Optical Ceramics Based on Yttrium Oxide Doped with Tetravalent Ions

Introduction to strain characterization methods in Transmission Electron Microscopy

Au speciation in sulfides (including “invisible” Au), which mostly controls the loss of Au during ore dressing, is discussed. Modern methods of analysis of Au speciation, with discussion of limitations by locality and sensitivity, are reviewed. The results of sulfide investigation by the methods of scanning and transmission electron microscopy, mass spectrometric analysis with laser ablation (LA–ICP–MS), the thermochemical method (study of ionic Au speciation), and automated “quantitative mineralogy,” are demonstrated for weakly metamorphosed VHMS deposits of the Urals (Galkinsk and Uchaly). Significant content of Au is scattered in sulfides, such as pyrite, chalcopyrite, and sphalerite, with quantitative predomination of pyrite. The portion of such “invisible” gold ranges from <10% (Galkinsk deposit) to 85% (Uchaly deposit). Major part of “invisible” gold occurs as micron- to nanoscale particles of Au minerals. The portion of gold structurally bound in pyrite lattice (from the bulk concentration of Au in pyrite) is estimated to be from few % (the Galkinsk deposit) to 20–25% (the Uchaly deposit). The presence of As and Sb in pyrite and sphalerite, as well as other trace elements (Te, Co, Mn, Cu, Hg, and Ag in both as well as Fe in sphalerite) stimulates the incorporation of Au in sulfide, but mostly in defect-associated, not isomorphic form. Micron particles of Ag sulfosalts (pyrargyrite, freibergite, stephanite, polybasite, pyrostilpnite, argentotetrahedrite, pearceite, proustite), Au–Ag alloys (from gold of high fineness to kustelite), Ag and Au–Ag tellurides (hessite, empressite, calaverite), and occasional Au–Ag sulfides (petrovskaite, uytenbogaardtite) were registered in the areas of Au enrichment of both deposits; selenotelluride (kurilite) particles were found on the Galkinsk deposit. Nanoscale (1–50 nm) native gold (spherical and disk-shaped particles, flakes) with a monocrystal diffraction pattern of some particles and a ring diffraction pattern of other particles was registered in the ores of these deposits by the methods of transmission electron microscopy. The low degree (or absence) of metamorphic recrystallization results in (1) predomination of thin intergrowths of sulfides, which is the main reason for the bad concentration of ores (especially for the Galkinsk deposit) and (2) the high portion of “invisible” gold in the massive sulfide ores, which explains the low yield of Au in copper and zinc concentrates, since it is lost in tailings with predominating pyrite.

Stacking faults in an Fe-35 mol%Al alloy with the B2 ordered superlattice structure have been investigated by a diffraction contrast method of transmission electron microscopy (TEM). The detailed observation by a phase contrast method of high-resolution transmission electron microscopy (HRTEM) has also been performed on the alloy. Two types of stacking faults were observed by HRTEM. In order to interpret the experimental images, computer simulations of HRTEM images based on different fault models have been carried out. The image simulations reveal that the model of the stacking faults deduced from the diffraction contrast method of TEM (i.e. the displacement vector R=a /2) cannot fit one type of the HRTEM images. In the present study, a possible model of the faults (R=(1 - √3)a /2) and a mechanism for their production are proposed.

The results of complex analysis of the parameters of the GaAs/AlGaAs semiconductor superlattice with a complex unit cell using mathematical modeling and experimental methods of transmission electron microscopy, energy-dispersive analysis, and spectroscopy of photoluminescence and photocurrent are presented. Suppression of the intraband static negative differential conductivity under strong interaction conditions between minibands and the inharmonic electron-dispersion law is shown.

It is well known that sinusoidal endothelial cell (SEC) damage during cold preservation of liver tissue is closely involved in early graft failure. The objective of this study was to investigate the involvement of apoptosis in the SEC damage induced by cold preservation and to demonstrate the protective effect of vascular endothelial growth factor (VEGF) on SEC injury, including apoptotic changes. Isolated SECs and liver tissue of Wistar rats were cold-preserved in University of Wisconsin (UW) solution, and the protective effect of VEGF was then investigated. Isolated SECs were cultured for 24 hr, and divided into the following 3 groups: Group A, in which the cells were cultured for an additional 27 hr, Group B, in which the cells were cold-preserved in UW solution for 3 hr, and then recultured for 24 hr, and Group C, in which 20 ng/ml of VEGF was added to both the culture medium and the UW solution of cells cultured according to the Group B protocol. Each group of SECs was morphologically examined using the phase contrast microscopic method and the transmission electron microscopic method (TEM), and quantitatively analyzed using the WST-1 assay. Rat livers were cold-preserved in UW solution and divided into the VEGF(+) group and the VEGF(-) group, depending on whether VEGF was added or not. Each group of livers were analyzed by scanning electron microscopic method (SEM) after 24 hr of preservation. The hyaluronic acid uptake rate (HUR) was also determined after 6 hr of preservation. After 24 hr of preservation and 6 hr of reperfusion, tissues were examined by TEM and by the terminal deoxynucleotidyl transferase d-uridine triphosphate nick end labeling (TUNEL) assay. The phase contrast microscopic method and the WST-1 assay showed a protective effect of VEGF against the injury to isolated SECs during cold preservation and subsequent reculturing. Apoptosis was detected immediately by TEM after isolation of SECs, and the number of apoptotic cells increased with the incubation time. This increase was accelerated after cold preservation. The scanning electron microscopic method and the hyaluronic acid uptake rate showed a protective effect of VEGF against SEC damage in the cold-preserved livers. In the liver tissue, the TEM and the TUNEL assay detected apoptosis of SECs only after cold preservation and subsequent reperfusion. VEGF suppressed the apoptosis of SECs induced by cold preservation in both isolated cells and liver tissue. We demonstrated that SEC damage in the cold preservation of liver tissue was caused mainly by apoptosis, which required subsequent reperfusion. Moreover, isolated SECs showed spontaneous occurrence of apoptotic changes during culture, and these changes were accelerated by the preceding cold preservation. This is the first report to demonstrate the apoptotic changes of SECs seen here were inhibited by VEGF.

Determination of asbestos fibres in air transmission electron microscopy as a reference method

A new transmission electron microscopic (TEM) method to determine differences between cationic polymers in solution

High power vertical cavity surface emitting laser (VCSEL) arrays with multiple emitters have been receiving remarkable attention currently due to their emerging applications in consumer market such as 3D sensing illumination laser source in mobile devices as well as in automotive LIDAR applications. Failure mode analysis will help provide useful information for VCSEL array design and process improvement. However, using solely general physical failure analysis techniques is insufficient. The challenge of failure mechanism study is how to locate and capture the small physical defects in the early stage since it may randomly occur in the entire active region of the emitter This work developed 3D transmission electron microscopy (TEM) method, that is, planar-view TEM together cross-section TEM, to investigate failure mode phenomenon in this kind of high power VCSEL arrays. Overstressed reliability testing intentionally create failure in VCSEL arrays where dim emitters are found. Optical microscope images can’t see any abnormality while infrared microscope can catch small ‘mouse-bite’ abnormality at oxide aperture. Planar-view TEM method is developed to isolate the target dim emitter and trim away most of the top and bottom DBR layers to keep the oxide layer and active region to thin enough where 200KV electron beam can penetrate planar-view lamella. The whole oxide aperture is achieved and scanning TEM images clearly show the ‘flower-like’ oxide blasters at oxide aperture periphery. It is from further oxidation of the oxide tip. Cross-section TEM reveal the oxide layer morphology where the further oxidation layer from oxide tip is thinner than the original oxide layer. The oxide tip further oxidation is possibly due to non-reaction steam in existence in the oxide causing the second oxidation of oxide layer during overstress test. This work demonstrate that 3D TEM method is good technique to catch small physical failure features in VCSEL arrays, which will help to analyze failure mode in high power VCSEL arrays for 3D sensing application.

Measurement of size and number concentration of polystyrene particles

Data on the distribution of iron in nitrogen-containing multiwall carbon nanotubes (N-MWCNTs) and changes in its chemical state and concentration under different parameters of irradiation by a pulsed ion beam are obtained by methods of transmission electron microscopy, X-ray photoelectron spectroscopy, and energy dispersion analysis. It is shown that the irradiation of N-MWCNTs with an energy density of 0.5 J/cm2 lead to the formation, on their lateral surfaces, of structures with a size of 2–10 nm, consisting of metallic iron encapsulated in a carbon shell. An increase in the energy density to 1–1.5 J/cm2 leads to a substantial removal of iron clusters from the tips of carbon nanotubes and a reduction in the amount of iron in the bulk of the N-MWCNT layer.

The paper presents the results of developing the method of obtaining magnetic liposomes (MLP) and magneto-liposomal (MLP) form of aminoalkylamide derivative of chlorine e6: 13(1)-N-(2 aminoethyl)amid-15(2),17(3)-dimethyl ether (I) on the basis of magnetite nanoparticles (MNP). Photosensitizer (PS) of chlorine e6 series (I) was obtained by chemical modification of chlorophyll a, isolated from Spirulina platensis by ethanol extraction. MNP were synthesized by thermal decomposing of iron (III) acetylacetonate in triethylene glycol. The MLP form of PS (I) was obtained by the rehydration method of thin lipid films. Inclusion of PS (I) into MLP was shown to be 50-60 %. The structure and size of the MNP, MLP and MLP form (I) were studied by the methods of transmission electron microscopy (TEM) and dynamic light scattering (DLS). The average sizes of MLP and MLP form (I), according to methods of DLS and TEM, were 173.0±67.4 nm and 204.6±84.5 nm, respectively.

389  Abstract—In present study, X-ray peak profile analysis (XPPA) by modified Williamson-Hall (W-H) models, namely W-H-isotropic strain model (W-H-ISM), W-H-anisotropic strain model (W-H-ASM) and W-H-energy density model (W-H-EDM), was employed to estimate the microstructural parameters such as, crystallite size, lattice strain, lattice deformation stress and deformation energy density from the powder diffraction data obtained for the microwave synthesized hydroxyapatite (HA) and fluorapatite (FA) nanoparticles prepared under identical processing conditions of mixing and aging. The as-prepared powder particles were also characterized by transmission electron microscopy (TEM) method. The average crystallite size values estimated for HA and FA by XPPA were correlated to their respective transmission electron microscopy (TEM) analysis results. In addition, the estimated values of HA and FA were correlated to their in-vitro dissolution characteristics studied by ethylenediamine tetra-acetic acid (EDTA) titrimetric method. It is found that the average crystallite size estimated by W-H models is in good agreement with TEM results. The controlled in-vitro dissolution behavior of FA was found to be resulted out of its higher crystallite size, lower lattice strain and lower dislocation density compared to that of HA.

Specimens of titanium alloy VT8, which is used for the manufacture of gas turbine engine elements, were investigated in the initial state and after fracture toughness testing by methods of transmission electron microscopy and diffraction analysis. The features of the microstructure, structure morphology, the nature of phase distribution and structural components were established. Defects in the crystal structure, the formations of dislocation inhomogeneities and local concentrators of internal stresses were identified using JEM-200CX transmission electron microscope. The scalar dislocation density is determined by the secant method. The study of VT8 titanium alloy samples before and after destruction, which is used for the manufacture of GTE elements, using the methods of transmission electron microscopy and diffraction analysis was made. Microstructural investigations for a detailed analysis of the structure features, morphology and phase formations distribution, as well as their components establishment, the nature of crystal lattice defects, the formation of dislocation inhomogeneities and local concentrators of internal stresses were performed on a JEM-200CX transmission electron microscope. The scalar dislocation density was measured by the secant method. It is shown that the studied samples of VT8 titanium alloy are characterized by a two-phase (α + β) microstructure in the form of large -phase plates, 0.15 ... 0.76 μm in size, interspersed with an insignificant amount of thin-plate β-phase, with a size of 0.04 ... 0.21 μm. Based on scalar dislocation densities, the level of local internal stresses in the places of dislocation accumulations, which are sources of crack formation, was analytically estimated. Dispersed particles of secondary phases characterized by different sizes and different structure morphologies were identified. The calculated dislocation densities and an estimate of the average distance over which they move in the process of deformation are used as the basis for creating a statistical map of localized deformation level indicators in the alloy structural components and on the fracture surface. It is shown that as a result of fracture after testing for low-cycle fatigue, the dislocation density increases, the level of local internal stresses increases, and the formation of a cellular structure in the α- and β-phases and deformation grain-boundary defects occurs. Keywords: VT8 alloy, dislocation structure, microstructure, transmission electron microscopy, local internal stresses.

Journal Article Practical Methods for Transmission Electron Microscopy of Polymers. Get access JSJ Vastenhout JSJ Vastenhout Dow Benelux B.V., Analytical Sciences, MC-SMX Discipline, P.O. Box 48, 4530 AA Terneuzen, The Netherlands Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 8, Issue S02, 1 August 2002, Pages 1238–1239, https://doi.org/10.1017/S143192760210239X Published: 01 August 2002

Effect of preliminary hydrogenation on formation of the ultrafine-grained structure in titanium alloy of Ti-Al- V-Mo system (VT16 grade) under severe plastic deformation was examined by the methods of transmission electron microscopy and X-ray diffraction analysis. Hydrogenation to 0.15 wt. % is found to decrease the value of plastic deformation (by ∼2 times) and treatment temperature (from 1023 to 923 K) during formation of the ultrafine-grained hierarchically organized internal structure in the VT16 alloy. Formation of the hierarchically organized internal structure in the VT16 alloy is shown to lead to an increase in yield strength, ultimate strength, and resistance to hydrogen embrittlement at room temperature as compared to the coarse-grained state.