Field Electron Microscopy Research Articles

Forming mechanism of single-channel multilayer laser cladding Fe60 process under different laser heat source operating mode

Continuous wave (CW) and pulsed wave are the two principal modes of operation used to control the laser heat source. Different laser heat source operating modes have an essential impact on the rapid cooling and heating temperature change rate during the cladding process, which directly determines the cladding layer quality. The laser cladding process is meaningful to quantitatively reveal the mechanism of single-channel multilayer cladding and forming under different laser heat source operating modes. In this article, a multi-field coupled 3D numerical model of the single-channel multilayer cladding process under different laser operating modes was proposed, and the thermal physical parameters of the cladding material were computed on the basis of Calculation of Phase Diagrams method. The mechanism of the impact of distinct operating modes on the multi-field coupled ephemeral evolution process of laser cladding was investigated by using the solid/liquid interface tracking technique, which comprehensively considers the light powder interaction between the powder waist beam and the laser beam under different operating modes. The temperature, flow, and stress fields were computationally solved for a single-channel multilayer cladding process. On the foundation of this study, the impact mechanism of pulse duty cycle and pulse frequency on the cladding behavior of single-channel and multilayers during pulsed laser cladding were dissected. The macroscopic morphology and microstructure of the cladding layer were observed by KEYENCE VH-Z100R ultra-deep field electron microscope, and the feasibility of the model was confirmed. This study provides a significant theoretical rationale for enhancing the cladding quality under different laser operating modes.

Electron Emission from High-Purity Copper Wires

Abstract: Field electron emission measurements were carried out on copper of 99.95% purity emitters, with apex radii in the nano and micrometer range. Samples have been prepared by electrochemical etching using phosphoric acid (H3PO4) solution. Measurements have been carried out under high vacuum environments with a base pressure of 10-7 mbar. Samples were installed in a field electron microscope (FEM) with an anode (tip)-to-cathode (screen) distance of 10 mm. Scanning electron microscope images, electrons spatial distribution behavior, and the current-voltage characteristics (I-V) have been studied and analyzed. Copper emitters have been prepared as electron sources and tested. The results showed a typical current-voltage characteristic from a coat emitter. The scanning electron microscope showed the sample geometry and cleanness. These copper electron emitters have been found to have significant aspects (high voltage breakdown mechanism) affecting the performance of advanced systems such as the electronic accelerator of The European Organization for Nuclear Research, known as CERN. This work aims to study this type of material to understand the high voltage breakdown phenomena in copper and the reasons behind it to provide a solution to such phenomena. Keywords: Field electron emission, Current-voltage characteristics, Copper tips, High vacuum.

Electron beams near surfaces: the concept of partial intensities for surface analysis and perspective on the low energy regime

Electron beam techniques are indispensable tools for the analysis of surfaces in fundamental as well as applied fields of science and technology. Significant improvements have been made in the past decades in the quantitative understanding of electron spectra, particularly with respect to the near-surface transport of signal electrons. The concept of partial intensities is a simple approach providing physical insight into transport of electrons in solids, a numerically convenient means for spectrum modelling and an essential ingredient for spectrum interpretation. The energy-dissipation process of energetic electrons in solids is discussed from the perspective of the partial intensities, offering a unified model for any type of electron beam technique, be it in the quasi-elastic (QE) or the continuous slowing down (CSD) regime. Examples are given for modelling and analysis of electron spectra such as X-ray photoelectron spectra (XPS), Elastic peak electron spectra (EPES) and electron energy-loss spectra (EELS). The physical model as well as the quantities for electron beam interaction with solids are reviewed, and methods for spectrum modelling and analysis are presented. The examples considered demonstrate the high level of accuracy nowadays attainable for characterisation of surfaces and nanostructures employing techniques using medium energy electrons (>100 eV). This is in contrast to the low energy regime, where a number of problems prevent a similar level of understanding. The topic of low energy electrons (LEEs) is rapidly gaining importance since in this energy range the involved electrons not only act as signal carriers, but also actively participate in electrochemical processes of importance in fields ranging from nanotechnology to life sciences. Issues of future importance in the field of LEEs are discussed and recent developments such as the 2-dimensional electron cascade in the scanning field electron microscope are highlighted.

Field Electron Emission Characteristics of Tungsten–Polyethylene Composite Material As a Source of Electron Emission

Abstract: This work provides an experimental study on the effects of polyethylene coating on the field electron emission characteristics of clean (uncoated) tungsten tips. Several tungsten tips, with different apex radii, have been prepared, coated with different thicknesses of polyethylene layers and then examined using a standard field electron emission microscope. Various field electron emission characteristics have been measured under high-vacuum conditions. These include current-voltage characteristics, Fowler-Nordheim plots, scanning electron micrographs and spatial current distributions (electron-emission images). Based on this work, it is proved that coating tungsten tips with polyethylene layers has caused dramatic improvements on the tip emission properties. In particular, coating the tips improves the current-voltage characteristics, which is reflected in lowering the extraction voltage, getting more stable emission currents, expressing the current-voltage characteristics using Fowler-Nordheim plots and finally, the spatial distributions of the emitted electrons for the coated tips are more stable and uniform. Keywords: Field electron emitter, Polyethylene dielectric layer, Composite emitter, Field electron microscope, Scanning electron microscope.

Biocontrol potential of Streptomyces sp. M4 and salvianolic acid B produced by it against Alternaria black leaf spot

The proposed study was designed to evaluate the biocontrol potential of Streptomyces sp. M4 and its bioactive metabolites (culture cells/cell free culture supernatant/EtOAc extract/salvianolic acid B) against Alternaria black leaf spot disease. The antifungal metabolite salvianolic acid B attacked A. brassicicola caused fungal abnormalities viz. loss of pigmentation, lysed spores, distorted hyphae and leakage of cellular contents were observed under bright field and scanning electron microscope. The bioactive metabolites in the culture supernatant were found to be thermostable (up to 70 °C), photostable and also stable under acidic and basic conditions. In in vitro experiment, treatment of fungal infected seeds with M4 antagonists (20% of culture supernatant/cells/EtOAc extract/salvianolic acid B) resulted in 82–96% seed germination, 60.71–86.20% healthy seedlings and 1470–2067 seedling vigour as compared to pathogen infected seeds. In vivo pot experiment, in which fungal spores (A. brassicicola) infected Raphanus sativus seeds were treated with Streptomyces sp. M4 culture cells/culture supernatant/EtOAc extract/salvianolic acid B (100 μg/ml), showed increase in various agronomic traits and decrease in disease incidence rate (4–16%) as compared to pathogen treated seeds. In vitro and in vivo studies unveiled that the Streptomyces sp. M4 and its bioactive metabolites could be used as potent biocontrol agents against A. brassicicola infected plants and therefore, to increase the resistance power of plants against pathogens.

How innovations in methodology offer new prospects for volume electron microscopy

Detailed knowledge of biological structure has been key in understanding biology at several levels of organisation, from organs to cells and proteins. Volume electron microscopy (volume EM) provides high resolution 3D structural information about tissues on the nanometre scale. However, the throughput rate of conventional electron microscopes has limited the volume size and number of samples that can be imaged. Recent improvements in methodology are currently driving a revolution in volume EM, making possible the structural imaging of whole organs and small organisms. In turn, these recent developments in image acquisition have created or stressed bottlenecks in other parts of the pipeline, like sample preparation, image analysis and data management. While the progress in image analysis is stunning due to the advent of automatic segmentation and server‐based annotation tools, several challenges remain. Here we discuss recent trends in volume EM, emerging methods for increasing throughput and implications for sample preparation, image analysis and data management.

Graphene Membranes for Multi‐Dimensional Electron Microscopy Imaging: Preparation, Application, and Prospect

AbstractTechnological breakthrough in electron microscopy (EM) has started a resolution revolution in EM imaging. Nowadays, the promotion of resolution demands a robust background‐noise‐free EM support for specimen preparation, which is a primary bottleneck of high‐resolution EM imaging. Owing to the atomic thickness and excellent physical properties, graphene has attracted widespread attention in the EM field to achieve high‐resolution multi‐dimensional imaging. However, it is still challenging to prepare high‐quality suspended graphene membranes. Problems like breakage, contamination and wrinkling reduce the quality of suspended graphene membranes, which inhibit their wide and killer applications in EM imaging. In this review, suspended graphene membranes are looked deeply into for multi‐dimensional EM imaging. This study begins with a brief introduction to EM development, followed by a discussion of the synthesis of high‐quality graphene. Then it summarizes various approaches to produce suspended graphene membranes and their killer applications in multi‐dimensional EM characterization, including high‐resolution 2D imaging, cryo‐EM 3D reconstruction, and 4D in situ liquid EM. Based on current achievements, the prospects of graphene membranes for more cutting‐edge applications are finally proposed.

Experimental analysis and prediction for the bonding strength of steel cord of conveyor belt under the temperature influence

To research the effect of temperature on the interfacial bonding strength of the steel cord rubber conveyor belt, an electronic universal material testing machine and a temperature control box were used as the test equipment. The withdrawal force of the steel cord skeleton of the rubber conveyor belt was tested in the temperature range of −30 °C to +40 °C. Concurrently, the interfacial morphology between the steel cord and rubber at different temperatures was observed by using an ultra deep field electron microscope. Finally, different bonding strength prediction models were established. The results show that the variation trend of the steel cord withdrawal force with displacement is the same at different temperatures. With the increase in temperature, the interfacial bonding strength between the steel cord and the rubber matrix decreases gradually; the second-order polynomial bonding strength prediction model can meet the prediction requirements of the steel cord bonding strength at different temperatures, and the errors are controlled within 5%.

An open-access volume electron microscopy atlas of whole cells and tissues.

Understanding cellular architecture is essential for understanding biology. Electron microscopy (EM) uniquely visualizes cellular structures with nanometre resolution. However, traditional methods, such as thin-section EM or EM tomography, have limitations in that they visualize only a single slice or a relatively small volume of the cell, respectively. Focused ion beam-scanning electron microscopy (FIB-SEM) has demonstrated the ability to image small volumes of cellular samples with 4-nm isotropic voxels1. Owing to advances in theprecision and stability of FIB milling, together with enhanced signal detection and faster SEM scanning, we have increased the volume that can be imaged with 4-nmvoxels by two orders of magnitude. Here we present a volume EM atlas at such resolution comprising ten three-dimensional datasets for whole cells and tissues, including cancer cells, immune cells, mouse pancreatic islets and Drosophila neural tissues. These open access data (via OpenOrganelle2) represent the foundation of a field of high-resolution whole-cell volume EM and subsequent analyses, and we invite researchers to explore this atlas andpose questions.

A novel wireless sample temperature control system for field ion, field electron, and atom probe techniques.

A novel sample temperature control system for field ion microscopy (FIM), field electron microscopy (FEM), and atom probe techniques based on wireless data transmission was designed, built, and applied for FIM and FEM studies of surface reactions. The system solves the longstanding problem of the temperature control of micrometer- to nanometer-sized samples during the operation in field emission based techniques. The new system can also be used for other applications requiring the specimen to be under high electric potential (tens of kilovolts or even higher). The chosen case studies of nanocatalysis demonstrate the capabilities and superior performance of the new temperature control system.

New U-Pb geochronology evidence for 2.3 Ga detrital zircon grains in the youngest Huronian Supergroup formations, Canada

Detrital zircon U-Pb ages from one sandstone and one claystone unit in the upper Huronian Supergroup, near Flack Lake, Ontario, Canada, provide new evidence for the maximum depositional age of the two youngest formations and reinterpretation of the depositional history of the upper Huronian Supergroup. The average age of the youngest zircon grains constrains the age of deposition to sometime after 2315 ± 5 Ma, but prior to intrusion of gabbro (Nipissing) dykes approximately 95 m.y. later. Clusters of late Archean age zircon are prominent in both samples, but a considerable addition from post-Archean sources is also present. The sample from the Bar River Formation contains a greater proportion of post-Archean material, which may be a result of grain-size bias. Our results are similar to U-Pb zircon ages determined from stratigraphically lower purported tuff beds in the Gordon Lake Formation, however our field and Scanning Electron Microscope (SEM) analyses demonstrate that the samples in the present study were not part of tuff units.

Characterization of Charge Reactions of Li-Air Battery Cathodes Studied with Field Ionization Methods

In recent years, lithium-air batteries have attracted significant interest due to increased energy density compared to currently available technologies such as lithium-ion batteries. The discharge process involves oxygen reduction to form LiO2, followed by further reduction to Li2O2 1. Meanwhile, oxygen evolution from the discharge deposits occurs during charge. The poor conductivity of Li2O2 2 requires the use of high overpotentials during charge, leading to side reactions that hinder battery performance1. A significant amount of work has been devoted at improving battery performance via cathode3 and electrolyte engineering4. In addition, several experimental and computational studies have attempted to understand the nature of the charge and discharge reactions through the use of electrochemical cells2,4-5. However, the complexity of electrochemical cells makes it difficult to gain fundamental insight of these processes. An alternative involves the use of ultrahigh vacuum (UHV) studies, where the ability to examine the influence of electrode potential on surface reactions is limited. This issue can be resolved by focusing on the effect of electric field on surface reactions since electric field is directly related to electrode potential. An example of a UHV technique is field ionization microscopy (FIM). In FIM, a Pt field emitter tip of approximately 350 Å radius is used as the substrate. The electric field on the surface is easily controllable by biasing the tip at moderate voltages (around 5 kV), to produce fields of up to 5 V/Å6. Reactions are carried out by adsorption of the species of interest (Li, O2, and a solvent representative of the electrolyte) followed by application of a baseline field. Adsorbed reaction products and their morphology can be monitored by FIM and field electron microscopy (FEM). Reaction intermediates and products can be detected by pulsed field desorption time of flight mass spectrometry (PFD-MS). In PFD, reactions products are formed under a base field, followed by desorption when a field pulse is applied. By varying the base field magnitude, pulse repetition frequency, and reaction temperature, it is possible to obtain information such as activation energies and possible reaction steps7. In this work, the kinetics of LiOx consumption in acetonitrile, a low DN solvent, will be studied using PFD and FIM. Namely, the focus of this work will be to characterize the effect of electric field, temperature, and reaction time on the rate of Li2O2 consumption during charge, as well as characterizing the lifetime of the LiO2 intermediate during charge. References Girishkumar, G; McCloskey, B; Luntz, A. C; Swanson, S; Wilcke, W. “Lithium-air battery: Promise and challenges”. Phys. Chem. Lett. 2010, 1, 2193–2203Viswanathan, V; Thygesen, K. S; Hummelshøj, S; Nørskov, J. K; Girishkumar, G; McCloskey, B. D; Luntz, A. C. “Electrical Conductivity in Li2O2 and its role in determining capacity limitations in non-aqueous Li-O2 batteries”. J Chem. Phys. 2011, 135, 214704Kwak, W. J; Lau, K. C; Shin, C. D; Amine, K; Curtiss, L. A; Sun, Y. K. “AMo2C/Carbon Nanotube Composite Cathode for Lithium-Oxygen Batteries with High Energy Efficiency and Long Cycle Life”. ACS Nano. 2015, 9, 4129–4137Laoire, C. O; Mukerjee, S; Abraham, K. M; Plichta, E. J; Hendrickson, M. A. “Influence of Nonaqueous Solvents on the Electrochemistry of Oxygen in the Rechargeable Lithium-Air Battery”. Phys. Chem. C. 2010, 114, 9178–9186Laoire, C. O; Mukerjee, S; Abraham, K. M; Plichta, E. J; Hendrickson, M. A. “Elucidating the Mechanism of Oxygen Reduction for Lithium-Air Battery Applications”. Commun. 2011 , 47, 9438-9440Rothfuss, C. J; Medvedev, V. K; Stuve, E. M. “The influence of the surface electric field on water ionization: a two-step dissociative ionization and desorption mechanism for water ion cluster emission from a platinum field emitter tip”. Surface Science. 2003, 554-555, 133-143Kruse, N. “Surface reaction kinetics on the atomic scale: studies by means of pulsed field desorption mass spectrometry”. Materials Science and Engineering A. 1999, 270, 75-82

Field Electron Emission Characteristics of Single-Walled Carbon Nanotube on Tungsten Blunt Tip

Recent investigations that are presented here illustrate the initial results that were obtained from a modified technique for holding the CNT on a W clean blunt tip. Field Electron Emission (FEE) has been investigated for single walled carbon nanotube (SWCNT) mounted on tungsten tip under (~10−8 mbar) vacuum conditions. The measurements recorded presented results showed that the CNT mounted on the W tip could emit electron current of at (0.7 V/μm) and reach up to (24 μA) of emission current at normal emission conditions. Such electron field emission tip was fabricated by electrolytically etching the high purity tungsten wire of (0.1 mm) in diameter in NaOH of (0.1) Molar solution, then mounting the single-walled carbon nanotube on the tip to be nearest to the tin oxide-coated and phosphorus glass anode. Such process was possible to be carried out under the microscope. A field electron microscope with a tip-screen separation at (~10mm) was used to characterize the electron emitter. The system was evacuated to an ultra-high vacuum level obtained after initial backing the system at up to (~180 °C) overnight. The emission characteristic has been investigated employing the I-V characteristics with Fowler-Nordheim plots and recording the emission images

Field-electron emission microscopy of carbon-saturated rhenium

The growth of carbon structures on the surface of a rhenium point field emitter has been studied by field electron microscopy (FEM). It is established that graphene formation takes place on close-packed crystal faces of rhenium and leads to decrease in their work function. For rhenium exposed in benzene vapors, the formation of graphene islands requires a much longer time than that for iridium. Heating of carbon-saturated rhenium point field emitter up to temperatures close to its melting point with subsequent cooling does not lead to changes in the work function and FEM image of the emitter surface. The observed phenomena are explained by high solubility of carbon in rhenium.

The potential use of single-particle electron microscopy as a tool for structure-based inhibitor design.

Recent developments in electron microscopy (EM) have led to a step change in our ability to solve the structures of previously intractable systems, especially membrane proteins and large protein complexes. This has provided new opportunities in the field of structure-based drug design, with a number of high-profile publications resolving the binding sites of small molecules and peptide inhibitors. There are a number of advantages of EM over the more traditional X-ray crystallographic approach, such as resolving different conformational states and permitting the dynamics of a system to be better resolved when not constrained by a crystal lattice. There are still significant challenges to be overcome using an EM approach, not least the speed of structure determination, difficulties with low-occupancy ligands and the modest resolution that is available. However, with the anticipated developments in the field of EM, the potential of EM to become a key tool for structure-based drug design, often complementing X-ray and NMR studies, seems promising.

The Influence of Electric Field on Lithium-Oxygen Battery Cathode Reactions

In recent years, lithium-air batteries have attracted significant interest due to increased energy density compared to currently available technologies such as lithium-ion batteries. The increased capacity in lithium-air batteries is due to charge/discharge reactions involving the formation of lithium oxide (LiOx) species1 However, issues such as loss of capacity due to irreversible oxidation reactions2, low capacity compared to the maximum theoretical capacity, high charging overpotentials, and the presence of parasitic reactions have limited their commercial deployment. Most of these issues occur in the cathode, where the lithium-oxygen deposits form. Recent work has focused in solving these issues via cathode engineering3-4 and improved electrolyte formulations5. In addition, there has been an increasing body of work aiming to understand the processes occurring in the cathode6-7. Most of these studies involve the use of electrochemical cells with subsequent characterization of the electrode. However, the complexity of electrochemical cells makes it difficult to gain insight regarding the nature of the cathode reactions. Instead, ultrahigh vacuum (UHV) surface science studies can be used to gain further insight regarding the surface reactions. In UHV studies, the ability to examine the influence of electrode potential on surface reactions is limited. This issue can be resolved by focusing on the effect of electric field on surface reactions since electric field is directly related to electrode potential. The effects of electric field on kinetics can be studied in a UHV system based on field ionization microscopy (FIM). A Pt field emitter tip of approximately 350 Å radius is used as the substrate. The electric field on the surface is easily controllable by biasing the tip at moderate voltages (around 5 kV), to produce fields of up to 5 V/Å8-9. The experiment is detailed in Fig. 1. Reactions are carried out by adsorption of the species of interest (Li, O2, and a solvent representative of the electrolyte) followed by application of a baseline field for a certain time and temperature. Adsorbed reaction products (LiOx) and their morphology can be monitored by FIM and field electron microscopy (FEM). Reaction intermediates and products can be detected by pulsed field desorption time of flight mass spectrometry (PFD-MS) and ramped field desorption (RFD). PFD-MS enables a survey scan of all species, while RFD probes the effects of electric field and temperature on surface reactions. In this work, the formation of LiOx deposits as a function of field, temperature, and coverage are studied with FIM and RFD. Reactions are conducted on both Pt and carbon-coated Pt tips, the latter to simulate a Li-O2 cathode. The differing field dependencies of LiOx deposit formation for different x will be used to estimate relative rates of LiOx formation in the Li-O2 battery. References Girishkumar, G; McCloskey, B; Luntz, A. C; Swanson, S; Wilcke, W. “Lithium-air battery: Promise and challenges,” J. Phys. Chem. Lett. 2010, 1, 2193–2203 2. Christensen, J; Albertus, P; Sánchez-Carrera, R. S; Lohmann, T; Kozinsky, B; Liedtke, R; Ahmed, J; Kojic, A. A Critical Review of Li/Air Batteries. J Electrochem Soc. 2012, 159, R1-R30Kwak, W. J; Lau, K. C; Shin, C. D; Amine, K; Curtiss, L. A; Sun, Y. K. “AMo2C/Carbon Nanotube Composite Cathode for Lithium-Oxygen Batteries with High Energy Efficiency and Long Cycle Life,” ACS Nano. 2015, 9, 4129–4137Lu, Y. C; Xu, Z; Gasteiger, H. A; Chen, S; Hamad-Schifferli, K; Shao-Horn, Y. “Platinum-Gold Nanoparticles: A Highly Active Bifunctional Electrocatalyst for Rechargeable Lithium-Air Batteries,” J. Am. Chem. Soc. 2010, 132, 12170–12171Laoire, C. O; Mukerjee, S; Abraham, K. M; Plichta, E. J; Hendrickson, M. A. “Influence of Nonaqueous Solvents on the Electrochemistry of Oxygen in the Rechargeable Lithium-Air Battery,” J. Phys. Chem. C. 2010, 114, 9178–9186Laoire, C. O; Mukerjee, S; Abraham, K. M; Plichta, E. J; Hendrickson, M. A. Elucidating the Mechanism of Oxygen Reduction for Lithium-Air Battery Applications. Chem. Commun. 2011 , 47, 9438-9440Black, R; Oh, S. H; Lee, J. H; Yim, T; Adams, B; Nazar, L. F. “Screening for Superoxide Reactivity in Li-O2 Batteries: Effect on Li2O2/LiOH Crystallization,” J. Am. Chem. Soc. 2012, 134, 2902–2905Rothfuss, C. J; Medvedev, V. K; Stuve, E. M. “The influence of the surface electric field on water ionization: a two-step dissociative ionization and desorption mechanism for water ion cluster emission from a platinum field emitter tip,” Surface Science. 2003, 554-555, 133-143Rothfuss, C. J; Medvedev, V. K; Stuve, E. M. “Cluster formation and distributions in field ionization of coadsorbed methanol and water on platinum,” Surface Science. 2015, http://dx.doi.org/10.1016/j.susc.2015.12.023 Figure 1

Investigating of the Field Emission Performance on Nano-Apex Carbon Fiber and Tungsten Tips

Field electron emission measurements have been performed on carbon-based and tungsten microemitters. Several samples of both types of emitters with different apex radii have been obtained employing electrolytic etching techniques using sodium hydroxide (NaOH) solution with different molarities depending on the material used. A suitable, home-built, field electron microscope (FEM) with 10 mm tip to screen separation distance was used to electrically characterize the electron emitters. Measurements were carried out under ultra high vacuum (UHV) conditions with base pressure of 10-9 mbar. The current-voltage characteristics (I-V) presented as Fowler-Nordheim (FN) type plots, and field electron emission images have been recorded. In this work, initial comparison of the field electron emission performance of these micro and nanoemitters has been carried out, with the aim of obtaining a reliable, stable and long life powerful electron source. We compare the apex radii measured from the micrographs obtained from the SEM images to those extracted from the FN-type _I-V_plots for carbon fibers and tungsten tips.

Large chip production mechanism under the extreme load cutting conditions

There has existed a great deal of theory researches in term of chip production and chip breaking characteristics under conventional cutting and high speed cutting conditions, however, there isn’t sufficient research on chip formation mechanism as well as its influence on cutting state regarding large workpieces under extreme load cutting. This paper presents a model of large saw-tooth chip through applying finite element simulation method, which gives a profound analysis about the characteristics of the extreme load cutting as well as morphology and removal of the large chip. In the meantime, a calculation formula that gives a quantitative description of the saw-tooth level regarding the large chip is established on the basis of cutting experiments on high temperature and high strength steel 2.25Cr-1Mo-0.25V. The cutting experiments are carried out by using the scanning electron microscope and super depth of field electron microscope to measure and calculate the large chip produced under different cutting parameters, which can verify the validity of the established model. The calculating results show that the large saw-toothed chip is produced under the squeezing action between workpiece and cutting tools. In the meanwhile, the chip develops a hardened layer where contacts the cutting tool and the saw-tooth of the chip tend to form in transverse direction. This research creates the theoretical model for large chip and performs the cutting experiments under the extreme load cutting condition, as well as analyzes the production mechanism of the large chip in the macro and micro conditions. Therefore, the proposed research could provide theoretical guidance and technical support in improving productivity and cutting technology research.

The versatile electron microscope: An ultrastructural overview of autophagy

Both light microscopy (LM) and electron microscopy (EM) are able to reveal important information about the formation and function of various autophagic compartments. In this article we will outline the various techniques that are emerging in EM, focusing on analyzing three-dimensional morphology, collectively known as volume electron microscopy (volume EM), as well as on methods that can be used to localize proteins and antigenic epitopes. Large cell volumes can now be visualized at the EM level by using one of the two complementary imaging techniques, namely Serial Block-face Scanning Electron Microscopy (SB-SEM) or Focused Ion Beam Scanning Electron Microscopy (FIB-SEM). These two block-face imaging methods reveal ultrastructural information from all membrane-bound organelles such as autophagic compartments to be visualized in a three-dimensional space, in association with their surrounding organelles. Another method which falls into the volume EM category is dual-axis electron tomography (ET). This method is more suited to reconstructing smaller volumes from areas of interest that require nano-structural detail to be confirmed such as membrane contact sites (MCSs) between autophagic compartments and various organelles. Further to this, to complement the morphological identification of autophagic compartments, immunolabeling can be carried out at the EM level to confirm the nature of various autophagic compartments depending on the localization of various antigens at a sub-cellular level. To determine this, various immunolabeling techniques can be carried out, namely the pre-embedding or the post-embedding immunolabeling methods. Examples of both of these methods will be described in this chapter. Correlative light-electron microscopy (CLEM) can be used to visualize the same autophagic organelles under the LM, followed by high-resolution imaging under the EM. Finally, cryofixation has revolutionized the EM field by allowing rapid immobilization of cells and tissue in the near native state, so samples are no longer prone to artefacts induced by chemical fixation. Collectively, this chapter will discuss the aforementioned capabilities of the EM in more detail, with a particular focus on autophagy, namely the impact of EM in the study of the morphology and biogenesis of the phagophore/isolation membrane (referred to as the phagophore hereafter).

Biprism electron interferometry with a single atom tip source

Experiments with electron or ion matter waves require a coherent, monochromatic and long-term stable source with high brightness. These requirements are best fulfilled by single atom tip (SAT) field emitters. The performance of an iridium covered W(111) SAT is demonstrated and analyzed for electrons in a biprism interferometer. Furthermore we characterize the emission of the SAT in a separate field electron and field ion microscope and compare it with other emitter types. A new method is presented to fabricate the electrostatic charged biprism wire that separates and combines the matter wave. In contrast to other biprism interferometers the source and the biprism size are well defined within a few nanometers. The setup has direct applications in ion interferometry and Aharonov-Bohm physics.