Electron Backscatter Research Articles

Experimental investigation of suspension-type abrasive water jet machining of nitrile rubber for positive displacement motor applications

The lightweight elastomers (such as nitrile rubber) frequently used in the Positive Displacement Motor (PDM) stator assembly are subjected to harsh environmental conditions. These elastomeric components are manufactured by primary casting/shaping methods, followed by secondary manufacturing/machining processes. The production of intricate shapes/sizes in single or batch-size elastomeric components using primary casting methods requires a customized mould to fulfil the requirement of sudden breakdown conditions, which is uneconomical. It necessitates an alternate production method that can satisfy the need for the elastomeric component at the stage of failure. The current research focuses on the possibility of producing nitrile rubber components using a non-conventional machining method, Suspension-type Abrasive Water Jet Machining (AWJM), suitable for batch production with better dimensional stability and versatility in shape/size. This work presents the experimental investigation of Suspension-type AWJM of nitrile rubber specimens (15 mm thick) using a custom-designed Tungsten Carbide (WC) nozzle under room-temperature condition. The top surface of the machined slot is analyzed to determine the mineral composition and abrasive particle embedding through Energy Dispersive Spectroscopy (EDX) and Backscatter Electron (BSE) detector. The Taguchi Orthogonal Array (OA) is employed to study the effect of the process parameters (Water Jet Pressure (WJP), Traverse rate (Vf), and Stand-Off Distance (SOD)) on the performance parameters (Kerf Taper Ratio (KTR), and Material Removal Rate (MRR)). The Analysis of Variance (ANOVA) is applied to check the statistical significance and percentage contribution of each process parameter on the performance of Suspension-type AWJM. The uniformity in the geometry of the machined slot is analyzed by the waviness patterns observed in the profile images of the cut specimen. The analysis of the EDX results reveals the presence of Manganese (Mn) and an increased percentage of Silicon (Si) particles near the top surface of the machined slot. The SOD influences KTR the most, whereas Vf highly influences MRR. It is observed that the waviness pattern is minimal at high WJP experimental runs. The outcome of this research work provides a quick and economical method of producing the PDM bushings instead of the casting/moulding method.

Enhanced µCT Imaging Protocol to Enable High-Resolution 3D Visualization of Microdamage in Rat Vertebrae

Contrast-enhanced μCT imaging has been used to provide non-destructive 3D images of microdamage, but at a lower quality than found in histology and 2D backscatter electron (BSE) imaging. This study aimed to quantify potential improvements in microdamage characterization by enhancing µCT scanning parameters. Eleven slides from 9 rat vertebrae (healthy = 3, osteolytic metastases = 3, mixed metastases = 3) previously stained for microdamage with BaSO4 and analyzed with BSE imaging (2μm voxel spacing) were used in this study. μCT imaging conducted under varying protocols (x-ray voltage, tube current, frame averaging) demonstrated enhanced scan parameters at 90 kVp, 44 µA, 0.5 mm aluminum filter, 8 times frame averaging, and 4.9 µm voxel spacing. Post-processing with Richardson-Lucy deconvolution further deblurred the μCT images. Labeled microdamage in the baseline, enhanced and deblurred μCT images were segmented and spatially quantified vs. BSE-labeled microdamage using a probability-based correlation metric at six inflation radii. Enhanced μCT scan parameters improved damage visualization and increased spatial correlation probability with BSE images. Deblurring improved the sharpness of stain boundaries but did not significantly improve spatial correlation probabilities in comparison to the enhanced scans. This enhanced μCT protocol facilitates 3D visualization of microdamage, an indicator of bone quality important to bone damage mechanics.

Geology, Petrography, and Mineralization of Sedimentary Hosted Strata-Bounded Barite Deposit at Gunga, Khuzdar District Balochistan, Pakistan

Gunga deposit is a type of sedimentary exhalative (SEDEX) deposit located in the northwest of Khuzdar Knot within the Kirthar Fold Belt (KFB) in the south-west of Khuzdar city. This deposit is formed during the late Triassic-Jurassic period due to rifting of the Gondwana supercontinent. being hosted with the Anjira Member of Jurassic Shirinab Formation, hosted the Strata bounded barite mineralization in these deposits contact with the siliceous and iron-rich gossan zones. The Baritic zone indicates the complex replacement of silica with the continuous silicification which is followed by massive to brecciated type Barite. Petrographically, barite has a very fine to coarse grain texture, anhedral to euhedral crystal shape, and forms dendritic crystal structure In the Back Scattered Electron (BSE) images, the crystal morphology of Barite exhibits well-developed elongated crystal structures with medium to coarse grain texture. Energy Dispersive X-rays (EDX) graphs indicates the high peaks of Ba, S, and O elements associated with sub-peaks rock-forming mineral elements (Si, Al, Na, K, and Ca) along with sub-peaks of ore-forming mineral elements (Pb, Zn, Fe, P, and Ni).

Recycling backscattered β rays in planar betavoltaic batteries using the double-sided structure

Backscattering of β rays is one significant part of energy losses in betavoltaic batteries. However, few works have been carried out on this basic physical process and no guidance has been provided to minimize the impact of the backscattered electrons on the efficiencies of betavoltaics. In this work, a double-sided structure is proposed to recycle the backscattered electrons and reduce the backscattering loss. A systematical investigation has been conducted to minimize the backscattering loss in planar betavoltaic batteries. The double-sided structure has great advantages for utilizing the multiple times backscattering of electrons between the radioactive source and the semiconductor unit and for recycling the backscattered electrons. Our results show that thin source layers, high-energy sources, and sources with smaller effective atomic numbers can enhance the recycling effect and reduce the backscattering loss. 147Pm2O3 sources with the highest emitting energy and 14C(PMMA) sources with the lowest effective atomic number can recycle the most backscattered energy using the double-sided structure with a thin source layer. The method and the suggestions proposed in this work can be greatly useful in the battery design as well as other scenes where the electron backscattering should be considered.

Surface Microstructure of Two Bioceramics: Calcium-Enriched Mixture and Cold Ceramic in Setting Environments with Different pH Values.

The pH of the setting environment could alter the surface characteristics of bioceramics. The present study aimed to assess the surface microstructure of calcium-enriched mixture (CEM cement) and cold ceramic (CC) in setting environments with different pH values. 12 dentin blocks with 3 mm height and internal diameter were prepared. CEM cement and CC were prepared and packed into the blocks. Samples in each bioceramics group (n = 6) were divided into 3 subgroups (n = 2) and exposed to acid, pH of 7.4, and alkaline pH for 1 week. Specimens were prepared for evaluation under a scanning electron microscope using backscattered electron (BSE) detectors. Monitoring of pH changes was rendered with a pH meter through the setting process. BSE detection in an acidic environment showed more amorphous microstructures in CC specimens in comparison to CEM cement. In pH of 7.4 and alkaline pH, more unhydrated structures were observed in CEM cement compared with CC samples. During the first 48 h of the setting process, the pH changes of setting environments were more rapid in the CEM cement group in comparison to CC samples. pH changes during the setting process of cement could affect the surface microstructure and physical properties. In acidic environments, the crystallization of CC cement is more disrupted than that of CEM cement.

Revealing the intensified preferred orientation and factors dominating the anisotropic mechanical properties of laser powder bed fusion Ti‐6Al‐4V alloy after heat treatment

Heat treatment is a general process to modify the unsatisfactory microstructure and properties of laser powder bed fusion (LPBF) Ti‐6Al‐4V. However, the effects of heat treatment on the preferred orientation and anisotropic mechanical properties have not been clarified yet. The main objective of this study was to identify the roles of heat treatment in the preferred orientation and mechanical properties of LPBF Ti‐6Al‐4V. The results indicated that α′-martensite with a weak {112̅0}α′ preferred orientation and minor retained β phase with a strong {100}β preferred orientation along the prior columnar β grains existed in the as-built specimen. After 750 °C heat treatment, α′-martensite was fully decomposed to α + β phases, and the {112̅0}α preferred orientation gradually intensified with increases in the heat treatment temperature, particularly after 950 °C heat treatment. The mechanism of the intensified {112̅0}α preferred orientation was proposed and verified by the Burgers orientation relationship and parent phase reconstruction using electron backscatter diffraction.Furthermore, the factors dominating the anisotropic mechanical properties of LPBF Ti‐6Al‐4V after heat treatment were investigated in this study. The results showed that, in the as-built, 750 °C, and 850 °C heat-treated conditions, the ultimate tensile strength and elongation of the horizontally-built specimens were slightly higher than those of the vertically-built ones due to the large spatter-induced disk-shaped pores. However, after 950 °C heat treatment, the elongation of the vertically-built samples exceeded that of the horizontally-built ones. This trend can be attributed to the significant intensification of the preferred orientation by the 950 °C heat treatment, which contributed to the higher Schmid factor and ductility of the vertically-built specimens.

On the influence of crystallographic orientation on superelasticity - Fe-Mn-Al-Ni shape memory alloys studied by advanced in situ characterization techniques

The superelasticity of iron-based shape memory alloys is strongly influenced by microstructural features such as crystallographic orientation, size and morphology of grains, character of grain boundaries as well as volume fraction of precipitates. Furthermore, elementary processes such as formation of dislocations, interaction of dislocations with the austenite/martensite phase boundary, and the interaction of different martensite variants result in functional degradation. Advanced in situ characterization techniques like digital image correlation (DIC) and infrared thermography (IR-TG) corroborated by ex situ high resolution electron backscatter diffraction (HR-EBSD) and electron contrast channeling imaging (ECCI) were used to investigate the functional stability of the superelasticity of Fe–Mn–Al–Ni single crystals and oligocrystals under tensile and compressive loading. The early stabilization of martensite during repeated loading was attributed, besides other mechanisms, to the interaction of different martensite variants leading to the formation of dislocations, locally pinning the austenite/martensite interface.

Optimization Design of MK-GGBS Based Geopolymer Repairing Mortar Based on Response Surface Methodology

There are several influencing factors in the preparation of MK (metakaolin)-GGBS (ground granulated blast furnace slag)-based geopolymer repair mortars, including the MK-GGBS ratio, the alkalinity of the alkali activator solution, the modulus of the alkali activator solution, and the water-to-solid ratio. There are interactions between these factors, such as the different alkaline and modulus requirements of MK and GGBS, the interaction between the alkaline and modulus of the alkali activator solution, and the influence of water throughout the process. The effect of these interactions on the geopolymer repair mortar is not fully understood, making optimization of the MK-GGBS repair mortar ratio difficult. Therefore, in this paper, the response surface methodology (RSM) was used to optimize the preparation of the repair mortar, with GGBS content, SiO2/Na2O molar ratio, Na2O/binder ratio, and water/binder ratio as influencing factors and 1 d compressive strength, 1 d flexural strength, and 1 d bond strength as evaluation indices. Additionally, the repair mortar's overall performance was assessed in terms of setting time, long-term compressive and bond strength, shrinkage, water absorption, and efflorescence. The results show that RSM was successful in establishing a relationship between the repair mortar's properties and the factors. The recommended values of the GGBS content, Na2O/binder ratio, SiO2/Na2O molar ratio, and water/binder ratio are 60%, 10.1%, 1.19, and 0.41, respectively. The optimized mortar meets the standard's requirements for set time, water absorption, shrinkage values, and mechanical strength, with minimal visual efflorescence. The back-scattered electron (BSE) images and energy dispersive spectroscopy (EDS) analysis show that the geopolymer and cement have good interfacial adhesion, and a denser interfacial transition zone exists in the optimized proportion.

Bohemian sandstone for restoration of cultural heritage sites: 3D microstructure and mass transport properties

We characterised the microstructure of sandstone from the Msene locality (Czech Republic) by combining X-ray computed micro-tomography, back-scattered electron imaging, chemical composition analysis and textural analysis and gas permeation. Both, 2D and 3D images were commonly processed by linking an anisotropic non-linear diffusion filter and a segmentation method based on power watershed. This approach guaranteed binarised outputs that were almost the same in wide ranges of spatial-filter and power-watershed parameters, i.e., subjective choices of the parameters played the negligible role. The rock pore structure was found to be statistically homogeneous and almost isotropic with perfectly connected pore space. We also partitioned the void and solid phases into either grains or pores and throats, which enabled us to study characteristic sizes and connectivity of partitioned regions. By comparing pore and throat sizes, we demonstrated the significant convergent-divergent nature of the pore space because the throat size covered at most one half of the total surface area per pore (cavity). In addition, we calculated coordination numbers for all pores (cavities) to verify almost perfect connectivity of internal pores with those at the external surface. Effective (macroscopic) transport properties of the reconstructed pore space were simulated and the results were validated by experimentally observing steady state flow of inert gas. These findings appear to be a favorable starting point for future investigation of consolidation procedures. The well-connected pore structure with minimum occurrence of dead-end pores suggests that the consolidation agent is very likely to flood the whole pore space.

Geochemistry of magnetite from the Mamupu Cu polymetallic deposit, Yulong belt, Tibet: Implications for magnetite genesis, stages and mechanism of formation

The Mamupu copper polymetallic deposit is characterized by multistage magnetite, but the genesis and fluid evolution process of this deposit are still obscure. Three types of magnetite were identified in Mamupu based on comprehensive textural observations and paragenesis. Mag1 occurs as subhedral to euhedral crystals, and smooth Mag1a and porous Mag1b can be distinguished under Backscattered Electron (BSE). Mag2 is characterized by 120° triple junction textures and has been replaced by hematite. Mag3 is commonly replaced by hydrothermal fluids and exhibits well-developed oscillatory zoning and core (Mag3a)-rim (Mag3b) textures. The geochemistry of Mamupu magnetite suggests that they are of hydrothermal origin. Mag1 has undergone extensive fluid-rock interactions, whereas the sharp contacts with Mag1a and Mag1b and the microporosity of Mag1b imply that the Mag1b was generated by the coupled dissolution reprecipitation of the Mag1a grains. This process may be triggered by low-temperature and high-salinity fluid produced by intensive water-rock interaction between ore-bearing magmatic-hydrothermal fluid and carbonate surrounding rock of the Jiaoga Formation. The 120° triple junction textures of Mag2 indicate that it was formed during a fluid-assisted recrystallization process, and Mag2 replaced by hematite represents the increase in oxygen fugacity. From Mag3a to Mag3b, the contents of V and Mn increased while the contents of chalcophile elements decreased, suggesting a decrease of oxygen fugacity and the precipitation of sulfide, which represents the beginning of the sulfide stage. Moreover, petrography and geochemistry data of magnetite represented that the breccia ore of Mamupu belongs to skarn mineralization. The geochemical characteristics of magnetite show that Cu-Au and W-Mo in Mamupu precipitated in different stages, representing the transformation from a relatively oxidized environment in the early stage to a relatively reduced environment in the late stage. These results reveal that trace elements in magnetite can be utilized to define the genesis and evolution of the skarn deposit. In addition, it can also restrict the precipitation mechanism of ore-forming elements in the deposits. However, detailed textural observations should be carried out before experimental research.

Formation mechanism of interdiffusion layer and mechanical properties of Al0.6CoCrFeNi high-entropy alloy/Ti composites

The 10 vol% Al0.6CoCrFeNi high entropy alloy (HEA) particles reinforced titanium matrix composites were fabricated successfully by hot pressing sintering under vacuum. The formation mechanism of interdiffusion layer and mechanical properties of the composites were studied through X-ray diffraction (XRD), scanning electron microscopy (SEM), back scattered electron (BSE), electron backscatter diffraction (EBSD) and compressive test. The results show that the interdiffusion layers composed of AlNi2Ti (BCC) and Ni-Ti mixed phases (FCC) are formed between the HEA particles and the matrix. The recrystallization mechanism of the composites is continuous dynamic recrystallization and second phase particle induced recrystallization. The concentration gradient and mixing enthalpy were the main driving force for the formation of phase in interdiffusion layer. The formation sequence of Ni-Ti mixed phases is NiTi2, NiTi and Ni3Ti. The compressive strength (1642 MPa) of the composites with the same strain (21.7%) is 86.1% higher than that of the pure titanium samples (882.5 MPa). During the compression process, cracking occurs at the Ni-Ti mixed phases interdiffusion layer.

Comprehensive Associations between Acidosis and the Skeleton in Patients with Kidney Disease.

Renal osteodystrophy (ROD) contributes substantially to morbidity in CKD, including increased fracture risk. Metabolic acidosis (MA) contributes to the development of ROD, but an up-to-date skeletal phenotype in CKD-associated acidosis has not been described. We comprehensively studied associations between acidosis and bone in patients with CKD using advanced methods to image the skeleton and analyze bone-tissue, along with biochemical testing. Cross-sectionally, acidosis was associated with higher markers of bone remodeling and female-specific impairments in cortical and trabecular bone quality. Prospectively, acidosis was associated with cortical expansion and trabecular microarchitectural deterioration. At the bone-tissue level, acidosis was associated with deficits in bone mineral content. Future work investigating acidosis correction on bone quality is warranted. Renal osteodystrophy is a state of impaired bone quality and strength. Metabolic acidosis (MA) is associated with alterations in bone quality including remodeling, microarchitecture, and mineralization. No studies in patients with CKD have provided a comprehensive multimodal skeletal phenotype of MA. We aim to describe the structure and makeup of bone in patients with MA in the setting of CKD using biochemistry, noninvasive imaging, and histomorphometry. The retrospective cross-sectional analyses included 180 patients with CKD. MA was defined as bicarbonate ≤22 mEq/L. We evaluated circulating bone turnover markers and skeletal imaging with dual energy x-ray absorptiometry and high-resolution peripheral computed tomography. A subset of 54 participants had follow-up. We assessed associations between baseline and change in bicarbonate with change in bone outcomes. Histomorphometry, microCT, and quantitative backscatter electron microscopy assessed bone biopsy outcomes in 22 participants. The mean age was 68±10 years, 54% of participants were male, and 55% were White. At baseline, acidotic subjects had higher markers of bone turnover, lower areal bone mineral density at the radius by dual energy x-ray absorptiometry, and lower cortical and trabecular volumetric bone mineral density and impaired trabecular microarchitecture. Over time, acidosis was associated with opposing cortical and trabecular effects: cortical expansion but trabecular deterioration. Bone-tissue analyses showed reduced tissue mineral density with increased heterogeneity of calcium distribution in acidotic participants. MA is associated with multiple impairments in bone quality. Future work should examine whether correction of acidosis improves bone quality and strength in patients with CKD.

Structural and Geochemical Assessment of the Coralline Alga Tethysphytum antarcticum from Terra Nova Bay, Ross Sea, Antarctica

Crustose coralline algae (CCA) occur from the tropics to the poles in photic benthic environments. Here, we report on some of the world’s southernmost and coldest CCA sites in Terra Nova, Ross Sea, Antarctica at 74°41′ S. The recently described red alga Tethysphytum antarticum is investigated for its skeletal architecture, its mineralogical and geochemical composition, as well as for its taxonomic classification. A phylogenetic analysis based on molecular genetics and the sequencing of the photosystem II protein D1 (psbA) gave a perfect match with T. antarcticum. Histological sections and micro-CT-scans provide new diagnostic details for the conceptacles (the reproductive organs of the alga). X-ray diffractometry and electron-microprobe measurements yielded a clear high-Mg calcite (~8 mol%) composition of the skeletal parts. Detailed back-scattered electron imaging of polished petrographic thin sections revealed a two-layered thallus (vegetative plant tissue), comprising an organic-rich irregularly calcified basal layer with rectangular cells, overlain by the main thallus. Elemental maps show relatively increased sulphur in the basal layer, clearly tied to organic cell walls. MgCO3 and SrCO3 were targeted with semiquantitative elemental mappings and in an ontogenetic quantitative spot transect. Compared with temperature (−1.95 °C to +1.08 °C), the MgCO3 (mol%) reflects this world’s coldest CCA site temperature with the lowest MgCO3 content of 7.9 ± 1.6 mol%. The along transect variability, however, shows with ~6 mol% a larger MgCO3 variability than expected for the 3 °C intra-annual temperature amplitude in Terra Nova Bay. This implies that in low amplitude settings the biomineralisation control on Mg/Ca ratios can outcompete its temperature sensitivity. Mark-recapture studies, next to the environmental logger station La Zecca are suggested, to perform a detailed growth rate and biomineralisation quantification.

Petrogenesis of Chatoyant Green Nephrite from Serpentinite-Related Deposits, Ospinsk, Russia: Insights from Mineralogy and Geochemistry

Ospinsk is an area in Russia well-known for mining the highest quality green nephrite in the world. However, the chatoyant green nephrite found here has not been studied to date. This study explores the mineralogy, geochemistry, and petrogenesis of chatoyant green nephrite collected from Ospinsk using polarizing microscope back-scattered electron images, scanning electron microscopy, Fourier transform infrared spectrometry, laser Raman spectroscopy, electron microprobe analysis, and laser ablation inductively coupled plasma mass spectrometry, and compares them with S-type green nephrite from other regions of the world. Tremolite is the main mineral constituent, and chromite, chlorite, graphite, and magnetite are accessory minerals in the samples. The chatoyant green nephrite from Ospinsk is serpentinite-related green nephrite. The Ti content of the chatoyant green nephrite from Ospinsk is significantly higher than that of green nephrite from other places. The chatoyant green nephrite deposit in Ospinsk is a contact metasomatic deposit related to ultramafic rocks. The ultramafic rocks first altered to serpentinite and later converted to tremolite after repeated thermal contact-based metasomatism. During the metasomatism of serpentinite into green nephrite, unilateral, compressive, and shear stresses caused by obduction forced directional growth of tremolite, resulting in chatoyancy.

High-Temperature Tensile Properties of a Cobalt-Based Co-20Cr-15W-10Ni Superalloy with a Bimodal Grain Structure

Cobalt-based superalloys are common materials for the manufacturing of various components used in aerospace applications. Conventional cobalt-based superalloys with a unimodal grain structure generally exhibit low strength and ductility at high temperatures. A bimodal grain structure of a cobalt-based superalloy, Co–20Cr–15W–10Ni (CCWN), was designed to achieve both high strength and ductility at high temperatures. The deformation behavior and tensile properties of a CCWN alloy with unimodal fine-grain (FG), coarse-grain (CG), and bimodal (FG/CG) structures were investigated at 900 °C. The microstructures and substructures after high-temperature deformation were examined via electron backscatter diffraction (EBSD) and electron channeling contrast imaging (ECCI) to determine the deformation mechanisms. The microstructural observation showed that the bimodal grain structure consisted of FG and CG domains. During high-temperature deformation at 900 °C, the FG structure was mainly deformed by dynamic recrystallization (DRX), maintaining a similar FG structure. The CG structure was mainly deformed by DRV, resulting in a small amount of DRX grains and a large amount of dynamic recovery (DRV) grains. However, the bimodal grain structures were mainly softened via DRX and transformed into a new bimodal structure, ultrafine grain (UFG) and FG. The FG domains tended to deform via dislocations, and the CG domains via twinning. The high-temperature tensile tests revealed that the bimodal-structured alloy exhibited both higher strength and ductility than those of the alloy samples with unimodal FG or CG structure. This is associated with the newly developed UFG/FG structures in the bimodal grain-structured samples during high-temperature deformation. This work may provide new insight into the development of high-temperature alloys with bimodal grain structures.

Ion microsource integrated with scanning electron microscope for sample preparation

The authors developed the Ar+ ion microsource, which can generate a filamentary ion beam of a few tens of µm at its half-power diameter with a target current up to 50 µA at − 4 kV extracting voltage. This comprises a ceramic discharge capillary of 1 mm in inner diameter and 10 mm long with a very small copper anode and a cathode outlet aperture of 0.5 mm in diameter at its ends. The arrangement has been examined in three alternative designs equipped with cathodes of different shapes and materials and two extraction voltage supply schemes, i.e., with the negatively biased sample and the earthed cathode or the earthed sample and the cathode at a floating positive potential (recommended solution). Numerous other factors were considered that can affect the standard SEM operation, such as excessive working gas leakage and jamming with discharge interferences, e.g., streamers. The microsource makes a compact structure that can be positioned above the sample inside a standard SEM without any changes to its original structure and collisions with standard modes of the SEM operation. Such a tool enables the removal of target microvolumes in chosen places, so it can be used for some technological purposes, such as making small apertures. However, its main goal is to uncover the bulk internal structure of the specimen, imaging it in a 3D form. Therefore, the microsource is placed on the movable arm and coupled with the semiconductor four-quadrant backscattered electron (BSE) detector, which enables 3D imaging of the uncovered structure with the multidetector method. This implies taking in one scan a set of images from four or five directions, using both material- and topography-sensitive channels of information (BSE and secondary electron SE), which facilitates their interpretation.

Chemical Behaviour of Copper in the Application of Unconstrained Cr-Ni-Al-Cu Metal Powders in Submerged Arc Welding: Gas Phase Thermodynamics and 3D Slag SEM Evidence

Unconstrained metal powders of Cu, Cr, Ni and Al were applied to submerged arc welding (SAW) to clarify the chemical behaviour of copper in this modified SAW process. Aluminium metal is avoided in SAW because it is easily oxidised. Excessive aluminium oxides in the form of slag or inclusions in the weld metal will lead to poor weld metal materials properties. Aluminium is an effective deoxidiser and can be used to prevent Cr and Ni loss to the slag by preventing oxidation of these metals. The results show that carbon steel was alloyed to 5.3% Cr, 5.3% Ni, 3.6% Al and 5.2% Cu at 80% Cr yield, 81% Ni yield, 54% Al yield and 79% Cu yield. BSE (backscattered electron) images of the three-dimensional (3D) post-weld slag sample show 3D structures within the slag dome. The 3D structures contain features of vapour formation and recondensation. In addition, nano-strands appear in the 3D structures and confirm the vaporisation and recondensation of fluorides. The chemical behaviour of copper metal powder added in SAW is to vaporise as metallic copper and incorporate in the Al-Si-Mg-Ca-Mn-Fe-Cu-Na-Cr-Ni fluoride. Copper, in combination with aluminium, has a stabiliser effect in SAW due to its formation of an initial alloy melt of low liquidus temperature, thus decreasing the temperature required to melt high-melting-point metals such as Cr into the weld pool. Although Al and Cu have similar vapour pressures at specific temperatures, it appears that Cu does not substitute for Al in the gas phase. Gas-slag-alloy thermochemical equilibrium calculations confirm the partial oxygen pressure lowering effect of aluminium and the vaporisation of copper as metallic copper with very little copper-fluoride species expected to form. The quantity of metallic copper vaporisation calculated in the gas-slag-alloy thermochemical equilibrium is much higher than the vaporisation quantity measured in welding. This may be due to recondensation of vaporised copper which is not accounted for in the equilibrium calculation at the set arc cavity temperature, as well as the effect of surface-active elements such as sulphur and oxygen in limiting the vaporisation reaction of copper.

Gradient characterization of steel-concrete interface at early ages

Steel-Concrete Interface (SCI) refers to the porous weak area at the interface between steel bar and cement matrix. This study proposes sophisticated methods for quantifying gradient properties and their evolution of SCI using back-scattered electron (BSE) imaging and nano-indentation. The gradient of SCI is identified through a robust statistical analysis. Distinct stratification structure of SCI is discovered, which can be demonstrated from the grayscale of BSE as well as the indentation modulus and hardness. The thickness of SCI increases with age and the increasing rates roughly decline with the increase of w/c. SCI can be divided into highly porous layer I and transition layer II according to the hierarchically porosity. The layer II is subdivided into II(a) and II(b) based on the gradient of mechanical properties, which is mainly caused by the spatial distribution of cement particles within SCI.

Characterization in respect to degradation of titanium-coated polypropylene surgical mesh explanted from humans.

Titanium-coated polypropylene (Ti-PP) mesh was introduced in 2002 as a surgical mesh for the treatment of hernias and shortly after for pelvic floor surgery, with the aim of improving biocompatibility when compared to non-titanised/regular PP mesh implants. The application of a titanium coating could also be beneficial to address concerns regarding the exposure of PP in an in vivo environment. Many studies have shown that PP, although it is widely accepted as a stable polymer, is subject to oxidation and degradation, such degradation affects the mechanical behavior, that is, the stiffness and tensile strength of PP mesh. Despite the wide clinical use of Ti-PP surgical meshes, no study has yet investigated the residual material properties post clinical deployment and subsequent explantation. In this study, two explanted Ti-PP mesh samples each having different incorporation durations from two patients were examined. Material analysis conducted within this study includes the following techniques: attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, low voltage - scanning electron microscopy (LV-SEM), backscattered electron (BSE) imaging, energy dispersive X-ray spectroscopy (EDS) and secondary election hyperspectral imaging (SEHI). The hypothesis of this study is that the Ti coating successfully shields the PP mesh from oxidative stress in vivo and thus protects it from degradation. The results of this analysis show for the first time evidence of bulk oxidation, surface degradation, and environmental stress cracking on explanted Ti-PP meshes.

Quantitative Microstructural Analysis by Correlative EPMA/EBSD/BSE Electron Microscopies Applied to Nuclear Ceramic

Abstract Electron microscopy maps were acquired in a mixed-oxide nuclear ceramic to probe independently and optimally grain structure [by Electron BackScattered Diffraction (EBSD)], porosity [by high-resolution BackScattered Electron imaging (BSE)], and elemental distributions [by Electron Probe MicroAnalysis (EPMA) in a separate instrument]. The maps were programmatically correlated spatially and integrated into a single multi-dimensional dataset allowing a correlative approach to assess the interdependence of key ceramic microstructural properties. Through the extraction of statistically representative non-random quantitative correlations between grain size, elemental enrichment, and intra-granular porosity that can be related to solid-state processes, the potency of the method is illustrated. The multi-layered hybrid maps produced by fusing data from the different acquisitions offer novel and unique insights into contiguous crystallographic, microstructural, and chemical features.