the Longmaxi Formation, Northwest Guizhou

AbstractFor further study on characteristics of micro-pores in the marine shale reservoirs in Northwest Guizhou, shale samples in the Lower Silurian Longmaxi Formation were selected to investigate effect of micro-pores on the characteristics of gas accumulation in shales, through methods of the argon broad ion beam-field emission scanning electron microscope and the nitrogen adsorption/desorption, analysis on the characteristics of micro-pores and related geochemical analysis. Results show that there are seven types of pores in the Longmaxi Formation shale, including interparticle pores, intraparticle pores, intercrystalline pores, dissolution pores, fossil pores, organic pores, and microfractures, among which the interparticle pores and organic pores are best developed. According to the nitrogen adsorption/desorption curves, the pore structures can be classified into three types, including the cylindrical pores with both opening ends, narrow parallel-plate pores and tapered parallel-plate pores with four opening sides. Diameter of micro-pores ranges from 2 to 64nm, mainly at 2-6nm. The diameter of micro-pores (less than 2nm) ranges from 0.4 to 1.8nm, The micro-pores with a diameter of 0.4-1.0nm contribute most to the pore volume. Pore volume is dominated by meso-pores (2-50nm) with a proportion of 83.1%. The micro-pores and meso-pores make major contribution to the specific surface area of pores with proportions of 20.1% and 79.3%, respectively. The total organic carbon (TOC) is the major factor controlling development of nanopores. Different pore types have different characteristics of gas occurrence and migration, indicating that nanopores provide favorable conditions for the occurrence and microscopic migration of gas in shales.

The Zona Pellucida Porosity: Three-Dimensional Reconstruction of Four Types of Mouse Oocyte Zona Pellucida Using a Dual Beam Microscope

In the last decade, the applicability of focus ion beam-field emission scanning electron microscopy (FIB-FESEM) in the biological field has begun to get relevance. Among the possibilities offered by FIB-FESEM, high-resolution three-dimensional (3D) reconstruction of biological structures is one of the most interesting. Using this tool, the 3D porosity of four different types of mouse oocyte zona pellucida (ZP) was analyzed. A surface analysis of the mouse oocyte ZP was first performed by SEM. Next, one oocyte per ZP type was selected, and an area of its ZP was completely milled, using the cut and view mode, in the FIB-FESEM. Through a 3D reconstruction of the milled area, a map of the distribution of the pores across the ZP was established and the number and volume of pores were quantified, thus enabling for the first time the study of the inner porosity of the mouse ZP. Differences in ZP porosity observed among the four types analyzed allowed us to outline a model to explain the changes that the ZP undergoes through immature, mature, predegenerative, and degenerative stages.

Evolution of microstructure and electrical conductivity of electroless copper deposits on a glass substrate

This paper describes the evolution of the microstructure and conductivity of electroless copper deposition on a glass substrate for applications in electronics manufacture. The glass was activated using a (3-aminopropyl)trimethoxysilane pre-treatment followed by a Pd/Sn catalyst. Surface morphology of the deposited copper films was characterized using a dual beam focused ion beam field emission scanning electron microscope, and together with atomic force microscopy, showed clearly that the roughness and grain size tended to increase with the plating time. Film thickness measurements showed a high initial deposition rate, which slowed to a constant level as the thickness increased above 100nm. This corresponded with the resistivity of the films which decreased rapidly as the thickness increased from 20 to 100nm, but then remained largely stable at a level approximately twice that of bulk copper.

Abrasive wear under multiscratching of polystyrene + single-walled carbon nanotube nanocomposites. Effect of sliding direction and modification by ionic liquid

Single-walled carbon nanotubes (NTs) and single-walled carbon nanotubes modified (NTms) by the room-temperature ionic liquid (IL) 1-octyl, 3-methylimidazolium tetrafluoroborate ([OMIM]BF 4) were added in a 1 wt.% to polystyrene (PS) and processed by compression or injection moulding to obtain PS + NT and PS + NTm, respectively. Friction coefficients and abrasive wear from penetration depth, residual depth and viscoelastic recovery were determined under multiple scratching. The effect of the moulding process, the additives and the sliding direction was studied. Compression moulded PS shows a transition to more severe damage after a critical number of successive passes. Addition of NTs or NTms to compression moulded PS induces a strain hardening effect and reduces friction, residual depth and viscoelastic recovery. Strain hardening is also observed in injection moulded PS with sliding in the longitudinal and random directions, but not in the transverse direction. The scratch resistance of PS + NTm depends on sliding direction. The lowest friction coefficient and residual depth values, and the highest viscoelastic recovery were found for injection moulded PS + NTm, in the sliding direction parallel to injection flow. Mechanisms of surface damage are discussed upon scanning electron microscopy (SEM), focused ion beam-field emission scanning electron microscopy (FIB-FESEM), 3D surface topography, surface roughness and profilometry observations.