Electron Optical Images Research Articles

Detrital quartz and quartz cement in Upper Triassic reservoir sandstones of the Sichuan basin: Characteristics and mechanisms of formation based on cathodoluminescence and electron backscatter diffraction analysis

The relationship between detrital quartz grains and silica cement is significant because cement is often a major cause of porosity reduction in oil and gas reservoirs, thus degrading hydrocarbon reservoir quality. On the other hand, the attributes of grain surfaces may inhibit cementation, thus preserving porosity in the reservoirs. In this study we focus on the microstructures in quartz grains and secondary overgrowths (quartz cement) in the heavily cemented sandstones from uplifted Upper Triassic siliciclastic rocks in the southern Sichuan basin, China. Electron backscatter diffraction (EBSD), optical, and cathodoluminescence (CL) imaging methods have been used to address the microstructural and crystallographic attributes of the detrital grains and their overgrowths. This study confirms that: (1) the overgrowth zones of quartz are clearly visible in optical and CL images; (2) all silica overgrowths are perfectly crystalline quartz; (3) quartz cements have a syntaxial relationship with the host detrital grain, indicating crystallographic continuity between the detrital quartz and its overgrowth; and (4) crystallographic maps confirm that Dauphiné twins commonly occur both in the detrital grains and in the quartz cement. Most Dauphiné twins are developed at grain–grain contacts, including the margins of detrital grains where they are in contact with quartz cement. Some twins are limited to a single grain, whereas others cross grain–cement boundaries. Based on these twin distributions, we can distinguish inherited twins from twins that formed during/after burial compaction. This study documents the grain deformation structures induced by sedimentary compaction, and these structures can be accurately illustrated by EBSD data.

Potassium persulfate‐mediated preparation of conducting polypyrrole/polyacrylonitrile composite fibers: Humidity and temperature‐sensing properties

AbstractConducting polypyrrole (PPy)/polyacrylonitrile (PAN) composite fibers were prepared by the polymerization of pyrrole in the presence of PAN fibers with potassium persulfate in an acidic aqueous solution. We obtained composite fibers containing concentrations of PPy as high as 1.14% and having surface resistivities as low as 0.6 kΩ/cm2 by changing the polymerization parameters, including the temperature and concentrations of pyrrole and oxidant. The tensile strength of 10.02 N/m2 and breaking elongation of 32.68% for the pure PAN fiber increased up to 10.45 N/m2 and 33.23%, respectively, for the composite fiber containing 0.13% PPy. The change in the resistivity of the PPy/PAN composite fiber during heating–cooling cycles in the temperature range of +5 to 120°C was examined. Scanning electron microscopy and optical microscopy images of the composite fibers showed that the PPy coating was restricted to the surfaces of the PAN fibers. Surface resistivity measurements, Fourier transform infrared spectroscopy, and thermogravimetric analysis techniques were also used to characterize the composite fibers. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Noniterative Exact Solution to the Phase Problem in Optical Imaging Implemented with Scanning Probe Microscopy

An object is characterized by its amplitude and phase. However, when acquiring optical data about such an object, using a recording medium such as a camera, phase information is lost. Crystallography experienced a breakthrough in phase retrieval for large molecular entities by Max Perutz's introduction of "heavy atoms" using the method of isomorphous replacement. The availability of scanning probe microscopy and its full integration with optical microscopy allows us to apply these X-ray concepts to implement "heavy atom" restoration of phase in optical phase retrieval. In analogy to the heavy atom method, we acquire Fourier intensities in place of an X-ray diffraction pattern, and in place of the heavy atom, we utilize a nanometrically translatable point source of light based on the propagating field of a cantilevered near-field scanning optical microscopic (NSOM) probe controlled by an atomic force microscope (AFM). This integration of NSOM/AFM technology with far-field imaging achieves robust phase retrieval independent of external parameters, leading to 3D optical imaging. The methodology has super-resolution potential, and thus, heavy atom restoration of phase with super-resolution (HARPS) shows the potential of transparently integrated scanning probe microscopy with optical and other imaging modalities such as electron or ion optical imaging.

Nanoparticles enhance brain delivery of blood–brain barrier-impermeable probes for in vivo optical and magnetic resonance imaging

Several imaging modalities are suitable for in vivo molecular neuroimaging, but the blood-brain barrier (BBB) limits their utility by preventing brain delivery of most targeted molecular probes. We prepared biodegradable nanocarrier systems made up of poly(n-butyl cyanoacrylate) dextran polymers coated with polysorbate 80 (PBCA nanoparticles) to deliver BBB-impermeable molecular imaging probes into the brain for targeted molecular neuroimaging. We demonstrate that PBCA nanoparticles allow in vivo targeting of BBB-impermeable contrast agents and staining reagents for electron microscopy, optical imaging (multiphoton), and whole brain magnetic resonance imaging (MRI), facilitating molecular studies ranging from individual synapses to the entire brain. PBCA nanoparticles can deliver BBB-impermeable targeted fluorophores of a wide range of sizes: from 500-Da targeted polar molecules to 150,000-Da tagged immunoglobulins into the brain of living mice. The utility of this approach is demonstrated by (i) development of a "Nissl stain" contrast agent for cellular imaging, (ii) visualization of amyloid plaques in vivo in a mouse model of Alzheimer's disease using (traditionally) non-BBB-permeable reagents that detect plaques, and (iii) delivery of gadolinium-based contrast agents into the brain of mice for in vivo whole brain MRI. Four-dimensional real-time two-photon and MR imaging reveal that brain penetration of PBCA nanoparticles occurs rapidly with a time constant of ∼18 min. PBCA nanoparticles do not induce nonspecific BBB disruption, but collaborate with plasma apolipoprotein E to facilitate BBB crossing. Collectively, these findings highlight the potential of using biodegradable nanocarrier systems to deliver BBB-impermeable targeted molecular probes into the brain for diagnostic neuroimaging.

Deposition of nanocrystalline diamond films on temperature sensitive substrates for infrared reflectance spectroscopy

We report on the deposition of nanocrystalline diamond films onto protected aluminum/pyrex glass mirrors in focused or linear antenna microwave plasma enhanced chemical vapour deposition systems. Quality of the diamond films is characterized by Raman spectroscopy, scanning electron microscopy and optical images. The best material quality and coating uniformity is achieved in the linear antenna system. Infrared reflectance spectroscopy reveals enhanced reflection from the substrates prepared in the linear antenna system compared to diamond coatings prepared in common focused plasma system on protected aluminium/pyrex glass mirrors as well as on polished Si wafers. Linear antenna system diamond coatings are thus the most promising for spectroscopic characterization of molecular grafting to diamond.

Microfabrication of 3D neural probes with combined electrical and chemical interfaces

This paper reports a novel neural probe technology for the manufacture of 3D arrays of electrodes with integrated microchannels. This new technology is based on a silicon island structure and a simple folding procedure. This method simplifies the assembly or packaging process of 3D neural probes, leading to higher yield and lower cost. Prototypes with 3D arrays of electrodes have been successfully developed. Microchannels have been successfully integrated into the 3D neural probes via isotropic XeF2 gas phase etching and a parylene resealing process. The probes have been characterized by scanning electron microscopy imaging, optical imaging, impedance analysis, and atomic force microscopy characterization of the electrode surface. Preliminary animal tests have been carried out to demonstrate the recording functionality of the probes. Flow characteristics of the microchannels were also preliminarily measured.

Characterization of Silicon Carbide Grit for Fickerts Used in Porcelain Tile Honing and Polishing Process

This paper presents results of morphological and dimensional characterization of silicon carbide (SiC) abrasives used in production of fickerts for the rotary plane honing and polishing process of porcelain tiles. For morphological characterization scanning electron microscopy (SEM) and optical reflection microscopy images were analyzed by software to determine the circularity factor of the particles. In order to analyze the particle size dispersion sieving and laser diffraction were used. Five samples within the same batch of abrasives and with different sizes were characterized. The results show a uniform dispersion with a small variation of the particles size. Regarding the form of particles, the angularity increases in the samples with smaller size. The employed procedure for the analysis of circularity factor is a method frequently used to characterize SiC particles.

A reassessment of late glacial – Holocene diatom oxygen isotope record from Lake Baikal using a geochemical mass‐balance approach

AbstractWe present a new palaeoenvironmental record of hydrological variability in Lake Baikal, based on re‐modelled δ18Odiatom values of diatom silica (δ18Omodelled), where the residual contaminants are identified and compensated for using electron optical imaging and whole‐sample geochemistry. δ18Omodelled interpretations are based on the balance between rivers with high δ18O values and rivers with low δ18O values. Isotopic variability is related to latitudinal differences in precipitation which feed these rivers. The δ18Omodelled record suggests that rather moist conditions prevailed in the Lake Baikal region during the latter stages of the Younger Dryas. Throughout the Holocene, episodes of low δ18Omodelled values are, in general, in good agreement with increases in percentage haematite‐stained grains in North Atlantic sediments (indicative of ice‐rafted debris events). Rivers with southerly catchments dominate fluvial input especially between c. 3.3 and 2 cal ka BP, concurrent with high precipitation in the Lake Baikal region. Copyright © 2011 John Wiley & Sons, Ltd.

Fabrication of in situ Cu/SiC composites using multi-pass friction stir processing: Evaluation of microstructural, porosity, mechanical and electrical behavior

In this study, multi-pass friction stir processing (MFSP) is used for improvement of microstructural and mechanical properties of in situ Cu/SiC composites. Field emission scanning electron microscopy and optical microscopy images indicate that multi-pass FSP notably enhances the separation and dispersion of SiC particles and also reduces the grain size in the composite matrix, SiC particles size and porosity contents. According to the results, higher microhardness values and remarkably enhanced tensile properties were caused by higher number of FSP passes. It was also found that the average friction coefficients of composites fabricated by multi-pass FSP were noticeably reduced compared to the pure copper. Addition of SiC particles led to enhancement of electrical resistivity of pure copper. A negligible difference between the electrical resistivity of composites fabricated by 1, 4 and 8-pass FSP was also detected.

Investigation of fretting fatigue behaviour under multiaxial non-proportional loading

Fretting fatigue is a structural mechanism observed when two contacting bodies are subjected to an oscillatory loading. The study on fretting fatigue behaviour of 60Si2Mn steel was conducted under condition of multiaxial non-proportional loading. The fretting fatigue lives corresponding to different cyclic axial stress amplitudes were tested with same rotation loading amplitude and contact normal pressure. The characters of frictional and wear surfaces and fracture morphology were analysed in detail by scanning electron microscopy and optical images. It is found the fretting fatigue life decreases but the work done by axial frictional force increases with the increase of the axial stress amplitude. Fretting fatigue crack initiates near the trailing edge of fretting contact zone and propagates at an angle of 45° along the axial direction at the existence of tangential shear stress produced by the rotation loading. Apparently, the fracture surface is not smooth and perpendicular to the axial direction of specimen.

Increasing of Hardness of Titanium Using Energetic Nitrogen Ions from Sahand as a Filippov Type Plasma Focus Facility

In this paper a 90 kJ plasma focus facility was used to the bombardment of the titanium substrate using nitrogen ion beams. From x-ray diffraction patterns, we investigated the structure properties of titanium nitride layer has been successfully deposited on the titanium substrate such as grain size microstrain and dislocation density. In this work we observed the growth of in grain size with increasing a number of deposition shots. Decrease in dislocation density and microstrain at higher deposition is the another results we observed in this work. The topography and morphology of TiN samples was studied by scanning electron microscopy (SEM) and optical microscopy images. From SEM micrograph, damage of surface and creation of pits and cracks was reported. The goniometric test indicate increasing in contact angle of water drop for irradiated samples in respect to the unirradiated samples. The Knoop microhardness of the samples is increased about 500%. With increasing of nitrogen ion flux, the microhardness increases.

Photonic crystal waveguides by direct writing of e-beam on self-assembled photonic crystals

Direct electron beam lithography technique is used for writing a variety of waveguide structures on thin films of polymethyl methacrylate (PMMA) and self-assembled three-dimensionally ordered photonic crystals made up of PMMA colloidal spheres. The waveguide structures fabricated on both these type of samples are characterized by scanning electron microscope and optical microscope images.

Influence of the particle type on the rheological behavior of Pickering emulsions

In order to get a better understanding of potential relationships among the microstructure and stability of Pickering emulsions, rheological studies were performed using differently modified disperable colloidal Boehmite alumina nanoparticles. Hysteresis loop measurements and dynamic (oscillatory) rheological measurements on two different emulsion systems were carried out in linear and non-linear regime at different storage time. Differential scanning calorimetry (DSC) results, transmission electron microscopy (TEM) and optical microscopy images of these emulsion systems were additionally analysed in respect to reveal the emulsions type and their microstructure. Pickering emulsion stabilized by moderately hydrophobic particles exhibited inhomogeneous structure, relative large yield stresses and thixotropic flow behavior, indicating a formation of a three-dimensional network. Emulsion stabilized by rather hydrophobic particles with a contact angle around 90°, was revealed to be an oil-in-water-in-oil multiple emulsion. The emulsion was homogenous and showed thixotropy, indicating the presence of a three-dimensional network. However, a phase separation slightly occurred in the storage time evaluated meaning that the stability of this emulsion need be improved.

The effects of encapsulation on deformation behavior and failure mechanisms of stretchable interconnects

In this paper, the effect of encapsulation on deformation behavior and failure mechanisms of stretchable interconnects is presented. Extensive numerical modeling is conducted for mechanical analysis of which the results are correlated with in-situ experimental observations. The numerical results reveal that by adding an encapsulation layer of various thickness (from 0.0 to 0.5 mm) on top of the stretchable interconnect, the out-of-plane deformation and in-plane geometrical opening are reduced. Consequently, not only the plastic strain in the metal increases but also the in-plane shear stress at the interconnect/substrate interface. In-situ electromechanical experiments combined with scanning electron micrographs and optical images confirm the numerical analysis. More specifically, it is found that two failure mechanisms are involved during the stretching process: interfacial delamination in a S-shape alongside the metal conductor and metal breakdown at the crests of the metal conductor. The encapsulated stretchable interconnect shows both failure mechanisms at a lower percentage elongation than the non-encapsulated stretchable interconnect. Even so, the onset point of interfacial delamination for the encapsulated stretchable interconnect occurs only at an impressive number of 63% elongation and metal rupture only at 120%. The in-plane shear strain contour, obtained by numerical simulation, agrees well with the delamination failure location observed in the experiment.

Theory of paraxial lateral aberrations of electrostatic imaging electrostatic electron optics based on asymptotic solutions and its verification

In imaging electron optics, study of geometrical lateral aberrations of third order and paraxial lateral aberrations of second order has traditionally been paid more attention to, but the existence of paraxial chromatic aberrations of third order and paraxial chromatic aberrations of magnification of third order was almost ignored, and the general form of paraxial lateral aberration has not been studied theoretically. In the present paper, the paraxial lateral aberrations expressed in general form have been derived emphatically on the basis of asymptotic solutions of paraxial equation. The relationship between the coefficients of asymptotic solutions has been investigated, which proves that the coefficients of asymptotic solutions are related each other. Through a bi-electrode electrostatic spherical concentric system model, two special solutions expressed by asymptotic solutions and accurate solutions in a bi-electrode electrostatic spherical concentric system have been deduced, and the paraxial lateral aberrations have been verified and tested, in which the aberration coefficients are solved by asymptotic solutions of paraxial equation. Result completely proves that the approach based on asymptotic solutions to solve the paraxial lateral aberrations are practicable and accurate enough. The paraxial chromatic aberration of magnification of third order and the paraxial chromatic aberration of third order have been firstly derived, and the Recknagel–Artimovich formula of paraxial chromatic aberration of second order which possess an greatest part in the whole paraxial lateral aberrations has been deduced and confirmed. A simple and clear form for expressing paraxial lateral aberrations of imaging electron optics is suggested for practical use. Results of the present paper will have theoretical value for aberration theory of imaging electron optics and practical significance for the design of image tubes.

Paraxial imaging electron optics and its spatial-temporal aberrations for a bi-electrode concentric spherical system with electrostatic focusing

The paraxial solutions play an important role in studying electron optical imaging system and its spatial-temporal aberrations, as was discussed in previous paper [1], but investigation of a bi-electrode concentric spherical system with electrostatic focusing directly from paraxial electron ray equation and paraxial electron motion equation has not been done before. In this paper, we shall use the paraxial equations to study the spatial-temporal trajectories and their aberrations for a bi-electrode concentric spherical system with electrostatic focusing. In the present paper, start from the paraxial ray equation and paraxial motion equation, the paraxial spatial-temporal trajectory of moving electron emitted from the photocathode has been solved for a bi-electrode concentric spherical system with electrostatic focusing. The paraxial static and dynamic electron optics, as well as the paraxial spatial-temporal aberrations in this system are then discussed, the general regularity of imaging in paraxial optical system has been explored. The paraxial spatial aberrations, as well as the paraxial temporal aberrations with different orders, have been defined and deduced, that are classified by the order of ( ɛ z / ϕ ac ) 1/2 and ( ɛ T / ϕ ac ) 1/2. Thus we get same conclusions about paraxial spatial and temporal aberrations as we have given in the previous paper and it completely shows that the paraxial spatial-temporal aberrations can be investigated directly from the paraxial ray equation and paraxial motion equation.

Static and dynamic imaging electron optics and spatial–temporal aberrations in a bi-electrode spherical concentric system with electrostatic focusing

In imaging electron optics, for a concentric spherical system composed of two spherical electrodes with electrostatic focusing, the electrostatic potential distribution and the spatial–temporal trajectory of electron motion can be expressed by analytical forms. It is naturally to take such system as an ideal model to investigate the imaging properties, as well as the spatial–temporal aberrations, to analyze its particularity and to find the clue of universalities and regularities. Research on this problem has important significance, which can afford theoretical foundation not only in studying static electron optics for the night vision devices, but also in studying dynamic electron optics for high-speed image converter tubes. In the present paper, based on the practical electron ray equation and electron motion equation for a bi-electrode concentric spherical system with electrostatic focusing, the spatial–temporal trajectories of moving electrons emitted from the photocathode have been solved, the exact and approximate formulae for image position and flight time of electrons, have been deduced. Start from solutions of spatial–temporal trajectories, the electron optical spatial–temporal properties of this system are then discussed. According to the definitions of spatial–temporal aberrations, the paraxial and geometrical lateral aberrations, as well as the paraxial and geometrical temporal aberrations, have been deduced, that are classified by the order of ε z / ϕ a c and ε r / ϕ a c .

Ductile and brittle material removal mechanisms in natural nacre—A model for novel implant materials

Nacre is a composite material found in the inner layer of sea shells. It consists of soft organic and hard inorganic components arranged in a complex hierarchical structure. Due to this arrangement, nacre exhibits outstanding mechanical properties (elastic modulus: 64.70 ± 3.50 GPa, hardness: 4.41 ± 0.45 GPa, density: 2.6 g/cm 3). Therefore, nacreous implant materials have a high potential in many fields. In medical science, these materials might be used for bone replacement. This article provides an insight into the material removal mechanisms occurring in the scratching of natural nacre. Scratch tests are a simplification of the grinding process and are used to investigate the influence of single input parameters on the material removal. Different scratch tool geometries and varying processing parameters are applied, so that the material removal efficiency can be evaluated by analyzing the process forces. Additionally, the scratch geometry is examined by using a scanning electron microscope (SEM) and optical profilometer images as well as photomicrographs. The results of these examinations provide knowledge on the machinability of nacre and also on the machinability of new nacreous materials.

Femtosecond laser induced fixation of calcium alkali phosphate ceramics on titanium alloy bone implant material

Femtosecond lasers provide a novel method of attaching bioceramic material to a titanium alloy, thereby improving the quality of bone implants. The ultrashort 30 fs laser pulses (790 nm wavelength) penetrate a thin dip-coated layer of fine ceramic powder, while simultaneously melting a surface layer of the underlying metal. The specific adjustment of the laser parameters (pulse energy and number of pulses per spot) avoids unnecessary melting of the bioactive calcium phosphate, and permits a defined thin surface melting of the metal, which in turn is not heated throughout, and therefore maintains its mechanical stability. It is essential to choose laser energy densities that correspond to the interval between the ablation fluences of both materials involved: about 0.1-0.4 Jcm(-2). In this work, we present the first results of this unusual technique, including laser ablation studies, scanning electron microscopy and optical microscope images, combined with EDX data.

Imaging electron-optics and spatial-temporal aberrations for a bi-electrode spherical concentric system with electrostatic focusing

In the present paper, based on the practical electron ray equation and the electron motion equation,for a bi-electrode concentric spherical system with electrostatic focusing, the spatial-temporal trajectories of moving electrons emitted from the photocathode are obtained, the exact and the approximate formulae for image position and flight time of electrons are deduced. Starting from the solutions of spatial-temporal trajectories, the electron optical spatial-temporal properties of this system are then discussed. A unified definition of spatial-temporal aberrations is given, in which the lateral aberration can be regarded as a combination of paraxial lateral aberration and geometrical lateral aberration; and the temporal aberration can be regarded as a comibination of paraxial temporal aberration and geometrical temporal aberration. All expressions of these corresponding aberrations are deduced.