Scanning Electron Microscopy Backscatter Research Articles

Phase evolution and microstructure of new Sr0.5Zr2(PO4)3-NdPO4 composite ceramics prepared by one-step microwave sintering

Sodium Zirconium Phosphate (NaZr2(PO4)3, hereinafter NZP) and monazite are both potential materials for immobilization of nuclear waste. In this work, novel (1-x)Sr0.5Zr2(PO4)3-xNdPO4 composite ceramics (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) for simultaneously immobilizing the simulated fission product (FP) Sr and trivalent minor actinide (MA) Nd were prepared by one-step microwave sintering technique, in which Sr and Nd were immobilized into NZP and monazite type structures, respectively. The phase evolution and microstructure of the samples were investigated by X-ray diffraction (XRD), Raman, and backscattering scanning electron microscopy (BSE). The results showed that the expected composite ceramics were successfully obtained by one-step microwave sintering at 1050 °C for 2 h. The as-prepared samples consisted of Sr0.5Zr2(PO4)3 and NdPO4 phases, and the content of the two phases varied regularly as x changed, generally conforming to the designed nominal chemical composition. Importantly, the composite ceramics presented the homogenous and dense microstructure. The relative density of the composite ceramics was more than 95%, meanwhile, the Vickers-hardness of the samples was higher than 600 MPa. It was indicated that NZP-monazite type composite ceramics could be a potential matrix for the simultaneous immobilization of actinide and fission product.

A coupled thermomechanical crystal plasticity model applied to Quenched and Partitioned steel

Quenched and Partitioned (QP) steel is a class of Advanced High Strength Steel (AHSS) that exhibits high strength and good ductility. These desirable properties are a consequence of the Transformation Induced Plasticity (TRIP) effect where retained austenite transforms into martensite under applied stress and strain. Accurate microstructural modeling of these advanced deformation mechanisms is critical for automakers to exploit QP steels for automotive weight reduction applications. In this work, the stress and martensitic transformation response of a QP1180 steel alloy are characterized using in-situ High Energy X-Ray Diffraction (HEXRD) uniaxial tension experiments. The initial microstructure is characterized using Electron Backscatter Diffraction (EBSD) and Scanning Electron Microscope (SEM) data. A novel thermodynamically consistent rate-dependent crystal plasticity formulation is used to simulate the large deformation behavior of QP steels that exhibit the TRIP effect. The TRIP effect is captured through a martensite variant selection and evolution scheme, which is governed by a driving force that accounts for various effects (i.e., temperature, orientation, hydrostatic pressure, and martensite surface energy). The constitutive model is implemented into a thermo-mechanical Crystal Plasticity (CP) Finite Element Method (FEM) formulation to study the effect of texture, phase morphology and temperature on the bulk material properties of QP1180 steel. A new method for incorporating thermal boundary conditions in CPFEM models is proposed. The constitutive model is calibrated using experimental stress-strain and martensite evolution measurements. Significant variance in transformation rate was observed, consistent with preferential transformation in the ⟨100⟩ crystal direction. Numerical experiments are conducted to study the effect of thermal and mechanical boundary conditions. Significant differences are observed between the simulations of interrupted and non-interrupted uniaxial tension as a result of the differences in the evolution of temperature. Additional numerical experiments were conducted that demonstrate the fidelity of the constitutive model for elevated temperatures and strain-rates, for several thermal boundary conditions. These simulations showed that the predicted RA and temperature evolution behaviors under quasi-static deformation were not accurately captured, either with adiabatic or isothermal boundary conditions. Finally, simulations showed that the RA and temperature evolution behavior under moderate strain-rates are accurately captured by adiabatic boundary conditions.

Direct Integration of Cold Sintered, Temperature-Stable Bi2Mo2O9-K2MoO4 Ceramics on Printed Circuit Boards for Satellite Navigation Antennas

Bi2Mo2O9-K2MoO4 (BMO-KMO) composite ceramics with >95% theoretical density were densified by cold sintering at 150 °C. XRD, Raman, back-scattered SEM and EDX spectroscopy indicated that the BMO and KMO phases coexisted in all composites without inter-diffusion and secondary phases. Temperature coefficient of resonant frequency with near-zero value ∼ -1 ppm/°C was acheived for BMO-10%KMO with pemittivity ∼ 31 and quality factor ∼ 3,000 GHz. Cold-sintered composite ceramics were directly pressed/integrated onto a printed circuit board (PCB) using the Cu metallisation as a ground plane for the design and fabrication of a circularly polarized microstrip patch antenna suitable for satellite navigation systems which achieved efficiencies 87% at 1561 MHz (BeiDou) and 88% at 1575 MHz (GPS/Galileo). The low cost, low energy integration of temperature stable, cold sintered ceramics directly onto a PCB represents a step change in substrate fabrication technology for RF devices.

Large Field/High Resolution Backscatter Scanning Electron Microscopy of the Paraventricular Nucleus of the Hypothalamus

The paraventricular nucleus of the hypothalamus (PVN) is critical in autonomic and endocrine control. A significant body of work has indicated that dysregulation in the PVN is associated with a variety of cardiovascular, metabolic, and reproductive diseases. Changes in the anatomical structure of brain networks leads to functional alterations. In this context, electron microscopy (EM) can provide nanometer resolution of normal/abnormal brain structures and individual organelles. However, an inherent limitation of traditional EM is the random sampling of an object within a large region of interest (i.e. PVN). This limited field of view approach is like a fishing expedition in that it does not allow for localization of subcellular changes in relation to the overall organization of the nucleus. To overcome this, here we propose an approach that utilizes large‐field of view high‐resolution scanning electron microscopy (SEM) of the PVN. This technique includes the development of zoomable, Google map‐like image sets to integrate cellular/organelle location within the overall PVN with ultrastructural detail. Perfused and post‐fixed brains from 16‐week‐old male C57Bl/6J mice were coronally sectioned into six 300μm slices containing the rostral to caudal extent of the PVN. The sections were fixed in osmium tetroxide (1%) and potassium ferrocyanide (1%), infiltrated with uranyl acetate (1%), dehydrated, and flat embedded in resin. Ultrathin sections (70 nm) containing the PVN were obtained and trimmed to 2×2mm. Sections were then placed on silicon wafers for imaging in a FEI Helios NanoLab™ 660 focused ion beam‐SEM equipped with a retractable concentric backscattering detector. As a first step (Figure 1A), the entire section was scanned and stitched at a low magnification (1000x). The low‐resolution data was used to precisely navigate to the area of the PVN. Subsequently, a higher resolution image of the PVN with an 82.88μm horizontal field width was acquired (10000x, 3072×2048pixels, 26.97 nm pixel size) for cellular identification and some ultrastructural detail (Figure B). Final high magnification images (80000x) with a horizontal field width of 5.18μm were taken within the PVN for imaging of single cells (Figure C). Using this approach, high‐magnification images were obtained with the same intensity and quality as images achieved with traditional transmission EM. All neuronal structures and subsynaptic features were readily identifiable, and could be placed within the overall anatomical construct of the PVN (Figure ). Collectively, this methodological advancement has the potential to facilitate robust neuroscience discovery into the PVN by relating high‐resolution data (neurons, glia, synapses, organelles etc) to a very precise and specific functional domain and context.Support or Funding Information1R01HL141393A) Representative unilateral PVN and surrounding regions imaged at a relatively low magnification (1000x) with large field of view SEM. B) A higher resolution (10000x) image of a portion of the PVN (red outline) was then obtained by using the image in A to navigate. The blue outline in A indicates the location of this image. C) High‐resolution (80000x) image of a single neuron within the PVN. The pink box in B indicates the anatomical location of this neuron in the context of the overall PVN.Figure 1

Porous Coatings in Retrieved Acetabular Components

BackgroundWe evaluated bone volume fraction in retrieved acetabular shells with 2 types of porous coatings: (1) titanium fiber mesh (HG) components and (2) tantalum metal coating (TM) components. MethodsEight HG shells were matched to 8 TM shells for patient age, body mass index, and gender. The mean age at index surgery was 69 (51-82) years, mean body mass index was 28 (21-40), and patients were evenly divided between male and female (4:4). The length of implantation was 40 (16-96) months for the TM group and 156 (108-216) months for the HG group. Shells were embedded and two 5-mm thick cross-sections were cut through the apex of each component for backscatter scanning electron microscopy assessment. Backscatter scanning electron microscopy images were segmented to threshold for metal, bone, and available space for ingrowth. Slices were assessed regionally for ingrowth at the rim, equator, and pole of the acetabular shell. Differences were assessed using general estimating equations, and P values were adjusted for multiple comparisons using the Holm-Bonferroni step-down procedure. ResultsThe mean bone volume fraction was 21 ± 17% for the HG shell and 7 ± 4% for the TM shell (P < .0001). The rim and pole regions both had less bone ingrowth than the equator. No association was found between bone ingrowth and length of implantation for either design. ConclusionAdequate bone ingrowth is a requirement for successful biological fixation, but the amount of ingrowth may not be a driving factor. Both implants studied had successful outcomes and long-term fixation despite the observation of low amounts of ingrowth.

Surface modification of flax nonwovens for the development of sustainable, high performance, and durable calcium aluminate cement composites

The aim of this paper is to evaluate the influence of sustainable surface treatments —performed on flax nonwoven fabrics as textile reinforcement— on the durability of calcium aluminate cement (CAC) based composites. Two treatments are considered: an alkaline treatment (for increased stability and adhesion), and a treatment with soybean oil (to reduce fiber degradation). The cement hydration was studied by analysis of back-scattered scanning electron microscopy images, which revealed variations nearby the fibers owing their capacity for water absorption and presence of oil on the surface. A retarding effect on cement hydration was observed on the composites prepared with the oil-treated fabrics. The composites containing the alkali treated fabrics had better mechanical properties and also the highest durability. For these composites it was found an optimized fiber-matrix adhesion and penetrability of the cement to the fabric.

The promising room-temperature magnetic refrigeration materials — Misch-metal (MM)2Fe17-xSix (x=0–1.5) compounds

The phase structure, magnetic properties, magnetocaloric effect (MCE) and relative cooling power (RCP) of MM2Fe17-xSix (x = 0–1.5) compounds were studied. The phase transition temperature was increased from 238 K to 366 K with the increase of Si content. The X-ray diffraction (XRD) patterns indicate that the MM2Fe17-xSix (x = 0–1.5) compounds crystallize primarily in a rhombohedral phase with Th2Zn17 type crystal structure coexisting with a small amount of the precipitation α-Fe phase. These results are reinforced by backscattered scanning electron microscope (SEM) images and electron energy dispersive X-ray spectroscopy (EDX) analysis. The maximum values of magnetic entropy change (ΔSM) for MM2Fe17-xSix (x = 0, 0.3, 0.6, 1.0) compounds are −2.1 J kg−1K−1, −1.3 J kg−1K−1, −1.5 J kg−1K−1, −1.8 J kg−1K−1 for field change of 0–2 T and −4.0 J kg−1K−1, −2.7 J kg−1K−1, −3.1 J kg−1K−1, −3.5 J kg−1K−1 for field change of 0–5 T. The estimated RCP values are larger than 100 J kg-1 and 350 J kg-1 for the field change of 0–2 T and 0–5 T, respectively. The working temperature range δTFWHM is larger than 50 K and 100 K with the field changes of 0–2 T and 0–5 T, respectively. The temperature range and RCP values are comparable to the second-order phase transition (SOPT) materials R2Fe17 (R = Pr, Nd) and Gd, but the cost of MM2Fe17-xSix is only about 25% and 10% compared with R2Fe17 (R = Pr, Nd) and Gd, respectively.

Investigation of ultrasonic deformation characteristics of ultrathin miniaturized TA1 foil

Ultrasonic vibrations (UV) are widely employed in various precision manufacturing processes to obtain high product quality and processing efficiency. However, the plastic deformation behavior of high-strength, low formability and ultrathin (<100 μm) materials during UV-assisted forming is not unveiled yet. Herein, the influence of UV on micro-deformation of ultrathin TA1 foil (20 μm) is investigated through UV-assisted uniaxial tensile tests at room temperature. The macro-mechanical behavior is demonstrated by the stress-strain curve and a numerical model is established by using a fifth-order polynomial to assess stress reduction. Moreover, electron backscatter diffraction (EBSD) analysis and scanning electron microscopy (SEM) are utilized to reveal the UV softening mechanism at the microstructural level. The results demonstrate that the microstructure has been significantly altered during the UV-assisted uniaxial tensile process. The systematic investigation of macro- and micro-mechanical behavior provides an enhanced understanding of the UV-assisted micro forming process.

Investigating the structural changes induced by SHI on W–SiC samples

The structural modification of tungsten-SiC samples irradiated with Xe26+ swift heavy ions (SHIs) was investigated. Tungsten (W) thin films were deposited on 6H–SiC using e-beam. After deposition, the W–SiC samples were irradiated by 167 MeV Xe26+ ions to fluences of 1012 cm−2, 1013 cm−2 and 1014 cm−2 at room temperature. The sample composition, phase identification, residual stress component and surface morphology were investigated with Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated that the as-deposited samples were composed of W and SiC, with no reaction between them. The samples irradiated to a fluence of 1012 cm−2 showed that a reaction between W and SiC took place resulting in the formation of WSi2 and WC phases. The samples irradiated to fluences of 1013 and 1014 cm−2 showed further reactions between W and SiC with WSi2 and WC being the only phases formed. The SiC substrate had bi-axial compressive stress which did not excess 700 MPa after irradiating to the highest fluence. The W layer deposited on SiC was flat and homogeneous after deposition. A textured surface with identifiable grains was observed after the SHI irradiations.

Examining the multi-scale complexity and the crystallographic hierarchy of isothermally treated bainitic and martensitic structures

In this work, differences and similarities between bainitic and martensitic structures obtained by isothermal heat treatments such as austempering, quench and partitioning (Q&P) and quench and tempering (Q&T), are investigated by multiple techniques including X-ray diffraction, electron backscatter diffraction, scanning and transmission electron microscopy and atom probe tomography. Results reveal that analogous lath-like ferritic structures with similar austenite content can be achieved by adjusting the isothermal holding temperature. However, certain variability in hardness is recorded, which is consistent with differences on the precipitation state revealed by the nano-scale examination of the structure, and with dissimilar crystallographic size distribution of ferritic grains.

Experimental study of the superplastic and hot deformation mechanisms of a Ti-6Al-2Sn-4Zr-2Mo Titanium Alloy

To clarify the hot deformation characteristics of Ti alloys, flow behaviour, micro structural evolution and deformation mechanisms were investigated in a Ti-6Al-2Sn-4Zr-2Mo alloy with two initial micro structure: an ultra-fine grained (UFG) and a fine-grained (FG) microstructure (dα=0,8 µm and dα=3 µm respectively) by isothermal interrupted tensile tests, SEM observations and through electron back scatter diffraction experiments. Depending on the test conditions and on the initial α grain size, the flow behaviour can exhibit steady state flow and/or hardening and/or softening. The microstructure and texture evolutions have been studied mainly by using electron backscatter diffraction (EBSD) technique and SEM observations. They evidenced in particular the occurrence of α grains growth as well as dynamic recrystallization (DRX). The different flow behaviour associated to the microstructure evolution is shown and discussed to clarify the main deformation mode that could be assume to occur depending on the microstructure, the temperature and the strain rate.

Cold sintered CaTiO3-K2MoO4 microwave dielectric ceramics for integrated microstrip patch antennas

CaTiO3-K2MoO4 (CTO-KMO) dielectric composites were successfully cold-sintered at 150 °C for 30 min with a uniaxial pressure of 200 MPa. X-ray diffraction, Raman spectroscopy, back-scattered SEM and energy dispersive x-ray mapping confirmed the coexistence of CTO and KMO with no evidence of interdiffusion and parasitic phases either between the two ceramic end-members or with Ag internal electrodes. As KMO concentration increased, the temperature coefficient of resonant frequency (TCF) and relative pemittivity (εr) decreased but the microwave quality factor (Q × f) increased. A near-zero TCF composition was obtained for CTO-0.92KMO composites which exhibited εr ∼ 8.5 and Q × f ∼ 11,000 GHz. A microstrip patch antenna was designed and fabricated using cold sintered CTO-0.92KMO as a substrate (40×40×1.4 mm), which gave a s11 of −14.2 dB and a radiation efficiency of 62.0 % at 2.51 GHz.

Biofunctionalization with a TGFβ-1 Inhibitor Peptide in the Osseointegration of Synthetic Bone Grafts: An In Vivo Study in Beagle Dogs.

Objectives: The aim of this research was to determine the osseointegration of two presentations of biphasic calcium phosphate (BCP) biomaterial—one untreated and another submitted to biofunctionalization with a TGF-β1 inhibitor peptide, P144, on dental alveolus. Materials and Methods: A synthetic bone graft was used, namely, (i) Maxresorb® (Botiss Klockner) (n = 12), and (ii) Maxresorb® (Botiss Klockner) biofunctionalized with P144 peptide (n = 12). Both bone grafts were implanted in the two hemimandibles of six beagle dogs in the same surgical time, immediately after tooth extraction. Two dogs were sacrificed 2, 4, and 8 weeks post implant insertion, respectively. The samples were submitted to histomorphometrical and histological analyses. For each sample, we quantified the new bone growth and the new bone formed around the biomaterial’s granules. After optical microscopic histological evaluation, selected samples were studied using backscattered scanning electron microscopy (BS-SEM). Results: The biofunctionalization of the biomaterial’s granules maintains a stable membranous bone formation throughout the experiment timeline, benefitting from the constant presence of vascular structures in the alveolar space, in a more active manner that in the control samples. Better results in the experimental groups were proven both by quantitative and qualitative analysis. Conclusions: Synthetic bone graft biofunctionalization results in slightly better quantitative parameters of the implant’s osseointegration. The qualitative histological and ultramicroscopic analysis shows that biofunctionalization may shorten the healing period of dental biomaterials.

Distribution of ASR gel in conventional wet-mix glass mortars and mechanically produced dry-mix glass blocks

The alkali-silica reaction (ASR) of recycled glass mortars prepared by the traditional wet-mix and the mechanically compacted dry-mix methods using a same aggregate-to-cement (A/C) ratio was examined based on the ASTM C1260 accelerated mortar bar test method. The test results showed the expansion values of the dry-mix glass blocks were within the threshold of ASTM C1260 while the wet-mix glass mortars were above the threshold. The mercury intrusion porosimetry (MIP) results of the dry-mix blocks showed a new peak in the larger pore size range between 10 µm and 100 µm in the differential curves, and the porosity in this ranges decreased after the ASR test. As revealed by scanning electron microscopy-backscattered electron (SEM-BSE) image analysis, the mitigation of ASR expansion and the decrease of porosity were mainly due to the distinctive different distribution of ASR gel in the dry-mix blocks. Compared to the ASR gel formed within the glass aggregate in the wet-mix mortars, the ASR gel in the dry-mix blocks was mainly observed on the surface of glass aggregates in the larger pores (between 10 and 100 µm). No ASR gel was observed in the interface between the glass aggregates and the cement paste of both the wet-mix mortars and the dry-mix blocks. The release of the swelling pressure of the ASR gel by the large pore in the dry-mix blocks suppressed the further development of cracks caused by ASR expansion.

Pulse Electrodeposited Copper from Lean Electrolytes Containing Additives

Introduction The standard method to manipulate and control deposit properties during electroplating is through the use of chemical additives. Many of these additives are coming under increased scrutiny due to their impact on the environment. For example, the Printed Circuit Board (PCB) Industry typically requires plated copper to have low electrical resistance coupled with good mechanical properties. Such specific properties are imparted by using bespoke electrodeposition processes where acid concentration and metal ions are prescribed through experience, typically 2.0 M H2SO4, and 0.6 M CuSO4. In addition, small amounts of additives are used to tailor deposit properties. However, new government regulations and green chemistry principles requires the minimisation of both metal ions as well as additives. Some recent work has shown that that micro-scale copper features, such as those required in PCBs, can also be deposited using an acid-free electrolytes containing low concentrations of copper. In such a case, the additive content also needs changing so the deposit produced has the similar properties as that obtained in the standard process. In general, therefore, an examination of the effect of pulse deposition in electrolytes containing low concentration of metal ions and supporting electrolyte; i.e. lean electrolytes, is needed. Although there has been some research of the synergy between pulse deposition and additive action [1-2], few have interrogated if pulse currents or additive actions dominate the microstructural evolution of a plated material. Indeed, these two aspects will become more important for lean electrolytes, where fewer anions from the supporting electrolyte (SO4 2- for the case of copper deposition) adsorb on the electrode surface. From a practical point of view, the amount of additive needed in lean electrolytes needs to be ascertained, and its use needs to be justified as a method of optimization of the plated material. Indeed, pulsing current could play a major role in deposit modification when additive levels are low. Scope of the Presentation This work examines the effect of lowering additives, metal ions and supporting electrolyte on deposited copper. The electrolyte used contained only 0.1 M CuSO4 and varying amounts of additives provided by a standard supplier for PCB manufacturing. Films have been deposited from electrolytes containing different concentrations of additives ranging from 17% to 200% of the levels recommended by the supplier using pulse and direct currents. Copper films of 25 mm thickness have been plated on stainless steel substrates following the recommendations provided by IPC-TM-650 (IPC-TM stands for The Institute for Interconnecting and Packaging Electronic Circuits Testing Methods) standard [3]. Both direct and pulse currents have been used for deposition. Direct currents were fixed at 40% of the maximum plating rate (or limiting current) and pulse current parameters used a pulse on time of 100 ms and a duty cycle of 25%. The grain size and deposit microstructure were examined using electron backscatter diffraction (EBSD) and scanning electron microscopy (SEM), respectively. These parameters were chosen because defect free foils could be produced reproducibly using these conditions. Our results showed that current pulsing produced finer grains in the absence of additives; and as additive levels were increased the effect of current pulsing on deposit properties was less pronounced. The results indicate that foils produced by pulsing currents produced deposits with fewer inclusions or defects at grain boundaries. This could be due to the desorption of additives during the off-time. These results show that current pulsing may become more important when leaner electrolytes are used. References N Imaz, E Garcia-Lecina, C Suarez, JA Diez, J Rodriguez, J Molina, V Garcia-Navas. IMF. (2009) 87(2), 64.A Ibanez, E Fatas: Surf. Coat. Technol. (2005) 191, 7.ASTM E-345 Standard Test Methods of Tension Testing of Metallic Foil.

Segregation in Aluminum-Zirconium Alloys, Electrodeposited from Ionic Liquids, and Its Modification By Pulse Plating

It is quite typical for aluminum-zirconium alloys, obtained by electrodeposition in chloroaluminate ionic liquids, to have two or more distinct phases with different Zr concentrations. The Zr content in one phase can be several times higher than in the other. In the present work we have studied this segregation in [EMIM]Cl*AlCl3 ionic liquid. Factors like temperature, current density, agitation, and concentrations of both zirconium and aluminum in the electrolyte were investigated. A proposed mechanism for this phenomenon is based on a possibility of two different pathways of zirconium reduction. One pathway is a 4-electron process, taking Zr4+ directly to metal. Another way is a 2-electron reaction via intermediate Zr2+ ions formed in the solution. The difference between these pathways includes variations in chloride ions concentration in the vicinity of the electrode surface, as well as variations in charge and structure of the double layer. The above variations exist only near the cathode surface, and have a limited life time. One approach to eliminating the segregation in the alloy is to utilize pulsed electrodeposition methods, allowing re-mixing and equilibration of the electrolyte during the off periods. As expected, shorter pulses and longer off times lead to more compositionally uniform deposits. Figure 1. Backscatter SEM image of a cross section of Al-Zr deposit. Light areas are zirconium-rich. Figure 1

Development of novel Moving Wave Front image processing algorithm and microstructural quantification of Tungsten Heavy Alloy

Tungsten Heavy Alloy (WHA) is used in various aerospace applications. This alloy has a two-phase microstructure with a contiguous matrix dispersed with nearly spherical tungsten particles. The properties of this alloy depend on microstructural parameters such as tungsten particle size, tungsten-matrix and tungsten-tungsten interface. In this work, a novel Moving Wave Front (MWF) image processing algorithm was proposed for automatic detection of the interface boundary between coalesced tungsten particles. MWF algorithm was used to measure the size and orientation of the tungsten-tungsten interface from a two-dimensional montage of backscattered Scanning Electron Microscope images. The bivariate size-orientation distribution was measured for undeformed and deformed samples. The obtained distribution in 2D was used to estimate three dimensional size-orientation distribution. The evolution of the tungsten-tungsten interface in 3D was studied as a function of thermo-mechanical deformation. A characteristic evolution of the 3D size and orientation of the tungsten-tungsten interface with deformation was observed.

Unobstructed Multiscale Imaging of Tissue Sections for Ultrastructural Pathology Analysis by Backscattered Electron Scanning Microscopy.

Ultrastructural analysis of healthy, diseased, or experimental tissues is essential in diagnostic and investigative pathology. Evaluation of large tissue areas with suborganelle resolution is challenging because biological structures ranging from several millimeters to nanometers in size need to be identified and imaged while maintaining context over multiple scales. Imaging with field emission scanning electron microscopes (FE-SEMs) is uniquely suited for this task. We describe an efficient workflow for the preparation and unobstructed multiscale imaging of tissue sections with backscattered electron scanning electron microscopy (BSE-SEM) for applications in ultrastructural pathology. We demonstrate that a diverse range of tissues, processed by conventional electron microscopy protocols and avoiding the use of mordanting agents, can be imaged on standard glass slides over multiple scales, from the histological to the ultrastructural level, without any visual obstructions. Our workflow takes advantage of the very large scan fields possible with modern FE-SEMs that allow for the acquisition of wide-field overview images which can be explored at the ultrastructural level by digitally zooming into the images. Examples from applications in pulmonary research and neuropathology demonstrate the versatility and efficiency of this method. This BSE-SEM-based multiscale imaging procedure promises to substantially simplify and accelerate ultrastructural tissue analysis in pathology.

Tribological performance of Yttrium (III) and Zirconium (IV) ceramics reinforced WC–10Co4Cr cermet powder HVOF thermally sprayed on X2CrNiMo-17-12-2 steel

In this paper, an experimental study has been performed on failure analysis of cermet coatings thermally sprayed on X2CrNiMo-17-12-2 stainless steel using a high-velocity oxy-fuel (HVOF) technique. A comparative study was carried out to investigate the microstructural, mechanical and tribological properties of pure and ceramic-reinforced WC–10Co4Cr cermet coatings. Two different feedstocks i.e. Yttrium-III (Yttria) and Zirconium-IV (Zirconia) were used to develop two different ceramic-reinforced WC–10Co4Cr powders. Tribological properties were tested with the help of laboratory scale pot tester. Coal ashes (i.e., fly ash and bottom ash) were used as the erodents. Different parameters like velocity, time, concentration of particles, and impact angle were varied during the tribological experiments. The microstructural analysis reveals the interlocked lamellae splats, pores and unmelted particles on the as-sprayed surfaces. Yttria reinforced WC–10Co4Cr coating exhibit superior tribo-resistance and mechanical properties. The zirconia reinforced WC–10Co4Cr coating has shown good wear resistance in fly ash slurry which possesses a weak acidic nature (pH = 6.32–6.09 for concentration range of 30–60 wt%). Microhardness of WC–10Co4Cr cermet was also improved with the addition of Yttria. The erosion mechanisms were analyzed by using backscattered X-ray scanning electron microscope (SEM), interactive 3D surface plots, and 2D pseudo-images.

Large Area SEM Backscatter Imaging of GABA Post-Embedding Immunogold, Web-Based Crowdsourcing Segmentation and Local Image Processing for Rigorous Quantification

Large Area SEM Backscatter Imaging of GABA Post-Embedding Immunogold, Web-Based Crowdsourcing Segmentation and Local Image Processing for Rigorous Quantification