Transmission Electron Microscopy Observations Research Articles

Improving the Long-Term Stability of PbTe-Based Thermoelectric Modules: From Nanostructures to Packaged Module Architecture.

Nanostructured lead telluride PbTe is among the best-performing thermoelectric materials, for both p- and n-types, for intermediate temperature applications. However, the fabrication of power-generating modules based on nanostructured PbTe still faces challenges related to the stability of the materials, especially nanoprecipitates, and the bonding of electric contacts. In this study, in situ high-temperature transmission electron microscopy observation confirmed the stability of nanoprecipitates in p-type Pb0.973Na0.02Ge0.007Te up to at least ∼786 K. Then, a new architecture for a packaged module was developed for improving durability, preventing unwanted interaction between thermoelectric materials and electrodes, and for reducing thermal stress-induced crack formation. Finite element method simulations of thermal stresses and power generation characteristics were utilized to optimize the new module architecture. Legs of nanostructured p-type Pb0.973Na0.02Ge0.007Te (maximum zT ∼ 2.2 at 795 K) and nanostructured n-type Pb0.98Ga0.02Te (maximum zT ∼ 1.5 at 748 K) were stacked with flexible Fe-foil diffusion barrier layers and Ag-foil-interconnecting electrodes forming stable interfaces between electrodes and PbTe in the packaged module. For the bare module, a maximum conversion efficiency of ∼6.8% was obtained for a temperature difference of ∼480 K. Only ∼3% reduction in output power and efficiency was found after long-term operation of the bare module for ∼740 h (∼31 days) at a hot-side temperature of ∼673 K, demonstrating good long-term stability.

External pressure induces the dysfunction of spermatogonia via triggering the intrinsic pathway of apoptosis.

Cryptorchidism, the failure of testes to descend into the scrotum, exposes the testes to higher temperature and external pressure. Scholars from Razi University found through research conducted at different pressure gradients (0, 25, 50, and 100 mmHg) and time gradients (2 and 4 h) that high hydrostatic pressure may lead to sperm apoptosis. In this work, we investigated the effect of external pressure on spermatogonia, exploring a new mechanism of male infertility caused by cryptorchidism. Various pressure gradients (0, 25, 50, and 100 mmHg) were applied to spermatogonia for different durations (0, 2, and 4 h) in the Cell Counting Kit-8 (CCK8) experiment. Morphological changes, cell ultrastructure, apoptosis rates, and the expression of apoptosis-related proteins (bax, bcl-2, caspase-3, and caspase-9) were assessed through immunofluorescence, electron microscopy, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) assay, flow cytometry, immunohistochemistry, real-time quantitative polymerase chain reaction (qPCR), and western blot. The cell viability assay showed that higher external pressure had a greater negative time-dependent impact on cell viability. Immunofluorescence results indicated that external pressure stimuli altered the morphology of spermatogonia. The results of TUNEL assay and flow cytometry demonstrated that external pressure stimuli induced apoptosis in spermatogonia. Transmission electron microscopy (TEM) observations showed the generation of apoptotic bodies, mitochondrial swelling, vacuolization, and mitochondrial cristae fusion. The results of immunohistochemistry indicated that pressure induced the expression of caspase-3 and caspase-9 proteins. qPCR and western blot analyses revealed an increased ratio of bax/bcl-2 and expression of caspase-3 and caspase-9. Methazolamide (cytochrome C inhibitor) blocked the pressure-induced cell apoptosis and inhibited the activation of caspase-3 while Z-IETD-FMK (caspase-8 inhibitor) did not. External pressure promotes spermatogonia apoptosis through the intrinsic apoptosis pathway, which may be one of the mechanisms of male infertility induced by cryptorchidism.

Oriented attachment of silver nanoparticles in DMSO by collapsing under thermal stress

Nowadays, understanding the behavior of nanoparticle agglomeration is crucial to gain insight into the fundamental physicochemical processes that govern particle interactions at the nanoscale. In this work, we are focused on the thermal collapse of silver nanoparticles (NPs) stabilized with sodium citrate in dimethyl sulfoxide (DMSO). Therefore, we investigated the parameters that influence the transition from nearly isolated particles to elongated Ag agglomerates using Dynamic Light Scattering (DLS) and Ultraviolet-Visible Spectroscopy (UV-Vis). In addition, we conducted an in-depth study of the near-particle-particle interaction within the agglomerate using High-Resolution Transmission Electron Microscopy (HRTEM) observations of the agglomerates. The HRTEM results suggest that in the elongation of the agglomerate, the oriented attachment within the initial cluster plays a crucial role in the alignment along the longitudinal axis. The aging colloid exhibits minimal agglomeration, suggesting that the driving force of the collapse phenomenon is predominantly thermodynamic rather than kinetic in nature, and that the surface chemical equilibria play a key role in the preferential orientation mechanism.

Unraveling the origin of the high reversibility in entropy-stabilized rocksalt-type (Mg0.2Co0.2Mn0.2Ni0.2Zn0.2)O anodes for lithium-ion storage

Entropy-stabilized rocksalt-type oxides, composed of multiple components, are increasingly recognized as highly promising materials for energy storage applications. In this study, a novel anode material, (Mg0.2Co0.2Mn0.2Ni0.2Zn0.2)O, demonstrates exceptional reversible specific capacity of 773.4 mAh g−1 even after 200 cycles at 0.1 A g−1. Density functional theory (DFT) analysis reveals superior electrical conductivity of (Mg0.2Co0.2Mn0.2Ni0.2Zn0.2)O compared to individual oxides like CoO, which has the potential to enhance electronic transfer to improve electrochemical performance. In situ transmission electron microscopy (TEM) observations confirm the reversible crystal structure of rocksalt-type (Mg0.2Co0.2Mn0.2Ni0.2Zn0.2)O anodes, with only ∼36.8 % volume expansion in four cycles. This investigation offers insights into the (de)lithiation process at a microscopic scale, shedding light on the origins of high reversibility and guiding the design of future high-entropy materials. Entropy-stabilized rocksalt-type (Mg0.2Co0.2Mn0.2Ni0.2Zn0.2)O oxides exhibit excellent properties, positioning them as promising candidates for lithium-ion batteries (LIBs) anode materials.

Flame made low Pt loading catalysts supported on different metal oxides for catalytic combustion of CO and CH4

Catalytic combustion is an effective approach to remove air pollutants from various emission sources. For this purpose, supported noble metal catalysts are preferred in commercial applications due to their outstanding catalytic activity for eliminating CO, hydrocarbon compounds and NOx. In this paper, we employ the flame spray pyrolysis method to prepare a series of Pt-based catalysts with four different supports (TiO2, ZrO2, MgO and ZnO) and variable low Pt loadings for catalytic combustion of CO and CH4. The performance of 0.5 Pt/TiO2 is the best in all samples, in which the T90 temperatures are 107 and 500 °C for 90% conversion of CO and CH4, respectively. To examine its thermal stability, a time-on-stream test at 700 °C for 420 min is carried out, resulting in a decrease of about 5% in the final conversion of CH4. The X-ray diffraction results show that TiO2 support is a mixed phase with a major amount of anatase and a small amount of rutile other than a pure phase of ZrO2, MgO and ZnO. Furthermore, X-ray photoelectron spectroscopy analysis and high-angle annular dark-field scanning transmission electron microscopy observation show that when the Pt loading is low, the Pt species exist as highly dispersed single atoms on the surface of the TiO2 support. As the Pt loading gradually increases, the state of the Pt species transitions from single atoms to Pt clusters, resulting in a decrease in dispersion. Ultimately, the Pt can successfully accumulate on the surface of the TiO2 nanoparticles, providing abundant active sites for efficient catalytic combustion reactions.

Improved camptothecin encapsulation and efficacy by environmentally sensitive block copolymer/chitosan/fucoidan nanoparticles for targeting lung cancer cells

In this study, thermo-sensitive poly(N-isopropyl acrylamide) (PNP) was polymerized with pH-sensitive poly(acrylic acid) (PAA) to prepare a PAA-b-PNP block copolymer. Above its cloud point, the block copolymer self-assembled into nanoparticles (NPs), encapsulating the anticancer drug camptothecin (CPT) in situ. Chitosan (CS) and fucoidan (Fu) further modified these NPs, forming Fu-CPT-NPs to enhance biocompatibility, drug encapsulation efficiency (EE), and loading content (LC), crucially facilitating P-selectin targeting of lung cancer cells through a drug delivery system. The EE and LC reached 82 % and 3.5 %, respectively. According to transmission electron microscope observation, these Fu-CPT-NPs had uniform spherical shapes with an average diameter of ca. 250 nm. They could maintain their stability in a pH range of 5.0–6.8. In vitro experimental results revealed that the Fu-CPT-NPs exhibited good biocompatibility and had anticancer activity after encapsulating CPT. It could deliver CPT to cancer cells by targeting P-selectin, effectively increasing cell uptake and inducing cell apoptosis. Animal study results showed that the Fu-CPT-NPs inhibited lung tumor growth by increasing tumor cell apoptosis without causing significant tissue damage related to generating reactive oxygen species in lung cancer cells. This system can effectively improve drug-delivery efficiency and treatment effects and has great potential for treating lung cancer.

Fabrication of bulk-sized W-1.1%TiC alloy with helium bubble retention via powder metallurgical route incorporated with helium ambient mechanical alloying

In the field of materials irradiation, it has been noted that incorporating helium (He) element into metals may have the beneficial effect of improving both strength and ductility in the high temperature region where creep occurs. In order to fabricate such new functional materials and apply them to a wide range of fields, it is necessary to establish new fabrication methods for bulk-size materials. In this study, bulk-sized W-1.1%TiC alloys containing He bubbles were fabricated by a powder metallurgical route using mechanical alloying in a He atmosphere and subsequent thermo-mechanical processing. Transmission electron microscopy observations showed that this fabrication process successfully incorporated nano-sized He bubbles into W-1.1%TiC. Since this fabrication process is free of radioactivation and irradiation-induced defects, it will facilitate research into the fundamental understanding of the independent effects of He bubbles on the physical and mechanical properties of various materials concerned.

Interaction between dislocation and heterogeneous interface in Cu/Fe laminated composites based on discrete dislocation dynamics

Bimetal laminated composites (BLCs) exhibit more outstanding mechanical properties than traditional alloys due to the interaction between heterogeneous interface boundary (HIB) and dislocation. However, the underlying physics of the dislocation motion and the strengthening effect has not been uncovered at mesoscopic scale. In this study, the detailed microstructure of the Cu/Fe HIB was obtained by transmission electron microscope (TEM) observation. The dislocation model was established using discrete dislocation dynamics (DDD), and several interactions between the dislocation and HIB were focused on, as well as the intrinsic strengthening mechanisms of the HIB. The results show that different HIB characteristics induce different interaction mechanisms such as absorption, slip transmission, slip on the HIB, emission from HIB and reflection by HIB, resulting in different strengthening effect on the BLCs. The HIB promotes slip of the dislocation emitted from the Fe, while prevents movement of the dislocation emitted from Cu. Since dislocation slip is more difficult in Fe, greater elastic deformation occurs before large-scale expansion of the dislocation, resulting in larger nominal yield strength. The presence of HIB increases the difficulty of dislocation movement compared to the single crystal structure, which in turn improves the overall strength of BLCs. Due to the different dislocation motion and strain gradient, the mechanism of that dislocation slip absorption by the HIB has optimal strengthening effect relative to other interaction mechanisms. The strengthening effect of other interaction mechanisms is influenced by the position of the dislocation emission, the type of interaction mechanism, and the angle between adjacent slip planes, etc. The outcome of present research sheds important insights into the design of HIB strengthening materials, such as multi- and nano- laminated composites.

Real-Space Visualization of Charged Polymer Network of Hydrogel by Double Network Strategy and Mineral Staining.

Hydrogels consist of three-dimensional (3D) and complicated polymer networks that determine their physical properties. Among the methods for structural analyses of hydrogels, the real-space imaging of a polymer network of hydrogels on a nanometer scale is one of the optimal methods; however, it is highly challenging. In this study, we propose a direct observation method for cationic polymer networks using transmission electron microscopy (TEM). By combining the double network strategy and the mineral staining technique, we overcame the challenges of polymer aggregation and the low electron density of the polymer. An objective cationic network was incorporated into a neutral skeleton network to suppress shrinkage during subsequent staining. Titania mineralization along the cationic polymer strands provided sufficient electron density for the objective polymer network for TEM observation. This observation method enables the visualization of local structures in real space and plays a complementary role to scattering methods for soft matter structure analysis.

Unified Solid Solution Product of [Nb][C] in Nb-Microalloyed Steels with Various Carbon Contents.

In this work, the solid solution product of [Nb][C] in the Nb-microalloyed steels with various carbon contents in the range of 0.20~1.80 wt.% was investigated by means of the extraction phase analysis method. The results showed that the Nb content in austenite tended to first decrease and then increase with the increase of carbon content in the steels. A unified solid solution product of [Nb][C] in austenite at different temperatures was obtained according to the results of the experimental steels. The Nb content in austenite of the experimental steels with high carbon contents was lower than that calculated by Ohtani's equation. The existence of NbC precipitates in the case and the core of the specimens carburized at 930 °C and 980 °C were verified by transmission electron microscopy (TEM) observations. The pinning effect of NbC precipitates on austenite grain growth was calculated according to the size and amount of NbC precipitates in the carburized case and the core of the carburized specimens. The calculated results of prior austenite grain sizes were in good agreement with the experimental results, which indicated that the unified solid solution product of [Nb][C] in Nb-microalloyed steels with various carbon contents was applicable for the low-pressure carburizing process.

Anodic oxidation of wireless niobium electrode in bipolar electrochemistry

The anodic oxidation of a wireless niobium substrate serving as a bipolar electrode (BPE) in a direct or alternating current electric field was investigated in detail via spectrophotometry, electrochemical measurement, glow discharge–optical emission spectroscopy, and direct microscopic observation. Niobium oxide was a suitable material for the experiment because it is amorphous and can be evaluated through conventional electrochemical methods. It also has a clear interference color, enabling easy optical evaluation. The effect of the BPE configuration (e.g., vertical and horizontal alignments) in the cell on the anodic oxidation area was also investigated visually using the interference color. Transmission electron microscopy observation was also performed for an accurate measurement of the thickness of the anodic film formed on the niobium BPE. Although the basic film formation behavior and film composition were consistent with those in conventional anodization, even in wireless operation, the effective voltage directly contributing to film formation was found to be lower than the applied voltage (30%–70% of the applied voltage), depending on the electrolysis conditions.

Unraveling the Unique Strong Metal-Support Interaction in Titanium Dioxide Supported Platinum Clusters for the Hydrogen Evolution Reaction.

Strong metal-support interaction (SMSI) is crucial to modulating the nature of metal species, yet the SMSI behaviors of sub-nanometer metal clusters remain unknown due to the difficulties in constructing SMSI at cluster scale. Herein, we achieve the successful construction of the SMSI between Pt clusters and amorphous TiO2 nanosheets by vacuum annealing, which requires a relatively low temperature that avoids the aggregation of small clusters. In situ scanning transmission electron microscopy observation is employed to explore the SMSI behaviors, and the results reveal the dynamic rearrangement of Pt atoms upon annealing for the first time. The originally disordered Pt atoms become ordered as the crystallizing of the amorphous TiO2 support, forming an epitaxial interface between Pt and TiO2. Such a SMSI state can remain stable in oxidation environment even at 400 °C. Further investigations prove that the electron transfer from TiO2 to Pt occupies the Pt 5d orbitals, which is responsible for the disappeared CO adsorption ability of Pt/TiO2 after forming SMSI. This work not only opens a new avenue for constructing SMSI at cluster scale but also provides in-depth understanding on the unique SMSI behavior, which would stimulate the development of supported metal clusters for catalysis applications.

Unraveling the Unique Strong Metal‐Support Interaction in Titanium Dioxide Supported Platinum Clusters for the Hydrogen Evolution Reaction

AbstractStrong metal‐support interaction (SMSI) is crucial to modulating the nature of metal species, yet the SMSI behaviors of sub‐nanometer metal clusters remain unknown due to the difficulties in constructing SMSI at cluster scale. Herein, we achieve the successful construction of the SMSI between Pt clusters and amorphous TiO2 nanosheets by vacuum annealing, which requires a relatively low temperature that avoids the aggregation of small clusters. In situ scanning transmission electron microscopy observation is employed to explore the SMSI behaviors, and the results reveal the dynamic rearrangement of Pt atoms upon annealing for the first time. The originally disordered Pt atoms become ordered as the crystallizing of the amorphous TiO2 support, forming an epitaxial interface between Pt and TiO2. Such a SMSI state can remain stable in oxidation environment even at 400 °C. Further investigations prove that the electron transfer from TiO2 to Pt occupies the Pt 5d orbitals, which is responsible for the disappeared CO adsorption ability of Pt/TiO2 after forming SMSI. This work not only opens a new avenue for constructing SMSI at cluster scale but also provides in‐depth understanding on the unique SMSI behavior, which would stimulate the development of supported metal clusters for catalysis applications.

Enhanced autophagy and phagocytosis of apoptotic lymphocytes in splenic macrophages of acute ethanol-treated rats: Light and electron microscopic studies.

Autophagy is a prosurvival mechanism for the clearance of damaged cellular components, specifically upon exposure to various stressors. In lymphoid organs, excessive ethanol consumption increases lymphocyte apoptosis, resulting in immunosuppression. However, ethanol-induced autophagy and related phagocytosis of apoptotic lymphocytes in the spleen have not been studied yet. Adult male Wistar rats were injected intraperitoneally either with 5 g/kg ethanol or phosphate-buffered saline (as a control group) and then sacrificed 0, 3, 6, and 24 hours after injection. Light and transmission electron microscopy (TEM) findings indicated enhanced T cell apoptosis in the white pulps of ethanol-treated rats (ETRs) compared with the control group, which peaked at 6 h and was associated with the accumulation of tingible body macrophages (TBMs). These macrophages exhibited an upregulated autophagic response, as evidenced by enhanced LC3-II (a specific marker of autophagosomes) expression, which peaked at 24h. In addition, double labeling immunofluorescence of LC3-II with lysosomal markers revealed the enhanced formation of autolysosomes in TBMs of ETRs, which was associated with suppression of p62 immunostaining, indicating the enhanced autophagic flux. Interestingly, this elevated autophagic response in ETR TBMs was accompanied by evidence of LC3-associated phagocytosis (LAP) of apoptotic splenocytes. This is based on TUNEL/LC3-II double labeling and TEM observations of phagosomes containing apoptotic bodies, enclosed within phagosomal membranes adjacent to the autophagic vacuoles. It can be concluded that enhanced prosurvival autophagy in splenic TBMs of ETRs and clearing of apoptotic lymphocytes via LAP may contribute to preventing secondary necrosis and autoimmune diseases.

Effect of surface high-density twinned structure on the fatigue crack initiation of Ti–6Al–4V

Fatigue crack initiation sites would transfer from surface to subsurface of metal specimens through shot peening (SP) or laser shock surface strengthening. This phenomenon is typically attributed to the introduction of compressive residual stress on the surface of the specimen during the surface strengthening process. In this study, Ti–6Al–4V specimens featuring a high-density twinned structure on their surfaces, which eliminated compressive residual stress, were fabricated. Fatigue test result revealed that fatigue crack initiation sites in specimens with twinned structures were predominantly located in the subsurface, near the junction area between the twinned structure and the matrix. This phenomenon was accompanied by an increase in fatigue life. The microstructural features in the fatigue crack source were analyzed using focused ion beam (FIB) coupled with electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM). It was observed that primary crack formed in badly oriented grains that are difficult to initiate dislocation slip according to the Schmid factor (SF). Nonetheless, TEM observations revealed the activation of basal <a> dislocations in these grains, potentially leading to crack nucleation along basal slip bands and subsequent propagation along the basal plane. Our results suggest that a high-density twin structure on the surface can enhance the fatigue strength of Ti–6Al–4V by transferring the fatigue crack source to the subsurface.

Interband cascade light-emitting diodes grown on silicon substrates using GaSb buffer layer

Interband cascade light-emitting diodes (ICLEDs) offer attractive advantages for infrared applications, which would greatly expand if high-quality growth on silicon substrates could be achieved. This work describes the formation of threading dislocations in ICLEDs grown monolithically on GaSb-on-Silicon wafers. The epitaxial growth is done in two stages: the GaSb-on-Silicon buffer is grown first, followed by the ICLED growth. The buffer growth involves the nucleation of a 10-nm-thick AlSb buffer layer on the silicon surface, followed by the GaSb growth. The AlSb nucleation layer promotes the formation of 90° and 60° interfacial misfit dislocations, resulting in a highly planar morphology for subsequent GaSb growth that is almost 100% relaxed. The resulting GaSb buffer for growth of the ICLED has a threading dislocation density of ∼107/cm2 after ∼3 μm of growth. The fabricated LEDs showed variations in device performance, with some devices demonstrating comparable light–current–voltage curves to those for devices grown on GaSb substrates, while other devices showed somewhat reduced relative performance. Cross-sectional transmission electron microscopy observations of the inferior diodes indicated that the multiplication of threading dislocations in the active region had most likely caused the increased leakage current and lower output power. Enhanced defect filter layers on the GaSb/Si substrates should provide more consistent diode performance and a viable future growth approach for antimonide-based ICLEDs and other infrared devices.

Foraminiferal detoxification breakdown induced by fatal levels of TiO2 nanoparticles

The increase discharge of titanium dioxide (TiO2) nanoparticles, derived from engineered material waste, exerts a detrimental impact on both the marine ecosystem and public health. The cytotoxicity of TiO2 nanoparticles on marine organisms should be imperatively understood to tackle the urgent concern for the well-being of marine life. Various concentrations of TiO2 nanoparticles have proven to reach fatal levels in aquatic organisms, requiring a deeper exploration of cytotoxicity. Notably, certain benthic foraminifers, such as Ammonia veneta, have been identified as capable of incorporating TiO2 nanoparticles into vesicles. However, these organisms exhibit a detoxification mechanism through exocytosis, as indicated by previous transcriptomic inferences. This presents the advantage of assessing the tolerance of foraminifers to TiO2 nanoparticles as pollutants and investigating the long-term effects of cytotoxicity. In this study, we scrutinized the distribution of TiO2 nanoparticles within cells and the growth rates of individuals in seawater media containing 1, 5, 10, and 50 ppm TiO2 nanoparticles, comparing the results with a control group over a 5-week period, utilizing A. veneta stain. Transmission electron microscopy observations consistently revealed high concentrations of TiO2 nanoparticles in vesicles, and their expulsion from cells was evident even with exposure to 5 ppm TiO2 nanoparticles. Under the control and 1 ppm TiO2 conditions, foraminifers increased their cell volume by adding a calcification chamber to their tests every 1 or 2 days. However, the 5-week culturing experiments demonstrated that foraminifers gradually ceased growing under 5 ppm TiO2 nanoparticle exposure and exhibited no growth at &amp;gt; 10 ppm concentrations, despite an ample food supply. Consequently, these findings with A. veneta suggest that the foraminiferal detoxification system could be disrupted by concentrations exceeding 5 ppm of TiO2 nanoparticles. The toxic effect of TiO2 nanoparticles on meiofauna, such as benthic foraminifers, have been poorly understood, though these organisms play an important role in the marine ecosystem. Environmental accumulation of TiO2 nanoparticles on the coast has already exceeded twenty times more than foraminiferal detoxification level. Future studies focusing on toxic mechanism of TiO2 nanoparticles are crucial to prevent the breakdown of the marine ecosystem through accelerating discharge of TiO2 nanoparticles into the ocean.

Unveiling interface engineering dynamics between Ti and Ga2O3 nanowire

In this study, we investigate the interfacial reactions between Ga2O3 nanowires (NWs) and Ti contacts during annealing processes through in-situ transmission electron microscopy (TEM) observations. A thin Ga3Ti2 intermetallic compound was observed to form at the Ti/Ga2O3 interface, coinciding with a transition in the NW device’s contact behavior from Schottky to ohmic upon annealing at 470 °C. Utilizing in-situ TEM, we monitored the evolution of the Ga3Ti2 layer, revealing Ga atoms as the primary diffusing species within the Ga2O3 NW, evidenced by asymmetric diffusion at the interface. Ga3Ti2 intermetallic compound effectively reducing the energy barrier between Ga2O3 NW and Ti electrode, contributing to linear electrical transport characteristics. This investigation underscores the significance of interface engineering and offers valuable insights for future electronic applications utilizing Ga2O3 NWs.

Influence of chemical composition on the room temperature plasticity of C15 Ca-Al-Mg Laves phases

The influence of chemical composition changes on the room temperature mechanical properties in the binary Ca33Al67C15 CaAl2 Laves phase were investigated in two ternary alloys with off-stoichiometric compositions with 5.7 at.% Mg substitution (Ca33Al61Mg6) and 10.8 at.% Mg and 3.0 at.% Ca substitution (Ca36Al53Mg11) and compared to the stoichiometric (Ca33Al67) composition. Cubic Ca-Al-Mg Laves phases with multiple crystallographic orientations were characterised and deformed using nanoindentation. The hardness and indentation modulus were measured to be 4.1 ± 0.3 GPa and 71.3 ± 1.5 GPa for Ca36Al53Mg11, 4.6 ± 0.2 GPa and 80.4 ± 3.8 GPa for Ca33Al61Mg6 and 4.9 ± 0.3 GPa and 85.5 ± 4.0 GPa for Ca33Al67, taken from our previous study, respectively. The resulting surface traces as well as slip and crack planes, were distinguished on the indentation surfaces, revealing the activation of several different {11n} slip systems, as further confirmed by conventional transmission electron microscopic observations. Additionally, the deformation mechanisms and corresponding energy barriers of activated slip systems were evaluated by atomistic simulations.

Corrosion resistance of polyvinyl butyral coatings enhanced by montmorillonite-chitosan composites

To improve the corrosion resistance of 304SS, a polyvinyl butyral/organic montmorillonite-chitosan (PVB/OMMT-Ch) composite coating was prepared by the spin coating method. The Montmorillonite was organically modified with Cetyltrimethylammonium Bromide and compounded with Chitosan to obtain OMMT-Ch. OMMT-Ch filler has been introduced into the polyvinyl butyral coating to improve the corrosion resistance of 304 stainless steel. Scanning electron microscope and transmission electron microscope observations showed that the introduction of chitosan made the montmorillonite layers rounded and loose, and the X-ray diffraction (XRD) results indicated that the interlayer spacing between the montmorillonite layers changed significantly, and the FT-IR results of the chitosan/montmorillonite insertion complexes were in good agreement with those of the XRD analyses, which showed that chitosan successfully inserted between the layers of montmorillonite. The corrosion resistance of the composite coatings in 3.5% NaCl solution was tested by Tafel polarization curves and electrochemical impedance spectroscopy. The results showed that the composite coatings doped with 0.5% OMMT-Ch had the best corrosion resistance with long-lasting protection of more than 160 days. This study suggests a novel approach for nanocomposites for dealing with the 304SS corrosion issue.